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 Page i 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 ...................................................................................................