REPORT
Wetland Delineation and Assessment for the Water Use Licence Application for the Upgrade of Bulk Water Services in Modimolle
Client: Tlhagontle Consulting Services Reference: MD2563 Revision: 01/Final Date: 31 October 2016
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ROYAL HASKONINGDHV (PTY) LTD
21 Woodlands Drive Building 5 Country Club Estate Woodmead
Johannesburg 2191 Transport & Planning Reg No. 1966/001916/07
+27 11 798 6000 T +27 11 798 6005 F [email protected] E royalhaskoningdhv.com W
Document title: Wetland Delineation and Assessment for the Water Use Licence Application for the Upgrade of Bulk Water Services in Modimolle Document short title: Modimolle Pipeline Wetland Assessment Reference: MD2563 Revision: 01/Final Date: 31 October 2016 Project name: Modimolle Pipeline Wetland Assessment Project number: MD2563 Author(s): Paul da Cruz
Drafted by: Paul da Cruz
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Disclaimer No part of these specifications/printed matter may be reproduced and/or published by print, photocopy, microfilm or by any other means, without the prior written permission of Royal HaskoningDHV (Pty) Ltd; nor may they be used, without such permission, for any purposes other than that for which they were produced. Royal HaskoningDHV (Pty) Ltd accepts no responsibility or liability for these specifications/printed matter to any party other than the persons by whom it was commissioned and as concluded under that Appointment. The quality management system of Royal HaskoningDHV (Pty) Ltd has been certified in accordance with ISO 9001, ISO 14001 and OHSAS 18001.
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Table of Contents
1 INTRODUCTION 1 1.1 Aims of the Study 1 1.2 Site Location and Description 1 1.3 Assumptions and Limitations 2 1.4 Definition of Surface Water Features, Wetlands and Hydric Soils 2 1.4.1 Surface Water Features 3 1.4.2 Wetlands 3 1.4.3 Riparian Zones 4 1.5 Wetland Delineation Techniques 7
2 Legislative Context 9 2.1 The National Water Act 9 2.2 The National Water Act and Riparian Areas 10
3 METHODOLOGY FOR ASSESSMENT 10 3.1 Detailed Wetland Crossing Assessment 10 3.1.1 Wetland Functional Assessment 11 3.1.2 Wetland State (Health) Assessment 12 3.1.3 Assessment of Ecological Importance and Sensitivity (EIS) 13 3.2 Identification of Wetland Impacts and Mitigation Measures 14
4 STUDY AREA BIOPHYSICAL ENVIRONMENT 14 4.1 Geology, Macro-geomorphology & Topography, and implications for drainage 14 4.2 Macro Drainage Characteristics 15 4.3 Vegetation Types 16 4.4 Land Types 16 4.5 Study Area Freshwater Conservation Planning Context 17
5 FINDINGS OF ASSESSMENT 19 5.1 Surface Water Typology and Occurrence 19 5.1.1 Channelled Valley Bottom Wetlands 25 5.1.2 Un-channelled Valley Bottom Wetlands 26 5.1.3 Seeps 26 5.2 Physical Characteristics of Wetlands in the Study Area 27 5.2.1 Soil characteristics 27 5.2.2 Wetland Vegetation 29
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6 RESULTS OF ECOSTATUS ASSESSMENTS FOR WETLAND UNITS IN THE STUDY AREA 33 6.1.1 DP-BS_1a-c 33 6.1.2 DP-BS_2a-b 35 6.1.3 DP-BS_3a-c 38 6.1.4 DP-BS_4 41 6.1.5 DP-BS_5 43 6.1.6 DP-BS_6 45 6.1.7 DP-BS_7 47 6.1.8 DP-BS_8a-c 50 6.1.9 DP-BS_9a-b 52
7 IMPACTS ASSOCIATED WITH THE PROPOSED PIPELINE 55
8 MITIGATION MEASURES AND CROSSING REHABILITATION PLAN 56 8.1 Pipeline Construction Mitigation Measures 56 8.1.1 Management of flow and silt prevention through the works area 58 8.2 Servitude Rehabilitation and Re-vegetation 58
9 REFERENCES 59
Table of Tables
Table 1 - Ecosystem services included in WET-EcoServices (Kotze et al, 2009) ...... 12 Table 2 - PES Categories assigned by the WET-Health Tool (MacFarlane et al, 2009) ...... 13 Table 3 – Ecological Importance and Sensitivity Scores as calculated by the wetland EIS Tool (Rountree et al, 2013) ...... 13 Table 4 – Wetland HGM Unit crossed by / within 500m Radius if the Pipeline ...... 20 Table 5 – Tiered classification for wetlands in the study area ...... 25
Table of Figures
Figure 1 – Locality Map...... 2 Figure 2 - Schematic diagram indicating the three zones within a riparian area relative to geomorphic diversity (Kleynhans et al, 2007) ...... 6 Figure 3 – The relationship between wetland state, functionality, EIS and impacts / pressures acting on a wetland ...... 11 Figure 4 – Quaternary catchments and drainage in the wider area ...... 15 Figure 5 – Limpopo Conservation Plan Freshwater Sensitive Features in the Study Area 19 Figure 6 – Wetland Occurrence in the Study Area ...... 21
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Figure 7 – Wetland Reaches 1&2 ...... 21 Figure 8 – Wetland Reaches 3&4 ...... 22 Figure 9 – Wetland Reach 5 ...... 22 Figure 10 – Wetland Reach 6 ...... 23 Figure 11 – Wetland Reach 7 ...... 23 Figure 12 – Wetland Reaches 8&9 ...... 24 Figure 13 – Signs of wetness (iron mottling) in unspecified material underlying a yellow- brown apedal B horizon in the wetland DP-BS_Vch_9a ...... 27 Figure 14 – Part of a soil sample from wetland DP-BS_Seep_1b showing the transition point between an E horizon and the underlying soft plinthic B horizon ...... 28 Figure 15 – Moribund stand of Imperata cylindrica in the seep wetland DP-BS_Seep_1a 29 Figure 16 – Un-channelled valley bottom wetland with Syzigium cordatum trees in the wetland in the reach DP-BS_Seep_2a ...... 30 Figure 17 – Un-channelled section of the reach of the valley bottom wetland DP- BS_Vu_8b; note the heavily thinned woody riparian margins of the wetland ...... 31 Figure 18 – A mix of Imperata cylindrica grass and the invasive plant Seriphium plumosum in the wetland DP-BS_Seep_6 ...... 32 Figure 19 – Track cleared into the seep component of the wetland near the WTW ...... 34 Figure 20 – Siltation observed in the upper part of the wetland reach ...... 36 Figure 21 – Dense stand of poplars in the wetland reach immediately downstream of the dam ...... 39 Figure 22 –Lateral wetland habitat in the reach that has been invaded by Eucalyptus trees ...... 41 Figure 21 –Livestock trampling in a wetter flow depression in the seep wetland ...... 44 Figure 22 –Part of the wetland with a natural vegetative composition (left) and another part having experienced extensive invasion by Seriphium plumosum (right) ...... 46 Figure 23 – Part of the reach in the Estate where natural wetland and riparian vegetation has been removed and replaced by grassy fairways (foreground), with a natural vegetative assemblage in the background ...... 48 Figure 24 – Example of felling of large trees within the riparian corridor of the reach, close to the correctional facility ...... 51 Figure 25 – Deposition of excess sediment within the wetland; note the presence of alien invasive trees in the background ...... 53
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Acronyms
Acronym Acronym description
CBA Critical Biodiversity Area
DWS Department of Water and Sanitation
EIA Environmental Impact Assessment
EIS Ecological Importance & Sensitivity
EMPr Environmental Management Programme
GN Government Notice
HGM Hydrogeomorphic
NEMA National Environmental Management Act
NWA National Water Act
PES Present Ecological Status
WMA Water Management Area
WULA Water Use Licence Application
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Glossary
Glossary Term Glossary Text
Alluvial Material / Sedimentary deposits resulting from the action of rivers, including those deposited deposits within river channels, floodplains, etc.
Anaerobic The absence of molecular oxygen.
Anthropogenic Originating in human activity.
Apedal A term indicating the a degree of aggregation of soil particles within a soil horizon, where the material is well aggregated, but without well-formed peds (individual soil aggregates); in the context of the South African Soil Classification System, apedal soils also include structureless soils (e.g. sands) and somewhat more structured soils than the above description.
Baseflow The component of river flow that is sustained from groundwater sources rather than from surface water runoff.
Colluvial Relating to gravitational forces that result in the transport and deposition of soil and / or rock fragments down hillslopes to the base of the slope.
Dystrophic A soil that suffered marked leaching that has resulted in the sum of exchangeable (as opposed to soluble) Calcium, Magnesium Potassium and Sodium being very low (<5cmol(+) per kg clay). Compare with mesotrophic.
E Horizon A greyish, bleached subsoil horizon with very weakly developed structure (being loose or friable in the moist state) that is usually paler in colour than the overlying topsoil horizon or the subsoil horizon that overlies it, due to the marked in situ net removal of colloidal matter.
Ephemeral A watercourse that flows at the surface only periodically.
Facultative Occurring optionally in response to circumstances rather than by nature; applied to wetland plants in this context – a facultative species is a species usually found in wetlands, but occasionally found in non-wetland areas.
Fluvial The physical interaction of flowing water and the natural channels of rivers and streams.
G Horizon A subsoil horizon that is naturally saturated with water for long periods to form dominant grey, low chroma colours (often with blue or green tints) with or without mottling, with the accumulation of colloidal (clay) matter in the horizon
Gleying The process by which a material (soil) has been or is becoming subject to intense reduction as a result of prolonged saturation by water. Gleyed soils are characterised by grey (due to an absence of iron compounds), blue and green
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colours (due to an absence of ferrous compounds).
Herb A small non woody plant in which the aerial parts die back at the end of every growing season.
Hydric / Hydromorphic Soils formed under conditions of saturation, flooding or ponding for sufficient Soils periods of time for the development of anaerobic conditions and thus favouring the growth of hydrophytic vegetation.
Hydrology The scientific study of the distribution and properties of water on the earth’s surface.
Hydromorphy A process of gleying and mottling resulting from intermittent or permanent presence of free water in soil. Results in hydromorphic soils.
Hydroperiod The term hydroperiod describes the different variations in water input and output that form a wetland, characterising its ecology – i.e. the water balance of the wetland.
Hydrophilic A hydrophyte.
Hydrophyte A plant that grows in water or in conditions that are at least periodically deficient in oxygen as a result of saturation by water – these are typically wetland plants.
Interflow The lateral movement of water, usually derived from precipitation, that occurs in the upper part of the unsaturated zone between the ground surface and the water table. This water generally enters directly into a wetland or other aquatic ecosystem, without having occurred first as surface runoff, or it returns to the surface at some point down-slope from its point of infiltration.
Knickpoint (= rejuvenation head) – A break of slope in the long profile of a stream which results from a fall of base level and the resultant downcutting, creating a new valley long profile below the former level. The knickpoint is found at the transition point between the two profiles, and migrates upstream. At a more localised level, a knickpoint can occur at the head of a gulley or erosion channel within a river or wetland.
Land type Distinct areas defined as part of the Land Type Survey of South Africa based on a unique combination of soil pattern, macroclimate and terrain form.
Macrophyte An aquatic plant that grows in or near water. Macrophytic plants can be emergent, submerged, or floating.
Mesotrophic Soil A soil that suffered leaching that has resulted in the sum of exchangeable (as opposed to soluble) Calcium, Magnesium Potassium and Sodium being low (5- 15cmol(+) per kg clay). Mesotrophic soils have medium base status. Compare with dystrophic.
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Obligate A species that almost always occurs in wetlands.
Orthic A Horizon A topsoil (surface) soil horizon that characterises most topsoil horizons; it is not characterised by a high degree of organic carbon and which does not have the strongly developed structure of the vertic or melanic A horizons.
Perched Water Table / A water table caused by the presence of water above an isolated relatively Aquifer impermeable underlying layer, some height above the normal aquifer level.
Plinthic Soils with plinthic characteristics contain an iron-rich, humus-poor mixture of clay with quartz and other highly weathered minerals, with the common occurrence of reddish redox concentrations in a layer that has a polygonal (irregular), platy (lenticular), or reticulate (blocky) pattern, formed by the segregation, transport, and concentration of iron. To qualify as being plinthic irreversible hardening, or a process of the development of hardening must be present (due to the process of repeated wetting and drying).
Ramsar Site (Wetland) A wetland designated under the Convention on Wetlands, called the Ramsar Convention (an intergovernmental treaty that provides the framework for national action and international cooperation for the conservation and wise use of wetlands and their resources). Ramsar Sites are wetlands of international importance that are recognised as being of significant value not only for the country or the countries in which they are located, but for humanity as a whole.
Reach A portion / stretch of a river / watercourse / wetland.
Redoximorphic Features within soil that are a result of the reduction, translocation and oxidation (precipitation) of Fe (iron) and Mn (manganese) oxides that occur when soils are saturated for sufficiently long periods of time to become anaerobic.
Riparian Zone The physical structure and associated vegetation of the areas associated with a watercourse which are commonly characterised by alluvial soils, and which are inundated or flooded to an extent and with a frequency sufficient to support vegetation of species with a composition and physical structure distinct from those of adjacent land areas.
Signs of Wetness Signs of wetness are signs of hydromorphism in soil, consisting of grey low chroma colours with or without sesquioxide mottles.
Soft Plinthic B Horizon A subsoil horizon created by a fluctuating water table characterised by grey colours (caused by gleying) and distinct reddish-brown, yellowish-brown and /or black mottles with or without hardening to form sesquioxide concretions. The horizon is non-indurated and can be cut with a spade when wet.
Watercourse A linear drainage feature; however it is important to note the legal context of the definition, in terms of the National Water Act and NEMA EIA Regulations. The Act defines a watercourse as (inter alia):
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. a river or spring; . a natural channel in which water flows regularly or intermittently; . a wetland, lake or dam into which, or from which, water flows . any collection of water which the Minister may, by notice in the Gazette, declare to be a watercourse as defined in the National Water Act A reference to a watercourse includes, where relevant, its bed and banks
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Specialist Declaration of Independence
I, Paul da Cruz, declare that I –
. act as an independent specialist consultant in the field of surface water assessment; . do not have and will not have any financial interest in the undertaking of the activity, other than remuneration for work performed in terms of the Environmental Impact Assessment Regulations, 2014; . have and will not have any vested interest in the proposed activity proceeding; . have no, and will not engage in, conflicting interests in the undertaking of the activity; . undertake to disclose, to the competent authority, any material information that have or may have the potential to influence the decision of the competent authority or the objectivity of any report, plan or document required in terms of the Environmental Impact Assessment Regulations, 2014; and . will provide the competent authority with access to all information at my disposal regarding the application, whether such information is favourable to the applicant or not.
PAUL DA CRUZ
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Executive Summary
Royal HaskoningDHV has been appointed by Tlhagontle Consulting Services to conduct a wetland assessment in the context of the undertaking of a Water Use Licence Application (WULA) for the proposed upgrading of bulk water services in the town of Modimolle in the Modimollle Local Municipality in the Limpopo Province. The primary component of the proposed upgrading is the construction of a pipeline for treated water transmitted from the Donkerpoort Water Treatment Works to the Bosveldsig Reservoir in the town.
Wetlands crossed by the proposed pipeline and those within a 500m radius of the proposed pipeline have been identified. Nine wetland reaches were identified in the study area (500m radial area) and two wetlands - two reaches of the Little Nyl River – are crossed by the alignment of the proposed pipeline. A number of wetland hydrogeomorphic types are found in the study area, including un-channelled and channelled valley bottoms and seeps. The wetlands all form part of the catchment of the Little Nyl River, which is important in a hydro-ecological and freshwater conservation planning context as this catchment is located upstream of the Nylsvlei floodplain, which has been designated as a Ramsar Site of international importance. Accordingly impacts on this river system could result in downstream impacts on the Ramsar Site.
The reaches of the Little Nyl River that occur within the study area take the form of valley bottom wetlands with lateral wetland habitat adjacent to a channel in the channelised sections of the system, rather than a classical riverine-riparian template, although the reaches typically display a wooded riparian fringe. Certain reaches of the Little Nyl take the form of unchannelled valley bottoms with extensive reedbeds and rushbeds that are permanently saturated with diffuse flow across the lateral width of the wetland. A number of seep wetlands that are located in the gently sloping terrain setting of the wide footslopes and midslopes adjacent to the Little Nyl valley floor are also located in the study area. Wetlands in the study area were generally noted to be characterised by a grass-dominated vegetative composition, as distinct from the surrounding woodland. The seep wetlands were typified by the predominance of often dense, moribund Imperata cylindrica. A slightly more diverse vegetation composition typified the valley bottoms which varied in character from Phragmites mauritianus reedbeds to an assortment of other obligate hydrophytes, often with a woody-dominated riparian margin.
The study area is located within the Bb93 land type which is characterised by the presence of a plinthic catena with dystrophic and/or mesotrophic primarily yellow apedal (unstructured) soils. The soils encountered in the wetlands in which soil samples were taken broadly corresponded with the soil assemblage of this landtype. Soils in both valley bottom and seep wetlands were noted to be predominantly apedal in character and most soil samples displayed a soft plinthic layer, in some cases accompanied by an overlying E horizon. Soft plinthic B horizons are typically formed by the presence of a rising and falling water table, with the soils being seasonally saturated to form hydromorphic conditions.
The state, functionality and ecological importance and sensitivity of all wetlands was determined, as detailed below.
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Crossing Point / 500m Wetland Reach PES Class EIS Class radius
DP-BS_Seep_1a-c Located within 500m radius B Moderate
DP-BS_VBuc_2a-b Located within 500m radius C High
DP-BS_VBuc_3a-c Crossing Point D Moderate
DP-BS_VBuc_4 Located within 500m radius B Moderate
DP-BS_Seep_5 Located within 500m radius B High
DP-BS_Seep_6 Located within 500m radius C High
DP-BS_VBch_7 Crossing Point C Moderate
DP-BS_VBch_8a-c Located within 500m radius C High
DP-BS_VBch_9a&b Located within 500m radius C Low
A number of potential impacts associated with the proposed pipeline have been identified, the most important of which are: . The disturbance of wetland habitat (substrate and vegetation) through the physical disturbance associated with the excavation and construction of a buried pipeline through the wetland that could adversely affect wetland habitat quality . The mobilisation of sediment from the works and potential erosion of wetland soils by flow in the channel through the works that would constitute pollution of the wetland. . The incorrect or incomplete rehabilitation of the pipeline servitude through the wetland that could result in development of erosion and subsequent siltation, as well as the proliferation of alien invasive vegetation.
A number of key mitigation measures have been specified to ensure that the above impacts do not materialise, or are mitigated to acceptable levels.
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1 INTRODUCTION
Royal HaskoningDHV has been appointed by Tlhagontle Consulting Services to conduct a wetland assessment in the context of the undertaking of a Water Use Licence Application (WULA) for the proposed upgrading of bulk water services in the town of Modimolle in the Modimollle Local Municipality in the Limpopo Province. The primary component of the proposed upgrading is the construction of a pipeline for treated water from the Donkerpoort Water Treatment Works to the Bosveldsig Reservoir in the town. The proposed pipeline crosses a number of surface water features (wetlands), and accordingly would constitute a water use in terms of Section 21 c)&i) of the National Water Act (Act No 36 of 1998) (NWA). A full wetland assessment has been undertaken in support of the WULA process.
1.1 Aims of the Study
The aims of the study are to:
. Assess all surface water features (wetlands) crossed and those surface water features within a 500m radius of the proposed pipeline; . map all wetland and riparian zone boundaries within the area of assessment . undertake assessments of the state, functionality and ecological importance and sensitivity of surface water features within the area of assessment; . assess the impact of the proposed pipeline on surface water resources; and . recommend suitable mitigation measures, if relevant, to ameliorate or remove predicted impacts
1.2 Site Location and Description
The Study Area is in the southern part of the Limpopo Province, within the Modimolle Local Municipality, located approximately 120km north of Pretoria (Tshwane). The alignment of the proposed pipeline traverses both urbanised areas in the environs of the town of Modimolle, as well as a rural setting. The majority of the study area falls within such a rural setting. This part of the study area is characterised by a combination of stock farms and game farms, with most of the properties being privately owned. Due to the nature of the stock / game farming landuse, much of the natural vegetation in the study area has been retained and the area has largely retained its natural characteristics. The majority of the length of the pipeline alignment is routed along an existing district road (the Donkerpoort Road), and as such the pipeline will be routed in an existing area of disturbance and transformation of natural habitat. The location of the Study Area is indicated in Figure 1.
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Figure 1 – Locality Map
1.3 Assumptions and Limitations
As discussed in section 1.4 below, a definition of wetlands that is slightly different to that provided by the National Water Act (Act No. 36 of 1998) has been provided in this report. The definition used is based primarily on the presence of hydric soils, rather than on the hydroperiod of the surface water body.
At the time of completion of this draft no pipeline construction methodology, including a wetland / river construction methodology had been made available by the proponent. Accordingly this has not been able to be analysed as part of the detailing of mitigation measures for the proposed pipeline.
Certain of the wetlands assessed had been burnt prior to the field assessment and accordingly the vegetation in these wetlands was not able to be utilised as part of the assessment of the wetland.
1.4 Definition of Surface Water Features, Wetlands and Hydric Soils
In the context of the delineation and assessment of surface water features in the study area, it is important to detail the definition of wetlands and hydric soils as well as of riparian zones in order to set the parameters for the investigation.
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1.4.1 Surface Water Features
In order to set out a framework in which to assess surface water features, it is useful to set out what this report defines as surface water resources. In this context the National Water Act (Act No. 36 of 1998) is used as a guideline. The NWA includes a number of features under the definition of water resources, i.e. watercourses, surface waters, estuaries and aquifers. The latter two features do not apply in the context of this study as this report does not consider groundwater (in the case of aquifers) and estuaries are coastal features, thus surface waters and water courses are applicable in this context. The Act defines a watercourse as (inter alia):
. a river or spring; . a natural channel in which water flows regularly or intermittently; . a wetland, lake or dam into which, or from which, water flows
The definition of a water course as used in the Act is taken to describe surface water features in this report. It is important to note that the Act makes it clear that reference to a watercourse includes, where relevant, its bed and banks. This is important in this report, as the riparian habitat associated with certain of the linear drainage features in the study area have been included as an important part of surface water features and are thus given consideration in this report.
It is equally important to note that the Act does not discriminate on the basis of being perennial, and any natural channel, however ephemeral, is included within the ambit of water resources. This definition is applied in this report.
1.4.2 Wetlands
The NWA defines a wetland as:
“land which is transitional between terrestrial and aquatic systems where the water table is usually at or near the surface, or the land is periodically covered with shallow water, and which land in normal circumstances supports or would support vegetation typically adapted to life in saturated soil.”
This definition alludes to a number of physical characteristics of wetlands, including wetland hydrology, vegetation and soil. The reference to saturated soil is very important, as this is the most important factor by which wetlands are defined.
Another widely used definition of wetlands is the one used under the Ramsar Convention; wetlands are defined as:
“areas of marsh, fen, peatland or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, fresh, brackish or salt, including areas of marine water the depth of which at low tide does not exceed six metres”
However the presence / absence of hydric soils is the primary determining factor used to define a surface water feature as a wetland.
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This determining factor has been utilised in this assessment. Wetland soils can be termed hydric or hydromorphic soils. Hydric soils are defined by the United States Department of Agriculture’s Natural Resources Conservation Service as being:
“soils that formed under conditions of saturation, flooding or ponding long enough during the growing season to develop anaerobic conditions in the upper part”.
These anaerobic conditions would typically support the growth of hydrophilic vegetation (vegetation adapted to grow in soils that are saturated and starved of oxygen) and are typified by the presence of redoximorphic features. The presence of hydromorphic (wetland) soils on the site of a proposed development is significant, as the alteration or destruction of these areas, or development within a certain radius of these areas would require authorisation in terms of the NWA and in terms of the Environmental Impact Assessment Regulations (2014) promulgated under the National Environmental Management Act, 1998 (Act No. 107 of 1998).
1.4.3 Riparian Zones This section briefly introduces riparian zones in terms of the hydromorphological and vegetation classification as per the VEGRAI (Riparian Vegetation Response Assessment Index) assessment methodology (Kleynhans et al, 2007) that has been developed to assess riparian zone state. The NWA defines riparian habitat as:
“The physical structure and associated vegetation of the areas associated with a watercourse which are commonly characterised by alluvial soils, and which are inundated or flooded to an extent and with a frequency sufficient to support vegetation of species with a composition and physical structure distinct from those of adjacent land areas”
As detailed in the guidelines for the delineation of wetlands and riparian areas (DWAF, 2005), riparian areas typically perform important ecological and hydrological functions, some of which are the same as those performed by wetlands. It is thus important that both wetlands and riparian areas be taken into consideration when making mandatory management decisions affecting water resources and biodiversity (DWAF, 2005).
Riparian areas include plant communities adjacent to and affected by surface and underground water features such as rivers, streams, lakes, or drainage lines. It is important to note that these areas may be a few metres wide along smaller systems or more than a kilometre in floodplains. Both perennial and non- perennial streams support riparian vegetation (DWAF, 2005).
Because riparian areas represent the interface between aquatic and upland ecosystems, the vegetation in the riparian area may have characteristics of both aquatic and upland habitats. Many of the plants in the riparian area require plenty of water and are adapted to shallow water table conditions. Due to water availability and rich alluvial soils, riparian areas are usually very productive. Tree growth rate is high. This is certainly the case in riparian zones in the study area as they typically contain trees and shrubs of a height, density and species diversity that is not present in the surrounding woodland.
Riparian areas are important as they perform the following functions (DWAF, 2005):
. storing water and thus assisting to reduce floods; . stabilising stream banks; . improving water quality by trapping sediment and nutrients;
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. maintaining natural water temperature for aquatic species; . providing shelter and food for birds and other animals; . providing corridors for movement and migration of different species; . acting as a buffer between aquatic ecosystems and adjacent land uses; . can be used as recreational sites; and . providing material for building, muti, crafts and curios.
These ecosystems may be considered ‘critical transition zones’ as they process substantial fluxes of materials from closely connected, adjacent ecosystems (Ewel et al, 2001)
As discussed below riparian habitat is important from a legislative perspective – in terms of the National Water Act.
In terms of the VEGRAI structure, riparian areas are divided up into three (3) vegetation zones: . Marginal Zone . Lower Zone . Upper Zone
This vegetation zone classification has been based upon: . periodicity of hydrological influence . marked changes in lateral elevation or moisture gradients . changes in geomorphic structure . changes in plant species distribution or community composition along lateral gradients
In spite of these zones being vegetative, they are also distinguished based on a combination of other factors including geomorphic structure and elevation along with vegetation. Elevation within the riparian zone is used as a surrogate for hydrological activation, which is taken to be moistening or inundation of the substrate by water in the channel. Figure 2 below (from Kleynhans et al, 2007) indicates a typical riparian zone:
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Figure 2 - Schematic diagram indicating the three zones within a riparian area relative to geomorphic diversity (Kleynhans et al, 2007)
Marginal Zone
The marginal zone incorporates the area from the water level at low flow (where present – if flow is not present areas that would be subject to baseflows would be included) to those features that are more or less permanently inundated. Vegetatively the marginal zone is typically characterised by the presence of hydrophytes that are vigorous in terms of abundance due to the near-permanent availability of moisture.
Lower Zone
The lower zone is the area of seasonal inundation (hydrological activation in this context is yearly inundation during high flows, or every 2-3 years), extending from the edge of the marginal zone to the point at which there is a marked increase in lateral elevation. This change in elevation may or may not be characterised by an associated change in species distribution patterns.
Upper Zone
The upper zone is characterised by hydrological activation on an ephemeral basis (less than every 3 years) and extends from the end of the lower zone to the end of the riparian corridor. The upper zone is usually characterised by steeper slopes and the presence of both riparian and terrestrial species, the latter typically having an enlarged structure as compared to the areas outside of the riparian area.
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1.5 Wetland Delineation Techniques
In the context of the site investigation, it is important to note the standard wetland delineation method that was employed.
Typically the presence of wetlands is determined through wetland delineation. The accepted procedure for wetland delineation in South Africa is based upon the Department of Water and Sanitation’s (DWS) (formerly DWA(F)) guideline ‘A practical field procedure for the identification and delineation of wetlands and riparian areas’ (DWAF, 2005), which stipulates that consideration be given to four specific wetland indicators to determine the boundary of the wetland.
The four wetland indicators are: . terrain unit - helps to identify those parts of the landscape where wetlands are more likely to occur; . soil form - identifies the soil forms, as defined by the Soil Classification Working Group (1991), which are associated with prolonged and frequent saturation; . soil wetness - identifies the morphological "signatures" developed in the soil profile as a result of prolonged and frequent saturation; and . vegetation - identifies hydrophilic vegetation associated with frequently saturated soils.
The guidelines do mention hydrology, although it is not listed as being one of the four indicators above. However the guidelines state that the delineation procedure is substantially facilitated by an understanding of the broad hydrological processes that drive the frequency of saturation (DWAF, 2005).
Under most circumstances the most important indicator of the presence of hydric soils is the soil wetness indicator, i.e. examination of redoximorphic features within the soil. The reason for this is that vegetation (the primary factor as defined under the National Water Act) can easily respond to changes in hydrology (e.g. the draining of a wetland), while the soil morphological signatures remain even if the wetland hydrology is altered.
In terms of the soil form indicator, the guidelines list a number of soil forms that are associated with the permanent zone of the wetland or the seasonal / temporary zones.
For an area to be considered a wetland, redoximorphic features must be present within the upper part of the soil profile (Collins, 2005). Redoximorphic features are the result of the reduction, translocation and oxidation (precipitation) of Fe (iron) and Mn (manganese) oxides that occur when soils are saturated for sufficiently long periods of time to become anaerobic. Only once soils within 500 mm of the surface display these redoximorphic features can the soils be considered to be hydric (wetland) soils. Redoximorphic features typically occur in three types (Collins, 2005): . A reduced matrix – i.e. an in situ low chroma (soil colour), resulting from the absence of Fe3+ ions which are characterised by “grey” colours of the soil matrix; . Redox depletions - the “grey” (low chroma) bodies within the soil where Fe-Mn oxides have been stripped out, or where both Fe-Mn oxides and clay have been stripped. Iron depletions and clay depletions can occur; and . Redox concentrations - Accumulation of iron and manganese oxides (also called mottles). These can occur as: o Concretions - harder, regular shaped bodies; o Mottles - soft bodies of varying size, mostly within the matrix, with variable shape appearing as blotches or spots of high chroma colours; and
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o Pore linings - zones of accumulation that may be either coatings on a pore surface, or impregnations of the matrix adjacent to the pore. They are recognized as high chroma colours that follow the route of plant roots, and are also referred to as oxidised rhizospheres.
Under most circumstances the presence or absence of redoximorphic features within the upper 500 mm of the soil profile alone is sufficient to identify the soil as being hydric (a wetland soil) or non-hydric (non- wetland soil) (Collins, 2005; DWAF, 2005), although it is very important to consider the soil form and the requisite presence of diagnostic horizons that may be deeper than 500 mm.
Vegetation in an untransformed state is a very useful way to support the delineation of a wetland, due to plant community transition from the middle of the wetland to the adjacent terrestrial area. The guidelines specify that when using vegetation indicators, that focus be placed on the plant communities, rather than individual indicator species. The dominant species in the area being assessed (hydrophytes or not) must be assessed to determine the presence of a wetland. The guidelines make reference to vegetation types typically found within the classical zones of a wetland (permanent, seasonal, temporary), but also makes reference to the classification methodology developed by Kotze and Marneweck (1999) as part of the Resource Directed Measures for Protection of Water Resources for Wetland Ecosystems which is based on the identification of obligate and facultative wetland species, and the relative coverage of these species in terms of whether the area being assessed is likely to display hydric conditions, possible display hydric conditions, or not at all.
Lastly, the hydrological framework for wetlands is covered in an appendix of the guidelines. This is based on the longitudinal classification of river channels into three different zones based on their hydrological activation: . A Section – baseflow never occurs, and the water table never occurs at the surface (typically headward channels); . B Section – channels within the zone of a fluctuating water table, only being characterised by baseflow when the saturated zone is in contact with the channel bed; and . C Section – channels that are always in contact with the zone of saturation, and thus always experiencing baseflow (i.e. being perennial in nature).
Typically wetland habitat will never occur in the A section due to the insufficient period of saturation, while Section B and C channels will contain wetland habitat due to a sufficient period of saturation. In terms of the classical zonation of a wetland, the permanent wetland zone will typically only be found in the C Section, while the B section is only characterised by the presence of seasonal and temporary zones.
Use was made of a GPS to identify important points (e.g. wetland boundaries). These GPS points were converted into a GIS shapefile to allow these points to be mapped and to facilitate the delineation of the surface water feature boundaries.
The field-based assessment was also used to confirm the hydrogeomorphic forms of all wetlands crossed by the alignment of the proposed pipeline and wetlands located within a 500m radius.
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2 Legislative Context
The following section briefly examines the legislation that is relevant to the scope of the surface water assessment. The stipulations / contents of the legislation and policy that is relevant to the study are explored.
2.1 The National Water Act It is important to note that water resources, including wetlands are protected under the NWA. ‘Protection’ of a water resource, as defined in the Act entails:
. Maintenance of the quality of the water resource to the extent that the water use may be used in a sustainable way; . Prevention of degradation of the water resource . The rehabilitation of the water resource
In the context of the current study and the identification of potential threats to the surface water features posed by the proposed development of the pipeline, the definition of pollution and pollution prevention contained within the Act is relevant. ‘Pollution’, as described by the Act is the direct or indirect alteration of the physical, chemical or biological properties of a water resource, so as to make it (inter alia)- . less fit for any beneficial purpose for which it may reasonably be expected to be used; or . harmful or potentially harmful to the welfare or human beings, to any aquatic or non-aquatic organisms, or to the resource quality.
The inclusion of physical properties of a water resource within the definition of pollution entails that any physical alterations to a water body, for example the excavation of a wetland or changes to the morphology of a water body can be considered to be pollution. Activities which cause alteration of the biological properties of a watercourse, i.e. the fauna and flora contained within that watercourse are also considered pollution.
In terms of Section 19 of the Act owners / managers / people occupying land on which any activity or process undertaken which causes, or is likely to cause pollution of a water resource must take all reasonable measures to prevent any such pollution from occurring, continuing or recurring. These measures may include measures to (inter alia): . cease, modify, or control any act or process causing the pollution . comply with any prescribed waste standard or management practice . contain or prevent the movement of pollutants . remedy the effects of the pollution; and . remedy the effects of any disturbance to the bed and banks of a watercourse
These general stipulations of the Act have ramifications for the proposed development as impacts on surface water features associated with the proposed development would be relevant in terms of the above stipulations of the NWA.
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2.2 The National Water Act and Riparian Areas
Riparian habitat is afforded protection under the National Water Act in a number of ways. Firstly reference in the National Water Act to a watercourse includes its banks, on which riparian habitat is encountered. Riparian areas are thus afforded the same degree of protection as the river beds and channels alongside which they occur.
Riparian habitat is also important in the context of resource quality objectives that are a critical part of the Act. In terms of Section 13(1) of the Act resource quality objectives must be determined for every significant water resource, and are central part of data type specifications relating to national monitoring systems and national information systems as determined in Section 137(2) and Section 139(2) of the Act respectively. Under Section 27 of the Act resource quality objectives must be taken into account in the issuing of any licence or general authorisation, and form a critical part of the duties of catchment management agencies. The purpose of resource quality objectives in the Act is to establish clear goals relating to the quality of the water resources. Resource quality is important in the context of riparian habitat as resource quality as defined in the Act means the quality of all aspects of a water resource and includes the character and condition of the riparian habitat. In terms of Section 26(4) of the Act, the need for the conservation and protection of riparian habitat must be taken into account in the determination and promulgation of regulations under the Act.
The above stipulations of the Act have implications for the proposed development; as identified further on in this report the proposed development may be associated with certain direct or indirect impacts on surface water features in the area, some of which may affect the physical characteristics of the feature. The activities that result in these impacts are likely to be needed to be licensed under the Act. The National Water Act also stipulates requirements for permitting which would need to be followed.
3 METHODOLOGY FOR ASSESSMENT
A focussed field assessment was undertaken. Wetland reaches crossed by the proposed pipeline and those within a 500m radius of the pipeline were assessed in the field. It is important to note that the entire extent of certain reaches within the 500m radius was not assessed, but representative reaches were assessed. The primary aim of the field assessment was to delineate the affected wetland reaches, and to gather data for the wetland EcoStatus assessments. The wetland delineation methodology is detailed in section 1.5 above.
3.1 Detailed Wetland Crossing Assessment
Wetlands have been characterised and assessed based on the findings of field assessment and utilising a number of tools as discussed below. In any assessment of wetlands, it is very important to assess and characterise wetlands based on four factors:
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. Wetland pressures / impacts . Wetland functionality . Wetland state . Wetland Ecological Importance and Sensitivity
These factors are separate, but closely interlinked as shown in Figure 3 below.
Ecological
Importance/ Sensitivity Functionality
Impacts / Pressures State
Figure 3 – The relationship between wetland state, functionality, EIS and impacts / pressures acting on a wetland
It is very important to understand the links between wetland functionality, ecological importance, pressures and state. As indicated in Figure 3 above wetland state is directly influenced by pressures acting on the wetland. Pressures / impacts may adversely affect the ability of a wetland to perform certain functions, but certain aspects of wetland functionality may be enhanced in that the wetland may be acting to ameliorate the pressure acting upon it. The state and ecological functionality of a wetland can be used to assign level of ecological value or sensitivity to the wetland, but the impacts acting on it can adversely affect its level of ecological sensitivity. These aspects are discussed in greater detail below.
It should be noted that access to certain of the crossings was not possible due to access restrictions from the landowners (where the assessor was not able to gain access). Fr these reaches wetland state, functionality and EIS were not assessed.
3.1.1 Wetland Functional Assessment
Wetland functionality was assessed using the WET-EcoServices methodology (Kotze et al, 2009). This methodology has been developed as a tool to identify the different aspects of functionality offered by a wetland. Wetland functionality is multi-faceted and includes a number of different but interlinked aspects such as hydrological functionality, ecological functionality, and socio-cultural functionality. The basis of the methodology is the identification of ecosystem services offered by an individual wetland or wetland unit. Ecosystem services as defined in WET-EcoServices are the direct and indirect benefits that people obtain from ecosystems. These benefits may derive from outputs that can be consumed directly; indirect uses which arise from the functions or attributes occurring within the ecosystem; or possible future direct outputs or indirect uses. Table 1 below lists the ecosystem services that are assessed through the WET- EcoServices methodology.
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Table 1 - Ecosystem services included in WET-EcoServices (Kotze et al, 2009) Flood attenuation Streamflow regulation Sediment trapping
Phosphate assimilation
Nitrate assimilation
geochemical Toxicant assimilation -
Erosion control
Water quality enhancement benefits
Carbon storage
Hydro benefits
Biodiversity maintenance Indirect Indirect benefits Provision of water for human use Provision of harvestable resources
Provision of cultivated foods Cultural significance Tourism and recreation
Education and research
Ecosystem services wetlands supplied Directbenefits by
The output diagram indicating the ecosystem services offered by the reach as produced by the WET- EcoServices assessment is included. WET-EcoServices does not provide an overall assessment of wetland functionality, but the spreadsheet tool developed to assign an EIS value to a wetland also calculates a hydrological / functional importance value associated with the wetland.
3.1.2 Wetland State (Health) Assessment
The WET-Health (MacFarlane et al, 2009) tool has been used to assess wetland state. The WET-Health tool has been designed by the Water Research Commission to assess the health or integrity of a wetland. Health of the wetland equates to wetland state as referred to in this study. The WET-Health technique assesses the hydrological, geomorphological and vegetative state of a wetland. It assigns wetland units assessed into an Ecological Category (EC) that reflects its state of degradation. Table 2 below indicates the PES (state) categories as assessed using the WET-Health methodology.
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Table 2 - PES Categories assigned by the WET-Health Tool (MacFarlane et al, 2009)
3.1.3 Assessment of Ecological Importance and Sensitivity (EIS)
Protection of freshwater ecosystems and biodiversity are a critical part of the purpose of the National Water Act. In this context and in the context of the need to protect water resources as espoused by the Act it is thus important to determine the ecological importance and sensitivity of a potentially affected water resource. The ecological importance of a water resource is an expression of its importance to the maintenance of biological diversity and ecological functioning on local and wider scales. Ecological sensitivity (or fragility) of a surface water feature refers to its ability to resist disturbance and its capability to recover from disturbance once it has occurred (resilience) (Rountree et al, 2013). Both abiotic and biotic components of the system are taken into consideration in the assessment of ecological importance and sensitivity (Rountree et al, 2013).
A rapid scoring system to evaluate Ecological Importance and Sensitivity of wetlands has been developed as part of the development of a manual for Manual for the Rapid Ecological Reserve Determination of Inland Wetlands (Rountree et al, 2013). The spreadsheet-based tool evaluates a number of factors to determine importance and sensitivity, including biodiversity value, landscape context and hydrological and water quality-related factors. A score from 0-4 is provided, with a score of 4 reflecting the highest degree of sensitivity to as indicated by Table 3 below.
Table 3 – Ecological Importance and Sensitivity Scores as calculated by the wetland EIS Tool (Rountree et al, 2013) Rating Explanation None, Rating = 0 Rarely sensitive to changes in water quality/hydrological regime Low, Rating =1 One or a few elements sensitive to changes in water quality/hydrological regime Moderate, Rating =2 Some elements sensitive to changes in water quality/hydrological regime High, Rating =3 Many elements sensitive to changes in water quality/ hydrological regime Very high, Rating =4 Very many elements sensitive to changes in water
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quality/ hydrological regime
An EIS class from very high, high, moderate to low is assigned.
3.2 Identification of Wetland Impacts and Mitigation Measures
All potential impacts that could be caused by the proposed pipeline development that would affect surface water features have been identified and detailed. Mitigation measures to either ensure that the identified impact does not materialise, or to ameliorate / limit the impact to acceptable levels have been stipulated, as part of a crossing-specific rehabilitation plan.
4 STUDY AREA BIOPHYSICAL ENVIRONMENT
4.1 Geology, Macro-geomorphology & Topography, and implications for drainage
The study area is underlain by the Nylstroom Subgroup of the Waterberg Group. In the Modimolle and Alma areas the lower part of the Waterberg Group is developed, in which the Swaershoek and the Alma Formations occur. The south-eastern part of the study area (closer to Modimolle) falls within the Alma Formation. The typical rock type in this formation is a greenish-grey greywacke, followed by feldspathic and micaceous sandstone and feldspathic grit. The parts of the study area traversed by the proposed alignment located along the eastern end of the Donkerpoort District road fall within the Swaershoek Formation. The Swaershoek Formation constitutes the base of the Waterberg Group and the Hoekberge to the west of Bela-Bela and the Swaershoek Mountains to the north of Modimolle are comprised of rocks from this formation. The formation is composed largely of reddish and brownish, medium- to coarse- grained sandstone with intercalations of siltstone, shale and conglomerate, and flows of trachytic lava with associated tuffaceous greywacke in the upper part thereof1.
The far north-western parts of the study area are underlain by a band of fine-grained felsic (intrusive igneous) rocks that form the low hills to the north of Modimolle. The Little Nyl River flows through these hills in a narrow valley and the presence of the hills allowed the Donkerpoort Dam to be constructed. The presence of this higher-lying topography with a south-facing aspect in the location of the proposed alignment entails that drainage is oriented towards the lower-lying areas of Modimolle and the very flat areas to the east (and eventually north-east), in which the Nyl River floodplain wetland is located.
The topography of the study area determines the nature of the drainage; the Little Nyl River in the vicinity of (downstream of) the Donkerpoort Dam is typically narrow and lies within a confined valley, with a limited cross-sectional width. The cross-sectional profile of the river widens slightly as it drains closer to the town of the Modimolle, so that it has a shallower and slightly wider cross-sectional profile in the vicinity of the town’s correctional facility and shopping mall, thus allowing the formation of a more depositional- dominated drainage system, as evidenced by the presence of a relatively wide un-channelled wetland in this part of the river’s course (reach DP-BS_8a-c). The terrain at the southern footslopes of the low hills
1 https://www.environment.gov.za/sites/default/files/docs/waterberg_statusquo_finalreport.pdf
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located to the north of the Modimolle is relatively gentle, allowing the development of a number of wide seepage wetlands (reaches DP-BS_5&6) located to the south of the Donkerpoort Road and pipeline alignment. These seepage wetlands drain into the Little Nyl River.
4.2 Macro Drainage Characteristics
The study area falls within the A16A quaternary catchment 2 , as indicated in Figure 4 above. This quarternary catchment is comprised of the uppermost reaches of the Nyl River catchment, including the entire course of the Little Nyl River and the upper Nyl River. The Nyl River is highly significant in a water resources and hydro-ecological context due to the presence of the Nylsvlei Ramsar Wetland which is located downstream of the study area (see Section 4.5 below). The Nyl River is a tributary of the north- ward draining Mogalakwena River which drains the eastern part of the Waterberg Mountains and is itself a tributary of the Limpopo River. The Study area thus falls within the Limpopo Water Management Area (WMA).
Figure 4 – Quaternary catchments and drainage in the wider area
2 The quaternary sub-catchment was used as the basic areal unit in early water resource planning in South Africa – the country was divided up into a series of fourth-order catchments based on runoff characteristics with catchment area being delineated inversely proportional to runoff – Midgely et al, 1994
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4.3 Vegetation Types
The majority of the study area falls within the Central Sandy Bushveld vegetation type (Mucina and Rutherford, 2006). This vegetation type that forms part of the Savanna Biome is characterised by Low undulating areas, sometimes between mountains, and sandy plains and catenas supporting tall, deciduous Terminalia sericea and Burkea africana woodland on deep sandy soils (with the former often dominant on the lower slopes of sandy catenas) and low, broad-leaved Combretum woodland on shallow rocky or gravelly soils (Mucina and Rutherford, 2006).
In spite of no distinct wetland vegetation types occurring in the study area (as mapped by the Mucina and Rutherford national vegetation classification assessment), wetlands and rivers in the study area are likely to display characteristics of the (Azonal) Subtropical Freshwater Wetlands vegetation type3, as well as the Subtropical Alluvial Vegetation. The Subtropical Freshwater Wetlands vegetation type is described as being characterised by flat topography supporting reedbeds, or being dominated by sedges and rushes, with the presence of water-logged meadows dominated by grasses in places. This vegetative description of subtropical wetlands best describes the vegetative composition of wetlands in the area, as distinct from the surrounding terrestrial vegetation. Another azonal vegetation type – the Subtropical Alluvial Vegetation Type is relevant to this study – it typically occurs on flat alluvial riverine terraces that support an intricate complex of macrophytic vegetation, marginal reedbeds, flooded grasslands and ephemeral herblands, as well as riverine thickets. Although no distinct areas of such alluvial vegetation occur in the study area, riparian vegetation along the reaches of the Little Nyl River in the study area displays a number of characteristics that are synonymous with this vegetation type.
4.4 Land Types
It is useful to examine the land types present within the study area, as the land type descriptions provide an indication of the dominant soil types typically present area that can be related back to the presence of soil types and soil forms associated with wetlands. Land types were defined as part of the Land Type Survey of South Africa that was commenced in the 1970s and which was completed in 2001. Individual land types were defined based on a unique combination of soil pattern, macroclimate and terrain form. The land descriptions that form part of this inventory provide the following data for each landtype4:
. Area of the land type (ha) . Climate zone number . Terrain units occurring (crests, scarps, midslopes footslopes and/or valley bottoms), their extent, slope angle, length and shape . Soils occurring (classified according to “Soil Classification: A Binomial System for South Africa”), within each terrain unit and within the land type as a whole . Soil depths, topsoil and subsoil clay content and texture of the lowest non-limiting horizon . Cross-section sketch of the land type . Summarised geology of the land type
The majority of the study area falls within the Bb93 landtype. ‘Bb’ (and ‘Ba’) landtypes have been defined by the presence of a plinthic catena with Dystrophic and/or mesotrophic red and/or yellow soils. Bb
3 The Nysvlei wetland system located to the east of the study area falls within the Subtropical Freshwater Wetlands vegetation type 4 http://www.agis.agric.za/agisweb/?MIval=content2_h.html&id=Landtypes_introduction
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Landtypes are characterised by primarily yellow, apedal soils, moderately (mesotrophic) to highly (dystrophic) leached (low to moderate fertility status), with a wide textural range, mostly sandy loam to sandy clay loam. Soils contain a greyish plinthic subsoil layer where iron and manganese accumulate in the form of mottles, due to a seasonally fluctuating water table. With time these mottles may harden (or even cement) to form concretions.
The Bb93 landtype is indicated as being relatively flat with relatively wide footslopes and midslopes in a gently sloping topographical context. The land type description indicates the following spatial distribution of topographic units: . Valley bottoms - 10% . Footslopes - 64% . Midslopes - 25% . Crests - 1%
Valley bottoms and footslopes accordingly comprise the majority of the spatial extent of the landtype, and allied with the dominance of plinthic soils, the occurrence of wetlands is likely to be relatively high.
Streambeds and soils dominated by the Longlands soil form (a plinthic and wetland soil form) comprise over 60% of valley bottoms. The remaining spatial extent of within valley bottoms are comprised of alluvial and other plinthic soil types. Footslopes are characterised by the dominance of apedal soils (60%) with yellow / brown (Clovelly soil form) apedal soils being dominant. The remainder of soil types occurring on footslopes include a mix of (wetland) soil forms with plinthic characteristics and those characterised by the presence of an E horizon.
The wetlands in the study area are located within valley bottoms and footslopes (seeps). Accordingly the soil forms present within these wetlands are likely to conform to the above soil type assemblages.
It should be noted that a small part of the study area occurs within the Fa270 and Fa284 land types. Fa land types are dominated by Glenrosa and / or Mispah soil forms, comprising of generally shallow soils consisting of a topsoil directly underlain by weathered rock (Glenrosa form) or hard rock (Mispah form), along with surface rock and steep slopes. However no wetlands or surface water features were found to be located within these land types.
4.5 Study Area Freshwater Conservation Planning Context
It should be stressed that all wetlands and surface water features in the study area are sensitive features, and should be treated as such, especially in the context of the overall (cumulative) loss of wetland habitat due to landuse-related pressures. This factor engenders an important level of sensitivity to the wetlands in the study area, in that these wetlands that remain are very important in the provision of ecosystem services, in particular those of water provision, flood attenuation and maintenance of biodiversity. This is an important factor that needs to be upheld in planning of any development, including linear developments, and in mitigating impacts of the proposed road on these wetlands.
It is important however to examine the context of systematic biodiversity and freshwater conservation planning initiatives that have identified areas of ecological and freshwater sensitivity, in order to determine whether there are surface water features of particular sensitivity within the study area, in order to contextualise the impacts of the proposed pipeline on these features.
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Two such databases that indicate ecological/ freshwater sensitivity are contemplated in this report; firstly the Limpopo Conservation Plan (LCP) (2013) which has a freshwater component which identifies sensitive wetlands and rivers and important areas within their catchments across the province. Secondly the National Freshwater Ecosystem Priority Area (NFEPA) database which has identified sensitive surface water features and catchment areas at a national scale. The LCP incorporates NFEPA features, and as such this database alone has been interrogated.
As with the other provincial conservation plans the Limpopo Conservation Pan (LCP) has designated Critical Biodiversity Areas (CBAs) and Ecological Support Areas (ESAs). A map of CBAs for Limpopo was produced as part of this plan and sites were assigned to CBA categories based on their biodiversity characteristics, spatial configuration and requirement for meeting targets for both biodiversity pattern and ecological processes (Desmet et al, 2013).
It is important to note that key wetland and river systems have been included in the LCP. In addition, targets were set for identified priority freshwater catchments and dolomite systems. Priorities for both rivers and wetlands from the NFEPA project were included. Accordingly the LCP has included Phase 1 River FEPA reaches and an associated buffer (designated as priority river reaches and associated priority sub-quaternary catchments under the plan), Phase 1 FEPA catchments, as well as FEPA wetlands and FEPA wetland clusters that have been designated as priority wetlands under the LCP. All other natural wetlands and a minimum buffer of 1km around major rivers were included as ESAs under the LCP (Desmet et al, 2013).
Figure 5 below indicates a number of sensitive aquatic features in the study area, as designated under the LCP. The following aquatic sensitive features occur in the study area: . Wetland FEPAs (status equivalent to a CBA) . All natural wetlands (status equivalent to an ESA) . 1km buffer on large rivers (status equivalent to an ESA)5 . Nylsvlei Support Areas
It should be noted that the Little Nyl River that flows through the study area has not been designated as a FEPA wetland or river; however the LCP has applied a 1km wide buffer to this river, which is indicated as a sensitive area, equivalent in status to an ESA.
The presence of a Ramsar wetland downstream of the study area is highly important, as upstream impacts in the catchment of the Nylsvlei Ramsar Wetland could exert a significant adverse impact on this highly sensitive aquatic feature. As such rivers and wetlands upstream of the Nylsvlei wetland and parts of their catchments have been designated as a sensitive aquatic feature in the LCP – the Nyls Vlei support areas (status equivalent to an ESA).
Only one FEPA river or wetland occurs in the study area – one of the seep wetlands that drains the footslopes of the hills to the north-west of Modimolle and which feeds into the Little Nyl River (wetland DP- BS_Seep_6) has been designated as a FEPA wetland.
5 It should be noted that a 100m buffer on rivers is also indicated, but this was undertaken in order to avoid false non-inclusion (due to GIS inaccuracies) of river associated planning units (Desmet et al, 2013).
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Figure 5 – Limpopo Conservation Plan Freshwater Sensitive Features in the Study Area
5 FINDINGS OF ASSESSMENT
5.1 Surface Water Typology and Occurrence
Although a number of wetlands occur in the study area, the assessment has revealed that two wetlands are crossed by the proposed pipeline, although a number of other wetlands occur in close proximity to the alignment of the proposed pipeline and occur in the wider area of the 500m radius. Each wetland in the 500m radius has been assigned a name (and number), based on the hydrogeomorphic form of the wetland. Table 4 below indicates the wetlands that are crossed by, and which occur within the 500m radius of the proposed pipeline.
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Table 4 – Wetland HGM Unit crossed by / within 500m Radius if the Pipeline # Wetland HGM Type Wetland Name Crossing Point / 500m radius
1 Seep DP-BS_Seep_1a&b Located within 500m radius
2 Valley bottom - unchannelled DP-BS_VBuc_1c Located within 500m radius
3 Valley bottom - unchannelled DP-BS_VBuc_2a Located within 500m radius
4 Valley bottom - channelled / Riparian DP-BS_VBch_2b Located within 500m radius
5 Valley bottom - channelled / Riparian DP-BS_VBch_3a Crossing Point
6 Valley bottom - channelled / Riparian DP-BS_VBch_3b Located within 500m radius
7 Seep DP-BS_VBch_3c Located within 500m radius
8 Valley bottom – channelled / Riparian DP-BS_VBch_4 Located within 500m radius
9 Seep DP-BS_Seep_5 Located within 500m radius
10 Seep DP-BS_Seep_6 Located within 500m radius
11 Valley bottom - channelled / Riparian DP-BS_VBch_7 Located within 500m radius
12 Valley bottom - channelled / Riparian DP-BS_VBch_8a&c Crossing Point
13 Valley bottom - unchannelled DP-BS_VBuc_8b Located within 500m radius
14 Valley bottom - channelled / Riparian DP-BS_VBch_9a&b Located within 500m radius
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Figure 6 – Wetland Occurrence in the Study Area
Figure 7 – Wetland Reaches 1&2
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Figure 8 – Wetland Reaches 3&4
Figure 9 – Wetland Reach 5
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Figure 10 – Wetland Reach 6
Figure 11 – Wetland Reach 7
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Figure 12 – Wetland Reaches 8&9
Wetlands and surface water features can be found all across a landscape. The landscape can be divided up into a number of units, each of which can contain wetlands. Wetlands occurring on these different terrain units typically differ in terms of their formative processes and hydrological inputs, and thus differ in terms of their functionality.
In the context of the study area, it is important to note that surface water features do not only occur in valley bottoms where depositional processes typically lead to valley bottom wetland formation – the landscape setting in which wetlands are most often encountered. Wetlands are also encountered on sloping ground adjacent to the valley bottom on the surrounding footslopes. These (seep) wetlands are rather characterised by colluvial processes and the input of sub-surface water inputs.
The classification of wetland form has been based upon the most updated wetland classification system for South Africa – the Classification System for Wetlands and other Aquatic Ecosystems in South Africa (Ollis et al, 2013). The system uses a six-tiered approach for classifying inland aquatic systems, including wetlands. Levels 4 and 5 (hydrogeomorphic (HGM) unit and hydrological regime respectively) are the focal points of the classification system – i.e. these describe the functional unit (Ollis et al, 2013). Table 5 below indicates the tiered classification for the different types of surface water features along the proposed alignment.
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Table 5 – Tiered classification for wetlands in the study area Seep Wetlands Un-channelled Valley Channelled Valley Bottom Bottom Wetlands Wetlands Level 1 – System Inland Level 2 – Regional Central Bushveld Group 3 Setting (NFEPA WetVeg Group) Level 3 – Slope Valley Floor Landscape Unit Level 4 – HGM Unit Seep Un-channelled valley Channelled valley bottom bottom wetland wetland Level 4B – Seep With channelled outflow outflow characteristic Level 5A – Period Seasonally Inundated of inundation / Hydrological Regime Level 5B – Period Seasonally Saturated Seasonally Saturated / Permanently Saturated of Saturation Level 6 – Other Natural vs. Artificial - Natural descriptors Salinity - Fresh (non-saline) Substratum Type – Substratum Type – Substratum Type –Generally Generally sandy to loam Generally sandy to clay sandy to loam soils (some soils soils bedrock) Vegetation Cover – Vegetation Cover – Vegetation Cover – - -Vegetated – Vegetated – Herbaceous Vegetated – Herbaceous Herbaceous (Grasses, (Grasses, rushes and (Grasses, rushes and reeds herbs / forbs dominant) reeds dominant) with some dominant with shrubs and trees trees in a wooded outer riparian corridor -Un-vegetated – bedrock outcropping
5.1.1 Channelled Valley Bottom Wetlands
According to Ollis et al, 2013: “Channelled valley-bottom wetlands are characterised by their location on valley floors, the absence of characteristic floodplain features and the presence of a river channel flowing through the wetland.” It is important to note that water generally moves through the wetland as diffuse surface flow, although occasional, short-lived concentrated flows are possible during flooding events (Ollis et al, 2013).
In the context of the study area, channelled valley bottom wetlands are associated with the Little Nyl River that flows from the Donkerpoort Dam through the town of Modimolle and towards the Nyl River floodplain (Nysvlei Wetland). Although the Little Nyl system is fluvial in nature and could be termed as a riverine system, much of its length within the study area is more accurately described as a wetland system, rather than a purely riverine riparian system, with extensive lateral wetland habitat on either side of the main channel. In parts of its length (i.e. within wetland units DP-BS_2b,3b&7) it is characterised by the presence of a narrower partly bedrock-dominated channel with limited wetland habitat and a wooded riparian corridor, with more limited true wetland habitat; however downstream and upstream of these reaches the drainage system changes to a channelled valley bottom or even un-channelled valley bottom wetland system.
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In these channelled valley bottom wetlands, fluvial processes are the main hydrological drivers, with channelised baseflows sustaining a permanently inundated zone within the channel – i.e. an area of permanent hydrological activation. Spate flows that occur along the drainage system in the summer months are responsible for hydrologically activating the more elevated parts of the channel and surrounding terraces.
5.1.2 Un-channelled Valley Bottom Wetlands
Two reaches of the Little Nyl drainage system and another valley bottom wetland located at the Donkerpoort WTW in the study area were classified as being un-channelled. Under the Ollis et al 2013 classification system, an un-channelled valley bottom wetland is defined as being: “characterised by its location on valley floors, an absence of distinct channel banks, and the prevalence of diffuse flows”. These wetlands are generally formed when an upstream channel loses confinement and spreads out over a wider area, causing the channelised flow to spread out. In the case of the two reaches of the Little Nyl that are un-channelled, the terrain setting in which the river flows flattens out markedly as the system drains away from the foothills to the north, and the valley cross sectional profile widens. The wetland becomes a wider wetland characterised by the presence of dense Phragmites reedbeds as well as by stands of other sedges and rushes in a permanently saturated and inundated hydrological setting.
5.1.3 Seeps
A number of seep wetlands were encountered, being located within the terrain setting of sloping ground. Under the Ollis et al (2013) classification system, a seep is defined as: “A wetland area located on gently to steeply sloping land and dominated by colluvial (i.e. gravity- driven), unidirectional movement of water and material down-slope” In seep wetlands water inputs are primarily via subsurface flows from the upslope catchment of the wetland. Water movement through the seep is mainly in the form of interflow, with diffuse overland flow (known as sheetwash) often being significant during and after rainfall events (Ollis et al, 2013). The sloping terrain in the northern part of the study area that is associated with the footslopes of the hills to the north of the Donkerpoort District Road is conducive to the development of colluvial processes that are associated with seep wetlands. Movement of water down the slope, rather than the deposition of water within the wetland, is the predominant hydrological driver.
The analysis of soils within these seep wetlands (refer to section 5.2.1 below) appears to indicate that these seep wetlands are associated with the presence of a shallow (perched) water table that rises seasonally to form saturated soils at or near the surface, thus resulting in the development of wetland conditions. Anecdotal evidence from landowners in the area however suggests that some of these seep wetlands were originally associated with active springs, which have since disappeared.
Under the level 4 descriptor, seep wetlands can be distinguished between those that have channelled outflows, and those which do not. The former occurs in the study area, and all seeps are hydrologically connected to the Little Nyl drainage system.
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5.2 Physical Characteristics of Wetlands in the Study Area
5.2.1 Soil characteristics
Section 4.4 above has detailed the soil types associated with the Bb93 land type which occurs in the study area. The soils encountered in the wetlands in which soil samples were taken broadly corresponded with the soil assemblage of the Bb93 landtype. Soils in both valley bottom and seep wetlands were noted to be predominantly apedal in character, with the presence of yellow-brown apedal soils noted within certain of the wetlands sampled, as well as on the margins of all wetlands. In certain of the wetlands sampled a Pinedene soil form was encountered (displaying a yellow-brown apedal B horizon underlain by unspecified material with signs of wetness), with the soils outside of the wetland being classified as the non-wetland Clovelly soil form. In one of the seep wetlands (DP-BS_Seep_5) a Fernwood soil form (an Orthic A horizon underlain by an E horizon and unspecified material underlying the E) was encountered (corresponding with the likely hydrological processes in these wetlands of interflow driven by colluvial processes).
Figure 13 – Signs of wetness (iron mottling) in unspecified material underlying a yellow-brown apedal B horizon in the wetland DP- BS_Vch_9a
The presence of plinthic characteristics in the soils was the key structural factor related to the presence of hydric soils in most of the wetlands sampled within the study route. The plinthic material primarily took the form of a soft plinthic B horizon which was encountered in most of the wetlands sampled, occurring below
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an Orthic A horizon (a Westleigh soil form) or underlying an E horizon (a Longlands soil form), which more commonly occurred in certain of the seep wetlands in the study area (see above comment related to the presence of the E horizon and the hydrology of seep wetlands)6. The soft plinthic B horizon displayed signs of wetness in the form of a gleyed (light to dark) grey matrix, with the presence of distinctive iron (orange-red) mottling and oxidised rhizospheres, as well as manganese mottling and redox / clay depletions in many cases. The soft plinthic B horizon was in many cases underlain by non-distinctive gleyed, highly sandy (gravelly) material 7. In many cases signs of wetness (particularly iron mottling) occurred throughout the soil profile, becoming increasingly abundant and prominent with depth. Along with the presence of the soft plinthic layer, these redoximorphic features are clearly indicative of the presence of a rising and falling water table that saturates soils to the surface in these wetlands during the wetter summer season, allowing the development of hydric conditions in the soils.
Figure 14 – Part of a soil sample from wetland DP-BS_Seep_1b showing the transition point between an E horizon and the underlying soft plinthic B horizon
Only in the valley bottom settings were more clayey soils with a horizon that in one case displayed a distinctive G horizon (the valley bottom wetland DP-BS_Vuc_1c located adjacent to the WTW) encountered. In certain of the samples an upper clayey B horizon was immediately underlain by a sub- horizon that was conversely highly sandy and apedal in nature, although still gleyed.
6 No hard plinthic B horizons were encountered at any of the soil sampling points investigated. 7 Soft plinthic B horizons typically transition to non-distinctive gleyed material underlying the plinthic material
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5.2.2 Wetland Vegetation
Wetland vegetation was noted to be largely grass-dominated and wetlands (in particular the seep wetlands investigated in the study area) markedly differed in terms of vegetation composition when compared to the surrounding woodland. A limited number of grass species were encountered in the wetlands sampled, with the most commonly occurring species which was dominant in the seep wetlands and certain of the valley bottom wetlands being Imperata cylindrica. This species is typically a facultative hydrophyte in the wetter parts of South Africa, but in drier climates (as appears to be the case in the study area) is an obligate wetland species. In the seep wetlands large stands of Imperata cylindrica were encountered, being dense and moribund, especially where no livestock grazing occurs. In the study area this species appears to be indicative of wetlands that experience seasonal saturation (primarily due to a rising and falling water table).
Figure 15 – Moribund stand of Imperata cylindrica in the seep wetland DP-BS_Seep_1a
Valley bottom wetlands were typically characterised by a slightly more diverse assemblage of grass and sedge species. In these settings Imperata cylindrica typically occurred on the drier margins of the wetlands, along with Cyperus longus which typically occurred in this transitional part of the wetland. The wetter parts of valley bottom wetlands (including those parts of channelled valley bottom wetlands and central portions of un-channelled valley bottom wetlands) and flow depressions within seep wetlands were typically characterised by the presence of a variety of obligate hydrophytes, including Phragmites mauritianus, Cyperus dives, Typha capensis, Miscanthus junceus, Schoenoplectus corymbosus and a
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number of other herbs and forb species. Phragmites mauritianus occurred in a dense stands, and was often associated with areas of deposition, such as un-channelled areas and parts of wetlands upstream of impoundments.
The unchannelled reach of the valley bottom wetland that is located immediately downstream of the Donkerpoort Dam Wall (DP-BS_Vuc_2a) was noted to be characterised by a differing and more diverse assemblage of wetland vegetation, appearing to reflect a permanently saturated hydrological regime. This reach was characterised by the extensive presence of the obligate hydrophytes Leersia hexandra and Ischaemum fasciculatum, in addition to the species mentioned above, along with a large number of Syzigium cordatum trees that were not only restricted to the wooded riparian margins of the wetland, but which occurred in large numbers within the wetland.
Figure 16 – Un-channelled valley bottom wetland with Syzigium cordatum trees in the wetland in the reach DP-BS_Seep_2a
Certain reaches of the Little Nyl River, such as those upstream of the first pipeline crossing point (DP- BS_Vch_2b), and the reach that flows through the Koro Creek Estate ((DP-BS_Vch_7) were characterised by a vegetative structure that was dominated by a woody riparian corridor, and only limited wetland habitat along the channel, with certain sub-reaches being characterised by a bedrock-dominated channel. In these reaches flood terraces characterised by dense stands of Imperata cylindrica were present in places. A number of indigenous tree species were dominant in this riparian setting. The lower reaches of the Little Nyl, downstream of the R33 road crossing displayed a differing vegetation composition, with a wide bed being characterised by grasses, sedges and reeds, with a narrow to slightly wider wooded riparian corridor along the margins of the wetland. In places the transition to a wooded riparian corridor occurred where a
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(low to high) macro channel bank was present. The wooded riparian corridor was most pronounced and at its widest in the downstream part of the reach near the local correctional facility. It is important to note that the wooded riparian vegetation along the lower parts of the Little Nyl has been subject to significant levels of removal (felling) of mature riparian trees, presumably for firewood by inhabitants of the nearby township and associated informal settlements, to the degree that the degree of woody cover was significantly decreased.
Figure 17 – Un-channelled section of the reach of the valley bottom wetland DP-BS_Vu_8b; note the heavily thinned woody riparian margins of the wetland
Alien invasive species were present within most of the wetlands sampled, but generally at low densities, except in one case (DP-BS-Vch_3a-b). The most commonly-occurring alien invasive species encountered was Melia azedarach (Syringa) and Sesbania punicea, as well as Eucalyptus spp. and Populus alba. Other alien invasive species noted were Lantana camara and Morus alba. Parts of the reaches of the wetlands DP-BS_Vch_1a & 9a were noted to have been invaded by dense stands of the latter two species respectively. Alien invasive tree and shrub vegetation was most typically encountered on the margins of wetlands or in wooded riparian corridors, with the exception of Sesbania punicea which occurred in low densities in most of the wetlands sampled.
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Although not an alien species, the extensive presence of the shrub species Seriphium plumosum (formerly Stoebe vulgaris) in two of the seep wetlands (DP-BS_Seep_3c&6) needs to be noted. The species proliferates in disturbed or overgrazed areas8 and is not readily eaten by stock and is thus considered a problem plant in many parts of South Africa. The large crown of individual plants may easily cover an area of 1m², over-shadowing and pushing out all other species, especially grasses that need to compete with the extensive root system for water and nutrients (Avenant, 2015). In most parts of the country this species does not occur within wetland settings, however in the Limpopo Province and in the Waterberg District in particular, S. plumosum tends to invade sandy wetland areas and drainage lines, posing a significant threat to the sensitive ecosystems of the Waterberg area (Avenant, 2015). In the seep wetland reaches DP-BS_Seep_3c&6, large portions of the wetland area (estimated to be as much as 50% of the area of the respective seep component / reach assessed) has been invaded by this species, especially on the drier peripheries of the wetland where it replaces the wetland hydrophyte Imperata cylindrica. These seep wetlands are likely to have been significantly vegetatively degraded by the spread of this pioneer species (refer to section 7.1.3 and 7.1.6). S. plumosum was not observed in significant densities in any of the other (seep) wetlands investigated in the study area, although it was noted to be present in fairly high densities, but in a small non-wetland area located between the two seep compartments and along the road that bisects the wetland DP-BS_Seep_1a&b.
Figure 18 – A mix of Imperata cylindrica grass and the invasive plant Seriphium plumosum in the wetland DP-BS_Seep_6
8 http://www.plantzafrica.com/plantqrs/seriphplum.htm
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It is important to note that the vegetative composition at both of the pipeline crossing points of the Little Nyl River is impacted, with the crossing point at the R33 bridge ((DP-BS_Vch_7) being particularly so. In this case the pipeline is proposed to be aligned between the R33 road and the boundary wall of the Koro Creek Estate, and the pipeline would cross the river in the narrow section of the river located between the road bridge and the culverts associated with the estate’s boundary wall and adjacent access road. The vegetative state of this narrow section of the reach is highly impacted, with the natural riparian vegetation having largely been removed and the existing banks of the channel of the stream being invaded by Kikuyu (Pennisetum clandestinum). This state of vegetative alteration is significant as transformative impacts associated with the proposed pipeline will have less of a significant impact.
6 RESULTS OF ECOSTATUS ASSESSMENTS FOR WETLAND UNITS IN THE STUDY AREA
6.1.1 DP-BS_1a-c Wetland Hydrogeomorphic Units: . Seep – DP-BS_Seep_1a&1b . Un-channelled Valley Bottom – DP-BS_Vu_1c
Wetland State PES Hydrology PES Geomorphology PES Vegetation B A B
Overall PES Class: B
Pressures acting on the Wetland / Impacts: . The Donkerpoort district road bisects the seep wetland (reach 1a) and is a hydrological barrier, partially altering the hydrology of the wetland. . Parts of the wetland have been invaded by Populus spp. (upstream of the Donkerpoort district road); and the invasive species Seriphium plumosum is present in the peripheries of the wetland, but not within it. . Two tracks have recently been cleared within the seep wetland area close to the WTW, resulting in loss of wetland habitat and hydrological impacts on the seep wetland components. . An area of the valley bottom HGM unit falls within the WTW fence and is thus mowed and short sections of the valley bottom are culverted adjacent to the WTW. . Dumping of material was noted in the wetland adjacent to the WTW.
Discussion: . The overall PES Score reflects a largely natural state, with few modifications. The wetland habitat within this wetland unit is largely intact in spite of the impacts described above. . The wetland unit is well vegetated with no signs of active erosion, and is thus geomorphologically intact. . There is only limited alien invasive plant proliferation, although the Populus spp. and Seriphium plumosum could further invade the wetland.
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Figure 19 – Track cleared into the seep component of the wetland near the WTW
Wetland Functionality
DP-BS_1a-c ecosystem services scores
Flood attenuation Education and research4.0 Streamflow regulation
Tourism and recreation 3.0 Sediment trapping 2.0 Cultural significance 1.0 Phospahte trapping 0.0 Cultivated foods Nitrate removal
Natural resources Toxicant removal
Water supply for human use Erosion control Maintenance of biodiversity Carbon storage
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Ecosystem Services supplied to a high degree: None
Ecosystem Services supplied to a moderately high degree: . Sediment Trapping . Phosphate Trapping . Nitrate Removal . Toxicant removal . Erosion control
Discussion: . The wetland is very well-vegetated and there is no evidence of removal of vegetation or soil disturbance and no evidence of erosion, hence the erosion control function. . The wetland displays moribund vegetation over most of its area and thus an effective sediment trapping function . Diffuse flows within the seep wetland will assist in the phosphate trapping and nitrate & toxicant trapping functions.
Wetland Ecological Importance and Sensitivity (score out of 4)
EIS Score - Ecological EIS Score- Hydrological 2.2 1.9 EIS Class: Moderate
Discussion: . Most of the wetland reach consists of a seep wetland with large areas of Imperata cylindrica wetland habitat that are seasonally flooded. The wetland is thus important in a wetland habitat context and in a hydrological (esp. streamflow regulation context). . The wetland is located upstream of a Ramsar wetland (of international significance) and is linked to the stream network and is thus significant in this regard.
6.1.2 DP-BS_2a-b
Wetland Hydrogeomorphic Units: . Un-channelled Valley Bottom – DP-BS_Vu_2a . Channelled Valley Bottom – DP-BS_Vu_2b
Wetland State PES Hydrology PES Geomorphology PES Vegetation D A B
Overall PES Class: C
Pressures acting on the Wetland / Impacts: . The Donkerpoort Dam is located immediately upstream of the reach; this is a large dam that is likely to have significantly altered the hydrology of the wetland by reducing inflows and by reducing flood peaks . The lower parts of the reach have been invaded alien vegetation.
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. Significant sedimentation (siltation) was noted in the un-channelled upper section of the reach; the sediment appears to emanate from the WTW discharge. . The Donkerpoort WTW discharges water into the reach, the water quality of this discharge is not known, but the silt observed in the wetland appears likely to emanate from the WTW and thus polluted water is being discharged into the reach.
Discussion: . The overall PES Score reflects a moderately modified state. In spite of the significant hydrological impact on the wetland, wetland habitat appears intact and the unchannelled section of the reach was noted to be highly saturated in spite of the current drought. . The wetland unit is well vegetated with no signs of active erosion, and is thus geomorphologically intact. . Although present in the lower part of the reach, alien invasive plant proliferation is limited in the overall context of the reach.
Figure 20 – Siltation observed in the upper part of the wetland reach
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Wetland Functionality
DP-BS_2a-b ecosystem services scores
Flood attenuation Education and research4.0 Streamflow regulation
Tourism and recreation 3.0 Sediment trapping 2.0 Cultural significance 1.0 Phospahte trapping 0.0 Cultivated foods Nitrate removal
Natural resources Toxicant removal
Water supply for human use Erosion control Maintenance of biodiversity Carbon storage
Ecosystem Services supplied to a high degree: None
Ecosystem Services supplied to a moderately high degree: . Streamflow Regulation . Sediment Trapping . Phosphate Trapping . Nitrate Removal . Toxicant removal . Erosion control . Carbon Storage . Maintenance of Biodiversity
Discussion: . The wetland is very well-vegetated and there is no evidence of removal of vegetation or soil disturbance and no evidence of erosion, hence the erosion control function. . Significant deposition of sediment (silt) was noted in the un-channelled part of the wetland reach; this part of the reach appears to be performing an effective role in this context; the presence of a farm dam is important in trapping the majority of this excess silt. . The un-channelled section of the reach was noted to be highly saturated, and is thus performing a significant role in storing and gradually releasing water, especially in the context of the current drought. . Large parts of the un-channelled section of the reach appear to be characterised by a high degree of organic wetland substrate, in the form of a floating marsh, hence the carbon storage function. . The un-channelled section of the reach contains large numbers of Syzigium cordatum trees, forming dense stands, which is an unusual wetland habitat. . The wetland, although not very wide in lateral extent contains significant amounts of un- channelled wetland in which diffuse flow occurs, and associated with a high level of surface roughness.
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Wetland Ecological Importance and Sensitivity (score out of 4)
EIS Score - Ecological EIS Score- Hydrological 3.0 2.7 EIS Class: High
Discussion: . Habitat diversity in the reach is high with channelled and un-channelled wetland habitat, open water and a wooded riparian verge, as well as areas of Syzigium cordatum trees that form wetland habitat with similarities to swamp forest; the rarity of this wetland habitat enhances its EIS score. . The wetland is upstream of a Ramsar wetland (of international significance) and is thus significant in this regard . The un-channelled nature of the much of the reach entails that it displays a very moderately high hydrological / functional importance
6.1.3 DP-BS_3a-c
Wetland Hydrogeomorphic Units: . Channelled Valley Bottom – DP-BS_Vch_3a . Channelled Valley Bottom – DP-BS_Vch_3b . Seep – DP-BS-Seep_3c
Wetland State PES Hydrology PES Geomorphology PES Vegetation E A E
Overall PES Class: D
Pressures acting on the Wetland / Impacts: . The Donkerpoort Dam is located upstream of the reach; this is a large dam that is likely to have significantly altered the hydrology of the wetland by reducing inflows and by reducing flood peaks . Most of the valley bottom component of the reach has been invaded by alien vegetation – mostly mature Eucalyptus and Poplar trees, with the latter forming dense stands in the lower part of the reach. This has significantly altered the vegetative state of the wetland, as well as increasing water uptake. . The seep component of the reach has been invaded by extensive stands of the pioneer plant Seriphium plumosum that has significantly degraded the wetland vegetative composition of this part of the reach. . Significant sedimentation (siltation) was noted in the upper section of the reach; the sediment appears to emanate from the district road that crosses the wetland at its upstream end. . There is a large dam in the reach that has transformed wetland habitat (resulting in wetland habitat loss) and which exerts a hydrological impact on the downstream parts of the reach. . A berm / wall was historically constructed on the western shore of the dam. By impounding seepage water from the seepage compartment and preventing it from flowing into the dam and thus into the downstream drainage network, the berm exerts a significant hydrological impact on the wetland.
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Discussion: . The overall PES Score reflects a significantly modified state. The wetland has undergone habitat transformation due to the presence of the dam and due to the proliferation of alien invasive and pioneer plant species into the wetland. The presence of the dam and the extensive stands of mature alien invasive trees (along with the impact of the upstream Donkerpoort Dam) has significantly altered the hydrological state of the reach. . The wetland unit is well vegetated with no signs of active erosion, and is thus geomorphologically intact.
Figure 21 – Dense stand of poplars in the wetland reach immediately downstream of the dam
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Wetland Functionality
DP-BS_3a-c ecosystem services scores
Flood attenuation Education and research4.0 Streamflow regulation
Tourism and recreation 3.0 Sediment trapping 2.0 Cultural significance 1.0 Phospahte trapping 0.0 Cultivated foods Nitrate removal
Natural resources Toxicant removal
Water supply for human use Erosion control Maintenance of biodiversity Carbon storage
Ecosystem Services supplied to a high degree: None
Ecosystem Services supplied to a moderately high degree: . Phosphate Trapping . Nitrate Removal . Toxicant removal . Erosion control . Carbon Storage
Discussion: . The wetland is very well-vegetated and there is no evidence of removal of vegetation or soil disturbance and no evidence of erosion, hence the erosion control function. . The dam in the unit is utilised for fishing, and the wetland thus performs a tourism and recreation function. . The seep compartment of the wetland is responsible for performing a water quality function, although this is hampered by the invasion of the wetland by pioneer plant species.
Wetland Ecological Importance and Sensitivity (score out of 4)
EIS Score - Ecological EIS Score- Hydrological 1.8 1.9 EIS Class: Moderate
Discussion: . Habitat diversity in the reach is high with channelled and un-channelled wetland habitat, open water and a wooded riparian verge; this factor enhances its EIS score. . The wetland is upstream of a Ramsar wetland (of international significance) and is thus significant in this regard . The high level of wetland habitat transformation and degradation however reduces its ecological and hydrological importance. . hydrological / functional importance
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6.1.4 DP-BS_4
Wetland Hydrogeomorphic Units: . Channelled Valley Bottom – DP-BS_Vch_4
Wetland State PES Hydrology PES Geomorphology PES Vegetation B A C
Overall PES Class: B
Pressures acting on the Wetland / Impacts: . Parts of the reach have been invaded by alien vegetation – mostly mature Eucalyptus trees. This has altered the vegetative state of the wetland, as well as increasing water uptake. .
Discussion: . The overall PES Score reflects a largely natural state. The only significant impact on the wetland reach is the presence of alien invasive trees. . Much of the reach is not characterised by wetland habitat, but this is due to the outcropping of bedrock and the concomitant incision and narrowing of the channel . The wetland unit is well vegetated with no signs of active erosion, and is thus geomorphologically intact.
Figure 22 – Lateral wetland habitat in the reach that has been invaded by Eucalyptus trees
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Wetland Functionality
DP-BS_4 ecosystem services scores
Flood attenuation Education and research4.0 Streamflow regulation
Tourism and recreation 3.0 Sediment trapping 2.0 Cultural significance 1.0 Phospahte trapping 0.0 Cultivated foods Nitrate removal
Natural resources Toxicant removal
Water supply for human use Erosion control Maintenance of biodiversity Carbon storage
Ecosystem Services supplied to a high degree: None
Ecosystem Services supplied to a moderately high degree: . Sediment Trapping . Erosion control
Discussion: . The wetland is very well-vegetated and there is no evidence of removal of vegetation or soil disturbance and no evidence of erosion, hence the erosion control function.
Wetland Ecological Importance and Sensitivity (score out of 4)
EIS Score - Ecological EIS Score- Hydrological 1.4 1.6 EIS Class: Moderate
Discussion: . The wetland is upstream of a Ramsar wetland (of international significance) and is thus significant in this regard . A certain degree of wetland habitat transformation and degradation and the small size of the wetland reduces its ecological and hydrological importance.
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6.1.5 DP-BS_5 Wetland Hydrogeomorphic Units: . Seep – DP-BS_Seep_5
Wetland State PES Hydrology PES Geomorphology PES Vegetation B A C
Overall PES Class: B
Pressures acting on the Wetland / Impacts: . Anecdotal evidence from the landowner suggests that there was historically a spring at the top of the wetland reach; this spring no longer exists and thus groundwater abstraction may have altered the natural hydrology of the wetland. A deep impoundment exists at the head of the wetland and this may trap any residual seepage from the spring, thus preventing it from moving into the lower sections of the wetland. . There is a high grazing presence in the wetland due to a large number of livestock, however the vegetation coverage still appears intact
Discussion: . The overall PES Score reflects a largely natural state, with few modifications. The wetland habitat within this wetland unit is largely intact. . The wetland unit is well vegetated with no signs of active erosion, and is thus geomorphologically intact in spite of the trampling of livestock. . There is very limited alien invasive plant proliferation, but the wetland is heavily grazed and wetter parts of the wetland are subject to trampling, exposing soils in places.
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Figure 23 –Livestock trampling in a wetter flow depression in the seep wetland
Wetland Functionality
DP-BS_5 ecosystem services scores
Flood attenuation Education and research4.0 Streamflow regulation
Tourism and recreation 3.0 Sediment trapping 2.0 Cultural significance 1.0 Phospahte trapping 0.0 Cultivated foods Nitrate removal
Natural resources Toxicant removal
Water supply for human use Erosion control Maintenance of biodiversity Carbon storage
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Ecosystem Services supplied to a high degree: None
Ecosystem Services supplied to a moderately high degree: . Phosphate Trapping . Nitrate Removal . Toxicant removal . Erosion control . Carbon Storage . Maintenance of Biodiversity
Discussion: . The wetland is very well-vegetated and there is no evidence of removal of vegetation or soil disturbance and no evidence of erosion, hence the erosion control function. . The wetland is located close to a number of stock points; hence nitrates and phosphates emanating from these areas could be trapped and removed by the wetland vegetation. . The wetland is relatively large, hence the carbon storage function.
Wetland Ecological Importance and Sensitivity (score out of 4)
EIS Score - Ecological EIS Score- Hydrological 2.4 2.1 EIS Class: High
Discussion: . This is a large seep wetland with large areas of Imperata cylindrica wetland habitat that are seasonally flooded. The wetland is thus important in a wetland habitat context and in a hydrological (esp. streamflow regulation context). . The wetland is located upstream of a Ramsar wetland (of international significance) and is linked to the stream network and is thus significant in this regard.
6.1.6 DP-BS_6
Wetland Hydrogeomorphic Units: . Seep – DP-BS_Seep_6
Wetland State PES Hydrology PES Geomorphology PES Vegetation B A D
Overall PES Score: C
Pressures acting on the Wetland / Impacts: . Anecdotal evidence from the landowner suggests that the wetland was much historically wetter, suggesting groundwater abstraction has led to a reduction of groundwater inflows to the wetland. . At least 50% of the wetland is estimated to have been invaded by the pioneer shrub species Seriphium plumosum, having likely replaced the naturally occurring hydrophyte grass species Imperata cylindrica. The ecosystem services associated with the grass species have thus been greatly reduced.
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. A high density of Warthogs (Phacochoerus africanus) in the wetland appears likely to responsible for the presence of a large number of areas of ‘shallow excavation’ in the wetland in which all grassy vegetation has been removed and the underlying sandy soils left exposed. In addition to leaving soils exposed to desiccation and subsequent erosion, this factor may also be assisting the spread of S. plumosum within the wetland. . A relatively incised dam in the lower end of the reach may be preventing water from moving into downstream sections of the wetland.
Discussion: . The overall PES Score reflects a moderately modified state. The wetland unit is geomorphologically and hydrologically largely intact but the vegetative assemblage / composition has been significantly altered from a natural state, thus degrading the state of the wetland. . The wetland unit is well vegetated with no signs of active erosion, although the actions of warthogs are creating numerous patches of exposed soil within the wetland.
Figure 24 –Part of the wetland with a natural vegetative composition (left) and another part having experienced extensive invasion by Seriphium plumosum (right)
Wetland Functionality
DP-BS_Seep_6 ecosystem services scores
Flood attenuation Education and research4.0 Streamflow regulation
Tourism and recreation 3.0 Sediment trapping 2.0 Cultural significance 1.0 Phospahte trapping 0.0 Cultivated foods Nitrate removal
Natural resources Toxicant removal
Water supply for human use Erosion control Maintenance of biodiversity Carbon storage
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Ecosystem Services supplied to a high degree: None
Ecosystem Services supplied to a moderately high degree: . Sediment Trapping . Phosphate Trapping . Nitrate Removal . Toxicant removal . Erosion control . Maintenance of Biodiversity
Discussion: . The wetland is very well-vegetated in spite of the presence of a number of excavated areas created by Warthogs, hence the erosion control function. . The input of groundwater that flows diffusely through the wetland during the wet season through dense stands of Imperata cylindrica in the wetter parts of the wetlands allows phosphates and nitrates that are potentially present within the groundwater to be removed. . The invasion of large parts of the wetland by the invader Seriphium plumosum has degraded a number of ecosystem services related to the presence of naturally occurring stands of I. cylindrica.
Wetland Ecological Importance and Sensitivity (score out of 4)
EIS Score – Ecological EIS Score- Hydrological 2.3 1.9 EIS Class: High
Discussion: . This wetland is designated as a FEPA wetland and is a large seep wetland with large areas of Imperata cylindrica wetland habitat that are seasonally flooded. The wetland is thus important in a wetland habitat context and in a hydrological (esp. streamflow regulation context). However the transformation of at least 50% of the wetland by Seriphium plumosum has degraded the wetland and reduced its ecological and sensitivity value. . The wetland is located upstream of a Ramsar wetland (of international significance) and s linked to the stream network and is thus significant in this regard.
6.1.7 DP-BS_7
Wetland Hydrogeomorphic Units: . Channelled Valley Bottom – DP-BS_Seep_7
Wetland State PES Hydrology PES Geomorphology PES Vegetation D A C
Overall PES Class: C
Pressures acting on the Wetland / Impacts: . A relatively large dam occurs in the upper part of the reach, altering the hydrology of the wetland and altering wetland habitat composition.
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. The reach of the Little Nyl is located downstream of the Donkerpoort Dam. Although a tributary of the river joins the reach between the reach and the dam, the Donkerpoort Dam is nonetheless likely to have altered the hydrology of the reach through the reduction in floodpeaks, and through the likely reduction of river flows, especially low flow volumes. . Natural wetland habitat along certain parts of the reach (although not large in aerial extent) has been replaced by fairways associated with the golf course, resulting in a degradation of wetland habitat in certain parts of the reach. . The immediate catchment of the reach has also been altered from a natural state through the presence of the golf course. . The lower-most part of the reach has been significantly transformed by the presence of the boundary wall of the Koro Creek Estate and associated culvert and the R33 Road crossing.
Discussion: . The overall PES Score reflects a moderately modified state. The wetland unit is geomorphologically and vegetatively largely intact but the hydrology of the reach has been altered through impoundments within the reach and by a large upstream dam. . Although small parts of the wetland and associated riparian zone have suffered removal of natural vegetation for golf course fairways and transformation due to the presence of road bridges at the lowest end of the reach, the remainder of the wetland vegetation in the reach was noted to be intact, and it appeared as if alien invasive vegetation over the majority of the reach had been removed. . The wetland is geomorphologically stable with no erosion noted along the reach.
Figure 25 – Part of the reach in the Estate where natural wetland and riparian vegetation has been removed and replaced by grassy fairways (foreground), with a natural vegetative assemblage in the background
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Wetland Functionality
DP-BS_7 ecosystem services scores
Flood attenuation Education and research4.0 Streamflow regulation
Tourism and recreation 3.0 Sediment trapping 2.0 Cultural significance 1.0 Phospahte trapping 0.0 Cultivated foods Nitrate removal
Natural resources Toxicant removal
Water supply for human use Erosion control Maintenance of biodiversity Carbon storage
Ecosystem Services supplied to a high degree: None
Ecosystem Services supplied to a moderately high degree: . Toxicant removal . Erosion control . Carbon storage
Discussion: . The wetland and riparian corridor is very well-vegetated in spite of the presence of the clearing for the gold course, hence the erosion control function.
Wetland Ecological Importance and Sensitivity (score out of 4)
EIS Score – Ecological EIS Score- Hydrological 2.1 1.3 EIS Class: Moderate
Discussion: . The wetland is relatively narrow in lateral extent, and thus wetland habitat is limited. It displays, limited habitat diversity (primarily riparian habitat, however in spite of some removal of wetland and riparian habitat the remaining habitat is in a good state and protected as part of a managed ‘eco-estate’. . The wetland is however upstream of a Ramsar wetland (of international significance) and is thus significant in this regard . The limited extent of the wetland entails that it displays a limited hydrological / functional importance
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6.1.8 DP-BS_8a-c
Wetland Hydrogeomorphic Units: . Channelled Valley Bottom – DP-BS_Vu_8a . Un-channelled Valley Bottom – DP-BS_Vu_8b . Channelled Valley Bottom – DP-BS_Vu_8c
Wetland State PES Hydrology PES Geomorphology PES Vegetation D A B
Overall PES Class: C
Pressures acting on the Wetland / Impacts: . The reach of the Little Nyl is located downstream of the Donkerpoort Dam. Although a tributary of the river joins the reach between the reach and the dam, the Donkerpoort Dam is nonetheless likely to have altered the hydrology of the reach through the reduction in floodpeaks, and through the likely reduction of river flows, especially low flow volumes. . The immediate catchment of the reach is subject to poor landuse practices such as extensive overgrazing, regular burning, removal of woody vegetation as well as excavations for building material, thus the catchment runoff is likely to have increased and is feeding a high level of sediment into the wetland. . Part of the lower catchment of the reach and a part of the riparian corridor of the wetland has been transformed through the development of a shopping mall, thus destroying habitat and likely increasing runoff from the hard surfaces of buildings and parking areas. . A dam in the lower part of the reach has resulted in transformation of wetland habitat.
Discussion: . The overall PES Score reflects a moderately modified state. The wetland unit is geomorphologically largely intact but the hydrology of the reach has been altered through impoundments within the reach and by a large upstream dam. . The wetland vegetation in the reach appears to be intact, however the naturally wooded riparian verges of the wetland have been significantly altered along parts of the reach by the thinning (felling) of large trees. . The wetland is geomorphologically stable with no erosion noted along the reach.
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Figure 26 – Example of felling of large trees within the riparian corridor of the reach, close to the correctional facility
Wetland Functionality
DP-BS_8a-c ecosystem services scores
Flood attenuation Education and research4.0 Streamflow regulation
Tourism and recreation 3.0 Sediment trapping 2.0 Cultural significance 1.0 Phospahte trapping 0.0 Cultivated foods Nitrate removal
Natural resources Toxicant removal
Water supply for human use Erosion control Maintenance of biodiversity Carbon storage
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Ecosystem Services supplied to a high degree: None
Ecosystem Services supplied to a moderately high degree: . Streamflow Regulation . Sediment Trapping . Phosphate Trapping . Nitrate Removal . Toxicant removal . Erosion control . Carbon storage . Provision of natural resources
Discussion: . The large un-channelled sections, as well as channelled sections where in many areas the channel is poorly developed are effective in retaining water and slowly releasing flows to the downstream catchment, hence the streamflow regulation function. . The extensive un-channelled sections of the wetland characterised by dense reedbeds and rushbeds in which diffuse surface flows occur are effective in trapping sediments, as well as performing water quality enhancement functions by trapping / removing any phosphates, nitrates and toxicants that emanate from the upstream reaches or the wetland’s catchment. . The wetland is very well vegetated and is thus effective in ensuring erosion control. . Although it is a degrading factor in the wetland, the reach provides natural resources in the form of wood and grazing for livestock belonging to residents of the nearby township.
Wetland Ecological Importance and Sensitivity (score out of 4)
EIS Score – Ecological EIS Score- Hydrological 2.4 2.7 EIS Class: High
Discussion: . Habitat diversity in the reach is high with channelled and un-channelled wetland habitat, open water and a wooded riparian verge. . The wetland is upstream of a Ramsar wetland (of international significance) and is thus significant in this regard . The un-channelled nature of the much of the reach entails that it displays a very moderately high hydrological / functional importance
6.1.9 DP-BS_9a-b
Wetland Hydrogeomorphic Units: . Channelled Valley Bottom – DP-BS_Vu_9a-b
Wetland State PES Hydrology PES Geomorphology PES Vegetation C A C
Overall PES Class: C
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Pressures acting on the Wetland / Impacts: . The immediate catchment of the reach is subject to poor landuse practices such as extensive overgrazing, regular burning, removal of woody vegetation as well as excavations for building material, thus the catchment runoff is likely to have increased and is feeding a high level of sediment into the wetland. . The lower parts of the reach have suffered extensive infestation by alien invasive vegetation (Eucalyptus spp.). . A track bisects the wetland and forms a hydrological barrier.
Discussion: . The overall PES Score reflects a moderately modified state. The wetland unit is geomorphologically intact but the hydrology of the reach has been altered through poor landuse practices in the immediate catchment of the reach. . The naturally wooded riparian vegetation along the reach has been significantly altered by the thinning (felling) of large trees, thus altering the wetland’s natural vegetative composition.
Figure 27 – Deposition of excess sediment within the wetland; note the presence of alien invasive trees in the background
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Wetland Functionality
DP-BS_9a-b ecosystem services scores
Flood attenuation Education and research4.0 Streamflow regulation
Tourism and recreation 3.0 Sediment trapping 2.0 Cultural significance 1.0 Phospahte trapping 0.0 Cultivated foods Nitrate removal
Natural resources Toxicant removal
Water supply for human use Erosion control Maintenance of biodiversity Carbon storage
Ecosystem Services supplied to a high degree: None
Ecosystem Services supplied to a moderately high degree: . Sediment Trapping . Phosphate Trapping . Toxicant removal . Erosion control
Discussion: . The wetland is partially effective in trapping sediment inflows resulting from runoff from the immediate catchment. . Although it is a degrading factor in the wetland, the reach provides natural resources in the form of wood and grazing for livestock belonging to residents of the nearby township.
Wetland Ecological Importance and Sensitivity (score out of 4)
EIS Score – Ecological EIS Score- Hydrological 1.5 0.8 EIS Class: Low
Discussion: . The wetland is small in extent, displays little habitat diversity, is moderately modified, due primarily to poor landuse factors within the wetland and its immediate catchment, and does not display any significant biodiversity value. . The wetland is however upstream of a Ramsar wetland (of international significance) and is thus significant in this regard . The limited extent of the wetland entails that it displays a very low hydrological / functional importance
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7 IMPACTS ASSOCIATED WITH THE PROPOSED PIPELINE
It is important to note that of the nine wetland reaches that occur within the study area, only two will be physically affected by the proposed pipeline. The remainder are not affected by the proposed development, although two of the seep wetlands located to the south of the Donkerpoort District Road (Wetland units DP-BS_Seep_5&6) are located very close to the proposed alignment and could be affected indirectly by the construction activities associated with the proposed pipeline.
It is important to note that both of the wetland crossing points of the Little Nyl River are located within or immediately parallel to an existing road, therefore the affected wetland reaches have already been impacted. The construction and development of an underground pipeline will thus represent a further potential impact to these two already impacted wetland reaches which is beneficial as the impacts of the pipeline would be of greater magnitude if an unimpacted reach were to be affected. Nonetheless the development of the pipeline (in particular the construction of it) could be associated with potentially significant impacts if mitigation measures are not implemented.
The primary impact associated with the proposed pipeline would be the disturbance of wetland habitat (substrate and vegetation) through excavation of the pipeline. The pipeline will be buried, and thus a pipeline trench will need to be excavated across the affected watercourses. This will result in the disturbance of substrate within and immediately adjacent to the watercourses. A trench line and adjacent working right of way will need to be established, thus vegetation in wetland (and riparian zone) within the footprint of the works will need to be cleared. The creation of a working right of way for machinery and the excavation of a trench would result in the felling and removal of all vegetation, in particular woody vegetation, where this exists. This would leave the servitude devoid of vegetation after construction, which is important for a number of reasons.
The presence of excavation of substrate in a context of flowing water could result in pollution of the downstream watercourse / wetland. The excavated substrate would be mobilised to create silt if running water was allowed to move through the works area and significant volumes of silt could be transported into the downstream river reach. This is significant as much of the substrate within the wetlands in the study area is unconsolidated and easily erodible if the vegetation cover that binds the underlying soil is removed. The greater the volume of flow within the Little Nyl, the greater the potential for silt to be transported downstream and the greater volumes of silt that could be mobilised. The transported silt could degrade the wetland habitat quality of the downstream reach, and the management of flow through the works area and prevention of silt mobilisation is accordingly very important. Flows within the channel of the wetland at the respective crossings will need to be managed, as detailed in Section 8.1.1 below.
The clearing of wetland vegetation from servitudes would leave the soils exposed to erosion, especially water-borne erosion which is significant in the context of flows within the river channel, as detailed above. In addition stormwater flows from the pipeline construction servitude in the immediate catchment of the wetland that slopes down to the wetland crossing. This stormwater inflow to the riparian corridor / wetland could be responsible for significant sediment (silt) input and could also be responsible for the initiation of a ‘knick point’ which may lead to development of gulley (donga) erosion within, or immediately adjacent to the riparian corridor. For this reason securing the servitude through measures such a re-vegetation is an important mitigation measure as discussed below.
The clearing of vegetation introduces another potential longer-term impact - that of the invasion of the wetland and riparian zone by alien invasive vegetation. The excavated and subsequently rehabilitated area would create a very convenient ‘entry point’ into the riparian zone and wider riverine corridor for alien
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invasive vegetation – such human-related disturbances further exacerbate the natural susceptibility of riparian ecosystems to invasion by alien plants, as the transformed habitat is highly suitable for colonisation by alien invasives, and is less suitable for the less aggressive indigenous riparian species (Holmes et al, 2005). Riparian zones are particularly vulnerable to invasion by alien plants due to their dynamic hydrology and opportunities for recruitment following floods (Holmes et al, 2005), with servitude clearing having a similar effect. Many alien invaders of riparian habitats in South Africa are tall trees with higher water consumption than the indigenous vegetation (Holmes et al, 2005), and this could affect the vegetation-groundwater balance. Although the actual spatial area of the cleared servitude is likely to be relatively small in the context of the wider wetland / riparian corridor, this could create a convenient foothold for the invasion of wider areas of the riparian corridor, although it is noted that at both wetland crossings alien invasive vegetation is already present within the riparian corridors.
There are a number of other general construction-related impacts on the two wetlands proposed to be crossed by the pipeline that could materialise if not prevented or mitigated:
. The uncontrolled interaction of construction workers with watercourses that could lead to the pollution of these watercourses, e.g. dumping of construction material into the drainage system, washing of equipment, etc. . The lack of provision of adequate sanitary facilities and ablutions on the servitude may lead to direct or indirect faecal pollution of surface water resources. . Leakage of hazardous materials, including chemicals and hydrocarbons such as fuel, and oil, which could potentially enter nearby surface water resources through stormwater flows, or directly into the sandy soils within watercourses. This may arise from their incorrect use or incorrect storage. This is not only associated with a risk of pollution of surface water, but with a risk of the pollution of shallow groundwater within the riparian zone. . The incorrect mixing (batching) of cement could lead to siltation and contamination of watercourses, as described above. . Inadequate stormwater management and soil stabilisation measures in cleared areas could lead to erosion that could cause the loss of riparian vegetation and which would lead to siltation of nearby watercourses.
8 MITIGATION MEASURES AND CROSSING REHABILITATION PLAN
Note: at the time of completion of this draft, the pipeline crossing methodology / method statement had not been made available by the applicant. Accordingly this has not been able to be incorporated into the section below, and generic mitigation measures have been specified.
8.1 Pipeline Construction Mitigation Measures
A number of mitigation measures can be specified to minimise impact on the two wetlands crossed. As an overarching principle, it is very important that these surface water features, although already impacted by the presence of road crossings must be recognised as sensitive features, with care being taken to avoid unnecessary impacts on them.
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. The footprint of the works area through these wetlands must be kept a narrow as possible, and be restricted to a width that allows construction vehicles and equipment to access the trench line. Where possible at either locations construction vehicles must use the roads to cross these features to avoid the unnecessary widening of the construction footprint in these riparian areas. In the case of the upstream crossing (DP-BS_3), construction vehicles should utilise the Donkerpoort Road for a working area as far as practically possible. . Stockpiling of excavated substrate must not occur inside wetland areas / riparian corridors, and must occur outside of the wetland / riparian areas. . It is recommended that excavated topsoil from the wetland / riparian corridor by stored separately to the underlying subsoil, so that the topsoil can be restored at the surface. The toposoil will contain a natural seedbank that will facilitate re-vegetation of the servitude through these wetlands. . The pipeline must be strung outside of the wetland / riparian area, and extra space for stringing the pipeline must not be created within the works area within the riparian zone of watercourses. . Both the trench line and working right of way must be clearly demarcated prior to any construction occurring through the affected watercourse. . The wetland / riparian boundaries must be demarcated at both crossing sites, in order to control entry of vehicles into these areas . No other stockpiles or lay down areas must be established within either of the two wetlands. . No storage areas for hazardous materials must be located within 100m of the outer edge of the two wetland areas crossed, or within any other 100m of any other wetland along the alignment. . Once vegetation has been removed from the working right of way within the two wetland crossings, the adjacent wetland areas / riparian zone that do not fall within the footprint of the works must be demarcated as a no-go area that must not be physically affected by the proposed works. . All static machinery (such as diesel pumps) that could leak oil / fuel into the wetland must operate on drip trays. Drip trays must be checked for the presence of oil and leaked oil must be safely disposed of, not into the environment. . All machinery working within wetlands must be checked daily for leaks of oil / fuel and removed immediately from the works area within the wetland if leaks are detected. . A spill kit must be retained at each of the crossing sites for the duration of the works in the event of a spill. Any soil / substrate that is polluted in the event of a spill must be fully removed from the wetland works area and safely disposed of, not into the environment. . Construction should ideally occur during the drier winter / early summer months, when the possibility of rainfall and thus flow within these drainage systems is reduced. . Once the pipe has been laid, the original substrate must be reinstated as far as possible (it is recognised that padding material may need to be laid adjacent to the pipeline to protect it). Any excess material that is not required for reinstatement must be removed from the riparian zone and placed elsewhere. . The channel and banks of each of the wetlands crossed must be restored to a pre-construction state as far as possible. It is very important that the channel be reinstated to a level that is similar to the upstream and downstream level, and no structures that could impound water behind them must be constructed across the channel. . Any track / road constructed within the channel and adjacent riparian zone must be fully removed once construction has ended as part of the process of restoring the affected wetlands to a pre- construction state. . It is recommended that construction phase stormwater controls be instated at the two wetland crossings, and also within their immediate catchments, especially at the upstream crossing (DP- BS_3). It is important that measures such as bunding (to divert stormwater runoff away from the
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wetland areas) and / or silt fences be placed in the working right of way to prevent stormwater that is likely to transport silt from entering the wetlands / riparian corridors.
8.1.1 Management of flow and silt prevention through the works area
. It is critical that flow within the channels of the two respective wetland crossings be properly managed during the works, as otherwise significant volumes of silt could be mobilised and transported into downstream reaches. . As an overarching principle, flows within the channels at the two crossing points must bypass the works area, and not be allowed to flow through the works (excavated) area. There are a number of methodologies that can achieve this aim: . The flows could be impounded behind a temporary impounded structure and then the flow within the channel can be pumped via a mobile pipe over / around the works area and discharged into the downstream wetland reach. . Flume pipes could be placed across the works area, discharging into the reach immediately downstream of the trench and works area, with the trench excavated underneath the flume pipes. . Either of the above methods could be utilised at the crossing points; at the upstream crossing point (DP-BS_3) the presence of the Donkerpoort District Road immediately upstream / adjacent to the pipeline alignment makes the impounding of water difficult, although the culvert mouth could be blocked in order to achieve this. . At the downstream (R33 - DP-BS_7) crossing point there is more space to create an small impounding structure within the channel. . The trench through the wetland must be dewatered, and maintained free of water through the duration of the works until reinstatement, in the case of seepage water into the trench. This water removed from the trench must not be directly discharged into the downstream wetland as it will be likely to contain silt in suspension. The water must either be discharged into a silt lagoon located outside of the boundary of the wetland / riparian zone and allowed to drain naturally back in to the wetland, or can be discharged directly into the environment, at least 20m from the outer edge of the wetland / riparian zone. . It is recommended that silt fences be erected in the downstream channel of the river, dependent on the flows in the channel. Silt trapped behind these fences must be manually removed and the silt disposed of outside of the wetland riparian area in an area where it will not be able to be remobilised back into the wetland. . All temporary works structures such as temporary impounding structures, silt fences, flume pipes etc. must be fully removed at the end of the works and their footprint rehabilitated at part of the wider rehabilitation, if required.
8.2 Servitude Rehabilitation and Re-vegetation
It is important that re-vegetation be undertaken to ensure that the works footprint does not remain devoid of vegetation and thus vulnerable to erosion water-borne processes. A number of mitigation measures are pertinent in this case and must be applied:
. The topsoil within the works area must be retained once excavation for the pipeline has been completed and must be reinstated over the pipeline as this will contain a natural seed bank that will assist with natural re-vegetation.
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. Bare areas, such as reinstated banks and terraces, and especially those areas vulnerable to erosion by water during flow events must be protected from erosion while re-vegetation is occurring. It is recommended that geotextile be used to cover such areas, staked into the ground to protect seedlings. . Monitoring of re-vegetated areas must be undertaken, and follow up re-vegetated measures undertaken if necessary. . It is critical that operational procedures for the rehabilitation and subsequent management of the servitude include measures to remediate any developing erosion and to remove and prevent proliferation of alien invasive vegetation. This should be undertaken at an interval of at least 3 months. Thus for a period after construction the servitude through riparian areas must be monitored for the development of erosion, as well as the growth of alien invasive plant species. . If erosion is noted to be developing, immediate measures must be taken to remediate the erosion. It is very important that the integrity of the riparian zone post-construction be checked . In the case of alien invasive vegetation, all such species must be fully removed and measures taken to prevent further proliferation. In this context it is also very important that parts of the servitude adjacent to the watercourses (outside of riparian zones) also be subject to similar measures as without this the servitudes outside of the riparian zones would become ‘springboards’ for proliferation into the riparian area.
9 REFERENCES
Avenant, P., 2015, Report on the National Bankrupt Bush (Seriphium plumosum) Survey (2010-2012). Department of Agriculture, Forestry & Fisheries; Directorate Land Use & Soil Management; Sub- directorate: Natural Resources Inventories & Assessments.
Collins, N.B., 2005, Wetlands: The basics and some more. Free State Department of Tourism, Environmental and Economic Affairs.
Department of Water Affairs and Forestry, 2005, A Practical field procedure for identification and delineation of wetlands and riparian areas, Final Draft
Desmet, P. G., Holness, S., Skowno, A. & Egan, V.T. (2013), Limpopo Conservation Plan v.2: Technical Report. Contract Number EDET/2216/2012. Report for Limpopo Department of Economic Development, Environment & Tourism (LEDET) by ECOSOL GIS.
Ewel, K.C., Cressa, C., Kneib, R.T., Lake, P.S., Levin, L.A., Palmer, M.A., Snelgrove, P. & Wall, D.H., 2001. Managing critical transition zones. Ecosystems 4, 452–460.
Kleynhans, C.J., Mackenzie, J., Louw, M.D., 2007. Module F: Riparian Vegetation Response Assessment Index in River EcoClassification: Manual for EcoStatus Determination (version 2). Joint Water Research Commission and Department of Water Affairs and Forestry report. WRC Report.
Kotze, D., and Marneweck, G., 1999, Guidelines for Delineation of Wetland Boundary and Wetland Zones, Appendix W6: Resource Directed Measures for Protection of Water Resources: Wetland Ecosystems, Department of Water Affairs and Forestry, Pretoria
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Kotze, D.C., Marneweck, G.C., Batchelor, A.L., Lindley, D.S., and Collins, N.B., 2009, WET-EcoServices - A technique for rapidly assessing ecosystem services supplied by wetlands. Water Research Commission Wetland Management Series - WRC Report TT 339/09, March 2009.
Macfarlane, D., Kotze, D.C. Ellery, W., Walters, D., Koopman, V, Goodman, P and Goge, M., 2009, WET- Health - A technique for rapidly assessing wetland health. Water Research Commission Wetland Management Series - WRC Report TT 340/09, March 2009
Midgley, D. C.; Pitman, W. V. and Middleton, B. J. (1994). Surface water resources of South Africa, 1990, Vol I–VI. Water Research Commission Reports No. 298/1.1/94 to 298/6.1/94,Pretoria.
Mucina, L., and Rutherford, M.C., 2006. The Vegetation of South Africa, Lesotho and Swaziland, Strelitzia 19, South African National Biodiversity Institute, Pretoria
Ollis, D.J., Snaddon, C.D., Job, N.M. and Mbona, N. 2013. Classification System for Wetlands and other Aquatic Ecosystems in South Africa. User Manual: Inland Systems. SANBI Biodiversity Series 22. South African National Biodiversity Institute, Pretoria
Rountree, M.W., Malan, H.L., and Weston, B.C., (eds.), 2013, Manual for the Rapid Ecological Reserve Determination of Inland Wetlands (Version 2.0). Report to Report to the Water Research Commission and Department of Water Affairs: Chief Directorate: Resource Directed Measures. WRC Report No. 1788/1/12
Soil Classification Working Group, 2006, Soil Classification – A Taxonomic System for South Africa, Memoirs on the Agricultural Natural Resources of South Africa, No. 15
31 October 2016 MODIMOLLE PIPELINE WETLAND ASSESSMENT MD2563 60
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