The Mekong River Commission
THE COUNCIL STUDY STUDY ON THE SUSTAINABLE MANAGEMENT AND DEVELOPMENT OF THE MEKONG RIVER, INCLUDING IMPACTS OF MAINSTREAM HYDROPOWER PROJECTS
BioRA PROGRESS REPORT 2: DRIFT DSS Set-up
DRAFT II
August 2015
Contents 1 Introduction ...... 1 1.1 The Council Study ...... 3 1.1.1 Aims ...... 3 1.1.2 Organisation ...... 3 1.2 The Biological Resources Assessment ...... 5 1.2.1 The BioRA Team ...... 5 1.3 Purpose of this document ...... 7 2 BioRA zones and focus areas ...... 8 2.1 BioRA zones...... 8 2.2 BioRA focus areas ...... 9 3 BioRA indicators ...... 11 3.1 Revised BioRA indicators ...... 11 3.2 Relation to draft MRC indicator framework ...... 11 4 Revised BioRA Links ...... 20 5 June/July work sessions ...... 28 5.1 OSP meeting ...... 28 5.2 OSV work sessions ...... 28 5.2.1 Agendas (6-11 July 2015) ...... 30 6 Status and trends assessment ...... 33 6.1 Purpose of the status and trends assessment ...... 33 6.2 Approach ...... 33 6.3 Historical change in the LMB ...... 35 6.4 Status and trends: Sediments and sediment transport ...... 37 6.4.1 Mekong River in Lao PDR (Chinese border to Nong Khai) ...... 37 6.4.2 Mekong River in Lao PDR / Thailand (Nong Khai to Pakse) ...... 39 6.4.3 Mekong River in Cambodia (Stung Treng to Chaktomuk confluence) ...... 41 6.4.4 Tonle Sap River and Great Lake ...... 42 6.4.5 Mekong Delta ...... 43 6.5 Status and trends: Geomorphology ...... 43 6.5.1 Bank erosion and bed incision ...... 44 6.5.2 Average bed sediment size ...... 46 6.5.3 Availability of exposed sand bars and islands in the dry season ...... 48 6.5.4 Availability of exposed rocky habitats in the dry season ...... 50 6.5.5 Depth of bedrock pools ...... 51 6.5.6 Water clarity ...... 54 6.6 Status and trends: Vegetation ...... 55 6.6.1 Channel_Extent of upper bank vegetation cover ...... 58 6.6.2 Channel_Extent of lower bank vegetation cover ...... 59 6.6.3 Channel_Extent of herbaceous marsh vegetation ...... 60 6.6.4 Channel_Biomass of riparian vegetation ...... 60 6.6.5 Channel_Biomass of algae ...... 61 6.6.6 Floodplain_Extent of flooded forest...... 61 6.6.7 Floodplain_Extent of herbaceous marsh vegetation ...... 63 6.6.8 Floodplain_Extent of grassland vegetation ...... 63
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6.6.9 Floodplain_Biomass of riparian/aquatic cover ...... 64 6.6.10 Floodplain_Extent of cyanobacteria ...... 65 6.6.11 Floodplain_Extent of invasive riparian plant cover ...... 65 6.6.12 Floodplain_Extent of floating and submerged invasive plant cover ...... 66 6.7 Status and trends: Macroinvertebrates ...... 67 6.7.1 Insects on stones ...... 69 6.7.2 Insects on sand ...... 70 6.7.3 Dry season emergence ...... 71 6.7.4 Burrowing mayflies ...... 71 6.7.5 Snail abundance...... 72 6.7.6 Snail diversity ...... 73 6.7.7 Neotricula aperta ...... 74 6.7.8 Bivalve abundance ...... 76 6.7.9 Polychaetes ...... 76 6.7.10 Shrimps and crabs ...... 77 6.7.11 Littoral invertebrate diversity ...... 78 6.7.12 Benthic invertebrate diversity ...... 78 6.7.13 Zooplankton abundance ...... 79 6.8 Status and trends: Fish ...... 80 6.8.1 Rithron resident species ...... 86 6.8.2 Main channel resident (long distant white) species ...... 87 6.8.3 Main channel spawner (short distance white) species...... 88 6.8.4 Floodplain spawner (grey) species ...... 89 6.8.5 Eurytopic (generalist) species ...... 90 6.8.6 Floodplain resident (black fish) ...... 91 6.8.7 Estuarine resident species ...... 92 6.8.8 Anadromous species ...... 92 6.8.9 Catadromous species ...... 93 6.8.10 Marine visitor species ...... 94 6.8.11 Non-native species ...... 95 6.9 Status and trends: Herpetofauna ...... 95 6.9.1 Ranid and microhylid amphibians ...... 96 6.9.2 Aquatic serpents...... 99 6.9.3 Aquatic Turtles ...... 101 6.9.4 Semi-aquatic Turtles ...... 104 6.9.5 Amphibians available for human consumption ...... 107 6.9.6 Aquatic/ semi-aquatic reptiles available for human exploitation ...... 108 6.9.7 Species richness of riparian amphibians ...... 110 6.9.8 Species richness of riparian reptiles ...... 111 6.10 Status and trends: Birds ...... 113 6.10.1 Medium / large ground-nesting channel species ...... 113 6.10.2 Small non-flocking landbirds of seasonally-flooded vegetation ...... 118 6.10.3 Large tree-nesting waterbirds ...... 123 6.10.4 Bank / hole-nesting species ...... 125 6.10.5 Flocking passerine of tall graminoid beds ...... 128 6.10.6 Large ground-nesting species of floodplain wetlands ...... 130
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6.10.7 Large ground-nesting species of floodplain wetlands ...... 132 6.10.8 Large channel-using species that require riparian forest ...... 135 6.10.9 Rocky crevice nester in channels ...... 138 6.10.10 Dense woody vegetation / water interface ...... 140 6.11 Status and trends: Mammals ...... 142 6.11.1 Irrawaddy Dolphin ...... 143 6.11.2 Otters ...... 145 6.11.3 Wetland ungulates...... 147 7 Preliminary reference data sets ...... 150 7.1 Reference period used ...... 150 7.2 Data entered into the DSS ...... 150 7.2.1 Hydrology (DSF)...... 150 7.2.2 Hydraulics (DSF): ISIS-ID and WUP-FIN ...... 151 7.2.3 Water quality and suspended sediments ...... 154 8 Layout and population of the DRIFT DSS for BioRA ...... 178 8.1 Setup ...... 179 8.2 Knowledge Capture ...... 181 8.2.1 Hydrology and hydraulics sub-section ...... 181 8.2.2 Water quality, Sediment and External indicators sub-sections ...... 183 8.2.3 Response curves sub-section ...... 184 8.2.4 Integrity ...... 186 9 Preliminary BioRA response curves ...... 187 9.1 DRIFT response curves ...... 187 9.1.1 Scoring system used ...... 188 9.1.2 Addressing data limitations ...... 189 9.2 Focus Area 1: Examples of preliminary response curves ...... 189 10 Next steps ...... 205 10.1 Schedule of follow-up BioRA activities ...... 205 11 References ...... 207 Appendix A. BioRA deliverables ...... 216 Appendix B. BioRA team members for June/July 2015 team meetings ...... 217 Appendix C. Annotated Table oF Contents for BioRA Specialist Reports ...... 218
List of Figures Figure 1.1 The Lower Mekong River Basin ...... 2 Figure 1.2 Council Study Assessment Framework ...... 4 Figure 2.1 Preliminary BioRA zones ...... 8 Figure 2.2 Preliminary BioRA focus areas ...... 9 Figure 4.1 Revised BioRA links for FA1 ...... 26 Figure 4.2 Revised BioRA links for FA2 ...... 26 Figure 4.3 Revised BioRA links for FA3 ...... 27 Figure 5.1 The BioRA Team in Vientiane (July 2015) ...... 29 Figure 6.1 Box and whisker plots showing suspended sediment concentrations (top) and average daily flow on monitoring days (bottom) at Chiang Saen (Koehnken 2014).
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The box encompasses the 25th to 75th percentile flows, while the ‘whiskers’ show the minimum and maximum values. The median value is shown as a line within the box...... 38 Figure 6.2 Comparison of flows and suspended sediment concentrations at Luang Prabang and Pakse between 1961 (left) and 2011 (right; plots from Koehnken 2012)...... 39 Figure 6.3 Map showing existing and planned hydropower projects in the LMB. From based on MRC Hydropower database...... 40 Figure 6.4 Map of sediment extraction in the LMB. Size of circle is relative to the volume of material extracted. Red, orange and bronw bars indicate proportion of sand, gravel and pebble extracted at each site, respectively...... 41 Figure 6.5 Grain-size distribution of suspended sediment at Prek Kdam, in the Tonle Sap River; 2011 – 2012 (Koehnken 2014)...... 42 Figure 6.6 Bank erosion and bed incision: Historic estimates as % relative to 2015 (100%) ...... 45 Figure 6.7 Median grain size and distance from river mouth of bed samples collected in 2011 (Koehnken 2012) ...... 47 Figure 6.8 Average bed sediment size: Historic estimates as % relative to 2015 (100%) ...... 48 Figure 6.9 Availability of exposed sand bars and islands: Historic estimates as % relative to 2015 (100%). Tonle Sap Great Lake was not assessed for exposed sandy bars and islands...... 49 Figure 6.10 Availability of exposed rocky habitats: Historic abundance estimates as % relative to 2015 (100%)...... 51 Figure 6.11 Thalwag long-section of the LMB showing occurrences of Deep Pools (MRC 2011)...... 52 Figure 6.12 Pool types identified in the LMB (MRC 2011)...... 53 Figure 6.13 Depth of pools: Historic estimates as % relative to 2015 (100%). Tonle Sap River, the Great Lake and the Delta were not assessed for depth of bedrock pools...... 53 Figure 6.14 Water clarity: Historic estimates as % relative to 2015 (100%) ...... 55 Figure 6.15 Channel_Extent of upper bank vegetation cover: Historic abundance estimates as % relative to 2015 (100%) ...... 59 Figure 6.16 Channel_Extent of lower bank vegetation cover: Historic abundance estimates as % relative to 2015 (100%) ...... 59 Figure 6.17 Channel_Extent of herbaceous marsh vegetation: Historic abundance estimates as % relative to 2015 (100%) ...... 60 Figure 6.18 Channel_Biomass of riparian vegetation: Historic abundance estimates as % relative to 2015 (100%) ...... 61 Figure 6.19 Cultivated areas in the Mekong Delta c. 1910 (http://www.odsas.net/scan_sets.php?set_id=404anddoc=43700andstep=5)...... 62 Figure 6.20 Floodplain_Extent of flooded forest: Historic abundance estimates as % relative to 2015 (100%) ...... 62 Figure 6.21 Floodplain_Extent of herbaceous marsh vegetation: Historic abundance estimates as % relative to 2015 (100%) ...... 63 Figure 6.22 Floodplain_Extent of grassland vegetation: Historic abundance estimates as % relative to 2015 (100%) ...... 64 Figure 6.23 Floodplain_Biomass of riparian/aquatic cover: Historic abundance estimates as % relative to 2015 (100%) ...... 65
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Figure 6.24 Floodplain_Extent of invasive riparian plant cover: Historic abundance estimates as % relative to 2015 (100%) ...... 66 Figure 6.25 Floodplain_ Extent of floating and submerged invasive plant cover: Historic abundance estimates as % relative to 2015 (100%) ...... 67 Figure 6.26 Insects on stones: Historic abundance estimates as % relative to 2015 (100%) ...... 69 Figure 6.27 Insects on sand: Historic abundance estimates as % relative to 2015 (100%) ...... 70 Figure 6.28 Dry season emergence: Historic abundance estimates as % relative to 2015 (100%) ...... 71 Figure 6.29 Burrowing mayflies: Historic abundance estimates as % relative to 2015 (100%) ...... 72 Figure 6.30 Snail abundance: Historic abundance estimates as % relative to 2015 (100%) ...... 73 Figure 6.31 Snail diversity: Historic abundance estimates as % relative to 2015 (100%)...... 74 Figure 6.32 Schematic showing the life cycle of Schistosomaisis ...... 75 Figure 6.33 Neotricula aperta: Historic abundance estimates as % relative to 2015 (100%) ...... 75 Figure 6.34 Bivalve abundance: Historic abundance estimates as % relative to 2015 (100%) ...... 76 Figure 6.35 Polychaetes: Historic abundance estimates as % relative to 2015 (100%) ...... 77 Figure 6.36 Shrimps and crabs: Historic abundance estimates as % relative to 2015 (100%) ...... 77 Figure 6.37 Littoral Invertebrate Diversity: Historic abundance estimates as % relative to 2015 (100%) ...... 78 Figure 6.38 Benthic invertebrate diversity: Historic abundance estimates as % relative to 2015 (100%) ...... 79 Figure 6.39 Zooplankton abundance: Historic abundance estimates as % relative to 2015 (100%) ...... 79 Figure 6.40 Generalized migration systems in the Lower Mekong Basin (Source: Poulsen et al. 2002a)...... 81 Figure 6.41 Capture fisheries production for Cambodia (2000-2013) (FA4- Kratie; FA5 – Phnom Penh; FA6- Tonle Sap River; FA7 – Tonle Sap Great Lake )...... 82 Figure 6.42 Variation in capture fisheries (fish and other aquatic animals) production by provinces in the Mekong delta (Source: GSO)...... 83 Figure 6.43 Rithron resident species: Historic abundance estimates as % relative to 2015 (100%) ...... 87 Figure 6.44 Main channel resident (long distant white) species: Historic abundance estimates as % relative to 2015 (100%) ...... 88 Figure 6.45 Main channel spawner (short distance white) species: Historic abundance estimates as % relative to 2015 (100%) ...... 89 Figure 6.46 Floodplain spawner (grey) species: Historic abundance estimates as % relative to 2015 (100%) ...... 90 Figure 6.47 Eurytopic (generalist) species: Historic abundance estimates as % relative to 2015 (100%) ...... 90 Figure 6.48 Floodplain resident (black fish): Historic abundance estimates as % relative to 2015 (100%) ...... 91 Figure 6.49 Estuarine resident species: Historic abundance estimates as % relative to 2015 (100%) ...... 92 Figure 6.50 Anadromous species: Historic abundance estimates as % relative to 2015 (100%) ...... 93 Figure 6.51 Catadromous species: Historic abundance estimates as % relative to 2015 (100%) ...... 94
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Figure 6.52 Marine visitor species: Historic abundance estimates as % relative to 2015 (100%) ...... 94 Figure 6.53 Non-native species: Historic abundance estimates as % relative to 2015 (100%) ...... 95 Figure 6.54 Ranid and microhylid amphibians (Rana nigrovittata): Historic abundance estimates as % relative to 2015 (100%) ...... 97 Figure 6.55 Ranid and microhylid amphibians (Hoplobatrachus rugulosus): Historic abundance estimates as % relative to 2015 (100%) ...... 98 Figure 6.56 Aquatic serpents (Enhydris bocourti): Historic abundance estimates as % relative to 2015 (100%) ...... 100 Figure 6.57 Aquatic serpents (Cylindrophis ruffus): Historic abundance estimates as % relative to 2015 (100%) ...... 101 Figure 6.58 Aquatic turtles (Amyda cartilaginea): Historic abundance estimates as % relative to 2015 (100%) ...... 102 Figure 6.59 Aquatic turtles (Malayemys subtrijuga): Historic abundance estimates as % relative to 2015 (100%) ...... 104 Figure 6.60 Semi-aquatic turtles (Cuora amboiensis): Historic abundance estimates as % relative to 2015 (100%) ...... 105 Figure 6.61 Semi-aquatic turtles (Heosemys grandis): Historic abundance estimates as % relative to 2015 (100%) ...... 107 Figure 6.62 Amphibians available for human consumption: Historic abundance estimates as % relative to 2015 (100%) ...... 108 Figure 6.63 Aquatic/ semi-aquatic reptiles available for human exploitation: Historic abundance estimates as % relative to 2015 (100%) ...... 110 Figure 6.64 Species richness of riparian amphibians: Historic abundance estimates as % relative to 2015 (100%) ...... 111 Figure 6.65 Species richness of riparian reptiles: Historic abundance estimates as % relative to 2015 (100%) ...... 112 Figure 6.66 Medium / large ground-nesting channel species (River Tern): Historic abundance estimates as % relative to 2015 (100%) ...... 115 Figure 6.67 Medium / large ground-nesting channel species (River Lapwing): Historic abundance estimates as % relative to 2015 (100%) ...... 117 Figure 6.68 Small non-flocking landbirds of seasonally-flooded vegetation (Jerdon’s Bushchat): Historic abundance estimates as % relative to 2015 (100%) ...... 119 Figure 6.69 Small non-flocking landbirds of seasonally-flooded vegetation (Mekong Wagtail): Historic abundance estimates as % relative to 2015 (100%) ...... 121 Figure 6.70 Small non-flocking landbirds of seasonally-flooded vegetation (Manchurian Reed Warbler): Historic abundance estimates as % relative to 2015 (100%) ...... 122 Figure 6.71 Large tree-nesting waterbirds (White-shouldered Ibis): Historic abundance estimates as % relative to 2015 (100%) ...... 125 Figure 6.72 Bank / hole-nesting species (Pied Kingfisher): Historic abundance estimates as % relative to 2015 (100%) ...... 127 Figure 6.73 Flocking passerines of tall graminoid beds (Baya Weaver): Historic abundance estimates as % relative to 2015 (100%) ...... 129 Figure 6.74 Large ground-nesting species of floodplain wetlands (Sarus Crane): Historic abundance estimates as % relative to 2015 (100%) ...... 132
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Figure 6.75 Large ground-nesting species of floodplain wetlands (Bengal Florican): Historic abundance estimates as % relative to 2015 (100%)...... 134 Figure 6.76 Large channel-using species that require riparian forest (Lesser Fish Eagle): Historic abundance estimates as % relative to 2015 (100%) ...... 136 Figure 6.77 Large channel-using species that require bank-side forest (Grey-headed Fish Eagle): Historic abundance estimates as % relative to 2015 (100%) ...... 137 Figure 6.78 Rocky-crevice nester in channels (Wire-tailed Swallow): Historic abundance estimates as % relative to 2015 (100%) ...... 140 Figure 6.79 Dense woody vegetation / water interface (Masked Finfoot): Historic abundance estimates as % relative to 2015 (100%) ...... 142 Figure 6.80 Irrawaddy Dolphin: Historic abundance estimates as % relative to 2015 (100%) ...... 144 Figure 6.81 Otters: Historic abundance estimates as % relative to 2015 (100%) ...... 147 Figure 6.82 Wetland ungulates (Hog Deer): Historic abundance estimates as % relative to 2015 (100%) ...... 149 Figure 7.1 Hydrographs and D/T1, T1/W thresholds for FA1 to FA3 ...... 151 Figure 7.2 Location of the cross-sections used for calculation of hydraulics parameters (larger blue crosses) for FA1 (cross-section M2172), FA2 (cross-section M1588), and FA3 (cross-section M1144) ...... 152 Figure 7.3 Depth time-series at FA1, FA2 and FA3 ...... 152 Figure 7.4 Velocity time-series at FA1, FA2 and FA3 ...... 153 Figure 7.5 Wetted perimeter time-series at FA1, FA2 and FA3 ...... 153 Figure 7.6 Floodplain areas covered by the WUP-FIN models for Nam Som Khram and Se Bang Fai in FA 3 (green outline)...... 154 Figure 7.7 Modelled time-series of area of floodplain at FA 3 (Se Bang Fai) ...... 154 Figure 7.8 Monthly median water quality values at Chiang Saen showing seasonal variability...... 159 Figure 7.9 Monthly median values for water quality parameters at Vientiane based on 1985 – 2008 WQMN monitoring results ...... 164 Figure 7.10. Monthly median water quality results for Nakhon Phanom 1985 – 2008...... 169 Figure 7.11 Median monthly values of water quality parameters at Pakse, 1985 - 2008...... 173 Figure 7.12 Suspended sediment rating curve and daily suspended sediment time-series based on rating curve for Pakse, based on 1997 - 2002 monitoring results...... 173 Figure 7.13 Median monthly values for water quality parameters at Kampong Cham, 1985 - 2008...... 176 Figure 8.1 The SETUP section of the DSS ...... 179 Figure 8.2 The “Indicator Pool” tab of the “Project indicators” module of the DSS ...... 180 Figure 8.3 The “Links” module of the DSS ...... 180 Figure 8.4 Parameters, threshold values and season start dates for the preliminary reference scenario at FA1...... 182 Figure 8.5 Season delineation for one year for the preliminary reference scenario at FA1 ...... 183 Figure 8.6 A section of the annual flow indicator values for the preliminary reference scenario at FA1 ...... 183 Figure 8.7 Time-series of indicator values for the external indicator “Shear stress” at FA1 ...... 184 Figure 8.8 The Geomorphology: Erosion (bank/bed incision) tab in the BioRA Response curves: Habitat and Biota module ...... 185 Figure 8.9 Values from the linked indicator time-series provided for each response curve ...... 185
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Figure 9.1 The relationship between severity ratings (and severity scores) and percentage abundance lost or retained as used in DRIFT and adopted for the DSS. (PD=present day AND = 100%)...... 189
List of Tables Table 1.1 BioRA management team ...... 5 Table 1.2 BioRA international/regional specialists ...... 6 Table 1.3 BioRA national specialists ...... 7 Table 2.1 Preliminary BioRA focus areas ...... 10 Table 3.1 Draft BioRA modelled time series indicators ...... 11 Table 3.2 Revised BioRA ecosystem indicators showing applicable focus areas for each ...... 14 Table 3.3 Relation to MRC Framework environmental indicators ...... 17 Table 3.4 Relation to MRC Framework social indicators ...... 19 Table 4.1 Links to hydrological indicators at FA1 ...... 20 Table 4.2 Links to hydraulic indicators at FA1 ...... 21 Table 4.3 Links to sediment indicators at FA1...... 22 Table 4.4 Links to water quality indicators at FA1 ...... 23 Table 4.5 Links to geomorphology and vegetation indicators at FA1 ...... 24 Table 4.6 Links to macroinvertebrate and fish indicators at FA1 ...... 25 Table 5.1 Schedule for the June/July 2015 work sessions in Phnom Penh ...... 28 Table 5.2 Schedule for the July 2015 work sessions in Vientiane ...... 29 Table 5.3 MONDAY 6th July 2015: Catch-up Sessions ...... 30 Table 5.4 TUESDAY 7th July 2015: Workshop: DSS – FA1/2 ...... 30 Table 5.5 WEDNESDAY 8th July 2015: Workshop: DSS – FA1/2...... 31 Table 5.6 THURSDAY 9th July 2015: Workshop: DSS – FA1/3 ...... 31 Table 5.7 FRIDAY 10th July 2015: Workshop: DSS – FA3/4 ...... 31 Table 5.8 SATURDAY 11th July 2015: Wrap-up meeting ...... 32 Table 6.1 Status and trends areas, shown in relation to the BioRA zones ...... 34 Table 6.2 Ecological status ratings ...... 34 Table 6.3 Key historical events affecting the LMB ...... 35 Table 6.4 Estimated 2015 ecological status for each of the geomorphology indicators ...... 44 Table 6.5 Summary of grain-size classes used in 2011 DSMP bed material survey ...... 47 Table 6.6 Estimated 2015 ecological status for each of the vegetation indicators...... 58 Table 6.7 Estimated 2015 ecological status for each of the macroinvertebrate indicators ...... 68 Table 6.8 Trends in pressures acting on fisheries in the BioRA zones since 1900 ...... 84 Table 6.9 Estimated 2015 ecological status for each of the fisheries indicators ...... 86 Table 6.10 Estimated 2015 ecological status for each of the herpetofauna indicators ...... 96 Table 6.11 Estimated 2015 ecological status for each of the bird indicators ...... 113 Table 6.12 Estimated 2015 ecological status for each of the mammal indicators ...... 142 Table 7.1 Data sources used for the construction of the water quality time series used in initial population of DRIFT DSS ...... 155 Table 7.2 Chiang Saen water quality results used to derive time-series for FA1...... 157 Table 7.3 Flow time-series and rating curves used to estimate susoended sediment concentrations and total nutrient values for FA1...... 160
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Table 7.4 Water quality time-series and monthly grouping of results at Vientiane, 1985 - 2007 ...... 162 Table 7.5 Daily flow series from Nong Khai (HYMOS) and rating curves used to estimate daily suspended sediments in FA2...... 165 Table 7.6 Time-series of WQMN water quality results and monthly grouping of results...... 166 Table 7.7 Observed flow and suspended sediment results at Nakhon Phanom and rating curves used to estimate daily time series for DRIFT input...... 169 Table 7.8 Water quality time-series and monthly grouping of water quality results for Pakse...... 170 Table 7.9 Time-series and monthly grouping of WQMN water quality results at Kampong Cham...... 174 Table 7.10 Graphs showing the rating curve (left) used to derive the estimated TSS time- series at Kampong Cham (right)...... 177 Table 8.1 Values from modelled time-series provided for each response curve ...... 185 Table 9.1 DRIFT severity ratings and their associated abundances and losses – a negative score means a loss in abundance relative to baseline, a positive means a gain...... 188 Table 9.2 Example for Geomorphology (Erosion (bank / bed incision)): Response curves and explanations for linked indicators ...... 191 Table 9.3 Example for Vegetation (Channel: Biomass riparian vegetation): Response curves and explanations for linked indicators ...... 195 Table 9.4 Example for Macroinvertebrates (Insects on stones): Response curves and explanations for linked indicators ...... 196 Table 9.5 Example for Fish (Rhithron species): Response curves and explanations for linked indicators ...... 198 Table 9.6 Example for Herpetofauna (Aquatic serpents): Response curves and explanations for linked indicators ...... 201 Table 9.7 Example for Birds (Medimum/large ground-nesting channel species): Response curves and explanations for linked indicators ...... 203 Table 10.1 Schedule of BioRA activities (as at 25th July 2015) ...... 205 Table 10.2 BioRA deliverables ...... 206
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1 Introduction
The Mekong River is the world's 12th longest river and the longest in south-eastern Asia, with an estimated length of 4 350 km. The river rises in the high plateau of Eastern Tibet and flows in a south-east direction through China, Myanmar, Lao PDR, Thailand, Cambodia and Viet Nam. It drains an area of 795 000 km², and discharges c. 457 km³ of water annually into the sea south-west of Ho Chi Minh City.
The Lower Mekong River (Figure 1.1) is about 3000 km long from the border between Lao PDR and Myanmar to the Sea, and includes the Tonle Sap System and the rich Mekong Delta in southern Viet Nam. These two systems are unique features of the Lower Mekong Basin (LMB), which affect both how the system functions and how people depend on it. The Tonle Sap Great Lake is a shallow lake in western Cambodia that links to the Mekong River via the 150-km long Tonle Sap River. During the wet monsoon season of June to November, the high waters of the Mekong River reverse the flow of the Tonle Sap River and increase the size of the lake from 2 600 to 10 400 km2. When the high waters of the Mekong River recede, the flow in the Tonle Sap River reverses again and drains the lake. This natural mechanism provides a unique and important balance to the Mekong River and ensures a flow of fresh water during the dry season into the Delta, which buffers the intrusion of salt water into the rich agricultural lands of the delta (MRC 2006).
Kratie is generally regarded as the point in the Mekong system where the hydrology and hydrodynamics of the river change significantly. Upstream of this point, the river generally flows within a clearly identifiable mainstream channel. In all but the most extreme flood years, this channel contains the full discharge with only local over-bank natural storage. Downstream from Kratie, seasonal floodplain storage dominates the annual regime and there is considerable movement of water between channels and floodplains, the seasonal refilling of the Great Lake and the flow reversal in the Tonle Sap. There is extreme hydrodynamic complexity in both time and space and it becomes impossible to measure channel discharge. Water levels, not flow rates and volumes, determine the movement of water across the landscape, although water level is driven by discharge and volume.
Since its establishment in 1995, the Mekong River Commission (MRC) has been involved in the collection of data and the development of models, both conceptual and mathematical, aimed at improving and demonstrating the understanding of the functioning of the LMB aquatic ecosystems, and the links between the people and the river. The result is an enormous body of data, understanding of life-histories and system functioning, and resources such as maps and mathematical models.
The MRC has used these data and models to aid decision-making in the region as it pertains to the LMB through the analysis of possible changes to river resources, and knock-on effects on the people that depend on them, in response to actual and proposed water-resource developments in the basin at large. Studies that have addressed this include Integrated Basin Flow Management (IBFM; 2004-2006; MRCS 2006) Basin Development Plan (BDP; 2004-ongoing; MRC 2011) SEA (ICEM 2010).
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Apart from IBFM, which was terminated before a planned 4th phase, the abovementioned studies did not include a systemic and systematic assessment of the impacts of developments on the river ecosystem or ecosystem services.
Figure 1.1 The Lower Mekong River Basin
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This lack was identified as a data gap, inter alia, in the recent revision of the Basin Development Plan. Subsequently, at the 18th Council Meeting of the MRC1, the Member Countries’ Prime Ministers agreed in principle to implement a study on sustainable management and development of the Mekong River including impact of mainstream hydropower projects, which addressed some of the existing data gaps. This agreement led to “The Council Study”.
1.1 The Council Study
1.1.1 Aims
The Council Study focuses on sustainable management and development of the Lower Mekong Basin (LMB)2. It aims to address uncertainties in assessing the impact of different development opportunities in the Mekong River Basin and to provide recommendations to facilitate informed development planning in the mainstream of the LMB.
The developments opportunities to be analysed may be located on the mainstream Mekong River or in any of the tributaries in the LMB. The analysis of impacts of these on the river ecosystem and people will be limited to the mainstem Mekong and Tonle Sap Rivers, Tonle Sap Great Lake and the Mekong Delta.
The stated objectives of the Council Study are to: further develop a reliable scientific evidence of positive and negative environmental, social, and economic impacts of water resources developments; integrate the results into the MRC knowledge base to enhance the BDP process, and; promote capacity and ensure technology transfer to Member Countries.
1.1.2 Organisation
The overall unified assessment framework of the Council Study is illustrated in Figure 1.2. The framework requires closely coordinating the activities of the various Thematic and Discipline Teams and successfully coordinating the technical inputs and integrating their outputs and deliverables. The Council Study is composed of six (6) Thematic Teams representing each development thematic area or sector, a cumulative assessment team, and five (5) cross-cutting Discipline Teams.
The Council Study major activities will be accomplished in the following general sequence.
Each Thematic Team formulates the water-resource development scenarios for each Thematic Area (Irrigation, Agriculture/Land Use, Hydropower, Flood Protection and Floodplain Management, Domestic and Industrial Water Use, and Navigation).
The Cumulative Assessment Team formulates the cumulative development scenarios in conjunction with the various Thematic Teams.
1 Held in Bali, Indonesia, November 2011 2 Impact area is Mekong Mainstream including a 15-km corridor area on both sides of the river and the Tonle Sap Great Lake and Delta floodplains.
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Figure 1.2 Council Study Assessment Framework
The Hydrologic Discipline Team through the use primarily of the MRC DSF and WUP-FIN models assesses the changes in flow, sediment transport, and water quality as a result of the developments under baseline and development scenarios.
The Biological Resource Discipline Team through the use of DRIFT assesses corresponding changes in the habitat, biodiversity, and other selected environmental indicators as a result of changes in flow, sediment transport, and water quality.
The Socio-Economic Discipline Team assesses corresponding changes in selected socio-economic indicators (i.e., livelihood, public health, and nutrition among others) as a result of changes in flow, sediment transport, water quality, and ecosystem.
The Macro-Economic Discipline Team assesses the macro-economic impact (including distributional analysis of benefits and costs amongst communities, livelihoods, countries, and people of different socio-economic strata) of the changes in flow, sediment transport, water quality, and ecosystem.
The Climate Change Discipline Team provides technical support to the Discipline Teams to account for climate change impacts.
The Thematic and Discipline Teams and the Cumulative Assessment Team in collaboration prepare reports to document the environmental and socio-economic impacts of developments under the six (6) thematic areas or sectors separately and cumulatively, including recommendations on how to
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1.2 The Biological Resources Assessment
The objective of the Biological Resources Assessment (BioRA) is to provide clear and comparable information on the impacts of proposed thematic developments on the aquatic resources of Mekong River downstream of the China border, inclusive of the Tonle Sap Great Lake and the Mekong Delta.
The BioRA is under the management of the Fisheries Programme, MRCS, under the leadership of Dr So Nam.
Within BioRA, the DRIFT method (Brown et al. 2013) is being used to organise existing MRC data, information in the international scientific literature and expert opinion to provide a systemic and systematic picture for the LMB, Tonle Sap River, Tonle Sap Great Lake and the Mekong Delta ecosystems in terms of: their baseline ecological integrity (health); possible future changes in integrity, as described through the evaluation of the water-resource development scenarios for each representative zone/site/area; predictions of change in abundance/area/concentration (relative to baseline) for a wide range of ecosystem indicators.
The DRIFT process, as it is applied in BioRA, is discussed in various related BioRA documentation.
1.2.1 The BioRA Team
1.2.1.1 Management and DRIFT DSS
The BioRA management team members are listed in Table 1.1.
Table 1.1 BioRA management team
Role Name BioRA Lead/MRC-FP Programme Coordinator Dr So Nam Council Study Coordinator Dr Henry Manguerra Council Study Adviser Dr Vitoon Viriyasakultorn BioRA Team Technical Lead Prof. Cate Brown DRIFT DSS Manager Dr Alison Joubert Council Study Administrative Assistant Ms Manothone Vorabouth MRC-FP International Technical Adviser Mr. Peter Degen MRC-FP Capture Fisheries Specialist Mr. Ngor Peng Bun
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1.2.1.2 BioRA international specialists
The international specialists on the BioRA team are listed in Table 1.2.
Table 1.2 BioRA international/regional specialists
Discipline Name Country Geomorphology and Water Quality Lead Specialist Dr Lois Koehnken Australia Tonle Sap Processes Specialist Dr Dirk Lamberts Belgium Vegetation Lead Specialist Dr Andrew MacDonald USA Delta Macrophyte Specialist Dr Nguyen Thi Ngoc Anh Viet Nam Delta Microalgae Specialist Duong Thi Hoang Oanh Viet Nam Macroinvertebrate Lead Specialist Dr Ian Campbell Australia Fish Lead Specialist Prof. Ian Cowx England Fish Delta Specialist Dr Kenzo Utsugi Japan MRC Fish Specialist Dr Chavalit Vidthayanon Thailand Herpetology Lead Specialist Dr Hoang Minh Duc Viet Nam Bird and Mammal Lead Specialist Anthony Stones England
1.2.1.3 BioRA national specialists
The incorporation of the national specialists in the BioRA Team serves four main purposes: to source in-country information, and ensure its consideration in BioRA; to bring additional first-hand knowledge of the ecosystems into the assessments; to contribute towards development of the relationships (response curves) developed for indicators and in so doing provide Member Country review of the thinking under-pinning the assessment; to address one of the main objectives for the Council Study, viz. promote capacity and ensure technology transfer to Member Countries.
The national specialists assigned to the BioRA team are listed in Table 1.2. The selection of candidates was based on short-lists provided by the National Member Countries (NMCs).
None of the national specialists were nominated and appointed in time to take part in the Planning Meetings and Field Trip I, and of the national specialists only Dr Luu Hong Truong (Viet Nam) attended the Planning Meetings and Field Trip I. For this reason, a series of ‘catch-up’ presentations were made, which were designed to introduce the Council Study, the BioRA process and concepts to the national specialists and ensure that they were in a position to contribute to, and benefit from, the BioRA.
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Table 1.3 BioRA national specialists
Country Name Discipline Geomorphology Toch Sophon Cambodia Biodiversity, excl. fish Pich Sereywath Fish Dr Chea Tharith Geomorphology Dr Bounheng Soutichak Vegetation Thananh Khotpathoom Laos PDR Fauna, excl. fish Dr Phaivanh Phiapalath Fish Dr Kaviphone Phouthavong Water quality and macroinvertebrates To be decided Thailand Fish Chaiwut Grudpun Geomorphology TBD Viet Nam Biodiversity, excl. fish Dr Luu Hong Truong Fish Vu Vi An
1.3 Purpose of this document
This document is Deliverable 3 of BioRA. It is Progress Report 2: DRIFT DSS Set-up Report.
It describes the initial DSS set-up for EF assessments of the LMB in terms of: updated BioRA indicators and links (Sections 3 and 4); team meetings held in June and July 2015 (Section 5); the preliminary results for the Status and Trends Assessment (Section 6); the preliminary reference time-series used in the DSS set-up (Section 7); the layout of the DSS for BioRA (Section 8); example of the preliminary response curves (Section 9), and; next steps in the BioRA process (Section 10).
The list of BioRA deliverables is provided in Appendix A. The team members that attended the June/July meetings are listed in Appendix B, and an annotated Table of Contents for the BioRA speclaist reports is provided in Appendix C.
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2 BioRA zones and focus areas
The process for selecting the BioRA zones and focus areas is detailed in Progress Report 1: Indicators and Focus Areas.
2.1 BioRA zones
The BioRA zones are (Figure 2.1): BioRA Zone 1: Mekong River from the border with China to Pak Beng (confluence with Nam Beng). BioRA Zone 2: Mekong River from downstream of the Nam Beng to upstream of Vientiane. BioRA Zone 3: Mekong River from Vientiane to Nam Kam town (near confluences with Se Bang Fei and Nam Kam) BioRA Zone 4: Mekong River from Nam Kam to Stung Treng (Se San / Se Kong confluences). BioRA Zone 5: Mekong River from Stung Treng to Phnom Penh BioRA Zone 6: Tonle Sap River from Phnom Penh to the Tonle Sap Great Lake. BioRA Zone 7: Tonle Sap Great Lake. BioRA Zone 8: Mekong Delta from the Cambodian/Viet Nam border to the sea.
BioRA Zone 1
BioRA Zone 2
BioRA Zone 3
BioRA Zone 7 BioRA Zone 4
BioRA Zone 6 BioRA Zone 5
BioRA Zone 8
Figure 2.1 Preliminary BioRA zones
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2.2 BioRA focus areas
Each BioRA zone is represented by a BioRA focus area. The BioRA focus areas are shown in Figure 2.2 and listed in Table 2.1:
Figure 2.2 Preliminary BioRA focus areas
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Table 2.1 Preliminary BioRA focus areas
Approximate coordinates Name Description Upstream Downstream 19°51'31.9'' N 19°52'21.61'' N BioRA FA1 Mekong River upstream of Pak Beng 101°4'46.78'' E 101°5'58.74'' 18°12'28.48'' N 17°58'50.38'' N BioRA FA2 Mekong River upstream of Vientiane 102°7'33.74'' E 102°25'38.71'' 17°12'23.87'' N 16°49'14.27'' N BioRA FA3 Mekong River upstream of Se Bang Fai 104°48'21.92'' E 104°44'47.51'' 13°33'42.98'' N 13°31'45.12'' N BioRA FA4 Mekong River upstream of Stung Treng 105°58'18.55'' E 105°56'14.39'' Mekong River upstream of Kampong 12°17'52.84'' N 12°12'44.5'' N BioRA FA5 Cham 105°35'33.4'' E 105°32'14.93'' 11°52'43.46'' N 11°44'47.26'' N BioRA FA6 Tonle Sap River at Prek Kdam 104°46'57.76'' E 104°49'54.37'' 12°52'2.35'' N3 BioRA FA7 Tonle Sap Great Lake 104°5'1.18'' E 10°54'37.94'' N 4 BioRA FA8 Mekong Delta Coast 105°11'17.95'' E
3 Point in the lake. 4 There are nine distributary channels. Bassac arm: 9º34’14.70”N; 106º18’33.24”E.
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3 BioRA indicators
The preliminary indicators and links presented in BioRA Progress Report 1: Focus area and indicator selection were used as a basis for discussion, adjustment and rationalisation. This comprised: Distribution of Progress Report 1, with a request for comment/suggestions on the preliminary BioRA indicators. Within-team discussions leading to a rationalisation of the links for each indicator. Initial set-up of the DSS and population of response curves, which led to some adjsutments to both indicators and links.
The lists presented here have been extensively reviewed and revised by the Lead and National Consultants, but are still draft and may well be adjusted further on the basis on ongoing discussion and feedback from Council Study team members and the Member Countries.
3.1 Revised BioRA indicators
The revised BioRA indicators are provided as follows: modelled time-series indicators (Table 3.1); ecosystem indicators (Table 3.2).
3.2 Relation to draft MRC indicator framework
The possible relationships between the BioRA indicators and the environmental and social indicators in the MRC framework are provided in Table 3.3 and Table 3.4, respectively, to assist in the discussions between teams.
At this stage, the BioRA specialists have made the following suggestions with respect to the indicators in the MRC framework: distinguish between lateral and longitudinal migratory species, and between benthic and littoral invertebrates, zooplankton and diatoms species as the factors affecting them differ considerably; add schistomosmiasis to the ‘Level of resilience at community level’ as it is an important water-borne disease in the LMB.
Table 3.1 Draft BioRA modelled time series indicators
Code Indicator Hydrology MAR All Mean annual runoff Do Onset Dd Duration Dq Dry season Minimum 5-day discharge Ddv Average daily volume DRange Within-day range in discharge
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Code Indicator T1dv Average daily volume QmxiT1 Maximum instantaneous discharge Transition season 1 dQiT1 Maximum rate of change in discharge T1Range Within-day range in discharge Fo Onset Fd Duration Fq Maximum 5-day discharge Wet/flood season Fdv Average daily volume Fv Flood volume WRange Within-day range in discharge T2dv Average daily volume Transition season 2 T2Range Within-day range in discharge Season Hydraulics Dry T1 Wet T2 avCV Average velocity X X X X maxCD Maximum depth X X X X minCD Minimum depth X X X X Channel avCD Average depth X X X X SS Shear stress X X X X avWP Wetted Perimeter X X X X FpO Onset of inundation FpD Duration of inundation FPArea Inundated area avFpV Average velocity Floodplain5 maxFpV Maximum velocity avFpD Average depth maxFpD Maximum depth minFpD Minimum depth Sediment SedConc Sediment concentration SedGrain Sediment grain-size distribution SedFpD Floodplain deposition HSedOn Onset of high sediment delivery at the beginning of the wet season HSedDur Duration of high sediment delivery Water quality Salinity Salinity/conductivity (extent of salinity intrusion) Temp Temperature DO Dissolved oxygen TOTN Nitrogen species (Total Nitrogen, Nitrate + Nitrite, Ammonia) NO32 Nitrate + Nitrite TOTP Phosphorus species (Total Phosphorus, Dissolved reactive phosphorus) PO4 Phosphate Si Silica Pesti Pesticides
5 Including Tonle Sap Great Lake
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Code Indicator Herbi Herbicides OTHER LongConMain Longitudinal connectivity - mainstem LongConTrib Longitudinal connectivity - tributary LatCon Lateral connectivity
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Table 3.2 Revised BioRA ecosystem indicators showing applicable focus areas for each
Focus Areas Code Indicator Groups Taxa 1 2 3 4 5 6 7 8 Geomorphology Erosion Erosion (bank / bed incision) NA DBedsed Average bed sediment size (DRY) NA WBedsed Average bed sediment size (WET) NA Availability of exposed sandy habitats on bars DSandbarsE NA and banks in the dry season Availability of inundated sandy habitats on bars DSandbarsI NA Channel and banks in the dry season Availability of exposed rocky habitats in the dry DRockE NA season Availability of inundated rocky habitats in the dry DRockI NA season PDepth Depth of bedrock pools NA Clarity Water clarity NA Vegetation CUCover Extent of upper bank vegetation cover NA CLCover Extent of lower bank vegetation cover NA Extent of herbaceous marsh vegetation CHerb Channel NA (submerged, floating and emergent) CBioRip Biomass of riparian vegetation NA CBioAlg Biomass of algae (periphyton, plankton, benthic) NA FForest Extent of flooded forest NA FHerb Extent of herbaceous marsh vegetation NA FGrass Extent of grassland vegetation NA FBioRip Biomass of riparian/aquatic cover NA FBioBG Floodplain Extent of cyanobacteria NA FBioAlg Biomass of algae (periphyton, plankton, benthic) NA RipInv Extent of Invasive riparian plant cover Mimosa pigra Extent of floating and submerged invasive plant FloatInv Hyacinth cover Macroinvertebrates Hept Insects on stones Heptageniid mayflies Baet Insects on sand Baetid mayflies Emerge Dry season emergence NA Palin Burrowing mayflies Palingeniid mayflies SnailAb Snail abundance NA
Page 14 Focus Areas Code Indicator Groups Taxa 1 2 3 4 5 6 7 8 SnailDiv Diversity of snails NA Naperta Neotricula aperta Neotricula aperta BivalveAb Bivalves abundance NA Poly Polychaet worms NA Crust Shrimps and crabs NA LitDiv Littoral invertebrate diversity NA BenDiv Benthic invertebrate diversity NA ZooAb Zooplankton abundance NA CompInvBiomass Composite invertebrate biomass NA CompEmerge Composite emergence NA Fish Rithron Rithron resident species CRes Main channel resident (long distant white) species CSpawn Main channel spawner (short distance white) species FSpawn Floodplain spawner (grey) species Gen Eurytopic (generalist) species FRes Floodplain resident (black fish) ERes Estuarine resident species Anad Anadromous species Catad Catadromous species Marine Marine visitor species NonN Non-native species CompFishBiomass Composite fish biomass Herpetofauna Rana nigrovittata Ranid Ranid amphibians Hoplobatrachus rugulosus Enhydris bocourti AquSerp Aquatic serpents Cylindrophis ruffus Amyda cartilaginea AquTur Aquatic turtles Malayemys subtrijuga SAquTur Semi-aquatic turtles Cuora amboinensis AmphibUse Amphibians for human use NA RepUse Aquatic/semi-aquatic reptiles for human use NA SpAmphib Species richness of riparian/floodplain amphibians NA SpRep Species richness of riparian/floodplain reptiles NA
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Focus Areas Code Indicator Groups Taxa 1 2 3 4 5 6 7 8 Birds River tern CGround Medium / large ground-nesting channel species Lapwing TreeWB Large tree-nesting waterbirds White-shouldered ibis CHole Bank-/hole-nesting species Pied kingfisher Grambeds Flocking non-aerial passerine of tall graminoid beds Baya weaver Sarus crane FPGround Large ground-nesting species of floodplain wetlands Bengal florican Lesser fish eagle CForest Large channel-using species that require bank-side forest Grey-headed fish eagle CRock Rocky-crevice nester in channels Wire-tailed swallow WoodWater Dense woody vegetation / water interface Masked finfoot Jerdon’s bushchat SeaFV Small non-flocking land bird of seasonally-flooded vegetation Mekong wagtail Manchurian reed warbler Mammals Dolphin Irrawaddy dolphin Irrawaddy dolphin Otter Otters Otters - all species Ung Wetland ungulates Hog deer
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Table 3.3 Relation to MRC Framework environmental indicators
Assessment indicators Monitoring parameters Units Source Relevant BioRA indicators
Flooded forest area (Total Mekong '000ha BioRA Extent of flooded forest basin and Tonle Sap) Flooded marshes (Total Mekong basin Extent of herbaceous marsh '000ha BioRA and Tonle Sap) vegetation Wetland area Inundated grasslands (Total Mekong '000ha BioRA Extent of grassland vegetation basin and Tonle Sap) Inundated rice fields (Total Mekong '000ha - - basin and Tonle Sap) Disconnected wetlands ‘000ha BioRA Extent of floodplain pools Availability of exposed sandy habitats Availability of sandbars No. BioRA on bars and banks in the dry season Availability of rocky habitat including Availability of inundated rocky habitats No. BioRA rapids in the dry season River channel condition and habitats Number of deep pools No. BioRA Depth of bedrock pools Percentage cover of riparian Extent of upper bank vegetation cover % BioRA vegetation within river channels Extent of lower bank vegetation cover Total sediment extraction (by region) tonnes / yr NA: Included in CS scenarios Extent of bank erosion '000 ha/yr BioRA Erosion (bank / bed incision) River bank erosion Length of river banks at risk of bank erosion as a result of induced ’000m - Erosion (bank / bed incision) geomorphological changes Main channel resident (long distant white) species Main channel spawner (short distance Migratory fish CPUE Biomass, no. BioRA white) species Floodplain spawner (grey) species Anadromous species Aquatic biodiversity Catadromous species Viable migratory fish routes km BioRA See Text Eurytopic (generalist) species Non-migratory fish CPUE Biomass, no. BioRA Floodplain resident (black fish) Non-native species Other aquatic animals (OAA) Biomass, no. BioRA Composite invertebrate biomass
Page 17 Assessment indicators Monitoring parameters Units Source Relevant BioRA indicators
Ranid amphibians Aquatic serpents Semi-aquatic serpents Aquatic turtles Semi-aquatic turtles Irrawaddy dolphin Birds (all) Otters Ungulates Littoral invertebrate diversity Benthic and littoral invertebrates, No./ location BioRA Benthic invertebrate diversity zooplankton, diatoms Algal biomass Listed threatened species No. - ? Total number and area of ecologically No; '000ha - - Ecologically significant areas significant areas (environmental hot spots) Proportion of ecologically significant % - - areas protected
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Table 3.4 Relation to MRC Framework social indicators
Assessment indicators Monitoring parameters Units Source Relevant BioRA indicators Erosion (bank / bed incision) Level of resilience at household 6 Nos and %HHs having river bank gardens No.; % + BioRA Average bed sediment size (DRY) level Extent of lower bank vegetation cover Food security Index; % + BioRA Composite fish biomass % of food from river aquatic resources % + BioRA Composite fish biomass Per capita consumption of fish and OAA/Ps Kg/cap/year + BioRA Composite fish biomass Nos of malaria cases and deaths No. - - Level of resilience at community level Nos of dengue cases and deaths No - - Nos of liver fluke cases No. - - Level of resources available for the cultural site Index ? - Location and timing of water related festivals Item + BioRA Hydrological and hydraulic indictors and events
Nos and % HHs engaged in - fishing as primary No.; % + BioRA Composite fish biomass or as secondary occupation or economic activity
HHs fishing habitats Ha + BioRA Composite fish biomass Hours/day; HHs fishing effort Composite fish biomass No.; CPUE HHs fish catches and disposal Kg; % + BioRA Composite fish biomass Proportion of population engaged in Nos and % of HH engaged collection of OOA/Ps Composite invertebrate biomass MRC sector activities as primary or secondary occupation or economic No; % Amphibians for human use + BioRA activity Aquatic/semi-aquatic reptiles for HHs collection of OAA/Ps Kg; % human use Nos and % HHs engaged in river transportation No.; % - - Nos and % HHs engaged in sand mining from No.; % +BioRA Average bed sediment size (DRY) riverbeds Nos and % of HHs engaged in tourism sector No.; % + BioRA Overall ecosystem integrity
6 +BioRA = BioRA data can contribute towards the evaluation.
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4 Revised BioRA Links
The revised BioRA linked indicators at FA1 are shown in Table 4.1 to Table 4.6. Note that there are no links from Herpetofauna and Birds to other indicators at FA1. The network diagrams of the full set of links for FA1 to FA3 are shown in Figure 4.1 to Figure 4.3.
Table 4.1 Links to hydrological indicators at FA1
f change f
duration
Mean annualrunoff Mean Dryonset Dryduration Q 5day Dry Min onset T1:T1 onset Wet Wet Q 5day Max Wet volume Flood dailyDry vol ave dailyT1 ave vol daily vol ave Wet dailyT2 ave vol T2recession slope Q instantaneous Drymax Q instantaneous T1max Q instantaneous max Wet Q instantaneous T2max change of rate Drymax o rate T1max change of rate max Wet change of rate T2max GEOMORPHOLOGY Erosion (bank / bed incision) y Ave bed sediment size (DRY) Ave bed sediment size (WET) Availability of exposed sandy habitat (DRY) y Availability of inundated sandy habitat (DRY) y Availability of exposed rocky habitat (DRY) y Availability of inundated rocky habitat (DRY) y Depth of bedrock pools y Water clarity VEGETATION C: Extent upper bank veg cover y C: Extent lower bank veg cover y C: Biomass riparian veg C: Biomass algae (periphyton,planktonic,benthic) y MACRO-INVERTEBRATES Insects on stones y Insects on sand y Dry season emergence Burrowing mayflies y Snail abundance Diversity of snails Bivalves abundance Shrimps and crabs Littoral Inverts diversity y Benthic Inverts diversity y Zooplankton abundance y FISH Rhithron resident y y y y Main channel resident (long distant white) y y y y y Main channel spawner (short distance white) y y y y y Floodplain spawner (grey) y y y y y Eurytopic (generalist) Non-native y HERPETOFAUNA Ranid y y y Aquatic serpents y Semi-aquatic serpents Species richness of riparian/FP amphibians y y Species richness of riparian/FP reptiles y BIRDS Medium/large ground-nesting channel spp Small non-flocking ;seasonally flooded veg
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Table 4.2 Links to hydraulic indicators at FA1
Chstress Shear
Dry: ave Ch Velocity Ch Dry:ave Velocity Ch T1:ave Ch ave Velocity Wet: Velocity Ch T2:ave Depth Ch Dry:ave Depth Ch Dry: min Depth Ch Dry:max Depth Ch T1:ave Ch ave Depth Wet: Depth Ch T2:ave stress Shear Ch Dry:ave Shear Ch stress T1:ave ave Wet: Shear Ch stress T2:ave perimeter Wetted Dry:ave perimeter Wetted T1:ave Wettedperimeter ave Wet: perimeter Wetted T2:ave FPinundation ave Onset Wet: inundation FP ave Duration Wet: FP ave inundation Area Wet: FP ave Depth Wet: GEOMORPHOLOGY Erosion (bank / bed incision) y y y y Ave bed sediment size (DRY) Ave bed sediment size (WET) Availability of exposed sandy habitat (DRY) y Availability of inundated sandy habitat (DRY) y Availability of exposed rocky habitat (DRY) y Availability of inundated rocky habitat (DRY) y Depth of bedrock pools y y y y Water clarity VEGETATION C: Extent upper bank veg y y C: Extent lower bank veg y y C: Biomass riparian veg y y C: Biomass algae (periphyton,planktonic,benthic) y MACRO-INVERTEBRATES Insects on stones Insects on sand Dry season emergence y y y Burrowing mayflies Snail abundance y Diversity of snails Bivalves abundance y Shrimps and crabs y Littoral Inverts diversity Benthic Inverts diversity Zooplankton abundance y FISH Rhithron resident Main channel resident (long distant white) Main channel spawner (short distance white) Floodplain spawner (grey) Eurytopic (generalist) Non-native HERPETOFAUNA Ranid y Aquatic serpents y Semi-aquatic serpents Species richness of riparian/FP amphibians Species richness of riparian/FP reptiles BIRDS Medium/large ground-nesting channel spp Small non-flocking;seasonally flooded veg
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Table 4.3 Links to sediment indicators at FA1
sizedistr
position
sizedistr
-
-
sizedistr sizedistr
- -
load
Dry: ave Sediment load Sediment Dry:ave load Sediment T1:ave Sedimentload ave Wet: Sediment T2:ave conc Sediment Dry:ave conc Sediment T1:ave Sedimentconc ave Wet: conc Sediment T2:ave grain Sediment Dry:ave grain Sediment T1:ave Sedimentgrain ave Wet: grain Sediment T2:ave FP de Sediment Dry:ave FP deposition Sediment T1:ave SedimentFP ave deposition Wet: FP deposition Sediment T2:ave SedimentOnset ave Wet: SedimentDuration ave Wet: GEOMORPHOLOGY Erosion (bank / bed incision) y y y y y y y Ave bed sediment size (DRY) y Ave bed sediment size (WET) Availability of exposed sandy habitat (DRY) Availability of inundated sandy habitat (DRY) Availability of exposed rocky habitat (DRY) Availability of inundated rocky habitat (DRY) Depth of bedrock pools y y y y y y Water clarity y y y y y y y y VEGETATION C: Extent upper bank veg C: Extent lower bank veg C: Biomass riparian veg C: Biomass algae (periphyton,planktonic,benthic) y MACRO-INVERTEBRATES Insects on stones Insects on sand Dry season emergence Burrowing mayflies Snail abundance Diversity of snails Bivalves abundance Shrimps and crabs Littoral Inverts diversity Benthic Inverts diversity Zooplankton abundance FISH Rhithron resident y Main channel resident (long distant white) y Main channel spawner (short distance white) y Floodplain spawner (grey) y y Eurytopic (generalist) y Non-native y HERPETOFAUNA Ranid y Aquatic serpents Semi-aquatic serpents Species richness of riparian/FP amphibians y Species richness of riparian/FP reptiles BIRDS Medium/large ground-nesting channel spp Small non-flocking;seasonally flooded veg
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Table 4.4 Links to water quality indicators at FA1
mainstem
-
phorous
Range(T2)
itrate + Nitrite
Salinity/conductivity
Dry: ave Temperature Dry:ave DissolvedOxygen Dry:ave Salinity/conductivity Dry:ave T1:ave Salinity/conductivity ave Wet: Salinity/conductivity T2:ave Oxygen Demand Chem Dry:ave Oxygen Demand Chem T1:ave Demand Oxygen Chem ave Wet: Oxygen Demand Chem T2:ave Nitrite + Nitrate Dry:ave Nitrite + Nitrate T1:ave N ave Wet: Nitrite + Nitrate T2:ave Phosphate Dry:ave Phosphate T1:ave Phosphate ave Wet: Phosphate T2:ave TotalNitrogen Dry:ave TotalNitrogen T1:ave TotalNitrogen ave Wet: TotalNitrogen T2:ave TotalPhosphorous Dry:ave TotalPhos T1:ave TotalPhosphorous ave Wet: TotalPhosphorous T2:ave continuity Longitudinal Continuity Tribs Longitudinal (W) (W) Continuity Lateral Range(D) day w/in Dry:ave Range(T1) day w/in T1:ave w/in Range(W) ave day Wet: day w/in T2:ave GEOMORPHOLOGY Erosion (bank / bed incision) y y y y Ave bed sediment size (DRY) Ave bed sediment size (WET) Availability exposed sandy habitat (DRY) y Availability inundated sandy habitat (DRY) y Availability exposed rocky habitat (DRY) y Availability inundated rocky habitat (DRY) y Depth of bedrock pools Water clarity VEGETATION C: Extent upper bank veg C: Extent lower bank veg C: Biomass riparian veg C: Biomass algae(periphyton,planktonic,benthic) y y MACRO-INVERTEBRATES Insects on stones y Insects on sand y Dry season emergence Burrowing mayflies y Snail abundance Diversity of snails y Bivalves abundance y Shrimps and crabs y Littoral Inverts diversity y Benthic Inverts diversity y Zooplankton abundance y FISH Rhithron resident y y y Main channel resident (long distant white) y y y Main channel spawner (short distance white) y y y y y Floodplain spawner (grey) y y y y Eurytopic (generalist) Non-native y HERPETOFAUNA Ranid y Aquatic serpents y Semi-aquatic serpents Species richness of riparian/FP amphibians Species richness of riparian/FP reptiles BIRDS Medium/large ground-nesting channel spp Small non-flocking;seasonally flooded veg
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Table 4.5 Links to geomorphology and vegetation indicators at FA1
Geomorphology Vegetation
(DRY)
ive floating&submerged ivefloating&submerged
exposed sandy habitat (DRY) habitat sandy exposed
inundated sandy habitat sandy (DRY) inundated rocky (DRY) habitat inundated
nktonic&benthic)
Erosion (bank / bed incision) Erosionbed / (bank sedimentsize (DRY) bed Ave sedimentsize (WET)bed Ave Availability Availability Availabilityrocky habitat exposed of Availability of pools bedrock Depth clarity Water cover veg upper bank Extent C: cover lower veg bank Extent C: veg herbaceous marsh Extent C: floatin (submerged, riparian Biomass C: veg (periphyton, algae Biomass C: pla forest flooded cover FP:Extent veg marsh herbaceous FP:Extent floati (submerged, cover FP:riparian/aquatic Biomass cyanobacteria FP:Extent (periphyton, FP:algae Biomass planktonic&benthic) riparianInvasive Banks: cover Invas Aquatic: cover GEOMORPHOLOGY Erosion (bank / bed incision) y Ave bed sediment size (DRY) y Ave bed sediment size (WET) y Availability exposed sandy habitat (DRY) y Availability inundated sandy habitat (DRY) y Availability exposed rocky habitat (DRY) y Availability inundated rocky habitat (DRY) y Depth of bedrock pools Water clarity VEGETATION C: Extent upper bank veg y C: Extent lower bank veg y C: Biomass riparian veg y C: Biomass algae (periphyton,planktonic,benthic) y y y MACRO-INVERTEBRATES Insects on stones y y y y Insects on sand y y y y Dry season emergence Burrowing mayflies y y Snail abundance y Diversity of snails y y Bivalves abundance y y Shrimps and crabs y y Littoral Inverts diversity y y Benthic Inverts diversity y y y Zooplankton abundance y y FISH Rhithron resident y Main channel resident (long distant white) y y y Main channel spawner (short distance white) y y y Floodplain spawner (grey) y y Eurytopic (generalist) y Non-native HERPETOFAUNA Ranid y y Aquatic serpents y Semi-aquatic serpents Species richness of riparian/FP amphibians y y Species richness of riparian/FP reptiles y y BIRDS Medium/large ground-nesting channel spp y Small non-flocking;seasonally flooded veg y y
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Table 4.6 Links to macroinvertebrate and fish indicators at FA1
Macroinvertebrates Fish
t distance distance t
worms (salinity worms indicator)
FishBiomass
native
-
stones on Insects sand on Insects emergence Dryseason mayflies Burrowing Snailabundance Diversitysnails of (schistosomaisis Neotriculaaperta host) Bivalvesabundance Polychaete crabs Shrimpsand LittoralInverts diversity diversity Inverts Benthic abundance Zooplankton biomass invertebrate Benthic emergence Composite resident Rhithron resident distant (long white)channel Main spawner (shor channel Main white) (grey) Floodplainspawner Eurytopic(generalist) Floodplain(black resident fish) resident Estuarine Anadromous Catadromous visitor Marine Non Composite GEOMORPHOLOGY None VEGETATION None MACRO-INVERTEBRATES None FISH Rhithron resident y Main channel resident (long distant white) Main channel spawner (short distance white) y Floodplain spawner (grey) y Eurytopic (generalist) y Non-native HERPETOFAUNA Ranid Aquatic serpents y Semi-aquatic serpents Species richness of riparian/FP amphibians Species richness of riparian/FP reptiles y BIRDS Medium/large ground-nesting channel spp y y Small non-flocking;seasonally flooded veg y y
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Figure 4.1 Revised BioRA links for FA1
Figure 4.2 Revised BioRA links for FA2
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Figure 4.3 Revised BioRA links for FA3
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5 June/July work sessions
A series of BioRA Team Meetings were held in June/July 2015. The purpose of these work sessions was to help the national consultants get up to speed with the Council Study in general, and BioRA in particular, to discuss and finliase the draft Status and Trends Assessments and do the initial set-up of the DRIFT DSS. Two sets of meetings were held, one at the MRC Secretariat in Phnom Penh (OSP) so that the team could interact with IKMP, and one at the MRC Secretariat Vientiane (OSV).
5.1 OSP meeting
The schedule for the week of June/July 2015 meeting in Phnom Penh is given in Table 5.1. The BioRA team members and NMC representatives who attended the meeting (Figure 5.1) are listed in Appendix B.
Table 5.1 Schedule for the June/July 2015 work sessions in Phnom Penh
Day Date Activity
Team Meeting: Catch-up Sessions MONDAY 29-Jun Meetings with IKMP Explanation of DRIFT DSS Navigation
Geomorphology and Vegetation Workshop: DSS – FA1 TUESDAY 30-Jun Meetings with IKMP
WEDNESDAY 01-Jul Geomorphology and Vegetation Workshop: DSS – FA1
Geomorphology and Vegetation Workshop: DSS – FA2 THURSDAY 02-Jul Meetings with IKMP
FRIDAY 03-Jul Geomorphology and Vegetation Workshop: DSS – FA2
5.2 OSV work sessions
The schedule for the week of July 2015 meeting in Vientiane is given in Table 5.2. The BioRA team members and NMC representatives who attended the meeting (Figure 5.1) are listed in Appendix B.
Page 28 Table 5.2 Schedule for the July 2015 work sessions in Vientiane
Day Date Activity Informal technical meetings: International Consultants. Finalise SATURDAY 04-Jul Status and Trends and load DSS Informal technical meetings: National and International SUNDAY 05-Jul Consultants work together to prepare presentations for Catch-up Meeting MONDAY 06-Jul Catch-up Sessions
TUESDAY 07-Jul Team Workshop: DSS – FA1/1
WEDNESDAY 08-Jul Team Workshop: DSS – FA1/2.
THURSDAY 9-Jul Team Workshop: DSS – FA3/4
FRIDAY 10-Jul Team Workshop: DSS – FA3/4
SATURDAY 11-Jul Team WRAP-UP Meeting
Figure 5.1 The BioRA Team in Vientiane (July 2015)
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5.2.1 Agendas (6-11 July 2015)
The daily agendas for the meetings held at OSV from the 6th to 11th July 2015 are provided in Table 5.3 to Table 5.8.
Table 5.3 MONDAY 6th July 2015: Catch-up Sessions
Time Activity Presenter/Facilitator 8:30 AM Welcome and Introductions So Nam 8:40 AM Presentation of agendas for the week Cate Brown 8:50 AM BioRA Introduction Cate Brown Water quality and geomorphology: Background and Lois Koehnken progress to date 9:50 AM Bounheng Soutichak Status and trends: Water quality and geomorphology Toch Sophon 10:30 PM TEA Vegetation: Background and progress to date Andrew McDonald 11:00 AM Thananh Khotpathoom/ Status and trends: Vegetation Dr Luu Hong Truong Macroinvertebrates: Background and progress to date Ian Campbell 11:40 AM Status and trends: Macroinvertebrates TBD Fish: Background and progress to date Prof. Ian Cowx Dr Chavalit Vidthayanon Dr Chea Tharith 12:20 AM Chaiwut Grudpun Status and trends: Fish Vu Vi An Dr Kaviphone Phouthavong 1:00 PM LUNCH Herpetofauna: Background and progress to date Hoang Minh Duc 2:00 PM Status and trends: Herpetofauna Pich Sereywath Birds and mammals: Background and progress to date Anthony Stones 2:40 PM Status and trends: Birds and mammals Dr Phaivanh Phiapalath 3:20 PM TEA 3:50 PM Links and relationship to MRC Indicators All 5:00 PM Close for the day
Table 5.4 TUESDAY 7th July 2015: Workshop: DSS – FA1/2
Time Activity Presenter/Facilitator 8:30 AM Explanation of activities for the day Cate Brown 8:40 AM Photographs and hydrology for FA1 and FA2 Team discussion 9:30 AM Explanation of DRIFT DSS Navigation Alison Joubert 10:00 AM TEA 10:30 AM Hand-out of DSS Alison Joubert 10:40 AM Discipline-specific Response Curves – FA 1/2. All 12:30 PM LUNCH 1:30 PM Discipline-specific Response Curves – FA 1/2. All 3:20 PM TEA
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Time Activity Presenter/Facilitator 3:50 PM Discipline-specific Response Curves – FA 1/2. All 5:30 PM Hand-in work to date To Alison Joubert
Table 5.5 WEDNESDAY 8th July 2015: Workshop: DSS – FA1/2
Time Activity Presenter/Facilitator 8:30 AM Hand-back of updated DSS Cate Brown 8:40 AM Discipline-specific Response Curves – FA 1/2. All 10:00 PM TEA 10:30 AM Discipline-specific Response Curves – FA 1/2. All 12:30 PM LUNCH 1:30 PM Discipline-specific Response Curves – FA 1/2 All 3:20 PM TEA 3:50 PM Discipline-specific Response Curves – FA 1/2 All 5:30 PM Hand-in work to date To Alison Joubert
Table 5.6 THURSDAY 9th July 2015: Workshop: DSS – FA1/3
Time Activity Presenter/Facilitator 8:30 AM Hand-back of updated DSS Cate Brown 8:40 AM Discipline-specific Response Curves – FA 1/2. All 10:00 PM TEA 10:30 AM Discipline-specific Response Curves – FA 1/2. All 12:30 PM LUNCH 1:30 PM Photographs and hydrology for FA3/4 Team discussion 3:20 PM TEA 3:50 PM Discipline-specific Response Curves – FA 3/4. All 5:30 PM Hand-in work to date To Alison Joubert
Table 5.7 FRIDAY 10th July 2015: Workshop: DSS – FA3/4
Time Activity Presenter/Facilitator 8:30 AM Hand-back of updated DSS Cate Brown 8:40 AM Discipline-specific Response Curves – FA 3/4. All 10:00 PM TEA 10:30 AM Discipline-specific Response Curves – FA 3/4. All 12:30 PM LUNCH 1:30 PM Discipline-specific Response Curves – FA 3/4. All 3:00 PM TEA 3:30 PM Report back on Focus Area 1 - Progress Cate Brown 5:30 PM Hand-in work to date To Alison Joubert
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Table 5.8 SATURDAY 11th July 2015: Wrap-up meeting
Time Activity Presenter/Facilitator 9:00 AM Feedback on the week Cate Brown 9:30 AM The way forward Cate Brown 10:00 PM TEA 10:30 AM Format of and deadline for specialist reports Cate Brown 11:45 AM Thanks and closure Henry Manguerra 12:00 AM Meeting Closed
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6 Status and trends assessment
6.1 Purpose of the status and trends assessment
For the Council Study, BioRA will be required to: describe the present ecological status of the LMB aquatic ecosystems; describe the past ecological status of the LMB aquatic ecosystems; describe ecological status for the future ecological status of the LMB aquatic ecosystems with and without the water-resource developments included in the scenarios.
The objective of the status and trends assessment is to provide a template to assist in delivering the required information. Essentially, it provides an estimate how the abundance of each indicator is deemed to have changed (if at all) from its condition in 1900, 1950, 1970 and 2000 (115, 65, 45 and 15 years ago, respectively) and identifies the main drivers of change.
This status and trends assessment: identifies and documents past and current pressures on the system; establishes the historical context for the 2015 LMB aquatic ecosystems, and enhances the understanding of how these have responded to past pressures; ensures that all specialists and disciplines are working within a common understanding of past and present pressures on the system.
It will also be used to: set the baseline conditions used as a reference point from which to make predictions7; provide the trends for projections of future exogenous baselines.
The status and trends assessments provided in this Progress Report are preliminary only and both the explanations and the estimates may be expanded and/or adjusted upon, pending further investigation and discussion, and comments received. The final status and trends assessments form part of the BioRA Specialist Reports.
6.2 Approach
Status and trends assessments were done for each of the preliminary indicators, and for each of the areas listed in Table 6.1. The areas are divided according to country because trends in development tend to be country-specific and are defined by national and regional demographics, politics and policies, rather than by physical or biological attributes. The relationships between the status and trends areas and the BioRA zones are also shown in Table 6.1.
For each indicator, the lead specialists: Described the 2015 ecological status (in terms of the ratings given in Table 6.2). Identified the five main anthropogenic drivers of indicator status.
7 The Baseline Scenario for the Council Study is yet to be decided.
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Table 6.1 Status and trends areas, shown in relation to the BioRA zones
Status and trends area BioRA zones Mekong River from the border with China to upstream 1 Mekong River in Laos PDR 1 of the confluence with the Nam Ngene Mekong River from downstream of the Nam Ngene to 2 Mekong River in Laos upstream of the confluence with the Huai Mong 2 PDR/Thailand Mekong River from downstream of the Huai Mong to 3 the Laos PDR/ Cambodian border Mekong River from the Laos PDR/Cambodian border 4 3 Mekong River in Cambodia to upstream of the confluence with the Prek Chhlong 5 Chaktomuk area Tonle Sap River from Phnom Penh to the Tonle Sap 4 Tonle Sap River 6 Great Lake 5 Tonle Sap Great Lake 7 Tonle Sap Great Lake Mekong Delta from the Cambodian/Viet Nam border 6 Mekong Delta 8 to the sea
Table 6.2 Ecological status ratings
Unmodified, A As close as possible to natural conditions. natural Modified from the original natural condition but not sufficiently to have B Largely natural produced measurable change in the nature and functioning of the ecosystem/community. Changed from the original condition sufficiently to have measurably Moderately C altered the nature and functioning of the ecosystem/community, modified although the difference may not be obvious to a casual observer. Sufficiently altered from the original natural condition for obvious D Largely modified impacts on the nature and functioning of the ecosystem/community to have occurred. Important aspects of the original nature and functioning of the Completely E ecosystem community are no longer present. The area is heavily modified negatively impacted by human interventions.
Assumed that 2015 quantity (in terms of abundance, area, volume, concentration, etc.) of the indicator was 100%, and then estimated what the quantity would have been as a relative percentage of 2015 in: 1900; 1950; 1970; 2000.
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This means that if the indicator is deemed to have declined relative to historic levels, then the historic estimates as % relative to 2015 (100%) would be >100, and if it has increased they will be <100. Provided evidence for the outcome of their evaluations.
6.3 Historical change in the LMB
The history of the Mekong Basin includes events that altered the land cover and land uses in the catchment, and in turn, influenced the condition of the river and its associated ecosystems. Historical events and political ideological changes over a wide range of spatial and temporal scales resulted in complex linkages to population, settlement and land use practices, and in turn had implications for the LMB habitats and ecological processes. Some of these events are key in understanding and contextualising changes in the aquatic ecosystems, as highlighted in Table 6.3. Table 6.3 is not intended as an exhaustive list of events that have affected the LMB, but as an illustration of the main sorts of actions and developments that have affected the aquatic ecosystems. The extent to which these are deemed to have affected various BioRA indicators is addressed in the discipline-specific status and trends assesments.
Table 6.3 Key historical events affecting the LMB
Date Actions/developments Consequences for LMB References
Colonisation of the 1800- Kakonen (2008) Mekong Delta Conversion of wetlands, French colonisation of and increasing 1893- 1953 Viet Nam, Cambodia and Brocheux (1995) Expansion of rice and control/restriction of Laos PDR other production in the flooding and salinity Shift from floating rice to 1975 -1994 Delta regimes Kakonen (2008) irrigated rice 1995- Aquaculture Tran et al. (2015). Introduction of three rice Increased application of 2000- Tran et al. (2015). crops per annum herbicides and pesticide
Rubber planations Smajgl and Ward Expansion of rubber (2013) Changes in flow and 1950- plantations and Le Zhang et al. sediment regimes deforestation Logging (2015) Li et al. (2008)
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Date Actions/developments Consequences for LMB References
Changes in demographics. 1939-1945 Second World War Grigg (1974) Removal of fauna and flora, e.g., rubber Chapman (1991); 1950-1953 Korean War plantations in Yunnan, Sidle et al. (2010) dol[phins in Cambodia and defoliants in Viet Nam. 1964/5-1973 American War Tran et al. (2015). Conflicts Reductions in fishing as fishing lot operations in Cambodia were limited
Khmer Rouge in Khmer Rouge Perrin et al. (1996) 1975-1979 Cambodia concentrated on dam Beasley (2007) construction and water reservoirs for irritated rice cultivation 1986&1992 Manwan 2003 Dachaoshan Changes in flow and Implementation of 2008/9 Gongguoqiao sediment regimes. Smajgl and Ward Lancang Cascade 2010/11 Jinghong (2013) HPPs 2014 Xiaowan Barrier effects. 2014 Nhuzhadu 1971 Nam Ngum 1 1994 Xeset 1 1998 Theun-Hinboun Changes in flow and 1999 Houay Ho Dam development sediment regimes. 2000 Nam Leuk Laos PDR tributaries 2009 Xeset 2 Barrier effects. Nam lik 2 2010 Nam Theun 2 2011 Nam Ngum 2 MRC (2011) Nam Pong 1966 Ubol Ratana 1967 Lam Phra Phloeng Changes in flow and 1971 Dam development Sirindhorn sediment regimes. 1972 Thailand tributaries Chulabhorn Pak Mun Barrier effects. 1994 Hua Na 2004 Lam Ta Khong
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Date Actions/developments Consequences for LMB References
1990 Dray Hinh 1 2001 Yali Falls 2006 Sesan 3 Dray Hinh 2 2007 Changes in flow and Dam development Viet Sesan 3a sediment regimes. Nam tributaries Buon Kuop
Buon Tua Sra 2009 Barrier effects. Sesan 4 Sre Pok 3 2010 Sre Pok 4 Mining of sediments Changes to sediment Bravard and 1800- Sand mining (mainly sand) from the budgets/habitats Goichot (2013) river bed and banks Increases transport links Greater Mekong Leinenkugel et al. 1992- and trade – increased Subregion Programme (2014) pressure on resources Other policies Cancellation of the 2013 Fishing Lot System in Increased fishing pressure Ouer et al. (2014) Cambodia
6.4 Status and trends: Sediments and sediment transport
6.4.1 Mekong River in Lao PDR (Chinese border to Nong Khai)
Flow and sediment delivery in this part of the LMB is dominated by inflows from the UMB. A summary of recent flow and sediment monitoring data shows that both flow and sediment transport have changed over the past few years, with a large reduction in the concentration of suspended sediments and a moderate reduction in the range of 25th to 75th percentile flows (Figure 6.1, Koehnken, 2014). Comparing recent and historical measurements suggests that the sediment load from the UMB has reduced by up to ~50 Mt/yr, with measured loads decreasing from ~60 Mt/yr to ~10 Mt/yr.
The change in the relationship between sediment delivery and flow is evident in Figure 6.2, where flow and suspended sediment concentrations for Luang Prabang and Pakse are shown. The flow results show that large flows continue to occur within the river. Relative to historic results, suspended sediment concentrations remain low throughout the year, and especially during the falling limb of the hydrograph which is when deposition is required to balance the erosion from the rising limb. These changes result in the sediment transport in this reach considered to be moderately modified: Category C.
There are no long-term estimates of bedload transport in the upper LMB (Mekong River in Lao PDR), but it is reasonable to suggest that the establishment of the Lancang Hydropower Cascade in the Upper Mekong Basin has also decreased the delivery of coarser material to the lower river.
These changes to sediment delivery are likely to translate to a large reduction in the potential for deposition and hence an increase in the propensity for bank and bed erosion.
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Figure 6.1 Box and whisker plots showing suspended sediment concentrations (top) and average daily flow on monitoring days (bottom) at Chiang Saen (Koehnken 2014). The box encompasses the 25th to 75th percentile flows, while the ‘whiskers’ show the minimum and maximum values. The median value is shown as a line within the box.
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Figure 6.2 Comparison of flows and suspended sediment concentrations at Luang Prabang and Pakse between 1961 (left) and 2011 (right; plots from Koehnken 2012).
6.4.2 Mekong River in Lao PDR / Thailand (Nong Khai to Pakse)
The reach of the Mekong River from Nong Khai to Pakse is characterised by the inflow of water and sediment from the ‘left bank’ tributaries in Northern Lao, with proportionately less water and sediment derived from the western (right bank) tributaries in Thailand.
As shown in Figure 6.2, the concentrations of suspended sediment are lower at Pakse relative to historic concentrations. This is attributable to the combination of the reduction in suspended sediment entering from the UMB, and a reduction in sediment entering from the Lao tributaries as a result of the establishment of hydropower projects. The likelihood is that a greater proportion of coarser bedload material than fine suspended sediments would be retained in these impoundments.
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Figure 6.3 Map showing existing and planned hydropower projects in the LMB. From based on MRC Hydropower database.
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Figure 6.4 Map of sediment extraction in the LMB. Size of circle is relative to the volume of material extracted. Red, orange and bronw bars indicate proportion of sand, gravel and pebble extracted at each site, respectively.
Sediment movement in the Nong Khai to Pakse reach is also affected by aggregate mining, which targets sand, gravels and pebbles (Figure 6.4). This material is generally transported as bedload, and its removal is likely to affect the local bed geometry and potentially increase bank erosion/bed incision through the steepening of river channel (both laterally and longitudinally).
Based on this combination of activities, the sediment load in this reach of the Mekong is considered to have reduced substantially. The reduction in sediment delivery to this reach is considered to be largely modified.
6.4.3 Mekong River in Cambodia (Stung Treng to Chaktomuk confluence)
The geomorphic attributes of the Mekong River in this reach include the inflow of the very large 3S River catchment (Srepok, Sesan Sekong), and the transition of the river from a partially bedrock controlled channel to a floodplain system. The floodplain system is more susceptible to changes in
Page 41 sediment transport affecting bank erosion over the long term because of the lack of bedrock controls. In addition, fine and medium sand, which may have been carried in suspension in the upper reaches of the river, will be more likely to be transported as bed material in this reach.
The inflow of additional water and sediment from the 3S likely to buffer some of the upstream impacts on the sediment load, however, the dams in the headwaters of the 3S also reduce sediment input relative to natural conditions. Estimates by Carling (2009) suggest that sediment loads from the 3S have reduced from ~18 Mt/yr to ~10 Mt/yr, which is consistent with the recent DSMP estimate of ~8.5 Mt/yr (Koehnken 2014).
Extraction of sand from this reach is also high, with > 10 Mt/yr reportedly removed from the area in 2011 (Bravard et al. 2014).
Due to the combined influence of reduced sediment loads from the UMB, tributaries and the 3S, including the probable large reduction in bedload material entering from tributaries, the reduction in sediment delivery to this reach is considered to be largely modified.
6.4.4 Tonle Sap River and Great Lake
The inflow to the Tonle Sap from the Mekong River begins during the onset of the highest flows, and persists throughout the peak wet season. During this time, large volumes of suspended sediment enter the Great Lake via the Tonle Sap River. The grain-size distribution of sediment transported in 2011 and 2012 is shown in Figure 6.5. As the water flows into the lake, the drop in velocity results in the creation of a delta at the confluence of the river and lake, suggesting that the suspended sediments within the Tonle Sap Great Lake are finer than the suspended load entering from the Tonle Sap River (recognising that some of the suspended sediment will be derived from other tributaries to the lake).
Figure 6.5 Grain-size distribution of suspended sediment at Prek Kdam, in the Tonle Sap River; 2011 – 2012 (Koehnken 2014).
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The overall sediment load in the Mekong has reduced substantially, however the fine-grained material which is transported in suspension to the Lake may have reduced relatively less due to the small grain sizes being less likely to be captured in a dam. The 3S System is also likely to provide additional sandy bedload some of which is probably removed through the sediment mining at the Chaktomuk confluence and in the Tonle Sap River (see Figure 6.5).
The Tonle Sap system also derives a large proportion of flow and sediment from the tributaries feeding the Tonle Sap Great Lake . These tributaries are largely unregulated, and likely provide flow and sediment regimes that are close to natural conditions.
Based on this inflow of additional tributaries, and the finer-grain sizes which characterise the sediment regime of the Tonle Sap Great Lake, the sediment supply to the lake is considered to be moderately modified.
6.4.5 Mekong Delta
The Mekong Delta is a highly modified geomorphic area owing to the presence and operation of the extensive canal system. The delivery of sediment to the Chaktomuk confluence has decreased due to sediment capture in dams and in-channel aggregate mining.
Recent investigations (Brunier et al. 2014) have documented extensive channel deepening in the delta in areas where sand mining has commonly occurred. It is estimated that c. 200 Mm3 of material has been removed from the Mekong and Bassac channels in the period 1998 – 2008 (Brunier et al. 2014). A comparison of satellite photos from 2003 and 2011 showed shoreline retreat over much of the delta front, including in areas that have been recognised as exhibiting very rapid rates of accretion over the past few thousand years (Anthony et al. 2013).
6.5 Status and trends: Geomorphology
The estimated 2015 ecological status for each of the geomorphology indicators is provided in Table 6.4. The definitions for the categories are given in Table 6.2. The expected trends in the indicators are discussed in Sections 6.5.1 to 6.5.6, respectively.
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Table 6.4 Estimated 2015 ecological status for each of the geomorphology indicators
Average Availability Availability Depth of bed of exposed of exposed Water Erosion bedrock sediment sand bars rocky clarity Area pools size and islands habitats 2015 2015 2015 2015 2015 2015 Mekong River D B C C B B in Laos PDR Mekong River in Laos PDR/ D B C C B B Thailand Mekong River D B B B B B in Cambodia Tonle Sap C B B NA B B River Tonle Sap C B NA NA NA B Great Lake Mekong Delta D B B NA B B
6.5.1 Bank erosion and bed incision
The incidence and rate of bank erosion / deposition or bed incision / aggradation (termed erosion from here on) is important for determining the physical structure of the river channel and associated floodplains, and effects habitat availability and quality. Bank erosion is controlled by the hydraulics of the river and the availability of sediment. In most natural river systems, the rising limb of a high flow event will induce bank erosion, whilst deposition associated with the falling limb will aggrade banks, resulting in a dynamic equilibrium (e.g. erosion and deposition do not occur in the same place, but are in balance at a reach scale). Bedload material plays an especially important role in determining bed incision and bank erosion, as it is this coarser material which forms the river channels.
There are no long-term systematic investigations of bank erosion in the LMB, and thus no maps showing the past or present distribution of erosion at the reach scale, or established rates of past or present bank erosion. There are historical aerial photos that could be used to document channel changes at the decadal scale, but this work has not yet been done.
The evaluation of bank erosion in the LMB is based on the understanding of changes to sediment transport in the Mekong, and how these changes are likely to translate to bank erosion. Based on the discussions in Section 6.4 the estimated historical status of bank erosion / bed incision relative to 2015 is shown Figure 6.6. This is subjective and is based on a general understanding of the flow regime and sediment budget of the LMB, as there are no established erosion rates or trends for the system. Although the flow regime has also been altered, particularly in the upper reaches, through a reduction in high flows and increase in dry-season flows, high flows, which are likely to induce bank erosion, still occur but are no longer balanced by sediment deposition associated with large sediment loads. Thus, 2015 levels of erosion in the LMB are enhanced relative to natural (Figure 6.6), with historic differences expected to be slightly greater in the upper reaches of the river.
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Bank erosion and bed incision 200
180 Mekong River in Laos PDR 160 Mekong River in Laos 140 PDR/Thailand 120 Mekong River in 100 Cambodia 80 Tonle Sap River 60 Tonle Sap Great Lake
40 Percentage to relative 2015 (100%) 20 Mekong Delta 0 1900 1950 1970 2000 2015
Figure 6.6 Bank erosion and bed incision: Historic estimates as % relative to 2015 (100%)
The anthropogenic drivers considered to have the greatest influence on bank erosion / bed incision include: 1 impoundments, which reduce sediment delivery and alter the flow regime; 2 sediment mining, which alters channel morphology and induces bank erosion through steepening; 3 land cover changes, which alter the quantity of sediment delivered to the river; 4 irrigation and other extractions which alter the flow regime.
The percentages used in Figure 6.6 are defined as: 50% ‘Natural’ extent and occurrence of bank erosion with natural sediment delivery and no dams; 60% Minor increase in extent and occurrence of erosion due to minor reduction in sediment delivery associated with aggregate mining and dams; 70% Moderate increase in extent and occurrence of erosion due to moderate reduction in sediment delivery associated with to aggregate mining and dams; 80% Major increase in extent and occurrence of erosion due to major reduction in sediment delivery associated with capture by dams and aggregate mining; 100% (2015 status) Very major increase in in extent and occurrence of erosion due to major reduction in sediment delivery associated with capture by dams and aggregate mining;
The 1900 rate is estimated to be about 50% of the present rate due to the following factors: in 1900 there was likely to be more native vegetation on the river banks which would have increased bank stability; there were no impoundments on tributaries; sediment extractions from the channel would be minimal; the hydrology of the delta was less modified; the flow and sediment regime was much closer to natural than is the case in 2015, so the river was likely in a dynamic-equilibrium with respect to bank erosion;
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there may have been additional sediment inputs due to land use changes which may have increased sedimentation relative to natural.
It is suggested that these relative rates of erosion persisted through the 1950s. Bank stability may have decreased due to increased clearing of river banks, which would exacerbate erosion. However, during this time land use changes are likely to have resulted in increased sediment input from the catchment, and so the erosive power of the water will have been less, which may have offset some of the erosion resulting from reduced cover.
By 1970, increased development, including development of river banks, sand extraction, floodplain draining or infilling and the development of some dams, is estimated to have increased the risk of bank erosion to a small degree. This is likely to have been in most pronounced in areas with the highest populations, such as the reaches downstream of Nong Khai.
By 2000, the first of the Langcang dams was operational, which would have altered flow and sediment delivery and increased bank erosion a small degree relative to previous conditions.
The largest change in bank erosion is probably associated with the commissioning of the Lancang cascade during the 2000’s, and the increase in sediment mining associated with increased construction activities during the same period.
6.5.2 Average bed sediment size
Sediment size is controlled by the sediment supply and flow regime of a river. For this exercise it is assumed that the capture of bedload in impoundments will result in an overall decrease in the availability of coarse material, which will push the median grain-size towards smaller grain sizes. It is recognised that impoundments can also result in a coarsening of bed material in the immediate downstream environment due to the winnowing of fines, and armouring of beds which typically occurs downstream of dams.
In the Mekong there is extremely limited information about the grain-size distribution of bed materials, with the 2011 Discharge Sediment Monitoring Project (reference) being the only comprehensive bed- material survey. The grain-size data from the survey are summarised in Figure 6.7, which shows the lower limit of the median grain-size class for the bed samples. The grain-size classes used for the analysis are summarised in Table 6.5. The results show that bed materials are typically composed of medium silt to medium sand, and sediment grain size generally decreases with distance downstream. Several of the sites with coarser material are located near tributary confluences, such as near km 1400 at the confluence of the Mekong and Nam Mang, or upstream of Km 500 where the 3S system enters, and probably reflect the inflow of coarser material from the sub-catchments.
The 2011 results reflect bed materials after 5 – 10 years of influence from the Lancang Cascade, existing tributary impoundments, and sand extraction activities. Although the dams are likely to have retained most bedload moving through the Lancang upstream of the dams, bedload material probably remains available due to stored material in the system, and input from tributaries, especially those in the high relief areas of northern Lao PDR.
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Figure 6.7 Median grain size and distance from river mouth of bed samples collected in 2011 (Koehnken 2012)
Table 6.5 Summary of grain-size classes used in 2011 DSMP bed material survey
Description Size class (mm) GRAVEL >4.75 Coarse 4.75-2 2-0.85 Medium 0.85-0.425 SAND 0.425-0.25 Fine 0.25-0.125 0.125-0.08 Coarse 0.08-0.063 SILT Medium 0.063-0.045 Fine 0.045-0.002 CLAY <0.002
The main anthropogenic drivers considered to have the greatest influence on the bed sediment size are: 1 impoundments, which reduce sediment delivery and alter the hydraulics of the system; 2 sediment mining, which remove larger sized sediment from the channel; 3 land cover changes, which can alter the distribution of sediment delivered to the river; 4 impoundments and water extractions, which alter the flow regime.
It is assumed that the conditions under which the 2011 results were obtained are similar to those in 2015, and reflect the present ‘100%’ status of the system. Figure 6.8 summarises the assessment of previous conditions based on the understanding of the system presented above. The river sections are considered to have had a somewhat coarser median bed material size in the past, due to the
Page 47 greater availability of coarse material, and lower rates of sediment mining. The sediment in the Tonle Sap Great Lake and the Delta are likely to have always been dominated by clay and fine silts.
Average bed sediment size 200
180 Mekong River in Laos PDR 160 Mekong River in Laos 140 PDR/Thailand 120 Mekong River in 100 Cambodia Tonle Sap River
relative to relative 2015 (100%) 80 60 Tonle Sap Great Lake
40 Percentage 20 Mekong Delta 0 1900 1950 1970 2000 2015
Figure 6.8 Average bed sediment size: Historic estimates as % relative to 2015 (100%)
Size classes are shown in Figure 6.8. The percentages used are defined as: 0% Median grain-size is smaller by 2 size classes or more 50% Median grain-size is smaller by 1 size class 100% 2015 conditions 150% Median grain-size is larger by 1 size class 200% Median grain-size is larger by 2 size classes or more 250% Sediment removed and bedrock exposed.
6.5.3 Availability of exposed sand bars and islands in the dry season
The availability of sub-aerially exposed sandy bars, islands and insets in the dry season is an important component of riverine habitat. The availability of sandy habitats is controlled by the presence of sandy depositional environments and the water level of the river. Hence, changes to sediment delivery, bank erosion or the flow regime will affect the availability of the sandy habitats.
As previously discussed, erosion in the LMB is considered to have increased since the commissioning and operation of the Lancang Cascade and other tributary impoundments due to a reduction in sediment supply. An increase in erosion will decrease the availability of sandy habitats due to the removal of material. Sand mining will also reduce the availability of sandy habitats.
The 2015 LMB flow regime is characterised by higher than ‘natural’ flows during the dry season in the upper basin due to the operation of the Lancang Cascade. These higher flows reduce the availability of sandy bars /islands. The prolonged higher flows also have the potential to inundate riparian vegetation on alluvial banks, which can alter habitat conditions.
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The increase in water level during the dry season decreases with distance downstream as the river widens, and the UMB inflow becomes a reduced percentage of the total flow.
During the wet season, peak flows are reduced in the upper LMB compared to historic results, presumably due to the retention of water within the impoundments of the Lancang cascade. This flow alteration is at a maximum in the upper LMB, and decreases downstream due to additional inflows from tributaries (especially unregulated tributaries).
Combined, these flow changes result in a decrease in exposure of the sandy habitat during dry seasons, and a small increase during wet season, relative to natural conditions (Figure 6.9). Because the changes to flow are most pronounced in the upper LMB, the most upstream areas (Mekong River in Northern Lao PDR; and Mekong River in Thailand / Lao PDR) are considered to be more impacted as compared to the downstream areas, where additional inflows and tidal influences exert a larger effect on water levels.
Availability of exposed sand bars and islands 200
180 Mekong River in Laos PDR 160 Mekong River in Laos 140 PDR/Thailand 120 Mekong River in 100 Cambodia 80 Tonle Sap River 60 Tonle Sap Great Lake
40 Percentage to relative 2015 (100%) 20 Mekong Delta 0 1900 1950 1970 2000 2015
Figure 6.9 Availability of exposed sand bars and islands: Historic estimates as % relative to 2015 (100%). Tonle Sap Great Lake was not assessed for exposed sandy bars and islands.
The main anthropogenic drivers of change in the exposure of sandy habitat include: 1 impoundments, which trap sediment and increase discharge during the dry season and decrease flow during the wet season; 2 sand mining, which can remove habitat; 3 other extractions that alter the flow regime.
The percentages used in Figure 6.9 are defined as: 120% Increased exposure associated with lower erosion rates and lower flows during the dry season associated with the unregulated flow regime; 100% 2015 conditions – reduced exposure due to increased bank erosion and higher flows during the dry season due to water level changes associated with flow regulation;
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50% Additional reduction in exposure associated with increased erosion flows during dry season and decreased flows during wet season as compared to 2015.
6.5.4 Availability of exposed rocky habitats in the dry season
The availability of sub-aerially exposed rocky habitats within the river channel in the dry season is important for providing appropriate riverine habitat for both flora and fauna. The availability of rocky environments is controlled by the presence of exposed bedrock and the water level of the river. Hence, changes to sediment delivery, erosion or the flow regime can affect the availability of the sandy habitats. With respect to the establishment of the Lancang Cascade, it is common that downstream of major dam developments an increase in erosion and decrease in sediment supply results in the removal of large quantities of sand and finer material and increased exposure of bedrock. The extent of this will be affected by the location and relative size of downstream tributaries. Damming of a river can also reduce availability due to submerging previously exposed bedrock, or increasing deposition of sediment on bedrock at the upstream end of the impoundment due to reductions in flow velocities.
Other activities can decrease the availability of rocky substrate include channel modification, such as blasting to improve navigation. Channel modifications affecting the availability of rocky habitat have occurred in the LMB, but are considered to be relatively small compared with the overall exposure of bedrock.
The 2015 LMB flow regime is characterised by higher than ‘natural’ flows during the dry season in the upper basin due to the operation of the Lancang Cascade. These higher flows reduce the availability of rocky substrate. The increase in water level during the dry season decreases with distance downstream as the river widens, and the UMB inflow becomes a reduced percentage of the total flow.
During the wet season, peak flows are reduced in the upper LMB compared to historic results, presumably due to the retention of water within the impoundments of the Lancang cascade. This flow alteration is at a maximum in the upper LMB, and decreases downstream due to additional inflows from tributaries (especially unregulated tributaries).
Combined, these flow changes result in a decrease in exposure of the rocky habitat during dry seasons, and a small increase during wet season, relative to natural conditions. Because the changes to flow are most pronounced in the upper LMB, the most upstream areas (Mekong River in Northern Lao PDR; and Mekong River in Thailand / Lao PDR) are considered to be more impacted as compared to the downstream areas, where additional inflows and tidal influences exert a larger effect on water levels.
In assessing the availability of rocky substrate, the decrease in exposure due to higher water levels has to be considered in the context of an increase in exposure due to increased bank erosion removing sediment from the underlying bedrock. It is likely that the balance between these processes varies with distance downstream, however, the increase in water level during the dry is considered to be the factor exerting the greatest change in 2015.
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The main anthropogenic drivers of change in the exposure of rocky habitat include: 1 impoundments, which trap sediment and increase discharge during the dry season and decrease flow during the wet season; 2 channel modifications, such as blasting for navigation; 3 other water extractions that alter the flow regime.
The percentages used in Figure 6.10 are defined as: 120% Increased exposure associated with flows during the dry season under the unregulated flow regime; 100% 2015 conditions – reduced exposure due to higher flows during the dry season; 80% Decreased exposure associated with higher flows during dry season and decreased flows during wet season as compared to 2015.
Availability of exposed rocky habitats 200
180 Mekong River in Laos PDR 160 Mekong River in Laos 140 PDR/Thailand 120 Mekong River in 100 Cambodia 80 Tonle Sap River 60 Tonle Sap Great Lake
40 Percentage to relative 2015 (100%) 20 Mekong Delta 0 1900 1950 1970 2000 2015
Figure 6.10 Availability of exposed rocky habitats: Historic abundance estimates as % relative to 2015 (100%).
6.5.5 Depth of bedrock pools
Pools provide important refuge and spawning habitat for long-distance transboundary migratory fish species, especially during periods of low flow. Over 400 ‘deep pools’ have been identified in the LMB based on local ecological knowledge and an analysis of hydrographic surveys (Figure 6.11; MRC 2011). The pools occur at a variety of geomorphic settings (Figure 6.12) in both bedrock and alluvial reaches.
An MRC (2006; 2011) investigation found that pools tend to be longer and deeper in downstream reaches as compared to upstream reaches, and identified a link between discharge volume and pool size. Depth, flow velocity, bed roughness and turbulence were all identified as important factors when considering pools as habitat for fish and aquatic organisms. Conlan et al (2008) found that sediment pulses move through pools in northern Lao PDR on an annual basis, highlighting the link between sediment delivery and flow regime for the maintenance of pools.
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Figure 6.11 Thalwag long-section of the LMB showing occurrences of Deep Pools (MRC 2011).
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Figure 6.12 Pool types identified in the LMB (MRC 2011).
It is assumed that pool depth is maintained by a combination of high flows, which provide the shear stress required to maintain the depth, and the timing of the sediment supply, such that deposition on does not occur at the end of the wet season. Flow changes in the LMB in the last 10 years include a small reduction in high flows, associated with operation of the Lancang Cascade, and a reduction in sediment supply. The timing of the onset of high flows in the upper LMB has been delayed somewhat, but peak flows continue to occur at approximately the same time as pre-Lancang Cascade. Based on these changes, it is suggested that the characteristics of pools in 2015 may be slightly but not majorly different from past or natural conditions (Figure 6.13).
Depth of bedrock pools 200
180 Mekong River in Laos PDR 160 Mekong River in Laos 140 PDR/Thailand 120 Mekong River in 100 Cambodia 80 Tonle Sap River 60 Tonle Sap Great Lake
40 Percentage to relative 2015 (100%) 20 Mekong Delta 0 1900 1950 1970 2000 2015
Figure 6.13 Depth of pools: Historic estimates as % relative to 2015 (100%). Tonle Sap River, the Great Lake and the Delta were not assessed for depth of bedrock pools.
The anthropogenic drivers considered to have the greatest influence on the depth of pools: 1 Impoundments, which increase discharge during the dry season and decrease flow during the wet season; 2 other water extractions that alter the lowflow regime. 3 climate change.
The percentages used in Figure 6.13 are defined as: 90% exposure associated with the unregulated flow regime; 100% 2015 conditions –increased depth during low flow associated with increases in flow levels, decreased depth during the flood season due to reduced peak water levels associated with flow regulation; 150% increased depth during dry season and decreased depth during wet season as compared to 2015 associated with potentially greater flow regulation.
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6.5.6 Water clarity
Water clarity is important for ecological systems as it controls the depth of light penetration which is important for plant growth, and affects organisms which depend on sight for feeding. Water clarity is related to the surface area of material suspended in the water column rather than the mass of suspended sediment; relatively low concentrations of very fine-suspended sediment can reduce water clarity as compared to higher concentrations of coarse grained material.
There are no direct measurements of water clarity available for the LMB, only Total Suspended Sediment concentrations (TSS - based on a grab sample of surface waters) or Suspended Sediment Concentration (SSC – based on a flow-proportional depth integrated suspended sediment sample). Grain-size distribution results are available for some of the SSC measurements, but not the TSS results.
The 2009 – 2013 DSMP monitoring results indicate that SSC in the upper LMB (Chiang Sean) is characterised by silt and fine to medium sand, and suspended material becomes finer with distance downstream, with clay and fine silt in the suspended load of the delta.
Recent photos and observations indicate that water clarity is low during periods of high flow, and increases during low flow periods. How water clarity in 2015 compares with previous conditions is difficult to evaluate, because even though there has been a very large decrease in the concentration of suspended sediments in the Mekong, this does not necessarily equate to a similarly large reduction in water clarity due to the continued presence of silt and finer sediment. Based on this, water clarity is estimated to have decreased a small amount relative to previous conditions (Figure 6.14).
The anthropogenic drivers considered to have the greatest influence on the water clarity: 1 impoundments, which increase discharge during the dry season and decrease flow during the wet season; 2 land-use changes, which can affect the concentration of sediments in runoff and tributary inflows; 3 in-channel barriers, which reduce flow rates and decrease suspended sediment concentrations.
The percentages used in Figure 6.14 are defined as: 80% reduced light penetration associated with unregulated flow regime; 100% 2015 conditions –increased clarity during low flow due to release of low sediment water from Lancang Cascade relative to natural, and slightly increased clarity during high flows due to large reduction in suspended sediment concentrations; 120% increased light penetration associated with potentially greater flow regulation leading to larger discharges of high clarity water, and lower concentrations of suspended sediment.
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Water clarity 200
180 Mekong River in Laos PDR 160 Mekong River in Laos 140 PDR/Thailand 120 Mekong River in 100 Cambodia 80 Tonle Sap River 60 Tonle Sap Great Lake
40 Percentage to relative 2015 (100%) 20 Mekong Delta 0 1900 1950 1970 2000 2015
Figure 6.14 Water clarity: Historic estimates as % relative to 2015 (100%)
6.6 Status and trends: Vegetation
The Mekong River flora and vegetation, or indeed the plant realm of Indochina as a whole, is one of the least known tropical regions of Asia and the world. Until recently (1990s), only cursory floristic inventories of Mekong River vegetation have been reported in Laos PDR and Cambodia (Dy Phon 1982; Frodin 2001; Rollet 1972; Legris and Blasco 1972; Vidal 1956-1960; 1979), these highlighting only a few dominant trees or shrubs that might define a given reach of the mainstream river system and Tonle Sap floodplain. Since those reports, the first and only, general botanical surveys undertaken within and along the LMB channels that fall within FA2-4 were initiated in the 21st century (Maxwell 2001, 2008, 2013; McDonald 2005). These brief studies provide only a glimpse of riparian plant species diversity, and an exceedingly generalized characterization of numerous plant communities, the latter dimension of biological diversity being equally important to, if not more informative than, species diversity. Maxwell’s observations are based on a couple of visits to each site during the wet and dry season, and cover an exceedingly broad swath of Laotian river fronts from Luang Prabang to Vientiane, the Siphandone region, and the closely connected river run between Stung Treng and Kratchie of northern Cambodia. His preliminary species lists account primarily for highly disturbed terrestrial forest communities that once surrounded the riparian vegetation (at least in terms of species numbers), the floristic compositions of which account for the vast majority of species reported in this region. The latter data are not of direct consequence to the water flows of the Mekong River per se, but the Mekong River was affected historically and substantially by their organic contributions to Mekong mainstream food chains.
The more interesting floristic elements that Maxwell records in the upper reaches of the LMB are those that exhibit narrow distributions and small, albeit dense, populations, within diverse riparian habitats against banks and islands. In each of his surveys, Maxwell admits and emphasizes openly, and almost in identical terms, that, “This can only be a preliminary study … A complete flora of the study area, including adjacent land habitats, would require frequent and extensive collecting”
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Box 6.1 Historic changes in the Mekong Delta
By far the greatest changes in vegetation have occurred in the Delta, although clearing of vegetation for agriculture, and urban and other development, has occurred throughout the LMB.
By the early nineteenth century, the Vietnamese kings had conquered and pacified the Delta by digging canals and establishing military (farm soldier) settlements. After the French arrived in 1867, the colonial government excavated a number of great canals for security and transportation. However, in the latter half of the 19th century there was considerable expansion of rice cultivation in the delta, particularly in the central part along the Tien Giang and the Hau Giang, two main tributaries of the Mekong River (Koji 2001). By the end of 19th century, many important canals had been built. After 1900, additional canal construction further accelerated the expansion of rice cultivation in the area. By the Great Depression of the 1930s, most of the Mekong Delta, except for the broad depression and the plain of reeds, had been converted to arable land. In the in the late 1950s, parts of the plain of reeds was cultivated. After the end of the Viet Nam War in 1975, many of the remaining areas were cleared for rice cultivation and shrimp farming (Yoko 1984; Brocheux 1995; Koji 2001). Socialist reforms after the War, led to rice fields owned by large scale farmers or absentee landlords being distributed to small scale or landless farmers, and a system of collectivized labour was introduced.
Large scale state farms were established as a model for propagating the socialist production system, not only in the Plain of Reeds and the Broad Depression, but in the entire delta. However, the placement of state farms was restricted to lands highly prone to deep flooding, acid emergence, and/or salt intrusion. In the Broad Depression, after spontaneous migrants exploited and denuded the original vegetation to cultivate rice, a vast area of 21,400 hectares was enclosed to establish and conserve Melaleuca forests, and a number of state farms were established in the surroundings. In addition to these areas, many state farms were established in the coastal plain of northwestern Kien Giang province, from Rach Gia to Ha Tien. This area was also highly prone to salt intrusion and acidification. Under the doi moi policy, the state farms were completely closed in 1997 (Koji 2001).
Intensification of Rice Cultivation after Doi moi policy, Many canals excavated by the central and provincial governments after socialist reform paved the way for great progress in rice cultivation in the Plain of Reeds and the Broad Depression. In addition, the introduction of high yielding varieties (HYVs) of rice played an important role in expanding rice cultivation in these areas. The HYVs, were first introduced to the Mekong Delta in 1968 and brought about a noticeable change in traditional rice cultivation and rice-based cropping systems (Tanaka 1995). They were adopted in the central part of the delta, such as Long An and Can Tho provinces, at the initial stage of introduction and were gradually disseminated to the periphery of the delta. In the Plain of Reeds and the Broad Depression, their adoption was delayed for quite a long time due to adverse environmental conditions to adopt the high yielding varieties. They had to wait for the complete disappearance of acid through consecutive washings with the fresh water available from the new canals.
Today, much of the delta has lost its natural habitat, although remnants of the once extensive peat swamp forests, freshwater forests and flooded grasslands are still represented in parts. There is no escaping the fact that the canal and associated agricultural activities have dramatically changed the face of the Delta. Previously inaccessible and uninhabited areas were settled, and surface water drained from the depression. Only relatively small areas of Melaleuca swamp forest and grassland and sedge-land remain (Safford and Maltby 1997; Tran Triet et al. 2000; Baltzer et al. 2001; Rundel 2009). There is evidence in the form of tree stump remains, suggesting that extensive areas of the delta were once forested (Kiet 1993), but the long human habitation in this area has meant that little is known of the original vegetation (Torell et al. 2003). Folklore and older community members also describe forested areas within the Plain of Reeds consisting of a number of tree species in addition to Melaleuca. Buried tree stumps from the genus Eugenia uncovered during agriculture activities corroborate this oral history.
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(Maxwell 2013: 38; see also Maxwell 2008: 42). The same assertion was made in the first systematic surveys of Tonle Sap Great Lake undertaken by McDonald (1996, 1997) in the 1990s. His work was based on only six weeks of fieldwork, yet these observations provided the first inventory and superficial characterization of the structure of the Great Lake’s endemic vegetation. Various misconceptions and errors that had been reported in previous scientific publications were noted, underscoring again severe limitations to our understanding of the Mekong’s ecological ‘producers.’
Another limitation that confronts the assessment of changes in water flows on biological systems is the fact that these late-arriving studies account for a native vegetation that is already highly disturbed (Maxwell 2001; 2008; 2013). So whatever we observe and characterize at this point in time is a far cry from what was operative in recent natural history. It is fortunate, however, that rocky substrates within the river’s channel in BioRA Zones 1-4 harbor relatively intact plant communities, as their rocky substrates harbour plants of little commercial value and are undesirable for rice cultivation. The latter observation does not apply, however, to Zones 5 and 8, where the natural vegetation of the floodplain is now reduced to small vestiges of native habitats. The denuding of the Mekong’s delta region was almost fully consummated by the early 20th under French colonial administration (Broucheux 1995: 7- 8); hence there is little concrete data on the specifics of this historical environmental revolution.
We can only assume that the natural vegetation removed by human activities more than a century ago bore some resemblance to what we observe in the floodplains of the Tonle Sap today, while still bearing in mind that the lower reaches of the delta were occupied widely by a mixture of Melaleuca (upper mangrove) and lower mangrove forests.
The current status of present-day vegetation is easily assessed by modern observation. The trends and historical changes, on the other hand, are largely extrapolated by comparing and contrasting vegetation maps that date from the 1920s (Lecomte 1926), the early 1950s (US Army Map Service 1950-1954), a generalized French vegetation map from the Viet Nam war period (Service des Eaux, Forets et Chasse, 1972), and using GOOGLE EARTH for a modern perspective. There are two caveats that are in order here; one is that early 20th century maps usually denote natural marshes and rice fields with the same icon, which introduces an element of uncertainty as to where native and human-dominated landscapes begin and end; and two, the early maps were not elaborated with the use of remote sensing tools, and are therefore relatively less accurate and precise than modern cartography.
The estimated 2015 ecological status for each of the geomorphology indicators is provided in Table 6.6. The definitions for the categories are given in Table 6.2. The expected trends in the indicators are discussed in Sections 6.6.1 to 6.6.12, respectively. In the context of the status and trends assessments, it is important to note that the vegetation in the Delta had already been considerably altered by 1900, which is the start point of the assessments.
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Table 6.6 Estimated 2015 ecological status for each of the vegetation indicators
Area
rianvegetation
Channel_Extentof upperbank vegetation cover Channel_Extentof lowerbank vegetation cover Channel_Extentof herbaceousmarsh vegetation Channel_Biomassof ripa Floodplain_Extentof floodedforest Floodplain_Extentof herbaceousmarsh vegetation Floodplain_Extentof grasslandvegetation Floodplain_Biomass ofriparian/aquatic cover Floodplain_Extentof invasive riparianplant cover Floodplain_Floating andsubmerged invasiveplant cover 2015 2015 2015 2015 2015 2015 2015 2015 2015 2015 Mekong River C C NA C NA NA NA C NA NA in Laos PDR Mekong River in Laos C C B C E C NA C NA NA PDR/Thailand Mekong River C C B C NA NA NA D E NA in Cambodia Tonle Sap NA NA NA NA E E NA E E E River Tonle Sap NA NA NA NA E D D D D E Great Lake
Mekong Delta NA NA NA NA E E E E E E
Note: The status and trends assessment is incomplete for some of the vegetation indicators. This is because these indicators changed during the June/July meetings, and the status and trends information compiled beforehand was no longer relevant. The status and trends assessment for these indicators is underway, and will be included in the draft Vegetation Specialist Report.
Also: This assessment pertains to natural vegetation – not cultivated vegetation.
6.6.1 Channel_Extent of upper bank vegetation cover
The main anthropogenic driver considered to have the greatest influence on upper bank vegetation is land-use, primarily the denuding of upper river slopes by local communities seeking wood-fuel, house construction materials and clearing lands for mixed agriculture (for reviews see: Daconto 2001; Elliott 2001; Maxwell 2001, 2013; McDonald and Veasna 1996). The estimated historical changes in cover provided in Figure 6.15, indicate both cover and quality of remaining vegetation. In comparison to Laos PDR, relatively denser human populations in modern historical Cambodia (by about a factor of 3; Hirschman and Bonaparte 2012) have exacted more change in the lower reaches of the river. Some recent accounts of disturbance are described in the Siphandone by Maxwell (2001; 2013) and Elliott (2001).
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Channel_Extent of upper bank vegetation cover 200
180 Mekong River in Laos PDR 160 Mekong River in Laos 140 PDR/Thailand 120 Mekong River in 100 Cambodia 80 Tonle Sap River 60 Tonle Sap Great Lake
40 Percentage to relative 2015 (100%) 20 Mekong Delta 0 1900 1950 1970 2000 2015
Figure 6.15 Channel_Extent of upper bank vegetation cover: Historic abundance estimates as % relative to 2015 (100%)
6.6.2 Channel_Extent of lower bank vegetation cover
The main anthropogenic driver considered to have the greatest influence on lower bank vegetation is land-use, primarily the denuding of the upper river slopes by local communities seeking wood-fuel, house construction materials and clearing lands for mixed agriculture. The historical changes in cover provided in Figure 6.16, indicate both cover and quality of remaining vegetation.
Channel_Extent of lower bank vegetation cover 200
180 Mekong River in Laos PDR 160
140 Mekong River in Laos PDR/Thailand 120 Mekong River in 100 Cambodia Tonle Sap River relative to relative 2015 (100%) 80
60 Tonle Sap Great Lake 40 Percentage Mekong Delta 20
0 1900 1950 1970 2000 2015
Figure 6.16 Channel_Extent of lower bank vegetation cover: Historic abundance estimates as % relative to 2015 (100%)
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In the last decade Chinese dams have elevated the low-water levels during the dry season, and this has decreased the extent of lower bank vegetation cover through drowning (see note), and this seems to have increased in recent years, but this is based on my observations more than measurements.
Note: It would have been highly desirable to have been able to observe the extent to which rising water levels in Focus Areas 1 and 2, following dam developments in China, have affected bedrock channels. A personal trip (Dr McDonald) to the golden triangle revealed that bank stabilization developments (stone held in by wire mesh) has already extirpated vast swaths of lower bank vegetation.
6.6.3 Channel_Extent of herbaceous marsh vegetation
The main anthropogenic drivers considered to have the greatest influence on the extent of herbaceous marsh vegetation are land-use, primarily infilling wet areas and removal of vegetation for mixed agriculture. Herbaceous marshes in the upper reaches of the LMB are now mostly confined to small and scattered, ephemeral zones within the channel – primarily caused by shifting alluvia on top of natural depressions within rocky bedrock. These come and go naturally. Most of the herbaceous marshes that might have been located in the reduced floodplains of the Lao-Thai reaches of the LMB were probably converted into rice fields many centuries ago (see map of Lecomte 1926 for distribution of rice paddies in forested landscape). Some recent accounts of disturbance are described in the Siphandone by Maxwell (2001; 2013) and Elliott (2001).
Channel_Extent of herbaceous marsh vegetation 200
180 Mekong River in Laos PDR 160 Mekong River in Laos 140 PDR/Thailand 120 Mekong River in 100 Cambodia 80 Tonle Sap River 60 Tonle Sap Great Lake
40 Percentage to relative 2015 (100%) 20 Mekong Delta 0 1900 1950 1970 2000 2000
Figure 6.17 Channel_Extent of herbaceous marsh vegetation: Historic abundance estimates as % relative to 2015 (100%)
6.6.4 Channel_Biomass of riparian vegetation
The main anthropogenic driver considered to have the greatest influence on the biomass of riparian vegetation is historical land-use, primarily infilling wet areas for cities and rice fields and the removal
Page 60 of vegetation for mixed agriculture. Herbaceous marshes and scrubby vegetation in the reduced floodplains of the upper reaches of the LMB were probably converted into rice fields many centuries ago (see map of Lecomte 1926 for distribution of rice paddies in forested landscape). Some recent accounts of disturbance is described in the Siphandone region by Maxwell (2001; 2013) and Elliott (2001). The estimated historical changes are provided in Figure 6.18.
Channel_Biomass of riparian vegetation 200
180 Mekong River in Laos PDR 160
140 Mekong River in Laos PDR/Thailand 120 Mekong River in 100 Cambodia
80 Tonle Sap River
60 Tonle Sap Great Lake 40 Percentage to relative 2015 (100%) Mekong Delta 20
0 1900 1950 1970 2000 2015
Figure 6.18 Channel_Biomass of riparian vegetation: Historic abundance estimates as % relative to 2015 (100%)
6.6.5 Channel_Biomass of algae
Not completed.
6.6.6 Floodplain_Extent of flooded forest
The upper parts of the LMB have experienced substantial change, but floodplain forest vegetation was historically much more limited in the upper reaches relative to the lower reaches of the LMB. Most of the Delta’s marshlands and mangroves were converted during the early decades of the 20th century, when the French established rice production for export (Brocheux 1995). Between the late 1800s and c. 1930, 2 000 000 ha of mangroves in the western portion of the Delta (Mien Tay) were reduced to 0.33 ha (Figure 6.19). However, extensive mangrove swamps still existed in 1950s south of Ho Chi Min City and on the whole of the southern tip of Viet Nam. The estimation of 800% greater extent of flooded forest at the turn of the 20th century is probably conservative (Figure 6.20), but it is difficult to know how much of the delta was originally (prehistorically) a marshland rather than a flooded forest. These historical changes indicate both cover and quality of remaining vegetation.
The main anthropogenic drivers considered to have the greatest influence on the biomass of riparian vegetation are land cover changes, land use changes, irrigation, harvesting pressure, fire frequency; clearing of land for rice paddies, pasturage, canal/irrigation developments, and villages.
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Figure 6.19 Cultivated areas in the Mekong Delta c. 1910 (http://www.odsas.net/scan_sets.php?set_id=404anddoc=43700andstep=5)
Floodplain_Extent of flooded forest
800
700 Mekong River in Laos PDR
600 Mekong River in Laos PDR/Thailand 500 Mekong River in Cambodia 400 Tonle Sap River 300 Tonle Sap Great Lake 200 Percentage to relative 2015 (100%) Mekong Delta 100
0 1900 1950 1970 2000 2015
Figure 6.20 Floodplain_Extent of flooded forest: Historic abundance estimates as % relative to 2015 (100%)
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6.6.7 Floodplain_Extent of herbaceous marsh vegetation
As is the case for floodplain forests, the upper parts of the LMB have experienced substantial change, but herbaceous marsh vegetation was historically much more limited in the upper reaches relative to the lower reaches of the LMB. A complicating factor in assessing change in this vegetation is that historical maps rarely distinguish swampy regions from rice-producing regions; but Figure 6.19 verifies the boundaries of rice fields after the French initiated their program to expand agriculture in the early 20th century. Brocheux (1995: 1-16) notes that 220 000 ha. (= 2200 km2), or 25% of S delta (Mien Tray) marshlands were converted to rice paddies by the early part of the 20th century. He also indicates that the agriculture program was developed for the purpose of exporting rice. By the 1930s, most arable lands of the delta were producing cereal. The Plain of Reeds is only 12000 km2 today. Most of the herbaceous marshes that might have been located in the reduced floodplains of Laos PDR, Thailand and northern Cambodia were probably converted into rice fields many centuries ago (see map of Lecomte 1926 for distribution of rice paddies in forested landscape). Some recent accounts of disturbance are described in the Siphandone by Maxwell (2001; 2013) and Elliott (2001).
Floodplain_Extent of herbaceous marsh vegetation
600 Mekong River in Laos PDR
500 Mekong River in Laos PDR/Thailand 400 Mekong River in Cambodia 300 Tonle Sap River
200 Tonle Sap Great Lake
Percentage to relative 2015 (100%) 100 Mekong Delta
0 1900 1950 1970 2000 2015
Figure 6.21 Floodplain_Extent of herbaceous marsh vegetation: Historic abundance estimates as % relative to 2015 (100%)
6.6.8 Floodplain_Extent of grassland vegetation
Seasonally inundated grasslands have been targeted by rice cultivators as prime land for paddies. Consequently, the delta region has a miniscule representation of its original grasslands, one exception being the Plain of Reeds protected area, comprising a total of 12000 km2 today, but this also includes substantial Melaleuca forest cover. Historically, it is difficult to assess the original extent of seasonally inundated grasslands on the delta because early vegetation maps do not generally distinguish mixed-vegetation swamps from swampy grasslands and rice-producing regions; nevertheless, Figure 6.19 verifies the boundaries of rice fields after the French initiated their program to expand agriculture in the early 20th century. Various grasslands are ensconced within and on the northern boundaries of Tonle Sap Great Lake , most of which have survived intact until the early
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2000s. Since that time, about 30% of the grasslands have been converted into irrigated rice fields (Figure 6.22).
Floodplain_Extent of grassland vegetation
600 Mekong River in Laos PDR
500 Mekong River in Laos PDR/Thailand 400 Mekong River in Cambodia 300 Tonle Sap River
200 Tonle Sap Great Lake
Percentage to relative 2015 (100%) 100 Mekong Delta
0 1900 1950 1970 2000 2015
Figure 6.22 Floodplain_Extent of grassland vegetation: Historic abundance estimates as % relative to 2015 (100%)
6.6.9 Floodplain_Biomass of riparian/aquatic cover
The main anthropogenic drivers considered to have the greatest influence on the biomass riparian/aquatic cover on the floodplains are land cover changes, land use changes, harvesting pressure, fire frequency, invasives; primarily denuding of riparian woodlands and marshlands for wood-fuel, house construction materials, and opening lands for mixed agriculture. The estimated historical changes are provided in Figure 6.23. These historical changes indicate both cover and quality of remaining vegetation. Since rice fields produce about the same amount of biomass as marshlands on an annual basis (even if it isn’t included in the LMB food chain), the biomass numbers primarily reflect the demonstrable changes in flooded forest cover. As earlier noted, the upper parts of the LMB have experienced substantial change, but floodplain forest vegetation was historically much more limited in the upper reaches relative to the lower reaches of the LMB. Most of the Delta’s marshlands and mangroves were converted during the early decades of the 20th century, when the French established rice production for export (Brocheux 1995). Between the late 1800s and c. 1930, 2 000 000 ha of mangroves in the western portion of the Delta (Mien Tay) were reduced to 0.33 ha (Figure 6.19). However, extensive mangrove swamps still existed in 1950s south of Ho Chi Min City and on the whole of the southern tip of Viet Nam. My estimation of 800% greater extent of flooded forest at the turn of the 20th century is probably too conservative, but it is difficult to know how much of the delta was originally (pre-historically) marshland rather than flooded forest.
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Floodplain_Biomass of riparian/aquatic cover
800 Mekong River in Laos PDR 700
600 Mekong River in Laos PDR/Thailand 500 Mekong River in Cambodia 400 Tonle Sap River 300 Tonle Sap Great Lake 200
Percentage to relative 2015 (100%) 100 Mekong Delta
0 1900 1950 1970 2000 2015
Figure 6.23 Floodplain_Biomass of riparian/aquatic cover: Historic abundance estimates as % relative to 2015 (100%)
6.6.10 Floodplain_Extent of cyanobacteria
Not completed.
6.6.11 Floodplain_Extent of invasive riparian plant cover
Disturbances occasioned by wood collectors and the clearing of land for mixed agriculture makes natural vegetation more susceptible to invasive species. Two invasive species, namely Mimosa pigra (a thorny leguminous shrub) and Imperata cylindrica (a tall, deeply-rooted tropical grass), have overtaken many riparian habitats. The former species prefers partial submersion in water and therefore exhibits broader distribution in floodplains. The latter species survives in seasonally inundated areas, and therefore prospers on river banks. They can dominate the vegetation locally, and sometimes produce monocultures. Imperata grass has been in the region for a century, while Mimosa pigra was introduced in Asia in the 1970s. Only in recent times, due to disturbance, have they become a commanding vegetative feature of the LMB (Figure 6.24).
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Floodplain_Extent of invasive riparian plant cover 200
180 Mekong River in Laos PDR 160 Mekong River in Laos 140 PDR/Thailand 120 Mekong River in 100 Cambodia 80 Tonle Sap River 60 Tonle Sap Great Lake
40 Percentage to relative 2015 (100%) 20 Mekong Delta 0 1900 1950 1970 2000 2015
Figure 6.24 Floodplain_Extent of invasive riparian plant cover: Historic abundance estimates as % relative to 2015 (100%)
6.6.12 Floodplain_Extent of floating and submerged invasive plant cover
Canal and irrigation projects open corridors for floating invasives. But water hyacinth (Eichhornia crassipes) is already ubiquitous in the LMB and other invasive grasses, such as para grass (Brachiaria mutica), are now extending their ranges. All were absent from the LMB during the 19th century (Figure 6.25). Were it not for the massive floodwaters that fill the Tonle Sap Great Lake with water and then carry these floating water hyacinth out to sea, this floating plant would have done considerable damage to the native vegetation and fisheries of the Tonle Sap. On the other hand, para grass forms inter-linking, floating stems and creates ‘sud’ (a unified floating vegetation) within Tonle Sap Great Lake , and has the ability remain anchored during flood events.
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Floodplain_Floating and submerged invasive plant cover 200
180 Mekong River in Laos PDR 160 Mekong River in Laos 140 PDR/Thailand 120 Mekong River in 100 Cambodia 80 Tonle Sap River 60 Tonle Sap Great Lake
40 Percentage to relative 2015 (100%) 20 Mekong Delta 0 1900 1950 1970 2000 2015
Figure 6.25 Floodplain_ Extent of floating and submerged invasive plant cover: Historic abundance estimates as % relative to 2015 (100%)
6.7 Status and trends: Macroinvertebrates
Estimations of changes to invertebrates in the Lower Mekong system are challenging for several reasons. Firstly there is very limited data, with taxon specific results from comprehensive samples only available for the period 2003-2008. That is a limited time period and the data is not sufficient to draw confident conclusions about patterns of change over time. At any single sampling site there were at most three sampling occasions over time and for most sites only a single sampling occasion. Secondly samples are single point samples, and we are attempting to draw conclusions about extensive stretches of river. Often there are substantial local within-stretch variations, such as reduced water quality around cities, or substantial gradients as between the upstream and downstream areas of the delta, which make it difficult to decide on the rating of the stretch as a whole. The bioassessment data do demonstrate that the invertebrate assemblages of the basin were generally in good condition at least until 2011. Only one site was rated as poor condition in the 2011 data (MRC 2014), and based on data from 2004 to 2007, 40 of 51 sites were rated “excellent” or “satisfactory” and only 11 as “moderately impacted” (Campbell et al. 2009).
There are several important historical events and trends which will have impacted invertebrate assemblages in the river. The first was the Chinese communist revolution from 1946-49 and the Korean War from 1950-3. At that time China and other communist countries were cut off from supplies of rubber, which came largely from Indonesia, Malaya and Sri Lanka (Cain 2007). Consequently China undertook extensive development of rubber plantations in Fujian, Yunnan, Guangdong and Hainan Island during that period (Vogel 1989) and large areas of primary forest on steep hillsides were cleared in the vicinity of Jinhong to plant rubber trees.. We have no water quality data, but there must have been substantial erosion, and the fine particulates load into the river must have increased enormously. This would have impacted filter feeders and invertebrates living on stones, with the impacts being ameliorated further downstream. Secondly, during the American War in Viet Nam between 1960 and 1975 extensive chemical defoliation was carried out in the delta which
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must have severely impacted aquatic invertebrates in that stretch. The Foundation for Worker, Veteran and Environmental Health has documented areas that were sprayed with defoliants during that conflict (Stellman 2010). Thirdly, there has been rapid population growth in the region especially since the mid-1970s as peaceful governments came to power and with the Asian tiger economic growth. This led to rapid expansion of cities firstly in Thailand, then Viet Nam and then Cambodia and Lao. With population growth there has been impact on wetlands with reclamation and conversion from natural wetlands to rice fields, increased urban runoff, increased riverine navigation, intensification of agriculture and aquaculture with increased use of fertilizer and pesticide and increased discharge of urban waste water (MRC 2003; 2010; 2014). There has still been relatively little development of heavy industry in most of the Lower Mekong Basin. Finally, the construction of dams firstly in the upper Mekong and tributaries, and now in the Lower Mekong, is changing the pattern of sediment transport, with a recent decrease in suspended solids especially in Lao PDR.
The estimated 2015 ecological status for each of the macroinvertebrate indicators is provided in Table 6.7. The definitions for the categories are given in Table 6.7. The expected trends in the indicators are discussed in Sections 6.7.1 to 6.7.13, respectively.
Table 6.7 Estimated 2015 ecological status for each of the macroinvertebrate indicators
Area
Insectson stones Insectson sand season Dry emergence Burrowing mayflies Snailabundance Snaildiversity Neotriculaaperta Bivalve abundance Polychaets Shrimps and crabs Littoral invertebrate diversity Benthic invertebrate diversity Zooplankton abundance 2015 2015 2015 2015 2015 2015 2015 2015 2015 2015 2015 2015 2015 Mekong River in B B C C C C NA B NA C C C B Laos PDR Mekong River in B B C C C C B B NA C C C B Laos PDR/ Thailand Mekong River in B C C C C C B B NA C C C B Cambodia
Tonle Sap NA C C NA C C NA B NA C C C B River
Tonle Sap NA NA C NA C C NA B NA C C C NA Great Lake
Mekong NA B C NA D D NA C D C C C NA Delta
The hypothesized changes in aquatic invertebrates over time are based largely on expectations about their likely responses to the changes described previously. Most invertebrates have relatively short life-cycles (1-12 months; Dudgeon 1999), so populations will recover rapidly after pulse stressors are removed.
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6.7.1 Insects on stones
There are a number of aquatic insects that live only on stones and other hard surfaces in relatively fast current. Some, such as some baetids, heptageniids and other mayflies and caddises feed on algae and other biofilm material by scraping or brushing. Some, such as simuliids, need the surfaces as an attachment site (Merritt et al. 2008). If hard surfaces are covered by fine silt they are unable to attach, and their food is buried. If hard surfaces become more abundant the abundance of the insects will also increase. In the upper river their abundance would have been higher when the sediment load of the river was lower. Erosion from China would have decreased their abundance in the 1950s with recovery as erosion reduced up to the 1970s. Increasing forest clearance and more extensive bank use by people would have increased sediment load and reduced the rate of recovery, but recent drops in suspended solids load will have increased their abundance over the past 15 years. They are not present in the silty riverine sections such as the Tonle Sap River, or in the Tonle Sap Great Lake or Delta.
Insects on stones 200
180 Mekong River in Laos PDR 160 Mekong River in Laos 140 PDR/Thailand 120 Mekong River in 100 Cambodia 80 Tonle Sap River 60 Tonle Sap Great Lake
40 Percentage to relative 2015 (100%) 20 Mekong Delta 0 1900 1950 1970 2000 2015
Figure 6.26 Insects on stones: Historic abundance estimates as % relative to 2015 (100%)
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6.7.2 Insects on sand
A number of insect species, including some caenid mayflies and gomphid dragonflies live on sand in moderate current, where they feed on detritus. If sand is covered by fine silt they are unable to survive, and if sand is scoured out they will decline. If sand becomes more abundant their abundance will increase. In the upper river their abundance would have been similar to the present when the sediment load of the river was lower. Erosion from China would have decreased their abundance in the 1950s with recovery as erosion reduced up to the 1970s. Increasing forest clearance and more extensive bank use by people would have increased sediment load and reduced the rate of recovery, but recent drops in fine suspended solids load will have increased their abundance over the past 15 years. Caenids are not present in the Great Lake, and are only present in the upper sites in the delta. In the Delta they will be impacted to some extent by sand dredging, but probably to a greater extent by reducing water quality with increasing urbanization and farming intensification.
Insects on sand 200
180 Mekong River in Laos PDR 160
140 Mekong River in Laos PDR/Thailand 120 Mekong River in 100 Cambodia Tonle Sap River relative to relative 2015 (100%) 80
60 Tonle Sap Great Lake
Percentage 40 Mekong Delta 20
0 1900 1950 1970 2000 2015
Figure 6.27 Insects on sand: Historic abundance estimates as % relative to 2015 (100%)
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6.7.3 Dry season emergence
Dry season emergence applies for many of the aquatic insects, particularly Ephemeroptera and Trichoptera. It occurs everywhere, but particularly in the mainstream in Laos PDR and Cambodia. The drop in fine suspended solids, and increasing dry season flows will have reduced emergence somewhat in the past few years, especially in the upper reaches. The high sediment load in the 1950s probably reduced emergence in these reaches around the time of the Korean War. In the Great Lake and lower reaches reduced water quality from agricultural runoff and urban runoff will have had a slight negative impact.
Dry season emergence 200
180 Mekong River in Laos PDR 160 Mekong River in Laos 140 PDR/Thailand 120 Mekong River in 100 Cambodia 80 Tonle Sap River 60 Tonle Sap Great Lake
40 Percentage to relative 2015 (100%) 20 Mekong Delta 0 1900 1950 1970 2000 2015
Figure 6.28 Dry season emergence: Historic abundance estimates as % relative to 2015 (100%)
6.7.4 Burrowing mayflies
There are a number of species of burrowing mayflies in the Mekong including species from the Palingeniidae, Ephemeridae and Pothamanthidae, which all construct burrows in fine silts and clays in slow to moderate current where they feed on detritus (Edmunds et al. 1976, Merritt et al. 2008). If fine silt is reduced their abundance will also decline. If sand becomes more abundant they will decline. In the upper river their abundance would have been similar to the present when the sediment load of the river was lower. Erosion from China would have decreased their abundance in the 1950s because of increased turbidity reducing the quality of the suspended material (with less algae) with recovery as
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Burrowing mayflies 200
180
160 Mekong River in Laos PDR
140 Mekong River in Laos PDR/Thailand 120 Mekong River in 100 Cambodia Tonle Sap River 80
60 Tonle Sap Great Lake
Percentage to relative 2015 (100%) 40 Mekong Delta
20
0 1900 1950 1970 2000 2015
Figure 6.29 Burrowing mayflies: Historic abundance estimates as % relative to 2015 (100%)
6.7.5 Snail abundance
Aquatic snails (Gastropoda) primarily live and feed on solid surfaces. They are important in the Mekong because there is an extremely high diversity, of global significance, and they are also an important food for people living along the river. Increasing levels of fine suspended material will tend to negatively impact snails because it will decrease the availability of their preferred habitat, and substantial changes in water quality will also have a negative impact. In the upper mainstream the major impacts would be the increase in fine sediment from China during the 1950s and the current drop in fine sediment from dams. Around the Great Lake and the Tonle Sap river loss of habitat from clearing of flooded forest and increased sediment and even trampling disturbance along the river bank will be major factors. In the delta the defoliation and the clearance of riparian vegetation with increased human population, and deterioration of water quality are likely to be major factors.
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Snail abundance 200
180
160 Mekong River in Laos PDR
140 Mekong River in Laos PDR/Thailand 120 Mekong River in 100 Cambodia Tonle Sap River 80
Tonle Sap Great Lake 60
Percentage relative to 2015 (100%) 40 Mekong Delta
20
0 1900 1950 1970 2000 2015
Figure 6.30 Snail abundance: Historic abundance estimates as % relative to 2015 (100%)
6.7.6 Snail diversity
Aquatic snail diversity in the lower Mekong is extremely rich, according to Groombridge and Jenkins (2002) there are at least 121 described species of which 111 are endemic, but Attwood (2009) citing Davis (1979) suggests that there are at least 285 endemic species. Diversity will most likely be impacted by the same factors impacting gastropod abundance. Increasing levels of fine suspended material will tend to negatively impact snails because it will decrease the availability of t heir preferred habitat, and substantial changes in water quality will also have a negative impact. In the upper mainstream the major impacts would be the increase in fine sediment from China during the 1950s and the current drop in fine sediment from dams (Figure 6.31). Around the Great Lake and the Tonle Sap river loss of habitat from clearing of flooded forest and increased sediment and even trampling disturbance along the river bank will be major factors. In the delta the defoliation and the clearance of riparian vegetation with increased human population, and deterioration of water quality are likely to be major factors.
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Snail diversity 200
180
160 Mekong River in Laos PDR
140 Mekong River in Laos PDR/Thailand 120 Mekong River in 100 Cambodia Tonle Sap River 80
60 Tonle Sap Great Lake
Percentagerelative to 2015 (100%) 40 Mekong Delta
20
0 1900 1950 1970 2000 2015
Figure 6.31 Snail diversity: Historic abundance estimates as % relative to 2015 (100%)
6.7.7 Neotricula aperta
Neotricula aperta is the snail host of Schistosomaisis mekongi (Figure 6.32) an important parasite of humans along parts of the Mekong (Attwood 2009). The snail appears to be relatively widespread in Cambodia, Laos PDR and northeastern Thailand, but not all populations support the parasite. It is unclear whether the parasite is unable to infect snails in some populations, or whether it is a more recent invader which is still spreading through the basin (Attwood 2009). At present the parasite primarily occurs in the region from Pakse to the 3S rivers. As a gastropod, N. aperta will be subject to the same factors as the previous two indicators, this the drop in the 1970s due to fine sediment, but a long term increase is indicated based on Attwood’s suggestion that the species is dispersing – so the increase is indicative of a wider distribution rather than increased density (Figure 6.33).
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Figure 6.32 Schematic showing the life cycle of Schistosomaisis
Neotricula aperta 200
180 Mekong River in Laos PDR 160 Mekong River in Laos 140 PDR/Thailand 120 Mekong River in 100 Cambodia 80 Tonle Sap River 60 Tonle Sap Great Lake
40 Percentage to relative 2015 (100%) 20 Mekong Delta 0 1900 1950 1970 2000 2015
Figure 6.33 Neotricula aperta: Historic abundance estimates as % relative to 2015 (100%)
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6.7.8 Bivalve abundance
Bivalve molluscs feed by filtering fine suspended organic material from the water (Smith 2001). They require soft sediments in which to shelter and tend to be most abundant in large rivers. Populations are indicated as reducing in the 1950s due to increased sediment from China (which was probably relatively high in inorganic content and so not suitable as food material for bivalves) and more recently due to the drop in fine particulate suspended material. In the delta populations must have been severely impacted by defoliation. Harvesting by humans and dredging will also adversely impact bivalves.
Bivalve abundance 200
180 Mekong River in Laos PDR 160 Mekong River in Laos 140 PDR/Thailand 120 Mekong River in 100 Cambodia 80 Tonle Sap River 60 Tonle Sap Great Lake
40 Percentage to relative 2015 (100%) 20 Mekong Delta 0 1900 1950 1970 2000 2015
Figure 6.34 Bivalve abundance: Historic abundance estimates as % relative to 2015 (100%)
6.7.9 Polychaetes
Polychaetes are a group of worms which live in soft sediments and include many species which are tolerant of high salinity. They are commonly found in estuaries and only occur in this river system in the Mekong Delta (Pham Vien Mien 2002) where their abundance will be impacted by salinity, which will favour them over other groups of worms, and water quality which will negatively impact them. The defoliation will have had a substantial impact on polychaetes in the 1970s, and deteriorating water quality, and dredging in the delta will have negatively impacted populations more recently (Figure 6.35).
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Polychaets 200
180 Mekong River in Laos PDR 160 Mekong River in Laos 140 PDR/Thailand 120 Mekong River in 100 Cambodia 80 Tonle Sap River 60 Tonle Sap Great Lake
40 Percentage to relative 2015 (100%) 20 Mekong Delta 0 1900 1950 1970 2000 2015
Figure 6.35 Polychaetes: Historic abundance estimates as % relative to 2015 (100%)
6.7.10 Shrimps and crabs
Shrimps and crabs are important dietary items for people living along the river. Crabs require stony or solid substrata with shelter to survive, but shrimps are active swimmers persisting in the water column as well as sheltering in aquatic vegetation and amongst bed elements. Both feed on coarse and fine detritus and algae (Yule and Yong Hoi Sen 2004). In the 1950s the sediment from China would have adversely affected populations with impacts persisting through to 1970s. More recently harvesting by people, changes to littoral habitat, and changes in water quality have probably slightly negatively impacted these groups. In the delta, defoliation would have had a marked negative impact in the 1970s.
Shrimps and crabs 200
180 Mekong River in Laos PDR 160 Mekong River in Laos 140 PDR/Thailand 120 Mekong River in 100 Cambodia 80 Tonle Sap River 60 Tonle Sap Great Lake
40 Percentage to relative 2015 (100%) 20 Mekong Delta 0 1900 1950 1970 2000 2015
Figure 6.36 Shrimps and crabs: Historic abundance estimates as % relative to 2015 (100%)
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6.7.11 Littoral invertebrate diversity
Littoral invertebrate species diversity will have decreased slightly over most of the river over the total time period. Littoral invertebrates in environments such as this are often most affected by changes in runoff quality from urban and agricultural areas, as well as changes in habitat condition. The two most substantial impacts would have been the Chinese erosion in the upper river in the 1950s and defoliation in the delta in the 1970s. Around the Great Lake clearance of the flooded forest would have been an important factor contributing to littoral invertebrate decline.
Littoral invertebrate diversity 200
180 Mekong River in Laos PDR 160 Mekong River in Laos 140 PDR/Thailand 120 Mekong River in 100 Cambodia 80 Tonle Sap River 60 Tonle Sap Great Lake
40 Percentage to relative 2015 (100%) 20 Mekong Delta 0 1900 1950 1970 2000 2015
Figure 6.37 Littoral Invertebrate Diversity: Historic abundance estimates as % relative to 2015 (100%)
6.7.12 Benthic invertebrate diversity
Benthic invertebrates will be impacted by a similar range of factors to littoral invertebrate diversity, however because of their preference for soft sediments they will be favoured by increased fine particulate suspended material, as long as it contains sufficient organic content. On the mainstream benthic invertebrates will have been little affected by the erosion in China, but are probably being affected by the reduced FPM in the past few years. Defoliation would have had a marked effect in the delta with a recovery following. Reduced water quality will be impacting delta benthic assemblages currently, which is apparent in the MRC biomonitoring results
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Benthic invertebrate diversity 200
180 Mekong River in Laos PDR 160 Mekong River in Laos 140 PDR/Thailand 120 Mekong River in 100 Cambodia 80 Tonle Sap River 60 Tonle Sap Great Lake
40 Percentage to relative 2015 (100%) 20 Mekong Delta 0 1900 1950 1970 2000 2015
Figure 6.38 Benthic invertebrate diversity: Historic abundance estimates as % relative to 2015 (100%)
6.7.13 Zooplankton abundance
Zooplankton abundance will be impacted by flow regime (with more plankton present under low flow conditions) turbidity (more plankton when water is clear so more rapid algal growth) location (more plankton downstream) and water quality. Plankton in the upper stretches will have been negatively impacted by Chinese erosion, and positively by the recent drop in FPM. The constructed storages may also contribute plankton to the river. Further downstream increasing turbidity through increased bank erosion and increased navigation will decrease zooplankton (although that might be somewhat counteracted by increased fishing pressure reducing predator pressure). In the delta the defoliation will have negatively impacted zooplankton, but water quality will also have had (probably) a negative impact.
Zooplankton abundance 200
180 Mekong River in Laos PDR 160 Mekong River in Laos 140 PDR/Thailand 120 Mekong River in 100 Cambodia 80 Tonle Sap River 60 Tonle Sap Great Lake
40 Percentage to relative 2015 (100%) 20 Mekong Delta 0 1900 1950 1970 2000 2015
Figure 6.39 Zooplankton abundance: Historic abundance estimates as % relative to 2015 (100%)
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6.8 Status and trends: Fish
Overall, consumption of fish and other aquatic animals (OAAs) in the LMB is estimated at about 2.8- 3.2 million tonnes, with about one-fifth of this consumption comprising OAAs (MRC 2010; Hortle, 2007). Aquaculture contributes about 1.6 million tonnes and about one million tonnes of aquatic products are exported from the basin, so the total yield is in excess of 4.5 million tonnes. Capture fisheries contributes 1.9 - 2.6 million tonnes/year. At current first sale prices (US$ 1-1.80/kg) the total value of the fishery is US$ 3.7-7 billion per year but its value should also be judged by its replacement cost, profitability, contribution to food security and nutrition (MRC 2010). The livelihood benefit of the resource, in terms of nutrition, income and employment, is crucial, particularly for rural poor, who have few other livelihood options. Between 40 and 60% of the catch is dependent on fish species that migrate long distances along the Mekong mainstream and into its tributaries (Barlow et al. 2008), and these fish stocks are especially vulnerable to dams built in the middle and lower Mekong basin.
The Mekong fish communities are characterised by high diversity of fish species with many exhibiting complex life cycles that involve migration between different areas of the river, particularly upstream migration to spawning areas. The general understanding of migration patterns in the Mekong is that there are three main groupings: the lower migration system (from the Delta up to Khone Falls), the middle migration system (from Khone Falls up to Vientiane) and the upper migration system (from Vientiane up to China) (Figure 6.40; Poulsen et al. 2002). However, there are also a number of species that migrate between these zones, and some species (possibly as many as 30 and often commercially valuable white fishes) that migrate longer distances. For example, Pangasius krempfi, an important commercial species, spends a part of its life at sea and in the brackish water of the Mekong Delta before returning to spawn in fresh water. This anadromous fish travels at least 720 km to the Khone Falls, and possibly further upstream (Hogan 2007). According to Poulsen et al. (2002) at least one third of Mekong fish species need to migrate between downstream floodplains where they feed and upstream tributaries where they breed.
Spawning habitats Mekong fishes, are generally believed to be associated with: (1) rapids and pools of the Mekong mainstream and tributaries; and (2) floodplains (e.g. among certain types of vegetation, depending on species). River channel habitats are, for example, used as spawning habitats by most of the large species of pangasiid catfishes and some large cyprinids such as Cyclocheilichthys enoplos, Cirrhinus microlepis, and Catlocarpio siamensis that then rely on particular hydrological conditions to distribute the offspring (eggs and/or larvae) to downstream nursery rearing habitats. Floodplain habitats are used as spawning habitats mainly by black-fish species (Poulsen et al. 2002). For fishes that spawn in main river channels, spawning is believed to occur in stretches where there are many rapids and deep pools, e.g. (1) the Kratie–Khone Falls stretch; (2) the Khone Falls to Khammouan/Nakhon Phanom stretch; and (3) from the mouth of the Loei River to Bokeo/Chiang Khong. The Kratie-Khone Falls stretch and the stretch from the Loei River to Luang Prabang are particularly important for spawning (Poulsen et al. 2002).
To complete these migrations requires unobstructed passage upstream, as well as the capacity for adults, larvae and juveniles to migrate or drift downstream.
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Figure 6.40 Generalized migration systems in the Lower Mekong Basin (Source: Poulsen et al. 2002a).
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Capture fisheries form an important source of livelihoods and contribute massively to food security in the LMB. Fisheries takes place in all habitats across the region but are concentrated in terms of production volume in the middle and lower migration zones, especially I the delta and Cambodian floodplain and around the Tonle Sap / Great Lake system in Cambodia.
Unfortunately data to understand the trends in fisheries productivity and yield are heavily dependent on government statistical surveys and fisheries administration and MRC surveys, which tend to be unreliable, fragmented and grossly underestimate the catch. Nevertheless they do show basic trends in catches against which measures of status and impact can be measured.
Fisheries in the Cambodian sector of the Mekong show an upward trend in catches between 1996 and 2011 (Figure 6.41) but thereafter are unavailable because of a change in the governance of fisheries in Cambodia and disbanding of the lot system. Consequently data are no longer collected using formal reporting procedures. Catches from the dai fishery fluctuate widely and contributes between about 7500 and 46,000 tonnes (or about 7%) of Cambodia’s total annual landings of fish from the Mekong Basin (valued at more than US$6 million in 2006).
70,000
FA4 FA5 FA6 FA7 60,000 50,000 40,000 30,000 20,000 Production (tonnes) Production 10,000
0
1998 1995 1996 1997 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011
Figure 6.41 Capture fisheries production for Cambodia (2000-2013) (FA4- Kratie; FA5 – Phnom Penh; FA6- Tonle Sap River; FA7 – Tonle Sap Great Lake ).
The Vietnamese part of the Mekong delta is the most important fishery in Viet Nam contributing nearly 40 % of the total national production. Total capture fisheries production in the delta has increased from 552,240 t (1995) to over one million tonnes in 2012 (Figure 6.42), nearly doubling production during 17 years. Most of the production comes from marine fisheries and inland fisheries catch has declined in recent years. For example, in 2011 marine production accounted 88.0 % of the total capture production with only 12 % from inland production. Whilst there is an increase in marine production from 465,732 t in 2000 to 691,700 t in 2013 there has been a commensurate fall in inland (freshwater fish) from 188,873 t (2000) to 124,626 t in 2011 (Figure 6.42).
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1400 An Giang Đồng Tháp Cần Thơ Hậu Giang Vĩnh Long Tiền Giang Long An Bến Tre Kiên Giang Trà Vinh 1200 Sóc Trăng Bạc Liêu Cà Mau
1000 1000
800
600
400 (inland and marine) t t x marine) and (inland
200 Annual aquatic production from the Mekong Delta Mekong the from production aquatic Annual
0
1995 1996 1999 2000 2003 2004 2007 2008 2011 2012 2013 1998 2001 2002 2005 2006 2009 2010 1997 Figure 6.42 Variation in capture fisheries (fish and other aquatic animals) production by provinces in the Mekong delta (Source: GSO).
The fisheries of the Lower Mekong Basin are under stress from a number of pressures associated economic, social and infrastructural development over the past 150 years. The main pressures are agricultural land development including massive expansion of rice farming and deforestation, over exploitation of fisheries resources by intensive fishing pressure, hydropower development, mining, sand mining, urbanization and industrial development and associated pollution. In addition, climate change is affecting the hydrological regime and potentially overriding the other factors. Fishing pressure and deforestation have occurred from very early on because of food demand, population growth and forest clearance, especially during the Vietnam War period but again more recently. Intense fishing pressure became prominent in the 1950s associate with population growth but was prevalent later in the Laos PDR zone of the river. Fishing pressure also increased with improved access through infrastructural development (roads) and the use of modern fishing gears (nylon gill nets) being available at affordable prices, thus accessible for subsistence and commercial fisheries. Agriculture development has expanded since the 1970s, when the governments promoted irrigated rice cultivation by providing irrigation channels and pumping stations along the Mekong river and tributaries. Some of flooded forests have been converted to rice fields or other crop production. Considerable areas of natural lands and floodplains have been reclaimed for agriculture and aquaculture, which has reduced fisheries production. For example, rice farming has evoled from one crop per year in the Delta (floating rice: 6 months during the flood season) to production of up to three crops per year (each crop lasts for about 3 months). Intensive rice farming and aquaculture are promoted to increase productivity but
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have had a negative impact on inland fish production due to habitat loss and disconnection of the floodplain habitat. Rubber plantations have also boomed after the government gave land concessions to foreigners to invest in agricultural development including rubber, teak and cash crop such as bananas. All of these activities clear forest, which affects top soils and causes land slides, and increase sedimentation in the rivers. Flood mitigation and embankments are now common around big cities along the Mekong River. These have blocked fish migration into swamps and riparian floodplain areas, and have redcued the riparian vegetation that fish use as food and spawning habitat in the flooding period. Mining in the LMB has boomed since the early 2000s when foreign investors started mining, in particular gold, leading to soil degradation and toxic pollution to soils and rivers. Hydropower development is, however, one of the main pressures, as governments have set priorities to develop hydropower for overcome poverty. The dams act as barriers to fish migration to the upstream areas for spawning and feeding. The Mekong and tributaries dams development were intensified at the beginning of 2000s, when government declared Laos PDR will be the battery of ASEAN.
The change evolution in scale of intensity of these various pressures in different BioRA zones over time are illustrated in Table 6.8 and shows the main intensification was in the 1970s with a second expansion since 2000 (see also Section 6.3).
Table 6.8 Trends in pressures acting on fisheries in the BioRA zones since 1900
Pressure on fisheries 1900 1950 1970 2000 2015
Laos PDR FA1, FA2 & FA3
1. Intense fishing
2. Agriculture development
3. Flood mitigation
4. Deforestation
5. Rubber plantation
5. Mining
6. Hydro power
7. Alien species
Thailand FA2 & FA3
1. starting monocrop plantation
2. aquaculture promotion
3. Economic scale fisheries
4. Deforestation
5. Irrigation networks system
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Pressure on fisheries 1900 1950 1970 2000 2015
Cambodia FA4, FA5, FA6 & FA7
Intense fishing pressure
Agriculture development
aquaculture development
Deforestation
Hydropower
Mining
Climate change
Exotic species
Vietnam FA7 and FA8
Fishing pressure
Agriculture development
Aquaculture development
Deforestation
Urbanization + pollution
Climate change
Exotic species
The estimated 2015 ecological status for each of the fisheries indicators reflect the pressures described above and are provided in Table 6.9. The definitions for the categories are given in Table 6.2. The historical trends in the indicators since 1900 are discussed in Sections 6.8.1 to 6.8.11.
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Table 6.9 Estimated 2015 ecological status for each of the fisheries indicators
ecies
Area
distant white) distant white)
nativespecies
-
Rithron resident species Mainchannel resident (long species Mainchannel spawner white) (short distance species Floodplain(grey) spawner species Eurytopic (generalist) species Floodplain resident (black fish) Estuarine resident species Anadromousspecies Catadromousspecies sp Marinevisitor Non 2015 2015 2015 2015 2015 2015 2015 2015 2015 2015 2015 Mekong River C C C N/A B N/A N/A D D N/A E in Laos PDR Mekong River in Laos PDR/ C C C D D C N/A D D N/A D Thailand Mekong River C B N/A B N/A B N/A C C N/A C in Cambodia Tonle Sap N/A B N/A B N/A B N/A C C N/A C River Tonle Sap N/A B N/A C C B N/A B B N/A D Great Lake
Mekong Delta N/A B N/A C C B N/A B B B E
6.8.1 Rithron resident species
Rhithron species are rheophilic, main channel residents that inhabit rapids and riffle areas. They are generally sedentary, of small size and are equipped with suckers or spines to enable them to grip rocks and other submersed objects. They may also have elongated or laterally flattened forms that allow them to live in the interstitial spaces of the rock and cobble substrate. Species of this guild are found throughout FA1- FA4 but not below Kratie and their abundance declines as riffle/rapid habitat becomes less common downstream of Vientiane.
Activities that disturb the riffle structure, such as seasonal desiccation of riffles, increases in sediment load that choke the interstitial spaces, erosion or extraction of gravel or complete submergence of the riffle by impoundments, especially the latter, have affected this group although mostly in recent years (Figure 6.43). These species are also vulnerable to overexploitation.
The main anthropogenic drivers of change in rhithron species include: fishing pressure; gravel extraction; sedimentation; flow regulation.
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Rhithron species 300
Mekong River in Laos PDR 250
Mekong River in Laos 200 PDR/Thailand Mekong River in 150 Cambodia Tonle Sap River 100 Tonle Sap Great Lake 50 Percentagerelative to 2015 (100%) Mekong Delta
0 1900 1950 1970 2000 2015
Figure 6.43 Rithron resident species: Historic abundance estimates as % relative to 2015 (100%)
6.8.2 Main channel resident (long distant white) species
These are generally longitudinal migrants that move within the main river channel, or up and down tributaries, and do not enter the floodplain. They require relatively high dissolved oxygen levels, and as such they are sensitive to reductions in water quality. Most whitefish guild species have one breeding season per year that is closely linked to peak flows and rely on increased flow as cues for migration and maturation.
Species in this guild frequently are vulnerable to overexploitation and other human disturbances, and many have become locally extinct in the Mekong, and some are on the verge of extirpation, e.g. the giant Mekong catfish. These species have disappeared where the river is dammed, preventing migration, although they may respond favourably to fish passage facilities they suffer from downstream mortality passing through the impoundment and/or turbines. They are also vulnerable to changes in the timing of high flow events that are inappropriate to their breeding seasonality. They are affected if flow rates are too fast or too slow for the needs of drifting larvae. These species may be recovered by ensuring longitudinal connectivity by appropriate fish passage facilities or removal of cross-channel dams, and by ensuring the timing and quantity of flows are adequate to promote breeding and ensure the arrival of fry at the adult habitats. Proliferation of dams, especially in the tributaries, and overfishing are largely responsible for the slow decline of these species in the LMB (Figure 6.44).
The main anthropogenic drivers of change in long distance migrating whitefish species include: fishing pressure; dam development and flow regulation.
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Main channel resident (long distant white) species 300
250 Mekong River in Laos PDR
200 Mekong River in Laos PDR/Thailand Mekong River in 150 Cambodia
Tonle Sap River relative to relative 2015 (100%)
100 Tonle Sap Great Lake
Percentage Mekong Delta 50
0 1900 1950 1970 2000 2015
Figure 6.44 Main channel resident (long distant white) species: Historic abundance estimates as % relative to 2015 (100%)
6.8.3 Main channel spawner (short distance white) species
As was the case for the previous indicator, species in this guild are also longitudinal migrants, but tend to be more localised and can usually complete their life cycles within extended reaches of rivers and into tributaries. They may also undertake lateral migrations onto and off of the floodplain, which they use for breeding, nursery grounds and feeding. Fry may be resident at more upstream locals for a certain period and may occupy upstream floodplains.
These species are also vulnerable to damming and to lowered water quality that prevents migration, although they may respond favourably to appropriately designed fish passes. They are also adversely affected by changes in the timing of high flow events that are inappropriate to their breeding seasonality, as well as to changes in the quality of upstream breeding habitats, particular if they become choked with silt and/or have insufficient flow to aerate the developing eggs. The species may be recovered by ensuring longitudinal connectivity through fish passage facilities, and by ensuring the timing and quantity of flows are adequate to promote migration.
Species in this guild have started to greatly diminish in abundance (Figure 6.45) as a result of damming (hydropower and water control structures) in the tributaries. These structures disrupt migration and deny access to the floodplain for developing fry and juveniles8. The species may be recovered by ensuring longitudinal and lateral connectivity by fish passes, removal of cross channel dams or removal of lateral levees, and by ensuring the timing and quantity of flows are adequate to ensure access to the floodplain.
8 Either because flood levels are inadequate to flood riparian lands, or because these riparian floodplains are cutoff from the river by levees.
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Main channel spawner (short distance white) species 300
Mekong River in Laos PDR 250
Mekong River in Laos 200 PDR/Thailand Mekong River in 150 Cambodia Tonle Sap River 100 Tonle Sap Great Lake 50 Percentage to relative 2015 (100%) Mekong Delta
0 1900 1950 1970 2000 2000
Figure 6.45 Main channel spawner (short distance white) species: Historic abundance estimates as % relative to 2015 (100%)
The main anthropogenic drivers of change in short distance migrating whitefish species include: fishing pressure; dam development and flow regulation.
6.8.4 Floodplain spawner (grey) species
Species in this guild have declined in the Mekong (Figure 6.46) as the floodplains have become disconnected from the main channel and desiccated through poldering and levee construction, mainly to make way for rice production. These fish can thrive in shallow, isolated wetlands, rice-fields and drainage ditches, but are restricted from doing so because intensification of rice production, especially production of a third crop in the delta area, and the associated herbicide and pesticide use, which prevents colonisation of the rice fields. The species may be recovered by reconnection of floodplain water bodies to the main channel.
The main anthropogenic drivers of change in greyfish species include: fishing pressure; dam development and flow regulation; agricultural development, especially for rice production; isolation of the floodplain by urbanization and flood control.
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Floodplain spawner (grey) species 300
250 Mekong River in Laos PDR
Mekong River in Laos 200 PDR/Thailand Mekong River in 150 Cambodia Tonle Sap River
100 Tonle Sap Great Lake
Percentage to relative 2015 (100%) 50 Mekong Delta
0 1900 1950 1970 2000 2015
Figure 6.46 Floodplain spawner (grey) species: Historic abundance estimates as % relative to 2015 (100%)
6.8.5 Eurytopic (generalist) species
These species are extremely adaptable and are often tolerant of low dissolved oxygen concentrations, hence the reason for little deterioration of this guild (Figure 6.47). They are generally repeat breeders and/or breed during both high and low flow phases of the hydrograph; as such breeding may be independent of flow clues.
Eurytopic (generalist) species 300
250 Mekong River in Laos PDR
Mekong River in Laos 200 PDR/Thailand Mekong River in 150 Cambodia Tonle Sap River
100 Tonle Sap Great Lake
Percentage to relative 2015 (100%) 50 Mekong Delta
0 1900 1950 1970 2000 2015
Figure 6.47 Eurytopic (generalist) species: Historic abundance estimates as % relative to 2015 (100%)
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Species in this guild are usually fairly resistant to change, and thus considered eurytopic. In the Mekong, they are sensitive to river straightening and bank construction, and agricultural development and loss of flooded forest areas that has suppressed habitat availability in the floodplain. Species can be recovered by rehabilitating main channel diversity and floodplain habitat, particularly by reconnection of abandoned side arms and active backwaters.
The main anthropogenic drivers of change in eurytopic species include: fishing pressure; agricultural development, especially for rice production; isolation of the floodplain by urbanization and flood control.
6.8.6 Floodplain resident (black fish)
This guild consists of lentic species that are mainly floodplain residents that do not migrate but may move between floodplain pools, swamps, dead arm backwaters and the inundated floodplain. They are tolerant of complete anoxia, which can occur in isolated floodplain pools and wetlands. They are usually sedentary and sometimes show extremes of parental care with nest building and viviparity. They may also survive in low numbers in deoxygenated backwaters and in marginal and floating vegetation, and form important components in rice field and ditch faunas. This guild is negatively impacted in the Mekong (Figure 6.48) by floodplain reclamation schemes that have drained and/or filled the marginal water bodies and wetlands in which the component species live. They are also fished heavily.
Floodplain resident (black fish) 300
Mekong River in Laos PDR 250
Mekong River in Laos 200 PDR/Thailand Mekong River in 150 Cambodia Tonle Sap River 100 Tonle Sap Great Lake 50 Percentage to relative 2015 (100%) Mekong Delta
0 1900 1950 1970 2000 2015
Figure 6.48 Floodplain resident (black fish): Historic abundance estimates as % relative to 2015 (100%)
The main anthropogenic drivers of change in blackfish species include: fishing pressure; dam development and flow regulation; agricultural development, especially for rice production;
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isolation of the floodplain by urbanization and flood control.
6.8.7 Estuarine resident species
The lower reaches of the Mekong, in the delta, is characterised by brackish water mangroves and associated transitional water environment. The species comprising the estuarine resident guild are basically stenohaline, freshwater species that move with daily and seasonal changes in salinity and are sensitive to interventions, such as river mouth barrages or changes in the connectivity of mangrove systems with the sea and flow changes. They generally breed and feed in fresh water but move up and down the estuarine system depending on flow and their tolerance to salinity.
Species in this guild have been affected negatively by reductions in flow that allow saline waters to penetrate upstream or to occupy permanently the lower deltaic system and explain the decline in recent years (Figure 6.49). They have also been negatively affected by shrimp farming in delta and destruction of the mangrove forests. Finally, there has been a proliferation of fishing for marine and estuarine species that is compromising recruitment, especially to the coastal fishery.
Estuarine resident species
800 Mekong River in Laos PDR 700
600 Mekong River in Laos PDR/Thailand 500 Mekong River in Cambodia 400 Tonle Sap River 300 Tonle Sap Great Lake 200
Percentage to relative 2015 (100%) 100 Mekong Delta
0 1900 1950 1970 2000 2015
Figure 6.49 Estuarine resident species: Historic abundance estimates as % relative to 2015 (100%)
The main anthropogenic drivers of change in estuarine resident species include: fishing pressure; shrimp farming and destruction of the mangrove forestry; agricultural development, especially for rice production; isolation of the floodplain by urbanization and flood control.
6.8.8 Anadromous species
This guild is also be affected by loss in longitudinal connectivity, similar to long-distance whitefish migrants, preventing anadromous species reaching these upstream spawning and nursery habitats.
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This loss can take the form of reduced flows (natural or artificial) restricting the ability of fish to negotiate obstructions (natural or artificial). Their numbers in the Mekong have declined considerably in recent years because of dam and water resource development in tributary rivers (Figure 6.50).
Anadromous species 300
Mekong River in Laos PDR 250
Mekong River in Laos 200 PDR/Thailand Mekong River in 150 Cambodia Tonle Sap River 100 Tonle Sap Great Lake 50 Percentage to relative 2015 (100%) Mekong Delta
0 1900 1950 1970 2000 2015
Figure 6.50 Anadromous species: Historic abundance estimates as % relative to 2015 (100%)
The main anthropogenic drivers of change in anadromous species include: fishing pressure; dam development and flow regulation.
6.8.9 Catadromous species
These species require a lower salinity residence phase in their development, or species that use estuaries as transit routes between the marine and freshwater environments. They are distinguished from semi-anadromous species by the greater dependence on the freshwater phase of their life cycle and by the greater distance they penetrate into fresh waters. In the Mekong, these species have been affected by much the same conditions as affect the whitefish guilds and are threatened by interruptions to longitudinal connectivity, although they may respond favourably to fish passes, and by changes to the hydrograph at times critical to migration. They are equally affected by adverse changes to the marine ecosystems. Their numbers in the Mekong have again declined in recent years (Figure 6.51).
The main anthropogenic drivers of change in long distance migrating whitefish species include: fishing pressure; dam development and flow regulation.
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Catadromous species 300
Mekong River in Laos PDR 250
Mekong River in Laos 200 PDR/Thailand Mekong River in 150 Cambodia Tonle Sap River 100 Tonle Sap Great Lake 50 Percentage to relative 2015 (100%) Mekong Delta
0 1900 1950 1970 2000 2015
Figure 6.51 Catadromous species: Historic abundance estimates as % relative to 2015 (100%)
6.8.10 Marine visitor species
This guild consists of marine species that penetrate into fresh waters. They are stenohaline or euryhaline, and differences between the guilds are based on the relative use they make of the marine and freshwater habitats. Species in this guild have affected negatively by reductions in flow that allow saline waters to penetrate upstream or to occupy permanently the lower deltaic system and explain the decline in recent years (Figure 6.52).
Marine visitor species 200
180 Mekong River in Laos PDR 160 Mekong River in Laos 140 PDR/Thailand 120 Mekong River in 100 Cambodia 80 Tonle Sap River 60 Tonle Sap Great Lake
40 Percentage to relative 2015 (100%) 20 Mekong Delta 0 1900 1950 1970 2000 2015
Figure 6.52 Marine visitor species: Historic abundance estimates as % relative to 2015 (100%)
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They have also been negatively affected by shrimp farming in delta and destruction of the mangrove forests. Finally, there has been a proliferation of fishing for marine and estuarine species that is compromising recruitment, especially to the coastal fishery.
The main anthropogenic drivers of change in estuarine resident species include: fishing pressure; shrimp farming and destruction of the mangrove forestry.
6.8.11 Non-native species
This grouping has been included because of the proliferation of non-native species, especially the Delta and in areas around fishing facilities in Northern Laos and Thailand. The numbers have increased both from escape from fish farms and through deliberate stocking. They have exploded in their contribution to catches in recent years (Figure 6.53), partly because they are generalist species that can exploited niche made available through lost migratory species. This group is a good indicator of environmental degradation.
Non-native species 200
180 Mekong River in Laos PDR 160 Mekong River in Laos 140 PDR/Thailand 120 Mekong River in 100 Cambodia 80 Tonle Sap River 60 Tonle Sap Great Lake
40 Percentage to relative 2015 (100%) 20 Mekong Delta 0 1900 1950 1970 2000 2015
Figure 6.53 Non-native species: Historic abundance estimates as % relative to 2015 (100%)9
6.9 Status and trends: Herpetofauna
The estimated 2015 ecological status for each of the macroinvertebrate indicators is provided in Table 6.10. The definitions for the categories are given in Table 6.7. The expected trends in the indicators are discussed in Sections 6.9.1 to 6.9.8, respectively.
9 Entered by Technical Lead to illicit comment.
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6.9.1 Ranid and microhylid amphibians
This guild includes members of families Ranidae, Microhylidae and Dicroglossidae who are associated with water bodies for whole or part of their life-cycle. Two representative species have been selected to represent this guild; on each from Ranidae (Hylarana nigrovittata) and one from Dicroglossidae (Hoplobatrachus rugulosus). The population status of F. limnocharis in the LMB is similar to that of Hoplobatrachus rugulosus.
Table 6.10 Estimated 2015 ecological status for each of the herpetofauna indicators
-
Area amboinensis
Rananigrovittata Hoplobatrachus rugulosus Enhydrisbocourti Cylindrophisruffus Amydacartilaginea Malayemys subtrijuga Cuora Heosemysgrandis Amphibians human availablefor consumption Aquatic/semi aquaticreptiles human availablefor exploitation Speciesrichness of riparian amphibians Speciesrichness of riparian reptiles 2015 2015 2015 2015 2015 2015 2015 2015 2015 2015 2015 2015
Mekong River in C C NA NA NA NA NA NA C C C Laos PDR Mekong River in Laos PDR/ C C NA NA C NA NA NA C C C Thailand Mekong River in C C D NA C NA D D C C C Cambodia
Tonle Sap River NA C D C C NA D D C C C
Tonle Sap NA C D C C E D D C D C C Great Lake
Mekong Delta NA C D C C D E D C D C D
6.9.1.1 Hylarana nigrovittata (Blyth 1856)
The Black-striped frog (Hylarana nigrovittata), is known from southern Yunnan, China, and southern Myanmar through Thailand, Lao People's Democratic Republic, Viet Nam and Cambodia (Bourret 1942; Taylor 1962; Inger et al. 1999; Stuart 1999). However, it does not occur in Tonle Sap, the Cambodian floodplain and the Mekong Delta (Nguyen et al. 2009).
It is most often found between 200 and 600 masl. but ranges as widely as 60 - 1 200 masl. It inhabits gentle streams in evergreen forest, including evergreen galleries in deciduous forest areas (Inger et al. 1999; Stuart 1999). Eggs are deposited in the forest and tadpoles live in quiet sections of stream
Page 96 or in slow-moving water (Bain and Hurley 2011).
The main potential threats to this species are the loss of forest canopy over its streams and hydrological changes (van Dijk et al. 2004). Its range in the Lower Mekong Basin is threatened by habitat destruction and degradation for agriculture, wood and power plants (van Dijk et al. 2004).
Little is known about the population status of this species. The species is listed as Least Concern in IUCN Red List in view of its wide distribution and presumed large population. The species is subject to some threats but it is unlikely to be declining fast enough to qualify for listing in a more threatened category (van Dijk et al. 2004). Within the LMB, the species has been declining slightly in the last 15 years. The estimated historical changes in cover provided in Figure 6.54, indicate both cover and quality of remaining vegetation.
Rana nigrovittata 400.00
350.00 Mekong River in Laos PDR
300.00 Mekong River in Laos PDR/Thailand 250.00 Mekong River in 200.00 Cambodia Tonle Sap River 150.00
100.00 Tonle Sap Great Lake
Percentage to relative 2015 (100%) 50.00 Mekong Delta
0.00 1900 1950 1970 2000 2015
Figure 6.54 Ranid and microhylid amphibians (Rana nigrovittata): Historic abundance estimates as % relative to 2015 (100%)
The main anthropogenic drivers of change in ranid and microhylid amphibians include: land cover changes; impoundments; run-of-river abstractions; sediment mining; climate change.
6.9.1.2 Hoplobatrachus rugulosus
The East Asian bullfrog (Hoplobatrachus rugulosus) is widespread from central, southern and south- western China including Taiwan, Hong Kong and Macau to Myanmar through Thailand, Lao People's Democratic Republic, Viet Nam and Cambodia south to the Thai-Malay peninsula (Nguyen et al. 2009; Diesmos et al. 2004).
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The species lives in a variety habitat including paddy fields, irrigation infrastructure, fishponds, ditches, floodplain wetlands, forest pools, and other wet areas. The tadpoles live in pools and ponds (Bain and Hurley 2011). The adults are effective predators on other species of frogs and its larvae prey on tadpoles of other species. The tiger frog has been reported from sea level to 700 masl (Diesmos et al. 2004).
Hoplobatrachus rugulosus adapts well to wet rice culture, and has managed to thrive in these conditions, although harvesting pressure and agricultural pollution, specifically herbicides, pesticides, are very real threats. The species is listed as Least Concern in view of its wide distribution, tolerance of a broad range of habitats and presumed large population (Figure 6.55). The species as a whole is not under threat and the global population is stable (Diesmos et al. 2004), but it has become rare in the lowland areas because of over-exploitation, particularly the larger animals (Diesmos et al. 2004). Hoplobatrachus rugulosus is the most commonly exploited amphibian species in Viet Nam’s Mekong Delta, as a result the population in the Delta has declined greatly in the last 25 years (Hoang and Vo 2013; Nguyen et al. 2006).
Hoplobatrachus rugulosus 400
350 Mekong River in Laos PDR 300 Mekong River in Laos 250 PDR/Thailand Mekong River in 200 Cambodia Tonle Sap River relative to relative 2015 (100%) 150 Tonle Sap Great Lake 100
Percentage Mekong Delta 50
0 1900 1950 1970 2000 2015
Figure 6.55 Ranid and microhylid amphibians (Hoplobatrachus rugulosus): Historic abundance estimates as % relative to 2015 (100%)
The main anthropogenic drivers of change in the abundance of Hoplobatrachus rugulosus include: harvesting pressure; agricultural pollution; land use change;
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impoundments; abstractions.
6.9.2 Aquatic serpents
This guild is composed of viviparous species that lives entirely in water (mainstem and floodplain) and feeds mainly on fishes and other aquatic species. Change in flow, in terms of timing and duration of high and low flow regimes will directly influence their offspring or indirectly through their habitats and food availabilities (fishes).
Indicator species included members of Homalopsidae (e.g., Enhydris spp. and Erpeton tentaculatum) and Acrochordidae (e.g., Acrochordus spp).
6.9.2.1 Enhydris bocourti
The Bocourt’s water snake (Enhydris bocourti) is endemic to Southeast Asia including Thailand, Malaysia, Cambodia, and Viet Nam (Murphy 2007). Along Mekong River, this species is reported to occur in the Cambodian floodplain, the Tonle Sap Great Lake and the Mekong delta. It occurs in swamps, shallow lakes, pools and other stagnant water habitats. It feeds mainly on fish, but may also consume young frogs (Murphy 2007).
Over exploitation is the main threat to this species in its range in LMB. Habitat loss due to wetland conversion is also a cause of species decline.
At the second decade of the 20th century, Smith (1914) reported that Bocourt water snake was common in the rural areas surrounding Bangkok. There is reported decline of this species in Cambodia, due to the harvest and export of this species to China. For example, from 1991-2001 Zhou and Jiang (2004) reported about 16 000 live snakes being exported to China, representing 4% of the live snakes imported into China over this period. This species is heavily exploited in the Tonle Sap Great Lake in Cambodia, and populations are declining (Brooks et al. 2007). This species is among the most exploited reptile in Mekong Delta (Stuart 2000; Hoang and Ho 2013; Hoang and Vo 2013; Goodall and Simon 2010). The population appears to be in decline because fishermen report that they are more difficult to find than they have been in the past (Goodall and Simon 2010).
The main anthropogenic drivers of change in the abundance of Enhydris bocourti include: land use changes: including wetland conversion to paddy field and urbanisation; irrigation: drainage of wetland areas, habitat loss and degradation; harvesting pressure: overexploitation for food and crocodile farm, wildlife trade, skins; agricultural pollution: pesticides, fertilizer… impact on the snake and deplete their foods.
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Enhydris bocourti 400
350 Mekong River in Laos PDR
300 Mekong River in Laos PDR/Thailand 250 Mekong River in 200 Cambodia Tonle Sap River 150
100 Tonle Sap Great Lake
Percentage to relative 2015 (100%) 50 Mekong Delta
0 1900 1950 1970 2000 2015
Figure 6.56 Aquatic serpents (Enhydris bocourti): Historic abundance estimates as % relative to 2015 (100%)
6.9.2.2 Cylindrophis ruffus
The red-tailed pipe snake (Cylindrophis ruffus) occurs from Myanmar through southern China, and southward to Indonesia (Adler et al. 1992). It appears to be absent from much of Laos PDR except upper Mekong Lowland and Southern Lao Lowland (Bain and Hurley 2011). The species is quite common in Cambodia floodplain, the Tonle Sap and the Mekong Delta (Bain and Hurley 2011).
The species highly adapt to artificial habitats, and so land cover changes or land use changes are not major threats. However, overexploitation in Cambodian floodplain and Mekong delta is a significant threat to the population. The species is also subject to mortality from vehicles due to its abundance in road-side ditches (Wogan et al. 2012).
Wogan et al. (2012) assessed that the global population is more likely to be increasing than declining. However, in the Tonle Sap and the floodplain of Cambodia as well as in Viet Nam’s Mekong Delta it appears to be suffering rapid declines due to overharvesting. Stuart et al. (2000) mentioned that the species is declining at Tonle Sap due to massive scale of the aquatic snake trade. Brooks et al. (2007) estimated that this species accounted for 0.02-5% of all aquatic snakes traded at Tonle Sap. The species is most often found in reptile shops and markets in Viet Nam’s Mekong Delta for food (Hoang
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2013; Hoang and Vo 2014) and medicinal purposes (Stuart 2004). Reptile shop owners from Dong Thap, Hau Giang and Can Tho reported that the number of pipe snakes available from collectors has steadily declined and is 50% of that of 15 years ago.
Cylindrophis ruffus 400
350 Mekong River in Laos PDR
300 Mekong River in Laos PDR/Thailand 250 Mekong River in 200 Cambodia Tonle Sap River 150
Tonle Sap Great Lake 100
Percentage to relative 2015 (100%) 50 Mekong Delta
0 1900 1950 1970 2000 2015
Figure 6.57 Aquatic serpents (Cylindrophis ruffus): Historic abundance estimates as % relative to 2015 (100%)
The main anthropogenic drivers of change in the abundance of Cylindrophis rufus include: harvesting pressure; road infrastructure; agricultural pollution; ubanization (loss of habitat and shelters).
6.9.3 Aquatic Turtles
Aquatic turtles live and feed mainly in water bodies but lay their eggs on sandbars or river/stream banks. Change in flow, in terms of timing and duration of high flow regimes will directly influence their nesting places or indirectly through their habitats and food availabilities (fishes, snails).
Indicator groups and/or species include members of Trinonychidae (e.g., Amyda cartilaginea, Pelochelys cantorii) and Geoemydidae (e.g., Malayemys subtrijuga).
6.9.3.1 Amyda cartilaginea
The Asiatic softshell turtle (Amyda cartilaginea) is native to Brunei Darussalam; Cambodia; Indonesia; Lao People's Democratic Republic; Malaysia; Myanmar; Singapore; Thailand;
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Viet Nam. Along Mekong River, this species was recorded in Can Tho (Viet Nam), Stung Treng (Cambodia; Timmins 2006), Vientiane (Stuart and Plat 2004), and up to Ban Houaykhoualouang (Laos PDR; IUCN 2013).
Main threats to the softshell turtle include a decline in area of occupancy, extent of occurrence and/or quality of habitat and actual or potential levels of exploitation. The high demand for this species in the consumption trade, currently traded at levels of tons per day, contribute to the decline of global population. Furthermore, the species lays eggs on riverbanks and it is probably impacted by water regime changes due to hydropower operation.
At global scale, the species’ population was estimated to have reduced by at least 20% between c. 1990 and 2000 (or three generations), with a further reduction of at least 20% projected by c. 2010 (Asian Turtle Trade Working Group 2000a). Population in Viet Nam was estimated a reduction of up to 20% in some area due to habitat loss and degraded, overexploitation and illegal trade (MONRE and VAST 2007). In Ban Houaykhoualouang (Laos PDR) local residents reported a low number of ‘large’ individuals caught at the present time showing a sharp decline of this species. The same status was reported to the species in Stung Treng (Timmins 2006).
The main anthropogenic drivers of change in the abundance of Amyda cartilaginea include: land use changes; harvesting pressure; impoundments; sediment mining; climate change.
Amyda cartilaginea 400
350 Mekong River in Laos PDR
300 Mekong River in Laos PDR/Thailand 250 Mekong River in 200 Cambodia Tonle Sap River 150
Tonle Sap Great Lake 100
Percentage to relative 2015 (100%) 50 Mekong Delta
0 1900 1950 1970 2000 2015
Figure 6.58 Aquatic turtles (Amyda cartilaginea): Historic abundance estimates as % relative to 2015 (100%)
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6.9.3.2 Malayemys subtrijuga
The Malayan snail-eating turtle, Malayemys subtrijuga (Schlegel and Muller 1844), is native to Cambodia, Indonesia, Lao PDR, Malaysia, Thailand and Viet Nam (Asian Turtle Trade Working Group 2000b). Along Mekong River, the species has been recorded as far upstream as Vientiane (Stuart and Platt 2004).
Turtles live in canals, ponds, wetlands, including rice fields, where the water flows slowly. They eat mainly aquatic animals including crab, shrimp, insects, worms, small fish and snails with a preference on clams, and mussels (MONRE and VAST 2007). This species lays eggs on the banks and nesting season is from December to March.
Overexploitation, habitat loss and degraded, hydrological changes resulting from proposed dam construction on the upper Mekong and its tributaries are considered at serious threats to the species (Osborne 2000, Platt et al. 2008). The change of water regime could negatively affect turtle populations through habitat loss, a reduction in prey availability, and an increased loss of nests to flooding (Roberts 1993; Hogan et al. 2004; Platt et al. 2004).
At the global level, the species is considered Vulnerable. The same conservation status is recorded in Cambodia, Lao and Viet Nam while its status in Thailand is not uncommon but suffers from habitat impacts (Asian Turtle Trade Working Group 2000).
Malayemys subtrijuga is the most harvested turtle in Tonle Sap (Platt et al. 2008). The population in the Tonle Sap system is reported to have decline by as much as 90% due to overexploitation and egg collection. In Viet Nam, the population is estimated to have been reduced by c. 50% due to exploitation plus habitat loss and agricultural pollution (MONRE and VAST 2007).
The main anthropogenic drivers of change in the abundance of Malayemys subtrijuga include: harvesting pressure; wildlife trade; land use changes; agricultural pollution.
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Malayemys subtrijuga 2500
Mekong River in Laos PDR 2000 Mekong River in Laos PDR/Thailand 1500 Mekong River in Cambodia
1000 Tonle Sap River
Tonle Sap Great Lake 500 Percentage to relative 2015 (100%) Mekong Delta
0 1900 1950 1970 2000 2015
Figure 6.59 Aquatic turtles (Malayemys subtrijuga): Historic abundance estimates as % relative to 2015 (100%)
6.9.4 Semi-aquatic Turtles
This guild is composed of most members of Geoemydidae and the unique species of Platysternidae. These species live in grasslands, and riverine and swamp forests. They are classified as terrestrial and freshwater species, and nest on sandbars and riverbanks and also in the tidal areas of large estuaries. Changes in the timing and duration of high flows directly influence their nesting places.
Indicator groups and/or species include members of Geoemydidae (e.g., Cuora amboinensis, Heosemys grandis, Heosemys annandalii) and Platysternidae (e.g., Platysternon megacephalum).
6.9.4.1 Cuora amboinensis
The Malayan box turtle, Cuora amboinensis, is native to Bangladesh, Cambodia, Lao, Viet Nam; Vulnerable in India, Indonesia, Malaysia, Thailand (Asian Turtle Trade Working Group 2000c). Within LMB, the species occurs in the Mekong Delta, the Cambodia interior and up to Champasak Province of Lao PDR (Bourret 1941).
Cuora amboinensis as the least common of the three species of turtles that are regularly harvested in Tonle Sap Biosphere Reserve (Platt et al. 2008). In Viet Nam’s Mekong delta, the species is under risk of extirpation due to habitat loss and over-exploitation (Hoang 2012; Nguyen et al. 2009). Unsustainable harvesting and trade to satisfy the still intensifying demand of Asian food
Page 104 markets is the main cause behind these species’ demise (Altherr and Freyer 2000).
Malayan box turtle populations are declining due to the current over-exploitation of turtles for national and international trade in Asian countries. The species is considered Endangered in Cambodia, Lao, Viet Nam and Vulnerable in Thailand (IUCN 2000). Altherr and Freyer (2000) reported that Cuora amboinensis is the most commonly imported Asian turtle in the US between 1993 and 1995 and have suffered a precipitous decline within the past decade.
In Mekong Delta, Nguyen et al. (2006) reported, on the basic of interviews with local people, that the number of Malayan box turtle has been greatly reduced recently compared to about ten years ago.
The main anthropogenic drivers of change in the abundance of Cuora amboinensis include: harvesting pressure; wildlife trade; land cover changes; agricultural pollution; climate change.
Cuora amboinensis 400
350 Mekong River in Laos PDR
300 Mekong River in Laos PDR/Thailand 250 Mekong River in 200 Cambodia Tonle Sap River 150
100 Tonle Sap Great Lake
Percentage to relative 2015 (100%) 50 Mekong Delta
0 1900 1950 1970 2000 2015
Figure 6.60 Semi-aquatic turtles (Cuora amboiensis): Historic abundance estimates as % relative to 2015 (100%)
6.9.4.2 Heosemys grandis
The giant Asian pond turtle (Heosemys grandis) is native to Cambodia; Lao People's Democratic Republic; Malaysia; Myanmar; Thailand; Viet Nam. The species is widespread in wetlands in lowlands
Page 105 and low hill terrain of Cambodia (Touch Seang Tana et al., 2000). In Lao PDR, some records of this species were reported from the limestone region of central Laos, and southern Laos (Stuart 1999; Stuart and Platt 2004). In Thailand, it is mainly found in southeastern and peninsular regions but probably in wet lowland areas throughout the country (van Dijk and Palasuwan 2000). It also occurs in the central and southern Viet Nam (Hendrie 2000).
The species inhabits rivers, streams, marshes, and paddy fields from estuarine lowlands up to about 400 m above sea level (Asian Turtle Trade Working Group 2000d). This species becomes sexually mature at about 6 to 10 years of age.
The species is impacted by targeted collection and habitat impacts. Targeted collection occurs for subsistence consumption throughout the species’ range, and has presumably been a feature since historical times. In recent years, however, collection has developed into an intensive, export –oriented business, shifting collection pressures from incidental local use to intensive harvesting across wide areas. Removing large numbers of mature reproducing individuals has a particularly severe impact on species whose life history has evolved to low annual reproductive output which is sustained for a long adult lifespan.
At global scale, the species is decline throughout its range. Within LMB, the population in Cambodia is considered to be of failry large, but details are lacking (Touch Seang Tana et al. 2000) while there is no information on population status in Laos PDR is available. In Thailand, most survey found Heosemys grandis to be uncommon to rare, and presumed to be depleted in most areas (van Dijk, 1999). No information on population status in Viet Nam is available (Hendrie 2000) but the species is estimated to reduce up to 20% due to overexploitation (MONRE and VAST 2007). In the Mekong Delta, population decline estimated at c. 50% in the last 15 years. Heosemys grandis is considered VU A1d+2d in Cambodia, Lao and Viet Nam. The limited data for Thailand suggest at least VU A1d.
The main anthropogenic drivers of change in the abundance of Heosemys grandis include: harvesting pressure: overexploitation and egg collection pose high threats to survival of the species; land use changes: habitat loss and degraded; change in water level and irregular hydrological regime will cause loss of habitat, nesting places; agricultural pollution: pesticides, fertilizers and other chemicals for agriculture development poisoned aquatic turtles and deplete their food; increase of temperature as a result of climate change, which may cause unbalance of sex ratio at birth of this turtle. The temperature of the eggs during a certain period of development is the deciding factor in determining sex, and small changes in temperature can cause dramatic changes in the sex ratio (Bull 1980).
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Heosemys grandis 400
350 Mekong River in Laos PDR
300 Mekong River in Laos PDR/Thailand 250 Mekong River in 200 Cambodia Tonle Sap River 150
100 Tonle Sap Great Lake
Percentage to relative 2015 (100%) 50 Mekong Delta
0 1900 1950 1970 2000 2015
Figure 6.61 Semi-aquatic turtles (Heosemys grandis): Historic abundance estimates as % relative to 2015 (100%)
6.9.5 Amphibians available for human consumption
Amphibians are one of sources of protein for villagers living along river and floodplain. Biomass of amphibians that are available for local human consumption will reflect their status at each site/village.
Up to now, most studies on biodiversity in general and amphibian in particular just focused on species richness and number of species that most harvested by local people than the amount or quantity of amphibians that are available for human consumption. Within LMB, the East Asian bullfrog Hoplobatrachus rugulosus, Asian grass frog Fejervarya limnocharis, crab-eating frog Fejervarya cancrivora are most exploited in the Mekong Delta and the floodplain while Limnonectes spp., Ordorrana spp. are often caught in upland areas (Hoang and Vo 2013; Nguyen et al. 2006; Timmins 2006).
Currently, there is no systematic survey on amphibian trade and exploitation and little is known about the trend of amount of amphibian being exploited. However, this amount is estimated steady decreased due to habitat loss, unsustainable harvesting, agricultural pollution and extreme climatic events.
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Amphibians available for human consumption 400
350 Mekong River in Laos PDR
300 Mekong River in Laos PDR/Thailand 250 Mekong River in 200 Cambodia Tonle Sap River 150
100 Tonle Sap Great Lake
Percentage to relative 2015 (100%) 50 Mekong Delta
0 1900 1950 1970 2000 2015
Figure 6.62 Amphibians available for human consumption: Historic abundance estimates as % relative to 2015 (100%)
The main anthropogenic causes of change are: land cover and land use changes; harvesting pressure; impoundments; agricultural pollution.
6.9.6 Aquatic/ semi-aquatic reptiles available for human exploitation
Aquatic and semi-aquatic reptiles are important food sources of local people. Biomass or quantity of aquatic/semi-aquatic reptiles available for human consumption and/or for farmed crocodiles will reflect their status at each site/village.
Aquatic and semi-aquatic reptiles including turtles, large lizards, and snakes are consumed for food and traditional medicine, or sold to traders who visit villages in most study areas along Mekong River (Hoang and Ngo 2014; Nguyen et al. 2006; Stuart 1999; Stuart et al. 2000; Stuart and Platt 2004; Stuart 2004; Timmins 2006). Most studies identified the number and
Page 108 extent of species being exploited by local people and others documented the amount harvested by day or season, and the trend of exploitation.
In Viet Nam, Stuart (2004) reported approximately 1900 individual reptiles of 21 reptile species, were found in reptile trade shops, of which 16 species were seen harvested by local people living in U Minh Thuong National Park, Kien Giang Province. In Dong Thap Province, Hoang (2013) reported that 16 species out of 34 species of snakes mainly the species of water snakes that are exploited by local people for food use and sale in food markets and 12 species is used for medicinal purposes. Among those species, there are three species recorded in all trade points across the province: Enhydris subtaeniata, Enhydris enhydris and common pipe snake Cylindrophis ruffus. The species of Elapids is become very rare, for instance, banded kraits Bungarus fasciatus and Cobra Naja atra were recorded at only one out of 26 points of investigation. In Long An Province, among the 17 species of reptiles recorded, thirteen were observed being sold in the market around Lang Seng NR (Nguyen et al. 2006).
In Tonle Sap, Cambodia, Stuart et al. (2000) reported that at the peak of the wet season between 1999 and 2000 estimated that upwards of 8 500 water snakes, mainly Enhydris genus, were harvested and sold per day, primarily for crocodile and human food. Brooks et al. (2007) provided an insight of fishing for low-value water snakes in the Tonle Sap. These authors reported that in 1975, aquatic resources were abundant and fishing was largely on a subsistence basis, with a low human population and no commercial fishing. Since 2000, severe decline in the availability of resources was observed by local people and the trend so a steady decline in the following year.
In Lao PDR, Stuart (1999) informed that local residents reported that turtles, monitor lizards and large snakes were more difficult to find in late 1990s than they had been in the early 1990s. It is estimated that the trend is continuing decline in Laos PDR due to increasing of human demands of arable lands and foods.
The main anthropogenic causes of change are: land cover changes; land use changes; urbanisation; harvesting pressure; agricultural pollution.
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Aquatic/ semi-aquatic reptiles available for human exploitation 400 Mekong River in Laos PDR 350
300 Mekong River in Laos PDR/Thailand 250 Mekong River in 200 Cambodia Tonle Sap River 150
100 Tonle Sap Great Lake
50 Mekong Delta 0 1900 1950 1970 2000 2015
Figure 6.63 Aquatic/ semi-aquatic reptiles available for human exploitation: Historic abundance estimates as % relative to 2015 (100%)
6.9.7 Species richness of riparian amphibians
Most amphibians are water dependent species. They prefer living in calm areas within stream and wetlands, low level of water fluctuation and low sediment flow. Change in river and sediment flow will lead to change in species richness of riparian and floodplain amphibians.
Species richness is the number of different species represented in an ecological community, landscape or region. Species richness is simply a count of species, and it does not take into account the abundances of the species or their relative abundance distributions. Based on available information on species richness of the focal areas of BioRA assessment, the species richness of riparian and floodplain amphibians are unchanged even though most species are now confined to protected areas, however, their status is somewhat reduced as a result of very low abundances of some of the remaining species (Figure 6.64).
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Species richness of riparian amphibians 400
350 Mekong River in Laos PDR
300 Mekong River in Laos PDR/Thailand 250 Mekong River in 200 Cambodia Tonle Sap River 150
100 Tonle Sap Great Lake
Percentage to relative 2015 (100%) 50 Mekong Delta
0 1900 1950 1970 2000 2015
Figure 6.64 Species richness of riparian amphibians: Historic abundance estimates as % relative to 2015 (100%)
The main threats to species richness are: land cover changes; harvesting pressure; agricultural pollution; climate change.
6.9.8 Species richness of riparian reptiles
Available information on species richness of riparian reptiles for each area in this BioRA assessment is very limited. In the Mekong Delta at least two species of crocodiles (Crocodilus porosus and C. siamensis) and one species of turtle, the Mangrove Terrapin (Batagur baska), have been extirpated (Nguyen et al. 2009). The estimated historic change in species richness is provided in Figure 6.65.
The Mangrove Terrapin has been documented in Tonle Sap Great Lake, but recent surveys have found no evidence and the species has almost certainly been locally extirpated (Platt et al. 2003).
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Species richness of riparian reptiles 400
350 Mekong River in Laos PDR
300 Mekong River in Laos PDR/Thailand 250 Mekong River in 200 Cambodia Tonle Sap River 150
100 Tonle Sap Great Lake
Percentage to relative 2015 (100%) 50 Mekong Delta
0 1900 1950 1970 2000 2015
Figure 6.65 Species richness of riparian reptiles: Historic abundance estimates as % relative to 2015 (100%)
Change in water volume, inundation depth, and timing of annual flood as well as erosion of sandbar, riverbanks and other riverine forests will cause in habitat change and reduce diversity of riparian reptiles. Long duration of flooding season will lead the riparian reptiles exposed to human pressure.
The main threats to species richness are: land cover changes; harvesting pressure; agricultural pollution; climate change.
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6.10 Status and trends: Birds
The estimated 2015 ecological status for each of the geomorphology indicators is provided in Table 6.11. The definitions for the categories are given in Table 6.2. The expected trends in the indicators are discussed in Sections 6.10.1 to 6.10.10, respectively.
Table 6.11 Estimated 2015 ecological status for each of the bird indicators
Area
shouldered shouldered
-
headed Fish headedFish
tailed Swallowtailed
-
-
RiverTern RiverLapwing Jerdon’sBushchat Mekong Wagtail Manchurian Reed Warbler White Ibis Pied Kingfisher BayaWeaver Sarus crane Bengal Florican Lesser Eagle Fish Grey Eagle Wire Masked Finfoot 2015 2015 2015 2015 2015 2015 2015 2015 2015 2015 2015 2015 2015 2015 Mekong River D B B NA NA E D NA E NA E NA B NA in Laos PDR Mekong River in Laos PDR/ D NA NA NA NA E D NA E NA E NA B NA Thailand Mekong River D NA NA B NA D D C E NA E NA B NA in Cambodia Tonle Sap NA NA NA NA D E D C E NA NA NA B E River Tonle Sap NA NA NA NA D E D C E D NA D NA E Great Lake
Mekong Delta NA NA B NA E E C C E E NA E NA E
6.10.1 Medium / large ground-nesting channel species
6.10.1.1 River Tern (Sterna aurantia)
The River Tern occurs across a wide range in southern Asia, an area of 5.1 million km2. It is found in Pakistan, India, Nepal, Bhutan, Bangladesh, Myanmar, Thailand, Laos PDR, Cambodia, Viet Nam and southern China (Yunnan; del Hoyo et al. 1996; 2007; BirdLife International 2012). It is one of 19 tern species described in the South-East Asian region (Robson 2008). The population of this bird is declining and it is currently classified under the IUCN Red List category as Near-Threatened (BirdLife International 2012). The global population is estimated at between 50 000 and 100 000 individuals (Delaney and Scott 2006). In the Lower Mekong Basin, the species has
Page 113 declined in abundance in Thailand, where it is now considered very rare (del Hoyo et al. 1996). The species has also declined in Laos PDR since the early 20th century (Thewlis et al. 1998), and is very close to being extirpated from the country (W. Duckworth pers. comm. 2015).
Up until the last decade, northeast Cambodia (Zone 3, FA4) supported the largest population of River Tern in Indochina; previous records from March to May 2007 were c. 78-104 birds seen from Koh Sompeay, c. 10 km below the Stung Treng Town to Koh Plong (Bejuizen et al. 2008); the same survey also found one large flock of 30-40 birds in the north end of Koh Preah, and another small flock of eight birds in the channel east of Koh Enchey. The Sesan River tributary was considered one of the most important habitats of this species (Bejuizen et al. 2008). The species is probably extinct as a breeder on the Tonle Sap and the Mekong below Kratie.
River tern has declined considerably in Laos PDR as there have only been a few records in recent decades such as four pairs recorded in Siphandone wetlands (Zone 3) in 2001 (Daconto 2001), and four pairs in northern Xayabouri Province (Duckworth et al. 1999), one pair at Ban Sompoy at the Sekong River tributary in 1997, and a further two pairs in Ban Namkong (Duckworth et al. 1999).
Current survey data from Louang Phabang to Vientiane Cities (Zone 1) confirmed absence of this species along the stretch (IUCN 2013), and it is considered highly likely that this species is extirpated in Laos PDR.
Similarly there are few, if any, recent records from the Thai stretch of the Mekong River – there is a record of a pair of birds frequenting a freshwater lake and marshy area in vicinity of the Yonok wetlands in Chiang Saen during 2008-2009 (P Round, pers. comm. email, 12 July).
The entire Mekong basin population is likely less than 250 birds, with northeast Cambodia supporting the only remaining viable population (Timmins 2008). The Mekong Ramsar and the central Kratie – Stung Treng (Zone 3, FA4) are now the last regional strongholds for the species with an estimated 45-70 birds and 100 birds respectively (Timmins 2006; 2008). Of concern was that a 2010-2012 study focusing on the latter population also found it to be steadily declining, with only 50-60 individuals estimated in the study area (A Claasen, cited in Goes 2013).
It is recently restricted to the upper Mekong River and its tributaries (Goes 2013), with sharp declines noted in the number of pairs in the largest breeding colony on the Mekong, and the number of breeding locations, during the period 2007-2011. In view of its historical and recent precipitous decline the species is considered extirpated in Lao PDR and likely so in Cambodia. Therefore, this species is critically endangered in the LMB. It may be heading towards extinction there within the next 10 years if no specific conservation action is carried out (Goes 2013), and without the careful management of water resource development projects.
Nesting areas are vulnerable to flooding, predation and disturbance (del Hoyo et al. 1996). Hunting, with nest robbery by people and domestic dogs were observed in the north-east Cambodia, including at the Sesan River. For example, on the Sesan on a sample of 12 monitored nests in 2003, 83% were on islands and 17% on mainland bars, all of these nests failed due to egg collection (67%), predation by animals (22%) and nest flooding (11%; Claasen 2004). The negative population trend in Laos PDR is probably due mainly to excessive human disturbance on sandbars (Thewlis et al. 1998),
Page 114 with populations of this species having collapsed in the last 50 years (Duckworth et al. 1999). Some previous observations show that pairs do not nest colonially. In some sections of the Mekong where the bird used to nest, is difficult to find the species today. Only three juveniles were found at Koh Preach and Koh Enchey colony during the 2006-7 survey (Bejuizen et al. 2008). Moreover, with human populations and economic growth, particularly the multitude of dam construction projects completed, underway or planned in South-East Asia (e.g. along the Mekong river (Goes 2013) and tributaries), this may increasingly threaten the species through changes to flow regime and flooding of nest-sites. Its habitat in the Upper Mekong may be threatened by the construction of dams in the Dayingjiang region of south-western Yunnan (Yang Liu in litt. 2011).
The River Tern is considered to be present at population levels of less than 5% of its 1900 populations along the Mekong (W. Duckworth pers. comm.; Figure 6.66). There is no information on the rate of decline, so it has been assumed that the decline between 1900 and 1970 is lower (c. 10% decline), than the decline from 1970 to 2015, which has been more pronounced because of human population increases along the river and the associated impacts of hunting.
River Tern (Sterna aurantia)
2000 Mekong River in Laos PDR
1500 Mekong River in Laos PDR/Thailand Mekong River in Cambodia 1000 Tonle Sap River
500 Tonle Sap Great Lake
Percentage to relative 2015 (100%) Mekong Delta
0 1 2 3 4 5
Figure 6.66 Medium / large ground-nesting channel species (River Tern): Historic abundance estimates as % relative to 2015 (100%)
The five main drivers of change for this species are considered to be: harvesting pressure (of eggs and chicks) declining fish stocks; damming on tributaries, contributed to reduction in fish stocks (e.g., Sesan and Sekong) faster than on the mainstream. This decline is most evident on the Sesan, possibly as a result of upstream dams in Viet Nam (Andrea Claasen, pers. comm.); disturbance to nesting colonies and habitats; mining on tributaries, e.g., Sekong (might result in poison-tainted fish, which will impact on tern populations).
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6.10.1.2 River Lapwing (Vanellus duvaucelii)
River Lapwing occurs across a wide range in southern Asia, an area of 1.5 million km2 (BirdLife International 2015). It is found from north-eastern India to Viet Nam (BirdLife International 2012, 2015), but at low densities throughout most of its range (Li et al. 2009). It is one of four Lapwing species described in the South-East Asian region (Robson 2008). This species is classified under IUCN Red List category as Near-Threatened (BirdLife International 2015). The global population is estimated at approximately up to 25 000 individuals. In the Lower Mekong Basin, the species has declined in abundance as there has been an approximate 50% decline on the tributaries such as the Sekong and Sesan (Claasen 2004, Bejuizen et al. 2008).
It inhabits larger rivers and lakes (Chandler 2009), preferring wide, slow-moving rivers with sand, rocky or gravel bars and islands (Duckworth et al. 1998). It feeds predominantly on insects, worms, small crustaceans, molluscs and mayflies. The river lapwing nests on sand banks from March to June. It lays two eggs on the ground/sandbars.
This species has been recorded widely in the Lower Mekong Basin especially in Cambodia and Lao PDR. In Cambodia the species is described as a local and uncommon resident on undisturbed riverine sandbars and islands during the dry season, and similar habitat during the rainy season (Goes 2013), although the wet season movements are poorly understood. It is restricted to the upper Mekong and its tributaries. The species was found as common during dedicated surveys of the Mekong Ramsar channel complex in 2005-2006 (Timmins 2006) and the central Kratie – Stung Treng section in 2006-2007 (Timmins 2008) and 2010-2012 (Andrea Claasen); along the tributaries, multiple records of variable numbers since 1994 (highest totals of 223 along the whole Sesan, May 1998; 72 birds along the lower Sekong, November 2002; 39 birds along the upper Sekong, December 2011; and 9 birds along the Srepok, February 2001). The population in the upper Mekong river system is unparalleled regionally, as few river stretches in Indochina and none in Thailand retain more than a few tens of birds (Timmins 2008), although hundreds of birds persist in north Laos (see above). The Cambodian population has likely a maximum range of 400-500 pairs, based on the ‘low to mid hundreds of birds’ estimated at each of the key Mekong areas (Timmins 2006, 2008) and recent Sesan and Sekong counts. The species has declined severely on the Sesan River – from 223 birds in 1998 to 102 birds in 2003, and 60 birds on a slightly shorter section in 2010. It is considered that the decline of the population on the central Stung Treng – Kratie Mekong is ongoing.
The lapwing occurs throughout the Mekong stretch and its tributaries in Laos PDR (Sekong, Se Sap, Nam Theun; Duckworth et al. 1999), and Cambodia (Sesan, Srepok) (Claasen 2004). About 200 birds were found along the Sesan River in northern Cambodia in 2008 (Bejuizen et al. 2008), and probably a similar number at the Stung Treng Ramsar Site (Zone 3, FA4).
A minimum of 230 River Lapwing were recorded between Luang Prabang to Vientiane (Zone 1, FA2), during wet season surveys ecological surveys (IUCN, 2013), with a 2012 dry season survey finding
Page 116 an estimated 207 territories (i.e., sites where between 1-3 birds were found; IUCN 2013). A survey in January 2000 from the town of Paklay to Vientiane city found 42 River Lapwings (Duckworth et al. 2002) and in 2004, 116–144 birds were recorded, mainly upstream and downstream of Sanakham Town.
During the 2011 wet season survey, > 230 birds were present in small groups (mainly duos) within the survey area. The largest group found was of >50 birds in the channel mosaic below Ban Khok Khaodo – just 20 km downstream of Paklay Town. Many birds were associated with small areas of exposed sedimentary formations and rocks in the channel, or in stretches where such channel bed features were rare, on sparsely vegetated patches of river bank. However, this bird was fewer recorded during the wet season survey (19 birds; IUCN 2013).
During the 2012 dry season count, the absence of breeders from otherwise ideal habitat around the two largest towns, Louangphabang and Paklay, joins with the well-established breeding absence from Vientiane city in showing that the breeders are much less tolerant of human activity than are Small Pratincole (Glareola lactea) and Little Ringed Plover (Charadrius dubius; IUCN 2013).
The species is not known as a breeding species from the Mekong in Viet Nam.
River Lapwing is considered to be present at population levels of c. 30% of its 1900 populations (W. Duckworth pers. comm.) along the Mekong mainstream (with a decline of 80-90% within the LMB catchment as a whole since 1900; Figure 6.67). The population was probably relatively stable until the 1960s or even 1970s; thereafter there was a precipitous decline in some areas, but a much shallower decline in others (e.g. Upper Cambodian Mekong; parts of the Mekong between Vientiane and Louangphabang, and even sections of the Mekong between Louangphabang and Xiangkok).
River Lapwing (Vanellus duvaucelii) 300
250 Mekong River in Laos PDR
Mekong River in Laos 200 PDR/Thailand Mekong River in 150 Cambodia
Tonle Sap River relativeto 2015 (100%)
100 Tonle Sap Great Lake
Percentage 50 Mekong Delta
0 1 2 3 4 5
Figure 6.67 Medium / large ground-nesting channel species (River Lapwing): Historic abundance estimates as % relative to 2015 (100%)
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The main drivers of change for River Lapwing are considered to be: incidental disturbance by people, dogs and livestock; harvesting pressure (of eggs and chicks); changes in flow regimes; habitat degradation.
6.10.2 Small non-flocking landbirds of seasonally-flooded vegetation
6.10.2.1 Jerdon’s Bushchat (Saxicola jerdoni)
Jerdon’s Bushchat has a large range across Asia, an area of 392 000 km2 (BirdLife International 2012). It is found in Bangladesh, China, India, Laos PDR, Nepal, Thailand, Viet Nam and Myanmar (BirdLife International 2012). It is one of three bushchat species described in the Southeast Asia region (Robson 2008). It is classified under the IUCN Red List category as of Least Concern. The global population has not been assessed but it appears to be stable. Within the Mekong River Basin, the species occurs along the Mekong channel stretch from the town of Paklay District, Xayabouri Province to Thanaleng, Vientiane City, defined as Important Bird Area, IBA LA006 (Ounekham and Inthapatha 2003). This stretch holds a significant population of this species in the world, especially at Paksang area (Duckworth 1997). On the Thai side of the border, IBA TH022 (‘Mekong channel near Pakchom’) extends for 160 km (Pimathi et al. 2004) apparently equivalent to that part of LA006 that lies on the international Thai–Lao border (IUCN 2013). A population density is c. three pairs of the bird occupying five hectares of mosaic habitat (Duckworth 1997).
This species is only known from north of Vientiane within the Lower Mekong Basin (Delacour and Jabouille 1927; Bangs and van Tyne 1931; Bourret 1943 and David-Beaulieu 1944). Between 1950 and 1990 no new bird observations were reported from Laos PDR. During intensive fieldwork from 1992-1995 the species was not found at any of the numerous sites surveyed (Thewlis et al. 1998), which were however mainly to the south of the historical records. Jerdon’s Bushchat was recorded patchily in both the Mekong channel and in hill grassland but not in Southern Mekong River (Thewlis et al. 1998; Duckworth et al. 1999). The species was mostly surveyed and recorded in the Mekong channel (Zone 1, FA2) and probably partly in the upper section of Zone 2, FA3. Some dozens of this species were recorded in January 2000 on the boat trip from the town of Paklay to Vientiane City (downstream of Zone 1; Duckworth et al. 2002). The record of this bird in the Lower Mekong Basin at Paksang (downstream of the Zone 1), 60 km upstream from the Vientiane City as 100-200 pairs identified in 6 squares km in March 1996 (Duckworth 1997) represents the most southerly known record of this species globally. Also, this species was recorded in hill grassland (especially stands of imperata) as small numbers were seen in Nam Xam National Protected Area, Houaphanh Province (Duckworth et al. 1999). Recent surveys in January 2012 (IUCN 2013) confirmed occurrence of many
Page 118 hundreds into the low thousands of the species during the dry season between Louang Phabang and Vientiane.
Potential threats to this species are considered likely to largely relate to habitat loss / change and disturbance. Human habitation densities and river use along most of this stretch of river are higher today than historically. This includes the creation of embankments, dredging of the river channel, and extracting gravel and sands. Proposed hydropower projects on the Mekong would modify the habitat so that many bird species, including Jerdon’s Bushchat, would be impacted.
The population of Jerdon’s Bushchat is not considered to have declined (Figure 6.68). The availability of its preferred habitat within the river channel north of Vientiane has remained largely unmodified from the information that can be derived from historic maps, so it seems feasible that population has remained fairly stable.
Jerdon’s Bushchat (Saxicola jerdoni) 200
180 Mekong River in Laos PDR 160 Mekong River in Laos 140 PDR/Thailand 120 Mekong River in 100 Cambodia 80 Tonle Sap River 60 Tonle Sap Great Lake
40 Percentage to relative 2015 (100%) 20 Mekong Delta 0 1900 1950 1970 2000 2000
Figure 6.68 Small non-flocking landbirds of seasonally-flooded vegetation (Jerdon’s Bushchat): Historic abundance estimates as % relative to 2015 (100%)
The main drivers of change for Jerdon’s Bushchat are considered to be: disturbance to the habitats; land use changes (as populations grow so might changes in land use practices on the islands); hunting pressure (hunting with bird nets); collecting eggs and chicks; embankment and other water related projects.
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6.10.2.2 Mekong Wagtail (Motacilla samveasnae)
Mekong Wagtail has a restricted linear range, just an area of 37 900 km2 (BirdLife International 2012). It is found in Cambodia, Laos PDR, Thailand and Viet Nam (BirdLife International 2012). It is one of seven wagtail species described in the South-East Asia region (Robson 2008). The main population of Mekong Wagtail is in Northeast Cambodia, extending upstream from Kampi to southern Laos - the Stung Treng Ramsar Site and the Lao-Cambodia border area that falls in Zone 3. This species was described to science as recently as 2001 (Duckworth et al. 2001). Although the population size has not been quantified it is preliminarily estimated at 6 000-15,999 individuals (BirdLife International 2012). It is classified under the IUCN Red List category as Near- Threatened as its population has decreased slightly (BirdLife International 2012). The species distribution area in Laos PDR is in the Important Bird Area, IBA LA020, LA021 and LA022 (Ounekham and Inthapatha 2003).
This species was described to science as recently as 2001 (Duckworth et al. 2001), so there is little evidence to comment on the historical population levels of Mekong wagtail. However, the species was previously overlooked as a form of white wagtail (Motacilla alba), and was in fact first collected in December 1972, on a tributary of the Mun river, Ubon Ratchathani Province, north-east Thailand. The species is present in Zone 3 and Zone 4. The first record of this bird in Viet Nam was in 2002 from Yok Don National Park, Da Lat Province, where it is likely to be a resident breeder (Le Tron Trai and Craik 2008). Two locations in Northeast Cambodia (Zone 3, FA4) where the birds were recorded in the wet season survey (August 2007), as two birds in Prek Preah River – 6 km from the mainstream, and one bird at a floodplain wetland – just 1.5 km inland, east of Sambor Town (Bejuizen et al. 2008). The most recent recorded this bird in the Lower Mekong Basin was on the road to Tmatboey in Cambodia (Eaton and Nelson 2015).
The species is highly tolerant of human presence, and its habitat is not particularly vulnerable to human-induced changes. However, hunting of resident birds along the Mekong, such as pratincoles and also wagtail species for food is likely to increase. The potential impact would result from currently proposed dams on the Mekong River, particularly those on sections where the river has a low gradient, that may disrupt long stretches of its riverine range by flooding the river channel (Birdlife International 2012), also generating irregular changes in Mekong flow system such as water level remains high during its breeding season (March-June).
This species was described to science as recently as 2001 (Duckworth et al. 2001). There is little evidence to comment on the historical population levels of Mekong wagtail, so it is assumed that the population has been present and stable since 1900, although the IUCN Red List suggests a decrease of perhaps 1% over the last decade, which is reflected within the table. The habitats in which the species typically occurs appear not to have undergone major change (Figure 6.69).
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Figure 6.69 Small non-flocking landbirds of seasonally-flooded vegetation (Mekong Wagtail): Historic abundance estimates as % relative to 2015 (100%)
The main drivers of change for Mekong Wagtail are considered to be: land use changes (as populations grow so might changes in land use practices on the islands); hunting pressure (hunting with bird nets); erosion protection measures, such as embankments; water resource development projects.
6.10.2.3 Manchurian Reed Warbler (Acrocephalus tangorum)
The Manchurian Reed Warbler has a wide range of distribution, an area of 490 000 km2 (BirdLife International 2015). It breeds in south-east Russia and northeast China, and winters in Thailand (mainly at Khao Sam Roi Yot), Indonesia, Cambodia and Laos PDR (BirdLife International 2012). It is one of 39 warbler species described in the South-East Asian region (Robson 2008). It is classified under the IUCN Red List category as Vulnerable because of a small and declining population as a result of habitat loss in both its breeding and wintering grounds (BirdLife International 2012). The population in Cambodia appears to be a major stronghold for the species. The global population estimate is 3 500-15 000 individuals (BirdLife International (2012), including the population in China which has been estimated at between 100-100 000 breeding pairs, and between 50-10 000 individuals on migration (Brazil 2009). In Cambodia, this bird was discovered as recently as 2001 (Duckworth et al. 2001), with the species recorded between January and May, mainly in the Tonle Sap grasslands at low densities
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(Goes 2013). Therefore, the Tonle Sap floodplain is potentially the most significant wintering site for the species, despite a very low density (Bird et al. 2012). It is believed to have declined there since 2005, at least locally, as it no longer occurs around Krous Kraom and is now infrequently recorded in Stoung-Chikreng where good habitat remains (J. Eaton pers. comm.). Overall, its population is suspected to be continuing to decline at a moderate rate due to habitat losses.
There are now records from the Northern Plains (Clements et al. 2005), from Mondulkiri Province close to the Viet Nam border and from the Tonle Sap floodplain (Zone 4a, FA6) where it is locally common (Bird et al. 2007). It occurs in central Laos (Zone 2, FA3) such as Paksan wetlands, Bolikhamxay Province (W. Duckworth in litt. 2012) and in Viet Nam. The paucity of recent sightings at well-watched and increasingly heavily-monitored and ringed sites (such as Bung Boraphet in Thailand) suggests it is genuinely very scarce (P. Round in litt. 2012).
Its population is declining due to habitat loss in both its breeding and wintering grounds (Birdlife International 2012; Figure 6.70). The bird has suffered greatly from encroachment with plantations of casuarinas, eucalyptus and coconut palms, and the establishment of prawn farms with salt and brackish water. Marshes where the bird occurs elsewhere are threatened by reclamation and urbanisation, and no freshwater swamp habitat lies within any protected area. Similarly, habitat loss and degradation is continuing at wetlands in Paksan District, an important stopover site in Laos PDR, where the tall emergent grasses favoured by the species are routinely removed by local people (W. Duckworth in litt. 2012). In Cambodia, the situation may be more promising as the species has been recorded in man-made headponds used for dry season rice cultivation, although its preference for tall dry grass habitat may render it susceptible to dry season burning which is extensive (Bird et al. 2007).
Manchurian Reed Warbler (Acrocephalus tangorum) 200
180 Mekong River in Laos PDR 160
140 Mekong River in Laos PDR/Thailand 120 Mekong River in 100 Cambodia Tonle Sap River 80
60 Tonle Sap Great Lake 40 Percentage to relative 2015 (100%) Mekong Delta 20
0 1900 1950 1970 2000 2015
Figure 6.70 Small non-flocking landbirds of seasonally-flooded vegetation (Manchurian Reed Warbler): Historic abundance estimates as % relative to 2015 (100%)
Population declines since 1900 are probably due to changes (e.g. habitat loss) occurring within the breeding area (Duckworth pers. comm. 2015; Figure 6.70). The study area population now is considered to be reduced to c. 40% of 1900 level (the delta habitat was already severely modified by
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1990), given the near complete loss of habitat in the delta and comparing the size of the delta with the BTSIA and the proportionately very small amounts of similar habitat associated with the main channel. For the purposes of this assessment it has been assumed that the population has declined by 40% since 1900.
The main drivers of change for this species are considered to be: habitat loss (wetland conversion); grassland and weeds burned; hunting pressure (hunting with bird nets, spotting); impoundments (flow changes).
6.10.3 Large tree-nesting waterbirds
6.10.3.1 White-shouldered Ibis (Pseudibis davisoni)
White-shouldered Ibis occurs in a small range of 88 900 km2, being found in Northeast Cambodia, extreme southern Laos and along one river in East Kalimantan, Indonesia (BirdLife International 2013). Cambodia currently supports a minimum of 95% of this global population (Wright et al. 2012; 2013). White-shouldered Ibis is one of five ibis species described in the Southeast Asian region (Robson 2008). The global population is estimated at c. 970 birds including several small populations in Indonesia (BirdLife International 2013), of which Cambodia supports 731-856 birds, a minimum of 95% of the global population (Wright et al. 2012, 2013, 2015). This species has been severely declining and is currently classified under the IUCN Red List category as Critically Endangered (CR). Its previous range was as a widely but patchily distributed species across much of Thailand, Laos PDR, south and central Viet Nam and Cambodia, parts of Myanmar, Kalimantan (Indonesia), Sarawak (Malaysia) and south-west Yunnan, China, but it has declined dramatically during the 20th century. It is extinct in Thailand, Malaysia (Sarawak), China (Yunnan) and close to extinction in Laos PDR and Viet Nam, and there are no recent records from Myanmar. This bird has been described as the most endangered and rarest large resident waterbird in South-East Asia (Timmins and Clements 2006a, cited in Buckton and Safford 2004). Within the Lower Mekong Basin, the white-shouldered ibis is now confined to just a few sites in northern Cambodia, southern Viet Nam and extreme southern Laos.
Within Cambodia, the species used to be much more common and widespread, even in open countryside, but is now extirpated from most of the country, although Cambodia currently supports a minimum of 95% of the global population (Wright et al. 2012; 2013), especially at the Western Siem Pang. Populations are extirpated in the southern regions, and on the verge of extinction in the northwest. It is very rare in the dry season in the Tonle Sap grasslands (recent records include a single at Wat Pognea Prom (Chikreng) in 2012, in Kompong Thom grasslands up to 12 at Baray – Chong Doung in 1999, followed by near annual records of one to three birds between January and
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July at Veal Sragnai, Kvao and/or Baray-Choung Doung BFCA), and has small isolated populations in the north of the country (Goes 2013). In the northeast it is locally fairly common at Siem Pang (Zone 3), the upper Mekong channel mosaic and Lomphat Wildlife Sanctuary (Ratanakiri). An extensive survey between Kratie and Strung Treng (Zone 3, FA4) in northeast Cambodia in November 2006 and March-April 2007 recorded an estimated 78-125 birds, but with a near absence of birds (single bird recorded) during the floods in July-August 2007 (Bejuizen et al. 2008), and fairly common during January-May 2010-2012 with a maximum of 124 birds during annual roost counts. The first census survey on this bird was undertaken in 2010 throughout the northeast Cambodia (Zone 3) and discovered at least 4 subpopulations including 226 birds at Western Siem Pang, 187 birds at Lomphat WS, 124 birds in Central section of the Mekong River, and 34 birds in Kulen Promtep WS (Wright et al. 2012). However, the species today has a very small population and has undergone a decline of a scale and magnitude greater than other large waterbirds in mainland South-East Asia (Buckton and Safford 2004).
Within Laos PDR, white-shouldered ibis is a very scarce bird, but has been recorded from Xe Pian from the Xe Kong Plains and from the Xe Pian river in the early-mid 1990s (Thewlis et al. 1998). Wildlife surveys at the nearby Houay Kaliang area of the Xe Pian NPA in eastern Khong district included sightings of Giant Ibis (Baird, 1997, Timmins et al. 1993, Evans, 1996), but not White- shouldered Ibis. Giant Ibis and White-shouldered Ibis were reported in Ban Khem and Kadian sectors, respectively (Round 1998). During the 2010 gibbon survey in Dong Khanthung NBCA, both Nam Phak and Kadien River were considered to support suitable habitats for ibises where peddle flats and some ponds are present (Phiapalath and Saysavanh 2010).
Within the Lower Mekong Basin this species has declined dramatically since 1900; it was previously common and widespread (Duckworth et al. 1999; Goes et al. 2001; Thomas and Poole 2003). It is considered to have declined by over 90% since 1900, and a figure of 5% of 1900 levels has been applied for 2015. There is no information on the rate of decline, so it has been assumed that the decline has been linear throughout the period 1900 – 2015, and equally along the length of the river.
Wetlands and grassland, such as pools, marshes, open grasslands or watercourses including wide rivers with sand and gravel bars are important for the species. Trapaengs (seasonal pools) are particularly favoured during the dry (breeding) season, with a shift to matrix sites such as long- and seasonally abandoned rice fields, grasslands (often inundated after high rainfall) and the dipterocarp forest itself after rainfall events (Wright et al. 2010 in Buckton and Safford 2004) and in the wet season (H. Wright in litt. 2012). The species has been recorded along the mainstream Mekong in Cambodia, wetlands and open ponds in paddy fields during dry season, also the mosaic of shrub and grasslands on the Tonle Sap floodplain (Wright 2012, Wright et al. 2012). The species is a non- colonial, site-faithful dry season breeder (Wright 2012). The bird feeds most on amphibians (81%) in waterhole substrates and some small invertebrates (Wright 2012). In Cambodia, it has been recorded nesting during the dry season (December-May) in remnant dry forest close to seasonally abandoned wet season rice paddy, large contiguous areas of dry forest and in flooded forest within the Mekong channel.
Within Viet Nam and probably Laos PDR, this species is almost extinct as a breeding species and now only occurs as a rare non-breeding visitor (Birdlife International 2013; Figure 6.71).
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White-shouldered Ibis (Pseudibis davisoni)
2000 Mekong River in Laos PDR
1500 Mekong River in Laos PDR/Thailand Mekong River in Cambodia 1000 Tonle Sap River
Tonle Sap Great Lake 500
Percentage to relative 2015 (100%) Mekong Delta
0 1900 1950 1970 2000 2015
Figure 6.71 Large tree-nesting waterbirds (White-shouldered Ibis): Historic abundance estimates as % relative to 2015 (100%)
The causes of the decline are probably as a result of disturbance from increased human activity around feeding areas, incidental killing and nest robbery, and, to a lesser degree, habitat loss, changes in micro-habitat at pools, as a result of the collapse of wild ungulate populations and changes in livestock husbandry practices (BirdLife International 2001). Human disturbance includes using the feeding sites of the bird for fishing, collecting vegetables etc., and in addition the use of ponds by domestic buffaloes.
The main drivers of change for this species are considered to be: human activity around feeding areas); habitat loss to agriculture; land use and land cover change; natural predation hunting including nest robbery and collecting eggs; transmission lines.
6.10.4 Bank / hole-nesting species
6.10.4.1 Pied kingfisher (Ceryle rudis)
Pied Kingfisher has an extremely large range, an area of 23.9 million km2. Although the population size is not known, it is not considered to be decreasing sufficiently rapidly to be of conservation concern (BirdLife International 2015). This species of kingfisher is widely distributed across Africa and Asia, with Europe forming <5% of the global range. It is one of seventeen kingfisher species in the South-East Asian region (Robson 2008). Although the population size is not known, it is not considered to be decreasing sufficiently rapidly to be of conservation concern (BirdLife International 2015). It therefore the species is classified under the IUCN Red List category as Least Concern (LC).
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Along the Mekong, there are very few sandbanks suitable for nesting other than those cut by rivers – the mainstream is particularly good, along with some of the lower tributaries. The value of the study area to bank / hole-nesting breeding species (such as Pied Kingfisher and Plain Martin) is thus very high.
Within Cambodia, the species is an uncommon to locally common resident, primarily associated with large rivers and their floodplains, but also occurring in swamp forest, streams, ponds and grasslands (Goes 2013).
The species was described as ‘common’ along the Mekong, Tonle Sap and Bassac rivers in Cambodia prior to 1970 (Thomas and Poole 2003). The distribution of this species in Cambodia is restricted to the Tonle Sap and Mekong-Bassac floodplains and the whole River Mekong plus its tributaries. There have been multiple sightings of the singles, pairs or family groups at various sites in the swamp forest and grasslands (various authors), with 75 birds counted during a fast boat journey between Phnom Penh and the open lake in April 2000, with the highest concentration of birds in the delta area (PD); 30 birds from a similar count in January 2008 (Olausson 2008).
Cambodia supports two population strongholds, one centred on the Tonle Sap Great Lake (Zone 4a) and the second along the upper Mekong River (Zone 3, FA4) and tributaries. The species is present along the Mekong from southern Kratie to the Laos PDR border, with maximum boat-based counts of 43 birds from the Laos PDR border to Kratie town in February 2000 (Poole et al. 2000), 40+ birds (20+ groups) in the central Kratie – Stung Treng section in 2006-2007 (Timmins 2008) and found common at the latter site in January-May 2010-2012 (AC); 25 birds at 13 sites on the Mekong Ramsar in 2005-2006 (Timmins 2006); along the Sekong, six birds from Stung Treng to Siem Pang in November 2002 (Timmins et al. 2003); along the Sesan, 36 birds in the upper section in May 1998 (Timmins and Men 1998) and eight birds in the lower section in January 1999 (FG); along the Srepok, only one bird in May-June 1998 (Timmins and Men 1998). The Tonle Sap’s complex maze of channels and creeks offer large expanses of suitable habitat which likely shelter a healthy population, and the upper Mekong river channel mosaic supports the bulk of the northeastern population (Goes 2013). The former is probably stable although comparison of 2000 and 2008 counts along the Tonle Sap River suggest some decline, and warrant more thorough assessment. The population in the northeast is declining, possibly severely. The whole stretch below and upper Kratie to Lao-Cambodia border is probably the largest localized population (Bejuizen et al. 2008) and part of Tonle Sap floodplain would be the second.
Within Laos PDR, the species was common in the upper Lao Mekong channel (here taken as between the China – Laos PDR border and Vientiane; Delacour and Greenaway 1940), and reportedly still occurred in the 1990s, at least around Chiang Saen (Duckworth 2002), although in numbers seemingly well below the habitat’s carrying capacity (Duckworth 2002). There is no doubt that Pied Kingfisher has undergone one of the steepest historical declines of any Lao bird (Duckworth 2002), although its status is less worrying than previously thought (W. Duckworth pers. comm.). The
Page 126 species was historically more commonly reported in the south of the country rather than the north especially in Champassak Province (Thewlis et al. 1998, Duckworth et al. 1999), but this may be reflective of survey effort.
Recent survey data from Luang Prabang to Vientiane yielded no record of this species along this stretch of the Mekong (IUCN 2013), although occasional individuals may persist or visit the area; the species is basically absent from the survey area. It was also recorded as very local in Viet Nam (Buckton and Safford 2002), apparently restricted to the Plain of Reeds in Dong Thap and Long An provinces. It remained a fairly common resident at Tram Chim (Zone 5, FA8) up until at least 1998 with a daily maximum of up to eight birds recorded.
Rapid changes in flow regimes and ecology of the river due to upstream dams may affect breeding success. The Pied Kingfisher is considered to have undergone the steepest historical decline of any bird in Laos PDR (Duckworth 2002), and as such is considered to be present at population levels of less than 5% of its 1900 populations (Will Duckworth pers. comm.). There is no information on the rate of decline, but it has been assumed that the decline is steeper since 1970 (Figure 6.72).
In Viet Nam, from 1900-1950, the French built and developed an extensive canal system, thus increasing available habitat; between 1950 and 1970 the War meant that this type of habitat was not further expanded. Since 1970, the canal system has been expanded further until 2000. In Viet Nam, we have assumed that the pied kingfisher population has increased threefold from 1900-1950 in line with the habitat increase, from 1950-1970 it remained stable, and from 1970-2000 it has increased by a further tenfold in line with the habitat increase.
Pied kingfisher (Ceryle rudis)
2000 Mekong River in Laos PDR
1500 Mekong River in Laos PDR/Thailand Mekong River in Cambodia 1000 Tonle Sap River
500 Tonle Sap Great Lake
Percentage to relative 2015 (100%) Mekong Delta
0 1900 1950 1970 2000 2015
Figure 6.72 Bank / hole-nesting species (Pied Kingfisher): Historic abundance estimates as % relative to 2015 (100%)
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The main drivers of change for this species are considered to be: harvesting pressure (of eggs and chicks); declining fish stocks; disturbance to nest sites; habitat change / loss through impoundments; pollution and chemical poisoning.
6.10.5 Flocking passerine of tall graminoid beds
6.10.5.1 Baya Weaver (Ploceus philippinus)
Baya Weaver has a wide world range as found across the Indian Subcontinent and South-East Asia, an area of 6.34 million km2 (BirdLife International 2012). It is one of three weaver species described in the South- East Asia region (Robson 2008). Although the population size has not been quantified it appears to be stable. It is classified under the IUCN Red List category as Least Concern (LC) (BirdLife International 2012). Baya Weaver is rare in Bhutan, Laos PDR, Tonkin and Annam (Robson 2008).
There are only a few records of this species in Laos PDR (Duckworth et al. 1999), with the species being more abundant in Cambodia as the species was regularly recorded in the Kratie area (Zone 3, FA4) during surveys in 2006 and 2007 (Bejuizen et al. 2008). In Cambodia, it has been recently observed in some numbers by the bird specialist group Birdtour Asia in northeast Cambodia (Eaton and Nelson 2015). In Viet Nam, thirty birds were seen at Tram Chim National Park, September 1998, but there were no observations in July 1999 (Buckton and Safford 2004). A record from Lang Sen came from identifying its distinctive nest shape with a probable small colony here in July 1999 (Buckton and Safford 2004). Four individuals and several active nests were located at Xeo Quyt in July 1999 (Buckton and Safford 2004), and at least 50 individuals and many nests at Bac Lieu bird sanctuary, August 1999 (Buckton and Safford 2004).
In Laos PDR10, the species was recorded in Xe Pian NPA, Vangvieng and other several sites along the southern Mekong (Thewlis 1996), also 30 birds per day were observed in Dong Khanthung, a seasonally flooded dry forest located to the west of Siphandone wetland (Zone 3, FA4) by Round (1998), at Ban Tha Dua in southern Vientiane City and Nam Ghong in Attapeu province (Duckworth et al. 1999). Paksan District in Bolikhamxay Province held a breeding colony in 1950, but this was not confirmed during the 1995 surveys (Duckworth et al. 1999). There are no records of this species along the Mekong from Louang Phabang to Vientiane, Laos PDR (Zone 1, FA2) and probably (Zone 2, FA3; IUCN 2013), although Golden Weaver was present. A group of four or more old nests,
10 This species is scarce and local in Laos, so it is difficult to detect.
Page 128 probably belonging to this species, was seen in trees amongst tall grass at the edge of a channel sandbank (at Don Sang), Paklay District, Xayabouri Province (IUCN 2013). .
The species is quite sensitive to human disturbance, the loss of its nesting habitat, especially the nest sites – tall and open tree on river banks. Overharvesting of nests for ‘decorations’ is a further threat to this species. Hunting and trapping is also a threat.
It has been assumed that the decline in Baya weaver has been 20% since 1900 (W Duckworth pers. comm.) and that the decline has been linear across the range of the species during this period (Figure 6.73).
The main drivers of change for this species are considered to be: land use changes; harvesting (direct and indirect); erosion protection measures, such as embankments; change in bank morphology as a result of water-resource developments.
Baya Weaver (Ploceus philippinus) 200
180 Mekong River in Laos PDR 160 Mekong River in Laos 140 PDR/Thailand 120 Mekong River in 100 Cambodia 80 Tonle Sap River 60 Tonle Sap Great Lake
40 Percentage to relative 2015 (100%) 20 Mekong Delta 0 1900 1950 1970 2000 2015
Figure 6.73 Flocking passerines of tall graminoid beds (Baya Weaver): Historic abundance estimates as % relative to 2015 (100%)
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6.10.6 Large ground-nesting species of floodplain wetlands
6.10.6.1 Sarus crane (Grus antigone)
Sarus Crane occurs across a wide range, an area of 1.83 million km2. The species has three disjunct populations in the Indian subcontinent, South-East Asia and northern Australia. The global population is estimated at 15 000-20 000 individuals (Archibald et al. 2003, BirdLife International, 2012). There are four Crane species in South-East Asia, of which the Sarus Crane (Grus antigone) has four subspecies. The subspecies that occurs in Lower Mekong Basin is Indochinese Sarus Crane (Antigone antigone sharpii) as previously known Eastern Sarus Crane (Blanford 1895). This subspecies is found in Cambodia, extreme southern Laos and south Viet Nam, but its suitable habitat range has declined dramatically. The current population of the Indochinese Sarus Crane is c.800-1 000 birds and its subpopulation in Myanmar of c.500-800 birds (Delaney and Scott (2006), BirdLife International 2012). Despite past declines, recent counts have shown some increase in the Southeast Asian population; however, the Indochinese population especially at Tram Chim National Park is highly unstable and susceptible to extinction if the current rates of habitat degradation continue (Archibald et al. 2003). It is suspected to have suffered a rapid population decline, which is projected to continue, as a result of widespread reductions in the extent and quality of its wetland habitats, exploitation and the effects of pollutants (BirdLife International 2012). Therefore, the Indochinese Sarus Crane is critically endangered in the LMB.
The Indochinese Sarus Crane – the Mekong Delta especially at Tram Chim National Park (Zone 5, FA8) supports the stronghold population of this subspecies in the Lower Mekong Basin. Part of this subpopulation has been well monitored at Tram Chim NP since 1988 with a maximum of 1,052 birds but declined to 665, 365, 187 and 48 in 1989, 1992, 1993 and 2001, respectively (Buckton and Safford 2004). The population has fluctuated in some years and rebounded to 469 birds in 1999 (Nguyen Van Hung in litt. 1999) and 562 individuals in 2008 (Evans et al. 2009 cited in Buckton and Safford 2004). A further decline has been noted subsequently with a sharp decline to 496 birds in 1999 and 167 birds in 2000, and by 2012, the number of birds at Tram Chin NP had declined to 52 (Tram Chim National Park monitoring programme).
A further site is the floodplain in Kieng Giang and An Giang Provinces where some dozens were regularly observed (Buckton and Safford 2004). The groups spending the dry season in the Viet Namese Mekong Delta represent over 30% of the population of the Indochinese sub species G.a. sharpii (Buckton and Safford 2004).
A further decline has been noted subsequently with a sharp decline to 496 birds in 1999 and 167 birds in 2000, and by 2012, the number of birds at Tram Chin NP had declined to between 80-150 birds (Birdlife International 2012). A further site is the floodplain (part of Zone 5) in Kieng Giang and An Giang Provinces where some dozens were regularly observed (Buckton and Safford 2004). In any case, it is estimated that the population of the Indochinese Sarus Crane is at least 1,000 birds, of
Page 130 which the groups spending the dry season in the Viet Namese Mekong Delta represent over 30% of the population (Buckton and Safford 2004).
Within Cambodia, and in the Mekong Delta, the species occurs at Boeung Prek Lapouv IBA in Takeo province and Kampong Trach IBA in Kampot Province (Seng Kim Hout et al. 2003 cited in Buckton and Safford 2004). Counts of up to 200 have been made in March and April in 1998 and 1999 at Ang Trapeang Thmor, Cambodia (BirdLife International 2001). However, the population has decreased in the country as maximum total counts at the sites to date are 155 birds in March 2002 and 48 birds in February 2003, respectively. In addition, four Sarus Cranes were observed in the Tonle Sap grasslands (Zone 4a, FA7) in 2015 (Eaton and Nelson 2015).
Within Lao PDR, the crane used to be widespread in central and southern Laos at sites such as Xe Pian and Dong Hua Sao NPAs in Champassak, with one pair at Ban Sompoy by Sekong River in Sanamxay District, Attapeu Province, Nong Luang in Savannakhet Province, prior to 1980 (Thewlis et al. 1998, Duckworth et al. 1999). However, there have only been a few records since 1996 (Duckworth et al. 1999), for example one bird was recorded in Dong Khanthung (Round 1998), a pair was seen at Nong Phue, Ban Nongkhe Sivilay (inside Xe Pian NPA) in 2001 (K. Poulson pers. comm.). This pair continued to visit Nong Phue, “an open pond located within jungle”, at Ban Nongkhe Sivilay regularly during 2000s. Also, there is a report from villagers of a pair occasionally visiting Nongben (pond) in 1999 at Ban Hinlat in Dong Khanthung (Phiapalath and Saysavanh 2010).
The crane was previously a breeding resident in Thailand but is now extinct there (Lekagul and Round 1991) and it is highly likely that the species will be extirpated in Laos PDR.
This species' population is suspected to have decreased considerably since 1900, owing to the loss and degradation of wetlands, as a result of drainage and conversion to agriculture, ingestion of pesticides, and the hunting of adults and collection of eggs and chicks for trade, food, medicinal purposes and to help limit damage to crops (Archibald et al. 2003). From 2001 to 2006, much of the seasonally inundated floodplains of the Ha Tien Plain were lost, mostly due to the expansion of shrimp farms. In habitats that are not well protected, the bird is shy and sensitive to human disturbance (in case of the habitat used in Xe Pian NPA, Laos PDR) (P. Phiapalath pers. comm.). In addition, collision with transmission lines may be a significant threat in parts of its range as has been observed in India (Sundar et al. 2000).
The status assessment refers to the population of Sarus Crane that occurs within the Lower Mekong Basin, but note that c. 50% of the sub-population is found in Myanmar. Sarus Crane is considered to be present at population levels of 5% of its 1900 populations along the Mekong, with the exception of the Tram Chim NP, the Viet Nam Delta where it is considered to occur at c. 50% of its 1900 levels. There is some information on the rate of decline for the population at Tram Chim NPA from 1,058 birds in 1988 to 562 birds in 2008 so it has been assumed that the decline has been linear throughout the period 1900 – 2015, roughly at 50% in the LMB (Figure 6.74).
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Sarus crane (Grus antigone)
2000 Mekong River in Laos PDR
1500 Mekong River in Laos PDR/Thailand Mekong River in Cambodia 1000 Tonle Sap River
500 Tonle Sap Great Lake
Percentage to relative 2015 (100%) Mekong Delta
0 1900 1950 1970 2000 2015
Figure 6.74 Large ground-nesting species of floodplain wetlands (Sarus Crane): Historic abundance estimates as % relative to 2015 (100%)
The 5 main drivers of change for this species are considered to be: habitat loss by converting to agriculture and shrimp farms in floodplain area; disturbance by human from fishing and by domestic buffaloes occupying its feeding sites (ponds) in dry season; indigestion of pesticides used in agriculture such as sugar crane plantation; some hunting and collecting eggs; potentially impact by collision with transmission lines.
6.10.7 Large ground-nesting species of floodplain wetlands
6.10.7.1 Bengal Florican (Houbaropsis bengalensis)
Bengal Florican has two disjunct populations as in the Indian Subcontinent and South-East Asia (BirdLife International 2001), an area of 84 500 km2 (BirdLife International 2015). It is found in Cambodia, India, Nepal and Viet Nam. It is found in Cambodia, India, Nepal and Viet Nam. A bustard species with a very small, declining population; a trend that has recently become extremely rapid and is predicted to continue in the near future, largely as a result of the widespread and on-going conversion of its grassland habitat for agriculture. It has declined dramatically and only survives in small, highly fragmented populations. It therefore classified under the IUCN Red List category as Critically Endangered (CR).
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The South-East Asian population occurs in Cambodia and may be extant in southern Viet Nam. The population in the Tonle Sap region, which supports the vast majority of the population of Cambodia, was estimated at between 312 and 550 (95% CI) based on surveys in 2012, with only 216 displaying males recorded (C. Packman in litt. 2013). This represents a 44% decrease from the previous survey in 2005, and a minimum of 294 displaying males had been recorded in 2007 (Gray et al. 2009). More than 50% of this population occurs on seasonally inundated grasslands within Kompong Thom province (Gray et al. 2009). This estimate, based on extent of available habitat in 2005 and known habitat loss between 2005 and 2007, represents a rapid decline owing to habitat loss, from a projected 3 000 individuals in 1997 (T. Gray, T. Evans and Hong Chamnan in litt. 2006). Given accelerating post-2005 grassland loss of 28% within 10 grassland blocks holding 75% of the estimated population (Gray et al. 2009), and a further 11% of habitat lost in four protected areas in 2008 (Evans et al. 2009), projected rates of decline will equate to over 80% during a three generation period (T. Gray, T. Evans and Hong Chamnan in litt. 2006). Recent assessment of habitat loss indicates that it has indeed been widespread and extensive between 2005 and 2012, and a number of sites identified as having blocks of grassland in excess of 10 km2 now contain little or no grassland (C. Packman in litt. 2013). Annual monitoring of Bengal Florican populations in Bengal Florican Conservation Areas (BFCAs) and adjacent areas in Cambodia during March-April 2008-11 indicates that whilst populations in some protected areas are stable, in other locations population declines are ongoing. Outside of protected areas there is likely to be very little suitable grassland habitat remaining (Mahood et al. 2012).
The species does not occur in Laos PDR or Thailand. Within Viet Nam, Buckton and Safford (2004) cited the species as ‘Rare, possibly Resident’. Although there were records from close to the delta in the 1920s, the first records from the delta consisted of several sight records of up to four in the vicinity of Tram Chim NP, Dong Thap Province from 1990-1994. One or two individuals were recorded in Dong Thap Province between 1997 and 1999, and the remains of a dead bird were retrieved from the Hat Tien Plain, Kien Giang Province in 1997. During a survey in Tram Chim in 1999, local people reported breeding at the site and claimed to have found eggs and chicks. Recorded from Tram Chim in 2000 (Diep Dinh Phong, SIE team). Some people were also familiar with the characteristic display of the species, and a member of national park staff claims to have seen the eggs of this species. By 2004, it was considered unlikely that the species would occur outside the Tram Chim NP within Dong Thap Province, as all other major grassland habitat fragments have been converted to rice agriculture (Buckton and Safford 2004). At that time, the extent of grassland within the Hat Tien Plain was more extensive and could potentially have been a more important area for the species.
The key threats are the extensive loss and modification of grasslands through drainage, conversion to agriculture and plantations, overgrazing, inappropriate cutting, burning and ploughing regimes, heavy flooding, invasion of alien species, scrub expansion, dam construction and inappropriate and illegal development (Brahma and Lahkar 2009, Evans et al. 2009; van Zalinge et al. 2009). In particular, the spread of dry season rice cultivation in Cambodia is rapidly converting existing grassland habitat. Land sales and concessions are often pushed through despite resistance from local villagers (Evans et al. 2009). Excessive hunting for sport and food may have triggered its decline, but owing to advocacy and law enforcement is no longer a serious threat, at least in Cambodia. At least in South Asia, most populations are small, isolated and vulnerable to local extirpation. Other threats may include human disturbance and trampling of nests by livestock. Detailed research into the species' ecology in Cambodia demonstrated that the effects of human disturbance are weak and annual
Page 133 burning is important for maintaining suitable habitat, supporting the idea that community-based grassland management that maintains traditional agricultural practices will benefit Bengal Floricans. This has implications for management in South Asia, where remaining (and declining) populations are largely confined to strict protected areas in which such practices may not be occurring (Gray et al. 2007). Further study has revealed that, whilst burned grassland is selected by males during the breeding season, unburned grassland and other habitats providing cover are selected by females, demonstrating the need for appropriate grassland management in conservation areas that provides a variety of habitats to ensure the survival of this species (Gray et al. 2009).
The population in this species has been widely documented in Cambodia since 1997, but there is little information on the population of the species prior to this, and there is no readily obtainable quantifiable information on the population in Viet Nam, other than the species is probably extirpated here (Figure 6.75). It is assumed that the Bengal Florican was present in the Mekong Delta – but the populations are unknown, but population size unknown.
The 5 main drivers of change for this species are considered to be: Land use changes particularly dry season rice cultivation at the expense of traditional agriculture, and conversion of dry forest (wintering quarters) into seasonal rubber plantations Market-driven hunting (in 1980s) but now ceased Inappropriate land management practices Disturbance to nest sites Trampling of nests
Bengal Florican (Houbaropsis bengalensis)
2000 Mekong River in Laos PDR
1500 Mekong River in Laos PDR/Thailand Mekong River in Cambodia 1000 Tonle Sap River
500 Tonle Sap Great Lake
Percentage to relative 2015 (100%) Mekong Delta
0 1900 1950 1970 2000 2015
Figure 6.75 Large ground-nesting species of floodplain wetlands (Bengal Florican): Historic abundance estimates as % relative to 2015 (100%).
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6.10.8 Large channel-using species that require riparian forest
6.10.8.1 Lesser Fish Eagle (Ichthyophaga humilis)
Lesser Fish Eagle has a wide range across from India to Brunei, in most of Southeast Asia, an area of 2.92 million km2 (BirdLife International 2015), but occurs at low densities. It has a moderately small population estimated at 15 000-75 000 birds which is thought to be declining (Birdlife International 2012). It is thought to be undergoing a moderately rapid population reduction. It is therefore consequently classified as Near-Threatened (NT). Populations within Myanmar and Lao PDR are considered to be of global conservation significance.
In the Lower Mekong Basin, the species in Cambodia has two small isolated populations as a scarce resident in the northeast and southwest (Goes 2013). In Thailand it is rare in west and south and in Laos PDR as small numbers persist in several catchments (although fragmentation of populations and their small size renders them vulnerable to local extinction). In Viet Nam it is rare to locally fairly common in west Tonkin and south Annam.
This species was historically present along the length of the Mekong mainstream. Some observations and records were made in Laos PDR and Cambodia. This bird was observed in Sekong, Nam Ou, Xe Banghiang, and its tributaries in central Laos (David-Beaulieu 1949-1950, Duckworth 1999). By the mid-1990s, it had been reduced to a few isolated populations in the main watersheds of Mekong’s tributaries. For instance in some catchments in Laos PDR, especially, Nam Ou and Sekong, a few dozen pairs each were recorded in 2005 (Tordoff et al. 2005).
Within Cambodia, present in the central Stung – Treng Mekong with regular records since 2000, with five records during extensive surveys between November 2006-July 2007 (Timmins 2008, Bejuizen et al. 2008), and noted as uncommon during field work during January 2010-May 2012, with six records involving perhaps 5-6 birds (AC); also recorded along the O’Talas, Srepok and the upper Sekong. However, this bird was not recorded during surveys in Cambodia (Buckton and Safford 2004) and in either Cambodia or Laos PDR (Eaton and Nelson 2015).
The species is vulnerable to disturbance, egg and chick harvesting and habitat degradation. Over- fishing and perhaps especially, pollution, may already have impacted a moderately small population. Hunting of adults and nestlings has been the major cause of decline in larger birds in Laos PDR (Thewlis et al. 1998), with loss of favoured nest sites affecting tree-nesting species such as the fish eagle, which would have continued to decline even had persecution been brought under control. Furthermore, it’s reliance on undisturbed forests makes it vulnerable to the development of hydro- electric dams (Goes 2013). A moderately rapid and on-going population decline is suspected on the basis of rates of habitat loss and degradation.
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Lesser Fish Eagle is considered to be present at population levels of c. 1% of its 1900 populations (W. Duckworth pers. comm.) along the Mekong. There is no information on the rate of decline, so it has been assumed that the decline has been linear throughout the period 1900 – 2015, and equally along the length of the river.
Lesser Fish Eagle (Ichthyophaga humilis)
100000 Mekong River in Laos PDR
80000 Mekong River in Laos PDR/Thailand Mekong River in 60000 Cambodia Tonle Sap River 40000 Tonle Sap Great Lake 20000 Percentage to relative 2015 (100%) Mekong Delta
0 1900 1950 1970 2000 2015
Figure 6.76 Large channel-using species that require riparian forest (Lesser Fish Eagle): Historic abundance estimates as % relative to 2015 (100%)
The main drivers of change for this species are considered to be: harvesting, especially egg and chick harvesting; habitat degradation including loss of nesting sites along forested rivers; over-fishing; human traffic in waterways; water pollution.
6.10.8.2 Grey-headed Fish Eagle (Icthyophaga ichthyaetus)
Although widespread, this species is now only locally common and may have a moderately small population, which is thought to be undergoing a moderately rapid population reduction owing to habitat degradation, pollution and over-fishing. It is therefore classified as Near Threatened (Birdlife International 2015). Within Indochina, the species is found in Thailand (formerly a widespread resident, now absent from north and centre, rare and local in the south), Laos PDR (now rare), Viet Nam (scarce in south, disappearing from north), Cambodia (regional stronghold for the
Page 136 species – the density at Prek Toal is the highest in the world, indicating that Tonle Sap is probably of very high regional and likely global importance for the species, Goes 2013).
Within the Lower Mekong Basin within Cambodia, this species is historically fairly common in the Tonle Sap floodplain (Thomas and Poole 2003); it has been recorded throughout the swamp forest during surveys since 1992, including 13 birds in the Boeng Rohal area (Battambang) in April 1997, and 10-17 birds at Boeng Chmma in September 2006, and common at Prek Toal (many sources). This species was formerly present in the southeast of the country, but it is now a rare non-breeding visitor to the Mekong-Bassac floodplain (Goes 2013). Within Tonle Sap, 32 different nests were found within an 80km2 in and adjacent to the core area on 6-13 December 2005 (Tingay et al. 2006), and annual monitoring recorded up to 58 nests in 2006-2010 (Sun et al. 2010). Parr et al. (1996) estimated over 100 pairs at Tonle Sap Great Lake in 1996.
Within Laos PDR, this species was perhaps less common than Lesser Fish Eagle, and has also declined (Thewlis et al. 1998). For example, in comparison with the estimate of 100 pairs from Tonle Sap Great Lake in 1996, current (2015) Laos PDR numbers are very low (Thewlis et al. 1998).
This is a poorly studied species thought to be in recent decline in many portions of its range, possibly as the result of habitat loss (deforestation and loss of wetlands), overfishing, siltation, human disturbance, and pesticide contamination (BirdLife International 2009), although Tingay et al. (2006, 2010) pointed out that these statements are based mostly on anecdotal evidence.
For the purposes of this assessment, Grey-headed Fish Eagle is considered to be present at population levels of c. 25% of its 1900 populations (W. Duckworth pers. comm.; Figure 6.77) along the Mekong. There is no information on the rate of decline, so it has been assumed that the decline has been linear throughout the period 1900 – 2015, and within the BTSIA.
Grey-headed Fish Eagle (Icthyophaga ichthyaetus) 1000
900 Mekong River in Laos PDR 800 Mekong River in Laos 700 PDR/Thailand 600 Mekong River in 500 Cambodia 400 Tonle Sap River 300 Tonle Sap Great Lake
200 Percentage to relative 2015 (100%) 100 Mekong Delta 0 1900 1950 1970 2000 2015
Figure 6.77 Large channel-using species that require bank-side forest (Grey-headed Fish Eagle): Historic abundance estimates as % relative to 2015 (100%)
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For the Delta, the species is present. There are sporadic records of its occurrence but the numbers have not been quantified. For this reason it was listed as 100%
The main drivers of change for this species are considered to be: hunting, especially egg and chick harvesting; habitat degradation including loss of nesting sites along forested rivers; over-fishing; human disturbance (Tingay et al. 2006 found a negative correlation between human habitation and nest site occupancy rates in Cambodia); pollution.
6.10.9 Rocky crevice nester in channels
6.10.9.1 Wire-tailed Swallow (Hirundo smithii)
Wire-tailed Swallow has an extremely large range in Asia, an area of 15.1 million km2 (BirdLife International 2015). The population size has not been quantified, but it is not believed to approach the thresholds for Vulnerable and is evaluated as Least Concern (BirdLife International 2012).The species is found in India, Bangladesh, Nepal (rare and local in lowlands), Bhutan (very rare at lower altitudes), China (rare visitor to Hainan), Myanmar (widespread, scarce to locally fairly common), Thailand (rare in west and south),Cambodia (scarce resident in the northeast and southwest), Laos PDR (small numbers persist in several catchments, although fragmentation of populations and their small size renders them vulnerable to local extinction), Viet Nam (rare to locally fairly common in west Tonkin and south Annam), Peninsular Malaysia (scarce to locally fairly common but declining) and east Malaysia, Brunei (scarce), Indonesia (uncommon to rare; BirdLife International 2001).
The 2015 population is estimated as being at 70-90% of the 1900 level (W Duckworth pers. comm.).
In north Laos, there is evidence of decline since 2000 to 2012, although the species peters out north of Oudanxay. Between Louangphagang and Vientiane, the species is not uniformly distributed (see IUCN 2013 for full details on numbers and distribution), with birds typically seen in singles, duos or in small groups of up to 8 birds.
Within Laos PDR, the species forms large post-breeding flocks by September (e.g., 40 on 2nd October 2004; and in the Ban Nasa–Paksang area, 163, 327; and 200 to 500 on 14th and 15th July 1996 and 26th September 1999, respectively; Thewlis et al. 1998; Duckworth et al. 2002). The species is not common north of the town of Louangphabang (Duckworth et al. 2002; Fuchs et al. 2007), but it remains widespread and common in the southern half of the country wherever wide rivers have suitably rocky stretches (Thewlis et al. 1998; Duckworth et al. 2002; Timmins and Robichaud 2005).
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The numbers along stretches of the river vary between wet and dry seasons, but it is considered that most wet-season birds present are missed, probably because the speedboat-drivers actively avoided, by a wide margin, areas of rocky channel whenever possible. It may be either because the species goes high to feed under certain conditions, or because it loafs in inconspicuous perches. Less likely is that birds leave the channel: other than the two out-of-channel sightings detailed above, W Duckworth has only once in Lao PDR seen the species outside the channel (near Pakxan, also within a few hundred yards of the channel).
In Cambodia (from where it was first recorded in 1995), it is a local resident restricted to the upper Mekong river and its tributaries, favouring rocky river stretches with rapids (Goes 2013), and nowhere recorded in large numbers. It was found to be fairly common to uncommon during field work in the central Kratie – Stung Treng Mekong (its main stronghold in the country with perhaps <100 birds) in January-May 2010-2012 (AC), with two colonies of at least five and two birds in 2006-2007 (Timmins 2008). The species may benefit in future from the introduction of man-made nest sites. For example, in 2010 in Stung Treng, it was reported to nest under the newly built Sekong bridge, and probably nesting under the Srepok bridge on 26 January 2010 (FG). There are stray records from the Tonle Sap Great Lake (dry season) and Phnom Penh (Goes 2013). At least some birds remain in the riverine habitat during the floods.
The percentage of the regional population within the study area is very high (certainly 50% and probably 75%; W. Duckworth pers. com.). Within Laos PDR, it might seem that for a small, non- colonial breeder, the only predictable threat to this species would be damming of large rivers, which could drastically reduce breeding habitat proportionate to the decrease in seasonal change in water levels. However, nests are easy to find, and Timmin’s suspicion (R. Timmins to W. Duckworth pers.comm.) is that within Cambodia, human robbery of nest contents may be suppressing numbers, particularly where channel outcrops are small and simple, and nests are thus easily found. Consistent with this, within the survey area, the gaps in distribution within areas of rocky channel tend to be in stretches with narrow and simple rocky outcrops. However, there is no way of telling that this is not a habitat-driven distribution pattern.
The estimate of the 2015 population is 70-90% of 1900 levels (W Duckworth pers. comm.). Thus a population of 80% of 1900 levels has been assumed across the species range with a linear decline during this period. Such as estimate has been omitted from Zone 4b, as the species only occurs here as an occasional species.
The main drivers of change for this species are considered to be: Seasonal change in water levels Human robbery of nests Human disturbance
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Wire-tailed Swallow (Hirundo smithii) 200
180 Mekong River in Laos PDR 160 Mekong River in Laos 140 PDR/Thailand 120 Mekong River in 100 Cambodia 80 Tonle Sap River 60 Tonle Sap Great Lake
40 Percentage to relative 2015 (100%) 20 Mekong Delta 0 1900 1950 1970 2000 2015
Figure 6.78 Rocky-crevice nester in channels (Wire-tailed Swallow): Historic abundance estimates as % relative to 2015 (100%)
6.10.10 Dense woody vegetation / water interface
6.10.10.1 Masked Finfoot (Heliopais personatus)
Masked Finfoot is patchily distributed from north-east India and Bangladesh, through Myanmar, Thailand, Cambodia, Laos PDR and Viet Nam to Peninsular Malaysia, Sumatra and Java (one record), Indonesia (BirdLife International 2001). Populations are apparently in steep decline throughout its range such that its population is now thought to number in the low thousands at most, and possibly fewer than 1 000 mature individuals (J. C. Eames 2007 cited in Goes 2013).
This elusive species has a very small and very rapidly declining population as a result of the ongoing loss and degradation of wetlands and especially riverine lowland forest in Asia; it therefore qualifies as Endangered (Birdlife International 2015).
The species is patchily distributed from northeastern India throughout Southeast Asia and Indonesia and is enigmatic (Goes 2013). Populations are apparently in steep decline throughout its range such that its population is now estimated at 1 000-2 500 birds (Birdlife International 2012).
The species is very rare and poorly known, and any assessments for this species within the Lower Mekong Basin will by their very nature be provisional. Masked Finfoot was not recorded in Laos PDR until 1993 The species was first recorded in 1993, and has since been found in the Xe Kong basin
Page 140 and in Dong Khanthung proposed NBCA (Duckworth et al. 1999). It is too early to judge the size of the presumed breeding population, but it is unlikely to exceed 100–200 pairs (JAT). However, there is no evidence it has ever been common along the Mekong mainstream (W. Duckworth pers. comm.). Observations from Laos PDR are from wide stretches of river (20 m or more) and slow-flowing with no emergent vegetation, although the banks had good cover (Thewlis et al. 1998). Within Cambodia it occurs probably mainly as a breeding visitor, in forested rivers and streams up to 300m, as well as in the Tonle Sap swamp forest. Given the large area of potentially suitable habitat around Tonle Sap Great Lake, the population in that area may be of high conservation significance, although repeated surveys have failed to locate anything but tiny numbers of individuals (C. M. Poole in litt. 1999), local people are familiar with the bubbling call and the species might prove more abundant than records suggest. It may potentially be overlooked in the BTSIA to the extent that there might be tens of them rather than the handful of birds that get seen (c. one record per year), but extent of populations not considered to be any larger than this (S. Mahood pers. comm).
The main threat is the destruction and increased levels of disturbance to rivers in lowland riverine forest, driven by agricultural clearance and logging operations and increased traffic on waterways. Habitats have been further degraded by the removal of bankside vegetation and changes in hydrology resulting from dam construction, and siltation. Hunting and collection of eggs and chicks have been recorded; indeed the species is easily caught at the nest making it prey to opportunistic human hunters. Observations from Laos PDR indicate that rather than taking flight, birds only flush at distances of 20 m and then fly to adjacent bankside vegetation, whilst others just walked onto river banks to hide in the vegetation: such behaviour (which has also been observed in Thailand) may make the species more susceptible to hunting during the dry season.
No empirical estimates exist for the current rate of decline, but as a species reliant on undisturbed wetlands declines are anticipated across its range given the pressure on riverine and mangrove habitats. Duckworth (pers. comm.) has estimated a very provisional estimate of current population being 1% of 1900 levels. This estimate has been applied across all zones (Figure 6.79).
The main drivers of change for this species are considered to be: destruction and increased levels of disturbance to rivers in lowland riverine forest, driven by agricultural clearance and logging operations and increased traffic on waterways; habitat degradation through the removal of bankside vegetation; changes in flow timing and volumes; changes in siltation; hunting and collection of eggs and chicks.
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Masked Finfoot (Heliopais personatus)
100000 Mekong River in Laos PDR
80000 Mekong River in Laos PDR/Thailand Mekong River in 60000 Cambodia Tonle Sap River 40000 Tonle Sap Great Lake 20000 Percentage to relative 2015 (100%) Mekong Delta
0 1900 1950 1970 2000 2015
Figure 6.79 Dense woody vegetation / water interface (Masked Finfoot): Historic abundance estimates as % relative to 2015 (100%)
6.11 Status and trends: Mammals
The estimated 2015 ecological status for each of the geomorphology indicators is provided in Table 6.11. The definitions for the categories are given in Table 6.2. The expected trends in the indicators are discussed in Sections 6.10.1 to 6.10.10, respectively.
Table 6.12 Estimated 2015 ecological status for each of the mammal indicators
Irrawaddy Otters Hog Deer Area Dolphin 2015 2015 2015
Mekong River in Laos PDR NA E NA
Mekong River in Laos PDR/Thailand NA E NA
Mekong River in Cambodia E E E
Tonle Sap River NA E NA
Tonle Sap Great Lake NA E NA
Mekong Delta NA E NA
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6.11.1 Irrawaddy Dolphin
Irrawaddy Dolphins (Orcaella brevirostris) have a discontinuous distribution in the tropical and subtropical Indo-Pacific, almost exclusively in estuarine and fresh waters. They are found in coastal areas in South and Southeast Asia, and in three rivers: the Ayeyarwady (Myanmar), the Mahakam (Indonesian Borneo) and the Mekong. There are freshwater subpopulations in three large rivers: Ayeyarwady (up to 1 400 km upstream) in Myanmar, Mahakam (up to 560 km upstream) in Indonesia, and Mekong (up to 690 km upstream) in Viet Nam, Cambodia and Laos PDR, and two marine-appended brackish water bodies or lakes: Chilika in India and Songkhla in Thailand.
No range-wide survey has ever been conducted for this species (Stacey and Leatherwood 1997). The Mekong River Irrawaddy dolphins inhabit a 118-mile stretch of the river between Cambodia and Laos PDR, and are scarce. At least 125 (95% CI = 114-152) were present in the Mekong River (Beasley et al. 2007), with recent surveys indicating dramatic range declines in the Mekong, with between 78 and 91 individuals are estimated to still exist (WWF). In April 2015, only 5 dolphins remained in Laos PDR, in a 6-km2 trans-boundary river pool (Chiteal Pool/Boong Pa Gooang) that spans the Laos-Cambodia border. The Mekong sub-population was classified as Critically Endangered in the 2004 Red List because the numbers of reproductively mature individuals were estimated to be decreasing.
Irrawaddy dolphins were first reported from the Mekong River in the mid-1860s by the Frenchman Henri Mouhout, who rediscovered the Cambodian Ankor ruins (Mouhot 1966). In early August 1860, Mouhout was traveling on the Tonle Sap River past Phnom Penh and he noted “shortly afterward we entered the Mekon [sic], which was only now beginning to rise ... here shoals of porpoises sail along with their noses to the wind, frequently bounding out of the water” (Mouhot 1966, p. 173). There were perhaps a few thousand individuals in the river between Khone Falls and the delta c. 1900 – 1920 (Beasley et al. in Campbell 2009). The first dedicated study of dolphins’ inhabiting the Cambodian Mekong River was conducted in 1968/69 by a French doctoral student, Renee Lloze, who observed dolphins along the river from the Viet Namese/Cambodian border north to just past Kratie township, including Tonle Sap Great Lake (Lloze, 1973). The only known historical reports of dolphins in the Viet Namese Mekong River are from the 1920s. These reports were apparently collected by Frenchmen Gruvel (1925) and Krempf (1924-1925; cited by Lloze 1973). These early records suggest that dolphins historically occurred throughout the lower Mekong River, from the bottom of Khone Falls, south to the Viet Namese Delta (including Tonle Sap Great Lake), perhaps numbering at least a few thousand individuals. No historical or contemporary dolphin records are known from the mainstream Mekong River north of the Khone Falls. As a result of political instability, war, and internal conflict, little research had been conducted on the Mekong dolphin population before the early 2000s. Thus, the historical range of this species included the Sekong River, from Cambodia into Lao PDR, the Tonle Sap, and far downstream in the Mekong River into Viet Nam (Baird and Mounsouphom 1997; Smith and Jefferson 2002). In addition to a reduced range, the current
Page 143 population is also greatly reduced from presumed historical levels which, on consideration of reported hunting levels the latter half of the 20th century (Smith and Jefferson 2002; Beasley 2007), may have been an order of magnitude larger than in 2010 (Ryan et al. 2011). There is evidence of direct persecution of the species for oil extraction in Tonle Sap Great Lake during the mid-1970s (Perrin et al. 1996), with the Khmer Rouge using the oil from dolphins in lamps, and motorbike and boat engines, and also ate dolphin meat. After the Pol Pot regime when guns were abundant throughout the country, Viet Namese and Khmer soldiers reportedly shot at dolphins for target practice. Many interviewees from Stung Treng Province in Cambodia reported that they had observed groups of dead dolphins floating downstream after the Pol Pot regime (Beasley 2007). In 1994, the population of the entire river was estimated at no more than 200 individuals (Baird 1994).
Irrawaddy dolphins are primarily threatened by bycatch, the accidental capture of aquatic animals in fishing gear. Habitat degradation, deeper pools becoming shallower, decline in prey abundance and boat traffic disturbance. Also pollution from agrochemicals are all believed to be taking a toll. Studies on dolphin populations elsewhere have also identified impacts of boat-related tourism that include changes in swim direction, lengthened inter-breath intervals, reduction in inter-individual distances, changes in the type of surface behaviours exhibited, reductions in resting behaviour, an increase in breathing synchronicity between individuals and increased rates of whistle production. These cumulative short-term effects may also result in serious long-term conservation concerns (Beasley 2007).
In 2005, the Irrawaddy dolphin population in the Mekong river was estimated to be declining at > 4.8% per annum on the basis of the mortality rate evident in the carcass recovery programme, and field evidence that few new borns survive for more than one month (Beasley 2007). Based on the estimated Mekong dolphin population size (Beasley 2007) and typical growth rate of a cetacean population (4% per year, calculated from Wade 1998), the most conservative level of anthropogenic mortality that the Mekong dolphin population can currently withstand is less than one individual per year (Beasley 2007; Figure 6.80).
Irrawaddy Dolphin
1000 Mekong River in Laos PDR
800 Mekong River in Laos PDR/Thailand Mekong River in 600 Cambodia Tonle Sap River 400 Tonle Sap Great Lake 200 Percentage to relative 2015 (100%) Mekong Delta
0 1900 1950 1970 2000 2015
Figure 6.80 Irrawaddy Dolphin: Historic abundance estimates as % relative to 2015 (100%)11
11 Entered by Technical Lead to illicit comment.
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There are estimates of ‘a few thousand’ in the river between Khone Falls and the delta’ c. 1900, but as counts are not accurate and the location of concentrations not known, the species has simply been recorded as 100% in Figure 6.80.
The main drivers of change for this species are considered to be: harvesting and sport shooting; by-catch, the accidental capture of aquatic animals in fishing gear; fishing competition from humans; in-breeding; disturbance by boats.
6.11.2 Otters
6.11.2.1 Hairy-nosed otter, Smooth-coated otter, Asian small-clawed otter, Eurasian otter
This mammal species guild comprises four species - Eurasian otter (Lutra lutra), Asian small-clawed otter (Aonyx cinerea), hairy-nosed otter (Lutra sumatrana) and smooth-coated otter12 (Lutrogale perspicillata). The last three of these species are endemic to tropical Asia, and almost all have disappeared from northern south-east Asia, and also north- east India (W. Duckworth pers. comm.). It is considered that there are no secure populations of any otter species in northern south-east Asia (W. Duckworth pers. comm.).
It is not possible to select a single species as an indicator species, as the majority of otter records are not identified to species. Historically, up to four species would have occurred throughout the Lower Mekong Basin, but currently numbers of all otter species are very low, and all are virtually extirpated.
The Eurasian otter is widespread across the Palearctic and so the Asian populations are of no global conservation significance based on current taxonomy (W. Duckworth pers. comm.), but nonetheless the populations have declined.
The smooth-coated otter is considered to be Vulnerable due to an inferred future population decline caused by habitat loss and exploitation (Hussain et al., 2008a), the hairy-nosed otter is considered to be Endangered due to past population declines. Based on estimated rates of decline, this species is suspected to have declined by up to 50% in the past 30 years due to illegal poaching and hunting, pollution, by catches and prey depletion due to over-fishing. The current rates of decline are expected to continue and further threaten this species. Throughout its entire range, hairy-nosed otter is under increasing pressure due to high levels of poaching (Hussain et al., 2008b), the Asian small- clawed otter is considered vulnerable due to a projected future population decline due to habitat loss
12 Depicted
Page 145 and exploitation. In the last few decades, the range of Asian small-clawed otter has shrunk, and the Eurasian otter is considered to be near threatened due to an ongoing population decline, but at a rate no longer exceeding 30% over the past three generations.
It is not possible to establish Hairy-nosed Otter’s pre-exploitation mainland range, but its populations are declining rapidly across mainland Southeast Asia, through trade-driven hunting (Duckworth and Hill 2008; Sheperd and Nijman 2014) and habitat degradation. The species is suspected to have declined by at least 50% or more in the past 30 years (based on Pacifici et al. 2013), and listed as Endangered. In all likelihood, the current rates of decline will to continue into the future.
In Viet Nam, the majority of Mekong Delta has been converted into rice fields, reducing the habitat of otters to a few parks (Dong et al. 2010). The investigation of hairy-nosed otter in Viet Nam dates back to 1925, with the first sighting in 1932, and a population was recorded in 2000 following the conducting of otter surveys in the Mekong delta from U Ming Thuong Nature Reserve (now a National Park) in Kien Giang Province. This species has been reported from low-lying peat swamp forests dominated by Melaleuca cajuputi in the lower Mekong.
Within Cambodia, hairy-nosed otters are found at Tonle Sap Great Lake (Olsson et al., 2007) where the otters live mainly in the flooded forest and scrub surrounding the lake. Like many predators the hairy-nosed otter occurs in low density and the number and frequency of sightings are very few. Surveys of the Mekong River between Kratie and Stung Treng towns in 2006-2007 recorded occasional tracks of both probably Lutra otters and also smooth-coated otters during the dry season, with local residents reporting that otters are still present in the eastern channels and Koh Pleng Island area of the western mainstream – if otters of any species do persist, it is in very small numbers (Bejuizen 2008).
Within Laos PDR, small numbers of otters seem to persist between Luangphabang and Vientiane (IUCN 2013), but this information is based solely on village reports. They have clearly been hunted out from most of it, but a few wary animals might persist, visit or have recolonised. If so, these animals may largely go undetected because of current unfamiliarity many residents have with otter signs, especially the younger generation who did not experienced otters when they were much more common than at present.
The two main species (Eurasian and hairy-nosed) live in non-flowing water bodies regardless of slit content and thus are unlikely to be affected by dams other than by changes in market connectivity, which would increase with dams particularly in the upper Cambodian reaches of the Mekong (W. Duckworth pers. comm.).
It is considered that otter numbers are now present at c. 3% of 1900 populations (W. Duckworth pers. comm.), and this figure has been applied as representing a linear decline fashion across all zones (Figure 6.81).
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Otters 3500
3000 Mekong River in Laos PDR
2500 Mekong River in Laos PDR/Thailand 2000 Mekong River in Cambodia
1500 Tonle Sap River relativeto 2015 (100%)
1000 Tonle Sap Great Lake
Percentage Mekong Delta 500
0 1900 1950 1970 2000 2015
Figure 6.81 Otters: Historic abundance estimates as % relative to 2015 (100%)
The main drivers of change for these species are considered to be: hunting for the wildlife trade, meat and traditional medicine habitat loss / degradation habitat disturbance such as sand mining and fishing activities pollution by-catch.
6.11.3 Wetland ungulates
6.11.3.1 Hog Deer (Axis porcinus annamiticus)
Hog deer has a wide distribution in Asia from India to Australia, but its population within each country is small and the range of the species is limited. The species has undergone dramatic range-wide declines, which have gone largely unnoticed. It therefore the species is classified under the IUCN Red List category as Endangered (EN) in 2008; prior to this the species was not categorized as threatened (Timmins et al. 2012, in Brook in press).
There are two subspecies - Axis porcinus annamiticus (A.p.a) and Axis porcinus porcinus (A.p.p) (Brook in press). Populations remain in Bangladesh, Northeast Cambodia, several areas of Myanmar, northeast India and Nepal (Humphrey and Bain 1990, Khan 2004, Maxwell 2007). There is uncertainty concerning the populations in Bhutan and Pakistan where there is a lack of data
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(Biswas and Mathur 2000, Biswas 2004). The species has been extirpated from many countries including Thailand, Laos PDR and Viet Nam (Duckworth et al. 1999). In the Lower Mekong Basin, Cambodia holds the only known wild populations of the Indochinese subspecies Axis porcinus annamiticus (Brook in press); this subspecies is just the same subpopulation reported in Myanmar (Maxwell et al. 2007).
The species has been extirpated from Laos PDR, Viet Nam, and Thailand. It has been reintroduced to a number of protected areas in the last of these, some of which require ongoing management (controlled burning to prevent succession and maintain grassland) and control of livestock in grasslands. The taxonomy of Axis porcinus is still under deliberation. Most published checklists and taxonomic authorities classify A. porcinus as a polytypic species with two subspecies, namely the nominate occurring in Pakistan, India, Bangladesh, Bhutan, Nepal and Myanmar, and A. p. annamiticus in Thailand, Laos PDR, Viet Nam, Cambodia and China. There is uncertainty as to where the geographic boundary lies between A. p. porcinus and A. p. annamiticus (although it is likely to be located in Myanmar or Thailand), and whether the taxa have come into contact in modern times (Maxwell et al. 2007).
The Hog Deer was previously widespread and common over much of lowland South and mainland Southeast Asia (Evans 1902), but during the mid- to late-20th century it underwent rapid range-wide declines as a consequence of hunting and conversion of floodplain grasslands to agriculture (Timmins et al. 2012; Wilson and Mittermeier 2011 cited in Brook in press).
The species is still heavily hunted, including the opportunistic taking of fawns by domestic dogs, and its range is limited by habitat loss and fragmentation. As the populations are now so small and isolated, there is a real risk of the population suffering from reduced viability as a result of inbreeding.
The Hog Deer is recognised as Endangered by IUCN, based upon a past reduction of 50% or greater in three generations (taken here as about 21 years), through a combination of population trends across its range. During the mid and later decades of the twentieth century, the global population underwent rapid range-wide reductions, with the almost total loss of Hog Deer from South-east Asia (when it was widespread and numerous in much of Cambodia, southern Viet Nam, lowland Thailand and probably plains Laos). The rate of population decline in the last 21 years in Cambodia, Viet Nam, Laos PDR, Thailand, China and Bangladesh has exceeded 90%, a continuation of similar declines from the 1950s onwards (Figure 6.82).
The main drivers of change for this species are considered to be: hunting and disturbance; habitat loss and fragmentation; land use change; inundation.
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Hog Deer (Axis porcinus annamiticus)
100000 Mekong River in Laos PDR
80000 Mekong River in Laos PDR/Thailand Mekong River in 60000 Cambodia Tonle Sap River 40000 Tonle Sap Great Lake 20000 Percentage to relative 2015 (100%) Mekong Delta
0 1900 1950 1970 2000 2000
Figure 6.82 Wetland ungulates (Hog Deer): Historic abundance estimates as % relative to 2015 (100%)
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7 Preliminary reference data sets
The reference data sets are those that DRIFT uses to: Determine seasonal thresholds with which to delineate seasons for all scenarios. Provide the input values for the X-axes for the construction of response curves for the DRIFT indicators. Provide a reference against which to predict ecosystem change.
It should be stressed that these data will not be used for final DRIFT calibration, and were used only to provide indicative ranges of parameters to allow for preliminary DSS set-up.
7.1 Reference period used
To be suitable for use in DRIFT, all the reference data sets must cover the same temporal period. As per the agreement between the NMCs, the reference period used for the purposes of the population of DRIFT response curves was 1985-2008. As a baseline scenario / reference data set has not yet been defined, the reference data sets, and thus the reference scenario used at this stage (July 2015) is referred to as the ‘preliminary reference scenario’.
7.2 Data entered into the DSS
7.2.1 Hydrology (DSF)
The hydrological time-series entered into the DSS were supplied by IKMP using the DSF models. The relevant parameters are: 1985-2008 climate (rainfall) data; 2007 level of infrastructure development; 2003 level of landuse; a daily time set.
The hydrographs for the 1985-2008 period for FA1 to FA3 are shown in Fig xx to xx together with the relevant D/T1 and T1/W thresholds.
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Figure 7.1 Hydrographs and D/T1, T1/W thresholds for FA1 to FA3
7.2.2 Hydraulics (DSF): ISIS-ID and WUP-FIN
The hydraulics imported into the DSS were supplied by IKMP using a combination of the DSF models (ISIS-ID) and WUP-FIN models, with the exception of: FA4 (Stung Treng) for which neither DSF nor WUP-FIN models were available; FA8 (Delta) for which the modelling is as yet incomplete.
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The 1-dimensional ISIS (ISIS-ID) model was used for all channel hydraulics at FA1 – 3. The locations of the cross-section selected for BioRA FAs 1 to 3 are provided in Figure 7.2. The ISIS model provided daily time-series of: mean water stage and depth (by subtraction of bed elevation) (the daily depth time-series for FA1 to FA3 are shown in Figure 7.3); mean water velocity in the channel; mean wetted perimeter.
ISIS was not set up for FA4, but rated cross-sections were available, therefore depth, wetted perimeter, and velocity were determined from the rated cross-sections.
At FA to FA3, a daily time-series of shear stress (SS) was calculate based on the slope (S) between the location of the cross-section and the nearest downstream cross-section, and depth at the cross- section (D) using the equation SS =10000 x S x D.
Figure 7.2 Location of the cross-sections used for calculation of hydraulics parameters (larger blue crosses) for FA1 (cross-section M2172), FA2 (cross-section M1588), and FA3 (cross-section M1144)
Figure 7.3 Depth time-series at FA1, FA2 and FA3
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Figure 7.4 Velocity time-series at FA1, FA2 and FA3
Figure 7.5 Wetted perimeter time-series at FA1, FA2 and FA3
For the floodplains associated with FA3, the WUP-FIN 3-dimensional model for Se Bang Fai (Figure 7.6) was used. There is also a WUP-FIN model available for Nam Som Khram, for which the data were generated, in case these are required in the analysis of scenarios.
The WUP-FIN models provided daily time-series of: Flooded area (Figure 7.7); Average depth; Maximum depth; and Average velocity.
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Figure 7.6 Floodplain areas covered by the WUP-FIN models for Nam Som Khram and Se Bang Fai in FA 3 (green outline)
Figure 7.7 Modelled time-series of area of floodplain at FA 3 (Se Bang Fai)
The hydrology and hydraulics for FA4, 5, 6, 7 and 8 have not yet been entered into the DSS.
7.2.3 Water quality and suspended sediments
Water quality and suspended sediment input to DRIFT for the Council Study baseline and development scenarios will be generated by the MRC DSF but because the calibration of the DSF for
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For water quality parameters the time-series were derived using the results from the Water Quality Monitoring Network, for the period 1985 – 2008. In the case of suspended sediments, rating curves were constructed relating river discharge to either the total suspended solids results available in the WQMN or the historic depth integrated suspended sediment sample data. The following sections provide more detail for how water quality indicators were derived (Table 7.1).
Table 7.1 Data sources used for the construction of the water quality time series used in initial population of DRIFT DSS
Focus Daily Flows from DSF Monthly Water Sediment Area (1985 – 2008) Quality FA1 Chiang Saen Chiang Saen Chiang Saen TSS13 FA2 Nong Khai Vientiane Nong Khai SSC14 FA3 Nakhon Phanom Nakhon Phanom Nakhon Phanom TSS FA4 Pakse Pakse Pakse SSC FA5 Kratie Kampong Cham Kampong Cham TSS
Note: The daily flow series used to derive Total Nutrients, TSS and SSC rating curves are based on observed flow data from HYMOS, while the flow series imported into DRIFT are those provided by the DSF models as described and illustrated in Section 7.2.1.
7.2.3.1.1 Water quality parameters excluding TN, TP or TSS / SSC Time series were derived for the following parameters: Physico – chemical parameters: Temperature, pH, Dissolved Oxygen, Electrical Conductivity, Alkalinity, Chemical oxygen Demand; Nutrients: Total Nitrogen, Ammonia, Nitrate + Nitrite, Total Phosphorus, Dissolved Phosphate; Anions: Sulphate.
The time-series were constructed using the measured monthly value as the result for each day in the month. In other words, the monthly value for March 1987 was applied to each day of March 1987. Where monthly data was missing in a particular year, the median of the whole time-series was subsistuted.
For each site, time-series of the monitoring results were constructed for the period 1985 – 2013 although the DRIFT time-series were limited to the period 1985 – 2008. The longer time-series were provided so potential future changes to range of water quality parameters could be considered during the construction of response curves for DRIFT. The datasets were also grouped by months to provide information about the monthly variability of the parameters at each site.
13 TSS = Total suspended solids determined on surface grab sample under WQMN. 14 SCC = Historic suspended sediment concentration determined on depth integrated samples. Data from MRC Master Catalogue
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Monitoring results for the parameters phosphate and silica are not available for the entire 1985 – 2008 period.
At several of the sites, there are abrupt changes in water quality or sediment concentrations around 2003. Many of these changes are consistent with the establishment and operation of dams in the upper Mekong Basin and probably reflect these changes.
7.2.3.1.2 Suspended sediments (TSS / SSC) For each site TSS and SSC (if available) values were plotted against the average daily flow on the monitoring day from the HYMOS database, and a rating equation was determined using a power function. This function was then applied to the daily flow values at the site to estimate daily suspended sediment concentrations.
SSC results were used for Nong Khai and Pakse. TSS results were used for Nakhon Phanom and Kampong Cham as no SSC values are available for 1985 – 2008. At Chiang Saen, both TSS and SSC values are available. The relationship based on flow / TSS was used to generate the daily time- step because they provide a better balance with respect to the downstream values (the SSC produce much higher sediment loads). This discrepancy is likely reflecting changes in sediment transport mechanism (proportion of sediment transported as bedload as compared to suspended load) combined with potential monitoring errors associated with the samplers used. This is an issue that is being explored and addressed by the IKMP modelling team as part of the incorporation of sediments into the DSF.
The calibration of suspended sediment for the DSF is in progress and the sediment time-series used to calibrate DRIFT will change in the future. The time-series generated as part of this work should be considered indicative only.
7.2.3.1.3 Presentation of data and results For each site, the available water quality results are presented as time-series and grouped by months. A summary of the results showing the median monthly value of each parameter is also presented to provide an indication of seasonal variability. For suspended sediment (TSS or SSC) and nutrients at some sites, the graphs used to derive rating equations are also presented.
7.2.3.2 FA1: Chiang Saen (upstream Pak Beng)
Water quality and suspended sediment results from Chiang Saen were used to derive the input time- series for FA1. The WQMN time-series results for Chiang Saen are shown in Table 7.2, and the flow series, rating curves and derived time-series for suspended sediments are contained in Table 7.3.
Several of the time-series show changes in 2003 which may be consistent with the establishment and commissioning of a hydropower project upstream and the associated discharge of water altered during impoundment. These water quality changes include increased concentrations of Fe (not
Page 156 shown), COD, TP, and low DO. The relationship between flow and TSS also changed at this time, and two different rating curves were derived to estimate TSS.
At Chiang Saen, the concentrations of total nutrients (TN, TP) show correlation with TSS concentrations, and daily estimates were derived using a rating equation based on the relationship between the total nutrient and total suspended solids concentrations. Similar to suspended sediment, two separate rating curves were derived for the periods pre- and post-2003 as the relationship between TSS and TN or TP abruptly changed at this time. The appropriate relationship was then used to generate the daily suspended sediment concentrations at the site for each day.
Table 7.2 Chiang Saen water quality results used to derive time-series for FA1.
Chiang Saen Time-series Monthly grouping of results 85 – 08
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Chiang Saen Time-series Monthly grouping of results 85 – 08
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Chiang Saen Time-series Monthly grouping of results 85 – 08
Figure 7.8 Monthly median water quality values at Chiang Saen showing seasonal variability.
TP and TN time-series are based on a regression between TN and TP and TSS in the water quality data set applied to TSS daily time series. The fit for TP is better than the fit for TN.
Comparison of TSS and SSC results shows differences between the sampling methods, and the large decrease in suspended sediment that occurred in 2004
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Table 7.3 Flow time-series and rating curves used to estimate susoended sediment concentrations and total nutrient values for FA1.
Chiang Saen Chiang Saen – Estimated
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Chiang Saen Chiang Saen – Estimated
7.2.3.3 FA2: Vientaine / Nong Khai
The WQMN water quality results from Vientiane were used to derive the input time series for FA2, with the exception of suspended sediment, which was derived using the depth integrated suspended sediment monitoring results and flow from Nong Khai. These monitoring sites are located just downstream of the limit of FA2, but were used because there are no mainstream WQMN sites located within FA2 which have historic results extending back to 1985. The water quality time-series and data grouped by month are shown in Table 7.4, and a graph showing the monthly variability of each of the water quality parameters is shown in Figure 7.9.
There are no TN results available prior to 2007 at Vientiane. The post-2007 TN results show a poor correlation with TSS, so TN cannot be estimated based on historic TSS values. TN does show a reasonable correlation with NO2+3 so a monthly TN time-series was constructed based on the relationship with NO2+3 and used to generate the daily time series 1985 – 2008. The rating curve and generated results are shown in graphs in Table 7.4.
Similarly, there are limited results for phosphate in the WQMN data set. The available phosphate values show a reasonable correlation with Total Phosphorus, so rating curve was constructed and used to generate monthly phosphate values, which were used as the basis for the daily time series. The correlation between TP and Phosphate suggests that most of the TP is attributable to dissolved phosphorus. Unlike at Chiang Saen, Total Phosphorus does not show a correlation with TSS, which is also consistent with the TP being dominated by dissolved species rather than particulates. The daily time-series for TP for DRIFT was based on the monthly monitoring values.
The Nong Khai suspended sediment monitoring results show a sharp decrease beginning in 2004. This large decrease is not reflected in the suspended sediment results at Chiang Saen, and the reason for the reduction is unknown. The best fit to the results is provided by using two different rating equations for the periods before and after 2004, however this produces a large step-change in the results. It was decided to estimated suspended sediment at the site based on one rating equation such that the decrease in concentrations was more gradual.
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Table 7.4 Water quality time-series and monthly grouping of results at Vientiane, 1985 - 2007
Vientiane Time-Series Monthly Grouping of Results 1985 - 2008
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Figure 7.9 Monthly median values for water quality parameters at Vientiane based on 1985 – 2008 WQMN monitoring results
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Table 7.5 Daily flow series from Nong Khai (HYMOS) and rating curves used to estimate daily suspended sediments in FA2.
Measured time-series Estimated time-series / rating curves
At the downstream sites, there was very poor correlation between the suspended sediment concentrations and total nutrients and much stronger correlations between the total nutrients and the dissolved nutrient parameters (PO4, NO2+3). This suggests that the majority of the total nutrients are attributable to dissolved species rather than particulates. At these sites the WQMN monitoring values were used to generate the daily time-series for DRIFT.
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7.2.3.4 FA 3: Nakhon Phanom (upstream Xe Bang Fai)
The water quality monitoring site of Nakhon Phanom is located in FA3 and the results have been used to derive the input time-series for DRIFT for this Focus Area. Median monthly values used for the water quality parameters shown in the summary. There were poor correlations between TP and TN and sediment parameters so the monthly monitoring results were used to derive the daily time series (Table 7.6). Median monthly values for the water quality parameters at Nakhon Phanom are shown in Figure 7.10.
There are no depth-integrated suspended sediment results for 1985 – 2008 at Nakhon Phanom, so the daily time-series for suspended sediment is based on the WQMN TSS results. There is a distinct change in flow and TSS between 1993 and 1994 so two different rating curves were derived and used (Table 7.7).
The following graphs show the rating equations used to derive the daily TSS values at Nakhon Phanom, and the daily flow at the site. The daily flow results increase and the TSS results decrease around 1993. The reason for these changes is unclear.
Table 7.6 Time-series of WQMN water quality results and monthly grouping of results
Nakhon Phanom time-series Nakhon Phaon Monthly Grouping
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Nakhon Phanom time-series Nakhon Phaon Monthly Grouping
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Nakhon Phanom time-series Nakhon Phaon Monthly Grouping
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Figure 7.10. Monthly median water quality results for Nakhon Phanom 1985 – 2008.
Table 7.7 Observed flow and suspended sediment results at Nakhon Phanom and rating curves used to estimate daily time series for DRIFT input.
7.2.3.5 FA 4: Pakse
Pakse is located at the upstream end of Focus Area 4. The time-series of water quality results at the site and results grouped by month are shown in Table 7.8. The median monthly values of the parameters are shown in Figure 7.11.
There are few TN results for Pakse. The relationship between TN and NO2+3 was used to estimate a monthly 1985 - 2008 time series of TN, with the monthly estimated time-series used to derive the daily time series for DRIFT (Figure 7.12).
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Table 7.8 Water quality time-series and monthly grouping of water quality results for Pakse.
Pakse time-series Pakse Monthly Grouping
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Pakse time-series Pakse Monthly Grouping
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Pakse time-series Pakse Monthly Grouping
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Pakse time-series Pakse Monthly Grouping
Figure 7.11 Median monthly values of water quality parameters at Pakse, 1985 - 2008.
Figure 7.12 Suspended sediment rating curve and daily suspended sediment time-series based on rating curve for Pakse, based on 1997 - 2002 monitoring results.
7.2.3.6 FA 5: Kampong Cham
Kampong Cham is located in Focus Area 5 and is representative of the reach. Water quality results have only been collected from the site since 1993. Where monthly values are not available, the median monthly values of the dataset were used to construct the DRIFT input time-series. Time- series graphs and the results grouped by month are shown in Table 7.9. Median monthly values for the parameters are shown in Figure 7.13.
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Limited TN results are available at Kampong Cham. There is not a good correlation between TN and NO2+NO3, so an extended TN time-series could not be easily estimates as at other WQMN sites. Monthly median TN values were used to construct the time-series for periods lacking monitoring results.
WQMN TSS results are available for Kampong Cham, but flow results are not available for the site, so flow results from Kratie were used for deriving a relationship between flow and TSS at Kampong Cham. (Table 7.9
Table 7.9 Time-series and monthly grouping of WQMN water quality results at Kampong Cham.
Kampong Cham Time-Series Kampong Cham Monthly Grouping
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Kampong Cham Time-Series Kampong Cham Monthly Grouping
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Kampong Cham Time-Series Kampong Cham Monthly Grouping
Figure 7.13 Median monthly values for water quality parameters at Kampong Cham, 1985 - 2008.
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Table 7.10 Graphs showing the rating curve (left) used to derive the estimated TSS time- series at Kampong Cham (right).
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8 Layout and population of the DRIFT DSS for BioRA
The DRIFT DSS has been set-up for BioRA. It was originally envisaged that three individual DRIFT DSSs would be set up: one for the Mekong and Tonle Sap rivers (FA1-6), one for the Tonle Sap Great Lake (FA7) and one for the Delta (FA8). Advances to the DSS software meant that this was unnecessary and all eight of the BioRA focus areas are now contained within a single DSS.
Population of the DSS involved: Detailing the project name, client and consultants involved BioRA. Setting up the system description, including: o focus areas and ‘arcs’ between focus areas that will be used for connectivity and other assessments; o photographs of focus areas. Defining the full suite of BioRA indicators. Linking each indicator to its driving indicators. Importing the reference hydrological data for the focus areas, and calculating the seasonal flow indicators. Importing the reference water quality data for the focus areas, and calculating the seasonal water quality indicators. Importing the reference sediment data for the focus areas, and calculating the seasonal sediment indicators. Creating, importing and calculating seasonal values for other indicators requested by the specialists (e.g. onset of the T1 season, the time at which sediment ‘delivery’ at a site has reached 20% of that year’s annual sediment load). Generating the inputs to the response curves for population by the BioRA specialists. Entering the preliminary response curves for each indicator. Entering the preliminary explanations of response in each indicator to a change in each linked indicator.
The reference data used in the initial set up of the DSS are discussed in Section 7, and are referred to as the ‘preliminary reference scenario’. They may or may not be similar to data used in Baseline Scenario, but this is dependent on the outcome of the Baseline Scenario discussions.
For this progress report, reference hydrological, hydraulic, water quality or sediment data were available for FA, FA2, FA3 and FA4, and have been entered into the DSS. Data for the other focus areas will be entered as and when they become available15.
The DRIFT DSS is divided into three main sections: Set-up, Knowledge Capture and Analysis. Set- up and Knowledge Capture for BioRA are discussed in Sections 8.1 and 8.2, repectively. Analysis is not yet relevant for BioRA.
15 Hydrological and hydraulic data for FA5, 6 and 7 were received from IKMP on 24th July 2015, and are being entered into the DSS.
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8.1 Setup
The SETUP section of the DSS comprises several sub-sections outlining the project details, delineation of the basin (focus areas and zones), scenarios, disciplines and indicators, and links between indicators (Figure 8.1).
Figure 8.1 The SETUP section of the DSS
The “System Description” sub-section includes modules for specifying the location of the focus areas, BioRA zones, the location of water-resource developments and for the inclusion of site photographs. Also specified are “paths” that determine which zones are linked to each other, and will be used later for assessing connectivity impacts (in the “Knowledge Capture” section).
The “Indicator selection” sub-section includes modules for specifying project and site indicators, and their links. The “Project indicators” module lists of all the indicators for each discipline (Figure 8.2) (“Indicator pool” tab), and the “Site indicators” module, shows which of these apply to each focus area.
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Figure 8.2 The “Indicator Pool” tab of the “Project indicators” module of the DSS
The links for each indicator are detailed in the “Links” module (as shown by the green cells in Figure 8.3). Note that red cells indicate that the link was switched off for calibration). For example, in Figure 8.3, erosion is linked to the duration of the wet season (wet duration).
Figure 8.3 The “Links” module of the DSS16
16 Note: This shows a subset of the geomorphology links as all indicators do not fit onto one screen in the DSS.
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8.2 Knowledge Capture
The KNOWLEDGE CAPTURE section of the DSS comprises several sub-sections for importing and processing the time-series of the main driver indicators and other external indicators, such as sediment and water quality, a connectivity sub-section, a response curve sub-section, and an integrity sub-section that relates to the status and trends of the ecosystem. The sub-sections of most relevance to the set-up are discussed below.
8.2.1 Hydrology and hydraulics sub-section
The “Hydrology and hydraulics” sub-section is used to import and analyse the time-series for the main driver indicators (flow for the Mekong river focus areas, and water level / depth for the Tonle Sap Great Lake).
8.2.1.1 Site calibration
The threshold values for defining seasons are set in the “Site calibration” module. The four seasons are: Dry season (D) Transitional 1 (T1) Wet season (W) Transitional 2 (T2)
The two threshold values required are the D/T1 threshold and the T1/W threshold. Parameters similar to those defined by Adamson (2007) were used to define the seasonal thresholds. For example, the T1/W threshold is the mean annual discharge and the first up-crossing above this value defines the start of the wet season (as per Adamson 2007).
Thus, for FA 1 (Pak Beng; Figure 8.4), the mean annual discharge in the reference data set is 3123 m3/s, so the start of the wet season is the the first up-crossing of 3123 m3/s (Figure 8.4). Thus, each year, when the (five-day average) dischare exceeds 3123 m3/s for the first time, the wet season is deemed to have begun. The start of the T1 season was set as the first up-crossing of 5.3 x the minimum dry season flow of 589.25 m3/s (Figure 8.4), which is 2389 m3/s. For each year, therefore, when the (five-day average) flow crosses 2389 m3/s for the first time, the T1 season is deemed to have begun. Figure 8.5 shows one year of season delineation for the preliminary reference scenario at FA1.
8.2.1.2 Calc flow indicators
Once the season threshold values are entered, all flow indicator values are calculated for each year of the reference period. Figure 8.6 shows a section of the results for FA1: for example, “Dd” which is the duration of the dry season, is 161, 189, and 200 days for the first three years of the time-series for the preliminary reference scenario.
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Parameters Threshold values
Season start dates
Figure 8.4 Parameters, threshold values and season start dates for the preliminary reference scenario at FA1
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Figure 8.5 Season delineation for one year for the preliminary reference scenario at FA1
Figure 8.6 A section of the annual flow indicator values for the preliminary reference scenario at FA1
8.2.2 Water quality, Sediment and External indicators sub-sections
Time-series indicators, other than the main driver, from external models or externally calculated, are imported into the DSS and analysed in the “Water quality”, “Sediment” or “External indicators” sub- section. For the BioRA FAs the external indicators are those listed in Table 3.1 under the headings Hydraulics, Sediment and Water Quality.
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The DSS uses the season onsets (as determined in Section 8.2.1) to calculate the relevant summary statistics for each season for the external indicators. Minimum, mean, and maximum values of each indicator are calculated for each of the four seasons (e.g. Figure 8.7).
Figure 8.7 Time-series of indicator values for the external indicator “Shear stress” at FA1
8.2.3 Response curves sub-section
8.2.3.1 Response curves: Habitat and Biota
In the “Habitat and Biota” module, each indicator within a selected discipline has a separate tab. On each indicator tab, a space is provided for completing a response curve for each linked indicator (e.g. Figure 8.8).
For flow, hydraulics, sediment, water quality and other external indicators, each response curve X- axis is pre-populated with values from the linked indicator for that focus area (Figure 8.8; Table 8.1).
In the case of response curves for links to other internal BioRA indicators, the y-axis values range between 0 and 250%, with median = 100% (Figure 8.9).
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Figure 8.8 The Geomorphology: Erosion (bank/bed incision) tab in the BioRA Response curves: Habitat and Biota module
Table 8.1 Values from modelled time-series provided for each response curve
the minimum feasible value for the input indicator or the minimum likely to be encountered in the scenarios (i.e. some value less than the MinBase) the minimum value ever encountered in the baseline scenario
a value intermediate between MinBase and Median
the median value of the preliminary reference scenario
a value intermediate between Median and MaxBase
the maximum value ever encountered in the baseline scenario the maximum feasible value for the input indicator or the maximum likely to be encountered in the scenarios (i.e. some value moe than the MaxBase)
Figure 8.9 Values from the linked indicator time-series provided for each response curve
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8.2.4 Integrity
The “Integrity” sub-section contains a number of modules that relate to the contribution of each indicator to the overall ecosystem integrity, the baseline discipline status (Ecological Status), and the relationship between abundance and integrity of each indicator (Abundance/integrity relationships). For BioRA, this information was obtained from the status and trends assessments (see Section 6).
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9 Preliminary BioRA response curves
9.1 DRIFT response curves
Response curves depict the relationship between a biophysical or socio-economic indicator and a linked indicator. For BioRA, Response Curves linked an indicator to any other indicator deemed to be driving change. The aim is not to ensure that every conceivable link is captured but rather to restrict the linkages to those that are most meaningful and can be used to predict the bulk of the likely responses to a change in the flow or sediment regimes of the river.
Response curves are constructed using severity ratings (Section 9.1.1).
The time-series approach means that the Response Curves are used to predict the likely seasonal change in an ecosystem indicator in response to the flow/sediment conditions experienced in that, or possibly preceding, seasons. For instance, the kind of question typically asked to facilitate setting the Min 5-day dry season discharge Response Curve for Rhithron fish species are: “If the dry season discharge declines from baseline values, what will be the consequences for the abundance of rhithron species?” Do rhithron species use the main river in the dry season? Do the available data show that rhithron species abundances change noticeably over the climatic range covered in the baseline, i.e., are they noticeably more abundant in wet years than in dry years, or vice versa? What kinds of habitats do adults of rhithron species use in the main river? Do they breed in the dry season? Do they breed in the main river or in the tributaries? Where do they lay their eggs? What sorts of habitat do fry, fingerlings and juveniles use in the main river? At what discharge(s) does the favoured habitat(s) disappear? What is the consequence of these habitats not being available for one season? If discharge reaches zero for one season, are there pools that the fish will be able to survive in? Can they survive for a dry season in pools? Do lower or higher dry season flows affect fishing pressure? What do the adults/juveniles/fingerlings/fry eat? How will the food base be affected by changes in dry season lowflows? Etc.
Often, a species will be expected to survive even an extremely-dry dry season, with possibly only minor changes (5-10%) in overall abundance if dry season flows drop to zero. If, however, the flows drop to this level in the dry season year after year, then the cumulative effect on populations is likely to be far greater. The time-series enable the DSS to capture this cumulative effect.
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9.1.1 Scoring system used
Into the foreseeable future, predictions of river change will be based on limited knowledge. Most river scientists, particularly when using sparse data, are thus reluctant to quantify predictions: it is relatively easy to predict the nature and direction of ecosystem change, but more difficult to predict its timing and intensity. To calculate the implications of loss of resources to subsistence and other users in order to facilitate discussion and tradeoffs, it is nevertheless necessary to quantify these predictions as accurately as possible.
Thus severity ratings are used to construct the Response Curves. These severy rating scale ranges from -5 (large reduction) to +5 (very large change; Brown et al., 2008; Table 9.1), where the + or – denotes an increase or decrease in abundance or extent. These ratings are converted to percentages using the relationships provided in Table 9.1. The scale accommodates uncertainty, as each rating encompasses a range of percentages; however, greater uncertainty can also be expressed through providing a range of severity ratings (i.e. a range of ranges) for any one predicted change (after King et al., 2003).
Table 9.1 DRIFT severity ratings and their associated abundances and losses – a negative score means a loss in abundance relative to baseline, a positive means a gain.
Severity rating Severity % abundance change 5 Critically severe 501% gain to ∞ up to pest proportions 4 Severe 251-500% gain 3 Moderate 68-250% gain 2 Low 26-67% gain 1 Negligible 1-25% gain 0 None no change -1 Negligible 80-100% retained -2 Low 60-79% retained -3 Moderate 40-59% retained -4 Severe 20-39% retained -5 Critically severe 0-19% retained includes local extinction
Note that the percentages applied to severity ratings associated with gains in abundance are strongly non-linear17 and that negative and positive percentage changes are not symmetrical (Figure 9.1; King et al. 2003).
For each year of hydrological record, and for each ecosystem indicator, the severity rating corresponding to the value of a flow (or other linked) indicator is read off its Response Curve. The severity ratings for each flow indicator are then combined to provide an indication of how abundance, area or concentration of an indicator is expected to change under the given flow conditions in each year, relative to the changes that would have been expected under baseline conditions in the catchment.
17 The non-linearity is necessary because the scores have to be able to show that a critically-severe loss equates to local extinction whilst a critically severe gain equates to proliferation to pest proportions.
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800
700
600
500
400
300
% of PD retained 200
100
0 -5 -4 -3 -2 -1 0 1 2 3 4 5 Severity Rating Figure 9.1 The relationship between severity ratings (and severity scores) and percentage abundance lost or retained as used in DRIFT and adopted for the DSS. (PD=present day AND = 100%).
9.1.2 Addressing data limitations
The main limitation for any assessment of ecosystem response to development is the paucity of data. This is a universal problem, as ecosystems are complex and we will probably never have complete certainty of their present and possible future characteristics. Instead it is essential to push ahead cautiously and aid decision-making, using best available information. The alternative is that water- resource development decisions are made without consideration of the consequences for the supporting ecosystems, eventually probably making management of sustainability impossible. Data paucity is addressed in the DRIFT process by accessing every kind of knowledge available – monitoring and other data specific to the LMB, general scientific understanding, international scientific literature and local wisdom – and capturing these in a structured process that is transparent, with the DSS inputs and outputs checked and approved at every step. The Response Curves (and the reasoning used to construct them) are available for scrutiny within the DSS and they, as well as the DRIFT DSS, can be updated as new information becomes available.
A second aspect of the paucity of data is that it is neither known what the river was like in its pristine condition nor exactly how abundant each ecosystem aspect (sand bars, fish, etc.) was then or is now. To address this, all DRIFT predictions are made relative to the baseline situation (there will be a little more, or a lot less, than today, and so on).
These inherent uncertainties also mean that the trends and relative position of the scenarios are more reliable predictors of the impacts of the scenarios than are their absolute values.
9.2 Focus Area 1: Examples of preliminary response curves
At the June/July BioRA team meetings the lead and national consulatnts started the process of propulating the BioRA DRIFT database. As discussed above, these curves are constructed to
Page 189 capture the known responses of the indicators to the climatic conditions that prevailed over the reference period, i.e., 1985-2008. For instance, monitoring data, if available, are used to determine whether an indicator increases in a wet or dry year, or a short or long wet season.
Examples of these curves for FA 1 (Pak Beng) are provided in Table 9.2 to Table 9.7. The BioRA response curves are in an early stage of development, and have been set-up for the reference time- series described in Section 7. At this stage the explanations written in summary without references, but will be expanded and referenced as the project proceeds. The preliminary response curves are presented here as examples only, and should not be misconstrued as the final product. All the preliminary curves and explanations completed to date are available for viewing in the DRIFT DSS on the Council study website.
Response curves are presented for: FA1 – Geomorphology indicators: Erosion (bank / bed incision) – Table 9.2; FA1 – Vegetation indicators: Channel: Biomass riparian vegetation – Table 9.3; FA1 – Macroinvertebrate indicators: Insects on stones – Table 9.4; FA1 – Fish indicators: Rhithron resident – Table 9.5; FA1 – Herpetofauna indicators: Aquatic serpents – Table 9.6; FA1 – Mammals and Bird indicators18: Medimum/large ground-nesting channel species – Table 9.7.
In Table 9.2 to Table 9.7, the graph in the header row shows the response of each of the example indicators to the combined linked indicators over the reference period. In these graphs, the red line gives the mean response and blue lines give the upper and lower limits, i.e., uncertainty.
Thereafter, for each example indicator, the response curves for each of its linked indicators are presented, together with graph showings the response of the example indicator to each individual linked indicator only19 over the reference period: In the response curves, the red line gives the mean response, and blue and green lines give the upper and lower limits, respectively. The y-axis for this curve is on the left. In the individual responses, the pink shaded areas show the annual value for the linked indicator, and the blue line shows the response of the geomorphology indicator to that linked indicators only. The y-axis for this curve is on the right.
Although some uncertainty is already built into the curves, the response ranges (Y2 in the response cruves in Table 9.2 to Table 9.7) have not yet been completed as these are done once the curves are closer to finalisation. Once completed, the ranges will capture the full uncertainty in the future predictions.
18 There are no mammal indicators for FA1. 19 i.e., all other linked indicators remain at their median values.
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Table 9.2 Example for Geomorphology (Erosion (bank / bed incision)): Response curves and explanations for linked indicators
Response curve Response to reference linked indicator and explanation
The longer the duration of the wet-season, the longer the relatively high shear stress will act on the banks and bed, leading to additional erosion.
The shorter the duration of sediment transport, the less sediment is available at the end of the wet / T2 season for deposition.
The timing of sediment onset determines how much sediment is available for deposition during the wet and T2 season. The later the sediment onset delivery, the higher the probability that sediment will be available for deposition during T2. Note that we have considered that late onset can also promote erosion.
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The smaller the grain-size, the more likely that sediment will remain in suspension and be transported through the system rather than be deposited. If everything else remains the same, erosion will increase relative to present conditions as there will be less deposition and the same erosion. The X-axis represents the median of the size classes, 0.00=<0.002: Grain size is 100% for the reference time-series.
T2 is a time of high potential sediment deposition due to decreasing water flows and water velocity. The presence of sediment during this time will increase the likelihood of sediment deposition. This factor is considered to have a strong control on net erosion over the annual cycle. As sediment load decreases, the likelihood of deposition decreases and net erosion increases.
A reduction in sediment load during T1 will decrease the likelihood of deposition and increase the likelihood of erosion. This factor is not considered as strong a control on erosion as sediment load during the wet or T2 seasons because (1) the T1 season is generally very short, and (2) net erosion will be more closely linked to erosion / deposition during the long wet season and deposition during T2 as water levels drop.
The higher the wet season average sediment load, the more river energy that is expended carrying sediment, the less energy available for erosion (Leopold et al. 1964).
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Lower sediment loads will decrease deposition and increase the likelihood of erosion
Erosion is directly related to the shear stress acting on the bed or the banks. The higher the shear stress, the higher the likelihood of erosion and vice versa. T2 is the season when deposition is most likely to occur, so an increase in shear stress during this period would both decrease the liklihood of deposition and increase the risk of erosion.
The wet season is the period when shear stress is highest and the risk of erosion is greatest, and likelihood of deposition is lowest. Increasing shear stress will directly increase liklihood of erosion.
Shear stress is directly proportional to erosion as it is the force of the water that can pickup and transport sediments.
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Shear stress is directly proportional to erosion as it is the force of the water that can pickup and transport sediments.
Biomass increases bank stability by increasing roughness of the bank, which reduces shear stress. Increasing the presences of biomass on the banks will reduce erosion rates, and decreasing biomass would be expected to increase erosion.
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Table 9.3 Example for Vegetation (Channel: Biomass riparian vegetation): Response curves and explanations for linked indicators
Response curve Response to reference linked indicator and explanation
The lower bank vegetation grows on rock, anchoring into cracks. Sand that is deposited on the banks of the river at FA1 smothers this vegetation. Thus, the more sand the less vegetation. Given that about half the bank is vegetated in FA-1, a 100 increase in sand on the banks equals a c. 50% decrease in vegetation.
Reduced dry season results in the drowning of lower bank vegetation due to longer inundation time. Increased dry should maintain the status quo for lower bank vegetation.
A heightened waterline in the dry season will decrease extent of lower bank vegetation (tentatively). [supposing two consecutive years of high water lines will drown submerged shrubs of the lower bank vegetation] A lowered waterline will encourage a shift of lower vegetation downward but no change in cover.
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Table 9.4 Example for Macroinvertebrates (Insects on stones): Response curves and explanations for linked indicators
Response curve Response to reference linked indicator and explanation
Invertebrates on stones require clean stones, preferably cobble size (about 10 cm diameter). If erosion increases of decreases substantially there will either be a bed of larger sized boulders or finer material, neither of which if preferred by this group.
Increased water clarity will mean a decrese in very fine sediment settlement on the stones, and possibly also lower abrasive force on the stone fauna, increasing biomass.
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Increased water clarity will increase algal growth on stones, and consequently allow increased insect biomass.
The minimum dry season flow will be the limiting habitat area during the dry season. Even zero flow for a short period will not eliminate species entirely (some individuals will survive as eggs or larvae in the stream bed) but will reduce populations.
Below 3 mg/L oxygen invertebrate assemblages will become impaired.
Rocky habitat is the habitat for these species, so increased area will increase overall abundance, while decreased area will decrease overall abundance.
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Table 9.5 Example for Fish (Rhithron species): Response curves and explanations for linked indicators
Response curve Response to reference linked indicator and explanation
Size of bed sediment impacts on rhithron because decline in sediment size can degrade habitat suitability for these species that typically required coarse bed materials for feeding and nursery habitat and fine sediments block interstitial spaces, the large material tends to be more appropriate habitat.
Benthic macroinvertebrates can be a major source of food for fish of all guilds. If there is less abundance/biomass there is likely a reduction in fish production of the guild. This relationship also extends to juvenile life stages, which rely of macroinvertebrates as a primary food source but can shift to other foods as the fish gets larger/older.
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The onset of the dry season represents a time rhithron species are able to migrate to shallower areas with suitable substrate for spawning, earlier onset allows the fish greater time to migrate but too late onset could asynchronise spawning migration and maturation. Also if dry season starts earlier, it is good for fish as they can mature in less stressful conditions prior to spawning.
The dry season duration is important to rhithron fishes as conditions over shallower waters and rapids become more suitable for breeding and growth. The longer the duration of the dry season but maintenance of flows and reasons depths the greater the opportunities to spawn and grow before the onset of torrential flows.
Water low flow minimum 5day during the dry season could have strong negative impacts (similar to deep pools) on fish populations as they often congregate/aggregate in deep pools during the dry season. Fish become stressed in the low water levels remaining in the rivers and are exposed to increased fishing pressure.
Rapid increases in flows can strand fish, especially juvenile life stages on the floodplains or flush fish downstream as their swimming tends to be weak. Rapid increases from rain events or hydropeaking can flush fish from their nursery areas, impacting on population resilience. Rhithron species are particularly vulnerable because they are found in the rapids and subjected to rapid fluctuations in flow velocities, although they are adapted to these conditions if the habitat conditions and heterogeneity is intact.
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Fish show various tolerances to dissolved oxygen but will survive in conditions above 7 mg/l. Most species will die below 2-3 mg/l except the more robust generalists and especially the black fishes that are physiologically and anatomically adapted to survive in very low oxygen conditions, including air breathing.
This indicator is used as a surrogate of nutrients [N and P] which underpin the food chain, as well as to habitat quality. As sediment concentrations declines nutrient delivery is expected to decline proportionally, especially the availability of P which is considered limiting to primary production. Less sediment loading also means the habitat is more suitable for larval fish hatching and nursing after fertilisation.
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Table 9.6 Example for Herpetofauna (Aquatic serpents): Response curves and explanations for linked indicators
Response curve Response to reference linked indicator and explanation
Riparian vegetation provides shelter, ambush place (for foraging) and foods for aquatic and semi-aquatic snakes. When it is lost, many snakes can no longer survive due to loss of habitat (). Biomass of riparian vegetation, especially of aquatic and semi-aquatic plants links to abundance of aquatic snakes. It is estimated that there would be a c. 40% decline if the biomass of riparian vegetation dropped to zero and an
increase of c. 20% if the biomass was c. 250% of 2015 levels.
Most water snakes in the LMB are among the top predators, feeding predominantly on fishes and amphibians, but also on other reptiles and crustacean (Voris and Murphy 2002). The fish biomass is considered be a main factor in determing the abundance of water snakes. It is estimated that there would be a c. 50% decline if the fish biomass dropped to zero and a c. 50% increase if the biomass was 250% of 2015 levels.
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Floods provide foods and support for the expansion of water snakes to new areas in the wet season. Thus, if the flood volume drops to lower levels this will result in a drop in snake abundance. Years with higher flod volumes are good for snakes, however, if floods are very high – this also poses a problem for the snakes.
Most water snakes prefer living in calm or slow moving water bodies (e.g. lakes, pools, littoral areas with vegetation). Therefore, strong average channel velocity is predicted to wash out water snakes away from their shelters.
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Table 9.7 Example for Birds (Medimum/large ground-nesting channel species): Response curves and explanations for linked indicators
Response curve Response to reference linked indicator and explanation
The species is described as a local and uncommon resident on undisturbed riverine sandbars and islands during the dry season, and similar habitat during the rainy season (Goes 2013). The concensus of opinion seems to be that the use of sandbars is much reduced due to human activities, with the species now more common within 'channel mosaic' habitats (most likely because they are less disturbed here). In channel mosaic stretches, the stream channel at low flow season comprises a rich and varied mix of extensive sand and gravel features, reaching out from banks as bars, and as islands, and extensive rock outcrops. These mosaic stretches often have wide colonisation by bushland and/or grassland. Among the bushland, Homonia riparia (Euphorbiaceae) is a predominant species. Thus, if there is a reduction in the availaiblity of exposed sandy habitat to zero, then this will result in a decline in the population of River Lapwing, which would likely move away from the area. If the availability of sandy habitat increases only a slight increase is expected as it is assumed that the population will have reached carrying capacity and/or there may be many other factors controlling population growth, e.g. human disturbance.
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While there is no published work on diet, the species eats insects off the ground mostly along edges of the water (both adults and young lapwings eat insects). Birds will pick insects up anywhere, but they mostly forage at wet sand areas along water margins. Occasionally around rocks and gravel, but not often compared to wet sand or mudflat areas. If there are no on stones available, then this expected to result in a decline of c. 30% of the population of River Lapwing. However, if the population of insects on stones increases by 50%, then it is considerd that the population of river lapwing will increase by 10%. If the availaibility of insects on stones increases by over or above 100%, then the population of river lapwing will potentially increase by 15% in both cases.
The total loss of littoral inverts diversity the population of River Tern/River Lapwing will be declined slighly - 10% as the birds would especially for River Lapwing but probably much lower for River tern because river insects are not its major diet. In case the loss by 75% and 50% of of the littoral inverts diversity their populations will be declined 10% equally. However, if the of the insects on stones is increased by 50% their populations will be increased very slighly - at 10%, then although the littoral inverts diversity is increased up to double and over the trend of positive change of the bird population will be increased by 15% and keeps stable at this figure of the growth.
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10 Next steps
10.1 Schedule of follow-up BioRA activities
The updated schedule of the next BioRA activities is provided in Table 10.1. The aim of the BioRA team is to complete population and most of the calibration of the DRIFT DSS for at least FA1-7, and to write-up the specialist reports that support the DSS by mid-December 2015. At that point the DRIFT DSS will be ready to run analyses of the water resources development scenarios for these sites as and when the results of the modelling of hydrological, sediment and water quality regimes for these become available. A list of the BioRA deliverables that accompany these tasks is provided in Table 10.2.
Table 10.1 Schedule of BioRA activities (as at 25th July 2015)
No BioRA Tasks Dates
1 Source and appoint lead specialists Complete
2 Preparation meeting, and indicator and site selection Complete – Progress Report 1
Field visit Part I Complete – Progress Report 1 3 Field visit Part II Cancelled
4 Collation and preparation of relevant data and information March – November 2015
5 Status and trends assessment Draft complete (this report)
DRIFT DSS Set-up (this report) 6 Knowledge Capture FA1-7: 17-24 September 2015
FA1-7: 17-24 September 2015, plus ongoing liaison to end 2015 7 Calibration FA8: TBD
8 Analysis of water-resource development scenarios FA1-7: 15 – 21 February 2016
Specialist reports (draft, excl. Delta) 13 November 2015
Specialist reports (internal review and revision; excl 9 21 December 2015 Delta)
10 Input to Thematic and Cumulative Reports Mid-2016
Page 205 Table 10.2 BioRA deliverables
Contracted No. Deliverables Revised dates Status dates Presentations for a day-long session on DRIFT, 1 November 2014 November 2014 Completed plus an overview of available EF methods Progress Report: Indicator and Site Selection and 2 February 2015 February 2015 Completed Field Visit Report
3 Progress Report: DSS Set-up Report March 2015 July 2015 This report
Specialist reports – excluding final Response 4 September 2015 December 2015 Ongoing Curve Motivations Progress Report: Populated and calibrated 5 DRIFT DSS - including final Response Curve October 2015 December 2015 Ongoing Motivations DRAFT Technical Report for the individual 6 December 2015 2016 Not started scenarios DRAFT Technical Report for the cumulative 7 February 2016 2016 Not started scenario
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11 References
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Appendix A. BIORA DELIVERABLES
No. Deliverables Contracted dates Revised dates20 Status Presentations for a day-long session on DRIFT, 1 November 2014 November 2014 Completed plus an overview of available EF methods Progress Report: Indicator and Site Selection and 2 February 2015 April 2015 Completed Field Visit Report 3 Progress Report: DSS Set-up Report March 2015 July 2015 This report Specialist reports – excluding final Response 4 September 2015 November2015 Started Curve Motivations Progress Report: Populated and calibrated 5 DRIFT DSS - including final Response Curve October 2015 December 2015 Started Motivations DRAFT Technical Report for the individual 6 December 2015 2016 Not started scenarios21 DRAFT Technical Report for the cumulative 7 February 2016 2016 Not started scenario
20 See Section 9. 21 In all likelihood, all the scenarios will be cumulative and this task will fall away (see Section Error! Reference source not ound.).
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Appendix B. BIORA TEAM MEMBERS FOR JUNE/JULY 2015 TEAM MEETINGS
Name Discipline OSP OSV Dr So Nam BioRA Task Leader: MRC Fisheries Programme X X Dr Henry Manguerra Council Study Coordinator X X Prof. Cate Brown BioRA Team Technical Lead X X Dr Alison Joubert DRIFT DSS Manager X X Manothone Vorabouth Council Study Administrative Assistant X Dr Lois Koehnken Geomorphology and Water Quality Lead Specialist X X Dr Andrew MacDonald Vegetation Lead Specialist X X Dr Ian Campbell Macroinvertebrate Lead Specialist X Prof. Ian Cowx Fish Lead Specialist (to Pakse) X Dr Chavalit Vidthayanon MRC Fisheries Programme X Dr Hoang Minh Duc Herpetology Lead Specialist X Anthony Stones Bird and Mammal Lead Specialist X Toch Sophon Geomorphology Cambodia Specialist X X Pich Sereywath Biodiversity, excl. fish Cambodia Specialist X X Dr Chea Tharith Fish Cambodia Specialist X Chaiwut Grudpun Fish Thailand Specialist X Dr Hoang Thanh Tung Geomorphology Viet Nam Specialist X X Vu Vi An Fish Viet Nam Specialist X Dr Bounheng Soutichak Geomorphology Laos PDR Specialist X X Thananh Khotpathoom Vegetation Laos PDR Specialist X Dr Phaivanh Phiapalath Fauna, excl. fish Laos PDR Specialist X Dr Kaviphone Phouthavong Fish Laos PDR Specialist X
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Appendix C. ANNOTATED TABLE OF CONTENTS FOR BIORA SPECIALIST REPORTS
The BioRA Specialist Report will comprise two volumes: 1 BioRA DRIFT DSS 2 BioRA Specialist Report.
Volume 2, BioRA Specialist Report, will comprise individual Sections for each of the BioRA disciplines. An annotated example of the Table of Contents for each discipline-section is provided below. The disciplines are: Geomorphology Vegetation (including algae) Macroinvertebrates (including zooplankton) Fish Reptiles and amphibians Birds Mammals.
Other relevant disciplines are hydrology, hydraulics, sediments and water quality. Data for these disciplines will be provided from the DSF by IKMP, and they will thus not form part of the BioRA Specialist Report.
The proposed basic Table of Contents for each discipline is as follows: D Discipline D.1 Introduction D.1.2 Objectives of the geomorphology component of BioRA As per Terms of Reference. D.1.4 Assumptions and limitations Including time limitations imposed by Contract. D.1.5 Abbreviations and acronyms This will be moved to a common section in the front of the document once all disciplines have completed their individual reports. D.2 Description of the BioRA zones and Focus Areas, with the focus on discipline A description of the discipline-relevant aspects of each Focus Area, and key differences between Focus Areas, if any. D.3 Discipline indicators This section should provide as detailed information (from the literature and existing data sets) about each indicators. Reasons for selection Definition If there were any obvious omissions with respect to indicators, why they were omitted If indicator species were used, what were they, how they were chosen Ecological and life-history characteristics of indicator guilds/taxa, where relevant Linked indicators and why they were selected If there were any obvious omissions with respect to links, why they were omitted.
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D.5 Status and trends As per Section 5 of this progress report D.6 Motivations for shape of response curves Detailed explanations, with reference to data and literature as appropriate, for the final shape of each response curve for each linked indicator. Includes a Figure for each Response Curve. D References
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