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ZITHOLELE CONSULTING
APPENDIX D3: Wetland Specialist Report
Wetland and Aquatic Assessment for the Proposed
Construction of Lined Canals as Part of the Strategic
Mine Water Management Project for Undermined
Areas of the Central Witwatersrand
For:
Donald Molapo
Council for Geoscience
280 Pretoria Street
Silverton
Pretoria
Tel no: 012 841 1537
Dmolapo@geoscience.org.za
By:
Wetland Consulting Services (Pty) Ltd
PO Box 72295 Lynnwood Ridge Pretoria 0040 Tel: 012 349 2699 Fax: 012 349 2993 Email: info@wetcs.co.za
REF: 2013/988
Wetland and Aquatic Assessment for the Proposed Construction of Lined Canals as Part of
the Strategic Mine Water Management Project for the Central Witwatersrand
DOCUMENT SUMMARY DATA
PROJECT: Wetland and Aquatic Assessment for the Proposed
Construction of Lined Canals within the Witwatersrand
Goldfields as part of the Strategic Mine Water Management
Programme.
CLIENT: Council for Geoscience
CONTACT DETAILS: Donald Molapo
Council for Geoscience
280 Pretoria Street
Silverton
Pretoria
Tel no: 012 841 1537
dmolapo@geoscience.org.za
CONSULTANT: Wetland Consulting Services, (Pty) Ltd.
CONTACT DETAILS: P O Box 72295
Lynnwood Ridge
0040
Telephone number: (012) 349 2699
Fax number: (012) 349 2993
E-mail: info@wetcs.co.za
i
TABLE OF CONTENTS
1 BACKGROUND INFORMATION 1
1.1 Terms of reference 2
1.2 Limitations 3
1.3 Study Area 3
1.3.1 Catchments 3
1.3.2 Geology and Soils 4
1.4 Soils 4
1.5 Vegetation 5
2 APPROACH 6
2.1 Wetland Delineation and Assessment 6
2.1.1 Delineation and Classification 6
2.1.2 Determination of the PES 6
2.1.3 Wetland Functional Assessment 7
2.1.4 EIS 7
2.2 Aquatic Ecosystem Assessment 8
2.2.1 Water Quality 8
2.2.2 Diatoms 8
2.2.3 Habitat Integrity 9
2.2.4 Fish 9
2.2.4.1 Fish Assemblage Integrity Index (FAII) 9
2.2.4.2 Species Intolerance Ratings 10
2.2.4.3 Fish Health Assessment 10
2.2.1 Aquatic Macroinvertebrates 10
2.2.2 Impact Assessment 12
ii
3 WETLAND ASSESSMENT - FINDINGS 13
3.1 Classification and Delineation 13
3.1.1 Canal 1 15
3.1.2 Canal 2 16
3.1.3 Canal 3 17
3.2 Present Ecological State 18
3.2.1 Canal 1 18
3.2.2 Canal 2 20
3.2.3 Canal 3 22
3.3 Functional Importance and EIS 25
4 AQUATIC ASSESSMENT – FINDINGS 26
4.1 Sampling Sites 26
4.2 Water Quality 28
4.2.1 On-Site Water Quality 28
4.2.1.1 pH 28
4.2.1.2 Electrical Conductivity (EC)/ Total Dissolved Solids (TDS) 28
4.2.1.3 Dissolved Oxygen (DO) 29
4.2.1.4 Water Temperature 29
4.2.2 Laboratory Analyses of water quality 30
4.2.3 Diatoms 30
4.3 Habitat Integrity 32
4.4 Aquatic Macroinvertebrates 36
4.5 Fish 37
5 IMPACT ASSESSMENT AND MANAGEMENT RECOMMENDATIONS 38
5.1 Impact Assessment 38
Construction Phase Impacts 38
iii
5.1.1 Increased sediment movement off the site 38
5.1.1 Loss of Vegetation, habitats and biota 38
Operational Phase Impacts 39
5.1.2 Decline in Water Quality 39
5.1.3 Loss of habitats and biodiversity 39
5.1.4 Reduced water retention and flood attenuation 40
5.1.5 Increased erosion and sedimentation 40
5.1.6 Altered flow regime 40
5.1.7 Loss of access to local communities 41
5.2 Recommendations and alternative approaches: 43
5.2.1 Consideration of alternative designs 43
5.3 Specific environment management programme for the proposed canals 44
5.3.1 Minimise disturbance due to stream diversions 44
5.3.2 Limit the use of concrete 44
5.3.3 Maintain the natural flow regime 45
5.3.4 Minimise erosion at canal inlets and outlets 45
5.3.1 Stormwater Management 45
5.3.1 Create habitats 45
5.3.1 Minimise sedimentation 46
5.3.2 Minimise water quality impacts 46
5.3.3 Habitat continuity 46
5.3.4 Manage Waste 47
5.3.5 Minimise Disturbance to Wetland Areas 47
5.3.6 Manage Spills 47
5.3.7 Alien vegetation 47
5.3.8 Rehabilitation 47
5.3.9 Maintenance and Monitoring 47
6 CONCLUSION 49
iv
7 REFERENCES 50
8 APPENDIX A: DIATOM RESULTS 53
9 APPENDIX B: SASS5 RESULTS 56
TABLE OF FIGURES
Figure 1-1. The locality and extent of the proposed western canals (C1 and C2). ......................... 1
Figure 1-2. Locality of the eastern canal (C3). ................................................................................. 2
Figure 1-3. Map showing the proposed canals (in red) in relation to quaternary catchments and
rivers. ................................................................................................................................................ 4
Figure 3-1. Diagram illustrating the position of the various wetland types within the landscape. . 13
Figure 3-2. Map showing the delineated and classified water resources within the vicinity of
Canal 1. .......................................................................................................................................... 15
Figure 3-3. Map showing delineated and classified water resources within the vicinity of Canal 2.
........................................................................................................................................................ 16
Figure 3-4. Map showing delineated and classified water resources within the vicinity of Canal 3.
........................................................................................................................................................ 17
Figure 3-5. Black and White Aerial Photograph of the area surrounding Canal 1 and mining-
associated impacts affecting the wetlands in the 1950’s. .............................................................. 19
Figure 3-6. Map showing the PES classification of water resources within the vicinity of Canal 1.
........................................................................................................................................................ 19
Figure 3-7. Photographs showing impacts observed within the vicinity of Canal 1 (Clockwise from
top left: Earthworks along and within the channel, sewerage discharge into the channel,
accumulation of precipitates in the unchannelled valley bottom wetland originating from upstream
mining activities, channel erosion and alien invasive species encroachment.) ............................. 20
Figure 3-8. Map showing the PES classification of water resources within the vicinity of Canal 2.
........................................................................................................................................................ 21
Figure 3-9. Photographs showing impacts observed within the vicinity of Canal 2, including
impacts to water quality, infilling and mining. ................................................................................. 22
Figure 3-10. Map showing the PES classification of water resources within the vicinity of Canal 3.
........................................................................................................................................................ 23
Figure 3-11. Photographs showing impacts observed within the vicinity of Canal 3, including
canalisation, water quality impacts, sedimentation and mining. .................................................... 24
Figure 4-1. Aquatic Sampling Sites Upstream and downstream of the proposed Canals – Canal
C1 (top), C2 and C3 (bottom). ........................................................................................................ 26
v
Figure 4-2. Photos taken upstream and downstream of sampling sites along Canal 1, from top to
bottom: C1, C2A, C2B .................................................................................................................... 34
Figure 4-3. Photos taken at aquatic sampling sites C2A and C2B (top row), C3A (second row)
and C3B (bottom row) .................................................................................................................... 35
Figure 4-4: Barbus anoplus collected at site C1A .......................................................................... 37
Figure 5-1. Example of stormwater attenuation facilities used along the Mhluzi River in
Middelburg, Mpumalanga. This approach could be applied to lateral inflows into Canal 1. ......... 46
LIST OF TABLES
Table 1-1. Table showing the mean annual precipitation, run-off and potential evaporation for
quaternary catchment C22A and C22B (Middleton et al 1990). ...................................................... 3
Table 2-1. Descriptive categories used to describe the present ecological status (PES) of biotic
components (adapted from Kleynhans, 1999). ................................................................................ 6
Table 2-2. Table explaining the scoring system used for the EIS assessment. .............................. 7
Table 2-3. Species intolerance ratings ........................................................................................... 10
Table 2-4: Descriptive categories used to describe the present ecological status (PES) of biotic
components (adapted from Kleynhans, 1999). .............................................................................. 11
Table 3-1. Hydro-geomorphic classification system (adapted from Brinson, 1993; Kotze, 1999;
and Marneweck and Batchelor, 2002). .......................................................................................... 14
Table 3-2. Areas of the different wetland types recorded on site. ................................................. 14
Table 4-1. Locality and description of aquatic sampling sites along Canals 1, 2 and 3. ............... 27
Table 4-2: In situ water quality recorded during the August 2013 survey ..................................... 28
Table 4-3 Water quality results for aquatic sampling sites. DWAF TWQR and limits are shown to
the right. Red shading indicates exceedances, orange indicates levels of concern and yellow
indicates elevated levels. ............................................................................................................... 30
Table 4-4. Ecological Classification for the Council for Geoscience Canal Project Sites in July
2013 based on diatom species composition recorded at each site. .............................................. 31
Table 4-5. List of dominant diatom species occurring at the Council for Geoscience Canal Project
sites, expressed as a percentage of the total sample. ................................................................... 31
Table 4-6. Results of the Index of Habitat Integrity Assessment ................................................... 33
Table 4-7. Summary of SASS5 Results for canal sites in July 2013. ............................................ 36
Table 4-8: Fish results from the August 2013 survey .................................................................... 37
Table 5-1 Impact Rating Table pre and post mitigation measures ................................................ 42
vi
INDEMNITY AND CONDITIONS RELATING TO THIS
REPORT
The findings, results, observations, conclusions and recommendations given in this report are based
on the author’s best scientific and professional knowledge as well as available information. The report
is based on survey and assessment techniques which are limited by time and budgetary constraints
relevant to the type and level of investigation undertaken and Wetland Consulting Services (Pty.) Ltd.
and its staff reserve the right to modify aspects of the report including the recommendations if and
when new information may become available from ongoing research or further work in this field, or
pertaining to this investigation.
Although Wetland Consulting Services (Pty.) Ltd. exercises due care and diligence in rendering
services and preparing documents, Wetland Consulting Services (Pty.) Ltd. accepts no liability, and
the client, by receiving this document, indemnifies Wetland Consulting Services (Pty.) Ltd. and its
directors, managers, agents and employees against all actions, claims, demands, losses, liabilities,
costs, damages and expenses arising from or in connection with services rendered, directly or
indirectly by Wetland Consulting Services (Pty.) Ltd. and by the use of the information contained in this
document.
This report must not be altered or added to without the prior written consent of the author. This also
refers to electronic copies of this report which are supplied for the purposes of inclusion as part of
other reports, including main reports. Similarly, any recommendations, statements or conclusions
drawn from or based on this report must make reference to this report. If these form part of a main
report relating to this investigation or report, this report must be included in its entirety as an appendix
or separate section to the main report.
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 1
1 Background Information
Wetland Consulting Services (Pty) Ltd was appointed by Council for Geoscience to prepare a
quote for a wetland and aquatic ecosystems assessment for the proposed canal construction as
part of the Strategic Water Management Project (SWMP). The purpose of the canals is to
reduce/prevent ingress of water into the undermined areas of the Central Witwatersrand. The
study is required to satisfy the requirements of the Basic Assessment/EIA.
The locality and extent of the proposed canals is indicated in Figure 1-1 and Figure 1-2. The two
western canals, labelled C1 and C2, are located west of the N1 Western Bypass along Main
Reef/Randfontein Road, Roodepoort. The eastern Canal (C3) is also located along Main Reef
Road between Primrose and Driefontein and north of Germiston (Ekhuruleni Municipality).
The design report refers to the canals 1, 2 and 3 as follows:
C1 = Durban Roodepoort Deep(DRD) West Rand 2,400 metre section
C2 = New Canada Dam (NCD) Central 600 metre section
C3 = Elburgsrpuit (ELB) East Rand 590 metre section
Figure 1-1. The locality and extent of the proposed western canals (C1 and C2).
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 2
Figure 1-2. Locality of the eastern canal (C3).
1.1 Terms of reference
The scope of work included:
Wetland Baseline Investigation:
Conduct a desktop and field investigation for the presence and extent of wetland areas
along the proposed canal routes;
Delineate and map the wetland areas within the study areas;
Classify wetlands according to HGM (see Marneweck and Batchelor, 2002) and the system
developed by Kotze, Marneweck, Batchelor, Lindley and Collins, 2004;
Determine the Present Ecological State (PES) and Ecological Importance and Sensitivity of
any wetlands on site using the Wetland Index of Habitat Integrity and/or WET-Health
methodologies as applicable; and
Compile a detailed wetland delineation and assessment report, including a map of
delineated wetlands and sensitive areas.
Aquatic Ecosystems Assessment:
Bioassessment: Ecological assessment of aquatic biota (aquatic macroinvertebrates,
diatoms, fish, habitats) within watercourses upstream and downstream of each canal.
Analysis of water quality samples for major anions and cations, total dissolved solids,
conductivity and pH.
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 3
Analysis according to River Health Programme methodologies, as appropriate (FAII, FHI,
SASS5, IHI, IHAS)
Present Ecological State (PES) in Ecological Importance and Sensitivity (EIS) of instream
habitats and riparian areas (DWAF, 1999a, b).
Impact Assessment and Management Recommendations:
Review of proposed infrastructure layout plans and current impacts;
Identification of expected and possible impacts, including cumulative impacts;
Recommendations of proposed mitigation and/or management of all wetlands;
Recommendations for biomonitoring, if appropriate
Identification of opportunities and concerns for water rehabilitation after construction;
Compile a report detailing all the above information
1.2 Limitations
The accuracy of the delineation may be limited by the accuracy of the Google Earth
imagery.
Due to the scale of the remote imagery used (Google Earth Imagery), as well as the
accuracy of the handheld GPS unit used to delineated wetlands in the field, the delineated
boundaries cannot be guaranteed beyond an accuracy of about 15m on the ground. Should
greater mapping accuracy be required, the wetlands would need to be pegged in the field
and surveyed using conventional survey techniques.
Reference conditions are unknown. This limits the confidence with which the present
ecological category is assigned. However, data collected during this study can serve as a
point of departure for future biomonitoring surveys;
Aquatic ecosystems vary both temporally and spatially. Once-off surveys such as this are
therefore likely to miss substantial ecological information, thus limiting accuracy, detail and
confidence.
1.3 Study Area
1.3.1 Catchments
The study area is located within the Highveld Ecoregion, Vaal River Catchment (Primary
Catchment (C). Canal 1 lies on the Klip River, while Canal 2 lies on a tributary of the Klip River,
both within quaternary catchment C22A (Figure 1-3). Canal 3 lies on the Elsburgspruit before its
confluence with the Natalspruit within catchment C22B (Figure 1-3). Information regarding mean
annual rainfall, runoff and evaporation potential per quaternary catchment is provided in the table
below (Middleton, B.J., Midgley, D.C and Pitman, W.V., 1990).
Table 1-1. Table showing the mean annual precipitation, run-off and potential evaporation for quaternary catchment C22A and C22B (Middleton et al 1990).
Quaternary Catchment
Catchment Surface Area
(ha)
Mean Annual Rainfall (mm)
Mean Annual Run-off (mm)
Potential Evaporation
(mm)
C22A 54 800 695 32 1600 - 1700
C22B 39 200 691.41 31.7 1600 - 1700
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 4
Figure 1-3. Map showing the proposed canals (in red) in relation to quaternary catchments and rivers.
1.3.2 Geology and Soils
This area is underlain by the Witwatersrand Supergroup, the Central Rand Group consisting of the
Turffontein Subgroup (layers of quartzite and conglomerate as well as shales) and
Johannesburg Subgroup (quartzite and conglomerates).
1.4 Soils
Mispah and Duplex soils are the dominant soil types, with Hutton soils dominating higher up on the
slopes. The geotechnical survey described the soils as follows:
The sub-soils encountered within the sites are generally sandy and appear to be very
loose to loose in consistency and the majority of holes collapsed due to nature of the
soils and a rapid ingress of water into the pits. Clayey soils were also encountered but
occasionally. These soils are mainly of alluvial origin and some are disturbed due to the
current artificial mining activities. Shallow rock at depths of between 1,0 to 2,0 was
encountered occasionally in some of the pits (C2 and C3). Heavy machinery may be
required if these depths need to be excavated.
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 5
1.5 Vegetation
Vegetation has been classified as Soweto Highveld Grassland (Mussina and Rutherford 2004)
and, historically, as Turf Highveld (Acocks 1953) and as Moist Clay Highveld Grassland (Low and
Rebelo 1996). The description given in Mussina and Rutherford (2004) is as follows: Gently to
moderately undulating landscape supporting short to medium-high, dense, tufted grassland
dominated by Themeda triandra and accompanied by grasses such as Elionurus muticus,
Eragrostis racemosa, Heteropogon contortus and Tristachya leucothrix. Wetlands, narrow stream
alluvia and occasional rocky outcrops may occur within the grassland. This grassland type is
considered endangered and “hardly protected”.
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 6
2 Approach
2.1 Wetland Delineation and Assessment
2.1.1 Delineation and Classification
Use was made of 1:50 000 topographic maps and geo-referenced Google Earth images to
generate a digital base map of the study site onto which the wetlands were delineated using
ArcView 9.1 and based on the method described in Thompson et.al. (2002).The extent and
approximate boundaries of the wetlands were then verified in the field. Field verification of the
desktop assessment was conducted using soil auguring and vegetation indicator species (see
Kotze and Marneweck, 1999 and DWAF, 2005) to verify whether or not the area delineated in the
desktop component met the criteria for classification as a wetland. Soil hydric indicators and
anecdotal evidence was used to gather information about the key determinants of the wetlands
identified.
2.1.2 Determination of the PES
The Present Ecological State (PES) assessment determines the level of disturbance to or
modification of a wetland relative to its natural state or reference condition. Both are rated on a
scale of A to F, with A being a natural or un-impacted system and F being a completely modified
and disturbed system (Table 2-1). The PES score is based on observed physical disturbance and
hydrological changes. Scores were assigned to the wetland using the tables developed by
Marneweck and Batchelor (2002), adapted from the document “Resource Directed Measures for
Protection of Water Resources, Volume 4, Wetland Ecosystems (DWAF, 1999).
Table 2-1. Descriptive categories used to describe the present ecological status (PES) of biotic components
(adapted from Kleynhans, 1999).
Mean* Category Explanation
Within generally acceptable range
>4 A Unmodified, or approximates natural condition
>3 and <=4 B Largely natural with few modifications, but with some loss of natural habitats
>2.5 and <=3 C Moderately modified, with some loss of natural habitats
<=2.5 and >1.5 D Largely modified. A large loss of natural habitat and basic ecosystem function has occurred.
Outside generally acceptable range
>0 and <=1.5 E Seriously modified. The losses of natural habitat and ecosystem functions are extensive
0 F
Critically modified. Modification has reached a critical level and the system has been modified completely with almost complete loss of natural habitat.
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 7
2.1.3 Wetland Functional Assessment
A general functional assessment of the wetlands using the level 2 assessment as described in
“Wet-EcoServices” (Kotze et al., 2005) was undertaken. This method provides a scoring system for
establishing wetland ecosystem services. It enables one to make relative comparisons of systems
based on a logical framework that measures the likelihood that a wetland is able to perform certain
functions.
2.1.4 EIS
“Ecological importance” of a water resource is an expression of its importance to the maintenance
of ecological diversity and functioning on local and wider scales. “Ecological sensitivity” refers to
the system’s ability to resist disturbances and its capability to recover from disturbance once it has
occurred. In determining the EIS of a wetland, the following factors are considered:
Biodiversity – i.e. the presence of rare and endangered species, populations of unique
species, species richness, diversity of habitat types, and migration/breeding and feeding
sites for wetland species.
Hydrology – i.e. sensitivity to changes in the supporting hydrological regime and/or
changes in water quality.
Functionality – i.e. flood storage, energy dissipation and particulate/element removal.
Ecological Integrity – taken from the result of the PES assessment
EIS was classified according to the following table (DWAF 1999).
Table 2-2. Table explaining the scoring system used for the EIS assessment.
Ecological Importance and Sensitivity categories Range of Median Ecological
Management Class
Very high >3 and <=4 A
Wetlands that are considered ecologically important and sensitive on a national or
even international level. The biodiversity of these floodplains is usually very sensitive
to flow and habitat modifications. They play a major role in moderating the quantity
and quality of water of major rivers.
High >2 and <=3 B
Wetlands that are considered to be ecologically important and sensitive. The
biodiversity of these floodplains may be sensitive to flow and habitat modifications.
They play a role in moderating the quantity and quality of water of major rivers.
Moderate >1 and <=2 C
Wetland that are considered to be ecologically important and sensitive on a provincial
or local scale. The biodiversity of these floodplains is not usually sensitive to flow and
habitat modifications. They play a small role in moderating the quantity and quality of
water of major rivers.
Low/marginal >0 and <=1 D
Wetlands that is not ecologically important and sensitive at any scale. The biodiversity
of these wetlands is ubiquitous and not sensitive to flow and habitat modifications.
They play an insignificant role in moderating the quantity and quality of water of major
rivers.
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 8
2.2 Aquatic Ecosystem Assessment
The goal of the characterization procedure is to determine the current status of the aquatic
environment and to evaluate the extent of site-related effects in terms of the selected ecological
indicator, as well as to identify specific important ecological attributes. In order to enable adequate
description of the fish within the aquatic environment it is recommended that the appropriate
stressor and response indicators be selected. Broad methodologies to characterize these
components are described below. These proposed methodologies are generally applied and
accepted (DWAF & USEPA):
Stressor Indicators:
In situ water parameter variables: These will include; pH, Dissolved Oxygen (DO), Electrical
Conductivity (EC) and water temperature measurements at selected sampling sites. In situ
water quality parameters will be used for interpretation of the biological data.
Laboratory analysis of water quality for major anions and cations.
Habitat Indicators
General Habitat Assessment: General description of the site. Parameters to be described
include site location (GPS reading); photographs (for future identification of major changes
and documentation of habitat conditions); watershed features (i.e. surrounding land use,
sources of pollution, erosion).
Index of Habitat Integrity (Kleynhans 1999)
Response Indicators
Ichthyofauna: Fish results obtained during the surveys will be compared between the
different sites. A fish health assessment will be done with each fish and this will be
compared to the different sites in the study area. The fish results will be interpreted using
the latest IUCN Red Data list as well as applicable Provincial and National databases.
Aquatic Macroinvertebrates: The SASS5 methodology (Dickens and Graham 2002).
Diatoms were sampled and analysed according to Taylor (2007)
2.2.1 Water Quality
Onsite measurements were taken of temperature, electrical conductivity and dissolved oxygen,
with additional laboratory analyses for major anions and cations, conductivity, TDS and pH.
These were interpreted in terms of ecological responses only. ICP-OES scans for metals were
also completed to provide baseline levels against future monitoring can be compared.
2.2.2 Diatoms
Diatoms provide a rapid response to specific physico-chemical conditions in aquatic
ecosystems and are often the first indication of change. The presence or absence of indicator
taxa can be used to detect specific changes in environmental conditions such as
eutrophication, organic enrichment, salinisation and changes in pH. Diatom slides were
prepared by acid oxidation using hydrochloric acid and potassium permanganate. Clean
diatom frustules were mounted onto a glass slide ready for analysis. Taxa were identified
mainly according to standard floras (Krammer & Lange- Bertalot, 2000). The aim of the data
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 9
analysis was to identify and count diatom valves (400 counts) to produce semi-quantitative
data from which ecological conclusions can be drawn.
2.2.3 Habitat Integrity
The Index of Habitat Integrity (IHI) was used to determine habitat condition. This approach is
based on the assessment of physical habitat disturbance (Kleynhans, 1997) and classifies the
present ecological state of instream and riparian habitat integrity according to the categories given
in Table 5-3, ranging from pristine/undisturbed to critically modified. The following disturbances
were considered:
• Water abstraction,
• Flow modification,
• Bed modification,
• Channel modification,
• Inundation,
• Exotic macrophytes,
• Solid waste disposal,
• Indigenous vegetation removal,
• Exotic vegetation encroachment and
• Bank erosion.
2.2.4 Fish
Fish are used as indicators of river condition as they are relatively long-lived and mobile, and
indicate longterm influences and general habitat conditions, integrate effects of lower trophic levels
and are consumed by humans (Uys et al., 1996). Fish samples were collected using a battery
operated electro-fishing device (Smith-Root LR24). This method relies on an immersed anode and
cathode to temporarily stun fish in the water column; the stunned fish can then be scooped out of
the water with a net for identification. The responses of fish to electricity are determined largely by
the type of electrical current and its wave form. These responses include avoidance, electrotaxis
(forced swimming), electrotetanus (muscle contraction), electronarcosis (muscle relaxation or
stunning) and death (USGS, 2004). Electrofishing is regarded as the most effective single method
for sampling fish communities in wadeable streams (Plafkin et al., 1989).
All fish were identified in the field using the guide Freshwater Fishes of Southern Africa (Skelton,
2001). Reference specimens were preserved for laboratory confirmation of field identifications and
the remainder of the fish released at the point of capture.
Due to the location of the sites within the catchment and the noticeable impacts observed from
satellite imagery, the expected presence of species is low in both diversity and abundance.
In order to assess the Red Data Book status of the expected fish assemblage, the IUCN Red List
of Threatened Species was consulted (IUCN, 2012).
2.2.4.1 Fish Assemblage Integrity Index (FAII)
The Fish Assemblage Integrity Index (FAII) uses the diversity and composition of fish populations,
their relative tolerance/intolerance to disturbance, frequency of occurrence and health, to assess
biotic integrity. This index measures the current integrity of the fish community relative to what is
derived to have been present under natural/unimpaired conditions. The integrity of the fish
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 10
assemblages is considered to provide a perspective on the broad biological integrity status of a
river/stream. However, it can only be applied where abundance and diversity are high enough,
which was not the case in this study.
2.2.4.2 Species Intolerance Ratings
Intolerance refers to the degree to which an indigenous species is unable to withstand changes in
the environmental conditions at which it occurs (Kleynhans, 1999). Four components were
considered in estimating the intolerance of fish species, i.e. habitat preferences and specialization
(HS), food preferences and specialisation (TS), requirement for flowing water during different life
stages (FW) and association with habitats with unmodified water quality (WQ). Each of these
aspects was scored for a species according to low requirements/specialization (rating = 1),
moderate requirement/specialization (rating = 3) and high requirement/specialization (rating = 5)
(Table 5-2). The total intolerance (IT) of fish species is estimated as follows:
IT = (HS + TS + FW + WQ)/4
Table 2-3. Species intolerance ratings
2.2.4.3 Fish Health Assessment
The assessment is conducted in such a way as to derive numeric values, which reflect the status
of fish health. The percentage of fish with externally evident disease or other anomalies was used
in the scoring of this metric (Kleynhans, 1999; Kilian et al., 1997). The following procedures were
followed to score the health of individual species at site:
Frequency of affected fish >5%. Score = 1;
Frequency of affected fish 2 – 5%. Score = 3; and
Frequency of affected fish < 2%. Score = 5.
This approach is based in the principle that even under unimpaired conditions a small percentage
of individuals can be expected to exhibit some anomalies (Kleynhans, 1999).
2.2.1 Aquatic Macroinvertebrates
Aquatic macroinvertebrates were assessed using the SASS 5 (South African Scoring System)
methodology. SASS5 is based on the presence or absence of sensitive aquatic
macroinvertebrates collected and analysed according to the methods outlined in Dickens and
Graham (2002). A high relative abundance and diversity of sensitive taxa present indicates a
relatively healthy system with good water quality. Disturbance to water quality and habitat results in
the loss of sensitive taxa. As this method was developed specifically for rivers, the methods of
collection and analysis were modified for wetlands and pans, where relevant.
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A A/B B B/C C C/D D D/E E E/F F
Two methods were used to classify the PES of sites based on aquatic macroinvertebrates. Sites
that were considered to be channelized wetlands, therefore having few stone biotopes, were
classified according to the guidelines given in Dallas (2007), which is based on modelled data from
the ecoregion. The PES of river sites was additionally assessed using MIRAI (Macroinvertebrate
Response Assessment Index) which classifies the PES of a site according to a comparison
between expected and observed taxa, as obtained from the SASS5 results, and takes into account
habitat diversity, suitability and/or availability, flow conditions as well as water quality.
Table 2-4 summarises the categories used to classify sites according to both aquatic
macroinvertebrates and fish.
Table 2-4: Descriptive categories used to describe the present ecological status (PES) of biotic components (adapted from Kleynhans, 1999).
CATEGORY BIOTIC
INTEGRITY DESCRIPTION OF GENERALLY EXPECTED CONDITIONS
A Excellent Unmodified, or approximates natural conditions closely. The biotic assemblages compares to that
expected under natural, unperturbed conditions.
B Good
Largely natural with few modifications. A change in community characteristics may have taken place
but species richness and presence of intolerant species indicate little modifications. Most aspects of
the biotic assemblage as expected under natural unperturbed conditions.
C Fair
Moderately modified. A lower than expected species richness and presence of most intolerant
species. Most of the characteristics of the biotic assemblages have been moderately modified from
its naturally expected condition. Some impairment of health may be evident at the lower end of this
class.
D Poor
Largely modified. A clearly lower than expected species richness and absence or much lowered
presence of intolerant and moderately intolerant species. Most characteristics of the biotic
assemblages have been largely modified from its naturally expected condition. Impairment of health
may become evident at the lower end of this class.
E Very Poor
Seriously modified. A strikingly lower than expected species richness and general absence of
intolerant and moderately tolerant species. Most of the characteristics of the biotic assemblages
have been seriously modified from its naturally expected condition. Impairment of health may
become very evident.
F Critical
Critically modified. Extremely lowered species richness and an absence of intolerant and moderately
tolerant species. Only intolerant species may be present with complete loss of species at the lower
end of the class. Most of the characteristics of the biotic assemblages have been critically modified
from its naturally expected conditions. Impairment of health generally very evident.
It must be emphasised that the A→F scale represents a continuum, and that the boundaries
between categories are notional, artificially-defined points along the continuum (as presented
below). This situation falls within the concept of a fuzzy boundary, where a particular entity may
potentially have membership of both classes (Robertson et al. 2004). These boundary categories
are denoted as B/C, C/D, etc.
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 12
2.2.2 Impact Assessment
Each impact identified was assessed in terms of:
Occurrence
• Probability of occurrence (likelihood of occurring), and
• Duration of occurrence (how long way it last?).
Severity
• Magnitude (severity) of impact (high, moderate or low severity), and
• Scale/extent of impact (national, regional, local or site-specific)
To enable a scientific approach to the determination of the impact significance (importance), a numerical value was linked to each rating scale. The sum of the numerical values defined the significance. The rating scale used is outlined below:
Probability:=P Duration:=D
5 - Definite/don’t know 5 - Permanent
4 - Highly probable 4 - Long-term (ceases with the
3 - Medium probability operational life)
2 - Low probability 3 - Medium-term (5-15 years)
1 - Improbable 2 - Short-term (0-5 years)
0 - None 1 - Immediate
Spatial Scale:=S Magnitude:=M
5 - International 10 - Very high/don’t know
4 - National 8 - High
3 - Regional 6 - Moderate
2 - Local 4 - Low
1 - Site only 2 - Minor
0 - None
Once the above factors had been ranked for each impact, the environmental significance of each impact was assessed using the following formula:
SP = (magnitude + duration + spatial scale) x probability
Significance was rated as High, Medium or Low as follows:
More than 60 significance points indicated high (H) environmental significance;
Between 30 and 60 significance points indicated moderate (M) environmental significance; and
Less than 30 significance points indicated low (L) environmental significance.
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 13
3 Wetland Assessment - Findings
3.1 Classification and Delineation
The National Water Act, Act 36 of 1998, defines wetlands as follows:
“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.”
The presence of wetlands in the landscape can be linked to the presence of both surface water
and perched groundwater. Wetland types are differentiated based on their hydro-geomorphic
(HGM) characteristics; i.e. on the position of the wetland in the landscape, as well as the way in
which water moves into, through and out of the wetland systems. A schematic diagram of how
these wetland systems are positioned in the landscape is given in the figure below, while the table
below provides more detail on the classification system as used in this report.
Figure 3-1. Diagram illustrating the position of the various wetland types within the landscape.
Of the hydrogeomorphic wetland types currently recognised, three hydro-geomorphic wetland
types were identified on site:
Channelled valley bottom wetlands;
Unchannelled valley bottom wetland and
Hillslope seepage wetland.
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 14
Table 3-1. Hydro-geomorphic classification system (adapted from Brinson, 1993; Kotze, 1999; and Marneweck and Batchelor, 2002).
Hydro-geomorphic
Type Description
Channelled Valley
Bottom
Valley bottom areas with a well defined stream channel but lacking characteristic
floodplain features. May be gently sloped and characterised by the net
accumulation of alluvial deposits or may have steeper slopes and be characterised
by the net loss of sediment. Water inputs from the main channel and adjacent
slopes.
Unchannelled
Valley Bottom
Valley bottom areas with no clearly defined stream channel, usually gently sloped
and characterised by alluvial sediment deposition, generally leading to a net
accumulation of sediment. Water inputs mainly from channel entering the wetland
and also from adjacent slopes.
Hillslope Seepage
Slopes on hillsides which are characterised by the colluvial movement of materials.
Water inputs are mainly from subsurface flow and outflow can be via a well-defined
stream channel connecting the area directly to a stream channel or outflow can be
through diffuse subsurface and/or surface flow but with no direct surface water
connection to a stream channel.
Table 3-2. Areas of the different wetland types recorded on site.
Wetland Type Area
(ha)
% of wetland
area
Canal 1
Channelled Valley Bottom
Wetland 20.87 73.15
Unchannelled Valley
Bottom Wetland 7.66 26.85
Canal 2
Hillslope Seepage Wetland 1.23 14.04
Channelled Valley Bottom
Wetland 7.53 85.96
Canal 3
Hillslope Seepage Wetland 0.21 12.00
Channelled Valley Bottom
Wetland 1.01 57.71
Canalised Valley Bottom
Wetland 0.53 30.29
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 15
Figure 3-2. Map showing the delineated and classified water resources within the vicinity of Canal 1.
3.1.1 Canal 1
The proposed canal route runs for the majority of its length within a wetland classified as a
Channelled Valley Bottom Wetland. Approximately midway along the length of the route, an
Unchannelled Valley Bottom Wetland enters the channelled valley bottom wetland from the east.
These wetland systems lie within an area which has undergone serious modification due to past
underground mining activities. Several large, inactive slimes dams lie within the immediate
catchments of the wetlands, and increased runoff and sediment movement off these slimes dams
has had a major influence on the characteristics of the wetlands. The channelled valley bottom
wetland flows from northeast to southwest and is a relatively narrow system confined along
sections by extensive rock outcroppings along its north western edge. The vegetation within the
wetland is dominated for most of its length by exotic tree species including Acacia mearnsii and
Eucalyptus sp. At the confluence of the two wetland systems mentioned above, extensive
sediment deposition has provided suitable conditions for the establishment of dense Phragmites
australis reedbeds. Although burnt at the time of the site visit, the vegetation within the
unchannelled valley bottom is also dominated by P. australis.
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 16
Figure 3-3. Map showing delineated and classified water resources within the vicinity of Canal 2.
3.1.2 Canal 2
Canal 2 is located mostly within channelled valley bottom wetland dominated by Phragmites reed
beds. The system clearly receives high volumes and velocities of urban storm water and has
become deeply incised. In addition, water quality has been seriously impacted by surcharging
sewers, of which one was evident downstream of Main Reef Road. Algae and slimes were evident
within the channel and the Dissolved Oxygen recorded upstream and downstream of the site was
a mere 2.3 and 0.7mg/l respectively, low enough to seriously restrict the survival of aquatic biota.
The wetlands have been modified by infilling, to the east, and mining activities to the west. The
mining footprint has extended into the wetland areas, further concentrating flows. The old slimes
dams and soil stockpiles situated to the west of the wetland have resulted in increased runoff,
sediment loads and mine-impacted seepage finding their way into adjacent wetlands. Where
sediments are deposited within these wetlands, they are colonised by Phragmites reed beds, this
explaining the dominance of Phragmites within the system.
There is a small area of hillslope seepage wetland to the east of the channel but this has been
impacted by infilling and was probably more extensive under natural conditions. Channelisation of
the valley bottom wetland would have resulted in a gradual drying of adjacent seepage areas as
water is lost from the system via the channel. Alien vegetation, including Acacia mearnsii (Black
Wattle) and Cortaderia selloana (Pampas Grass), was prolific in disturbed wetland areas.
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 17
Figure 3-4. Map showing delineated and classified water resources within the vicinity of Canal 3.
3.1.3 Canal 3
The wetland system associated with Canal 3 was, under natural conditions, an unchannelled valley
bottom wetland that gradually became increasingly channelized as a result of increased urban
runoff, as well uncontrolled discharges from the dam immediately upstream of the site. Currently,
the lower reaches of the affected wetland have been canalised by a deep trench which essentially
functions as a stormwater canal. As such, no wetland vegetation or natural habitats were evident
within the southern section. To the north, the system has become highly channelized, with
Phragmites reed beds predominating. Upstream impacts include a dam, old slimes dams, which
are in various stages of being removed, and illegal mining. These impacts have all contributed to
high sediment loads within the channel. Deposited sediments have been colonised by Phragmites
reeds. In addition, open sewers were observed, as well as a small cemetery, both potentially
impacting on water quality. Alien vegetation was prolific and included, amongst others, Acacia
mearnsii, Solanum mauritianum, Eucalyptus sp and Cortaderia Selloana.
Under natural conditions, there was probably a fairly extensive hillslope seepage wetland
associated with the valley bottom system. However, infilling, mining, dam construction and road
construction, together with the altered hydrology associated with erosion of the channel as a result
of stormwater runoff, has resulted in the loss and confinement of seepage areas. Seepage areas
that were observed on site had very little natural vegetation and were, for the most part, associated
with infilling or roads.
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 18
3.2 Present Ecological State
3.2.1 Canal 1
The wetlands along the route have been seriously impacted, predominantly by past mining
activities which continue to influence the wetlands, and current earthworks being undertaken along
sections of the channelled valley bottom wetland. Slimes dams upstream of both wetland systems
described have provided additional flows which appear to have led to an increase in the extent of
the wetlands, particularly in the case of the unchannelled valley bottom wetland. An assessment of
black and white aerial photographs dating from the 1950’s show the wetlands at that time, as well
as the extent of transported mine sediments within the wetlands (Figure 3-5). Increased surface
flows and large sources of sediments from the slimes dams have resulted in sediment transport
and deposition into the wetlands downstream. At the confluence of the two wetland systems,
transported sediment from the unchannelled valley bottom wetland has formed a depositional fan
across the channelled valley bottom wetland forcing flows to spread out across this broader
section of valley bottom. Downstream of the confluence, the naturally rocky terrain again confines
the wetland, and some areas of channel erosion and head cutting were observed. At the time of
the site visit, the section of wetland north of the R41 was being seriously affected by earthworks.
Both banks of the channel had been recently bulldozed and the vegetation removed (except alien
trees along the banks). Sediment has been deposited along the banks over the wetland
sediments, making an accurate determination of the wetland boundaries in this area difficult.
These earthworks have exposed the soils and sediment transport into downstream areas of the
wetland was evident. Due to past disturbance along the channel, alien vegetation encroachment is
an issue along large sections of the channel. Alien tree species, such as A. mearnsii and
Eucalyptus sp. occur extensively in the area.
Water quality within the wetlands is also a major concern, as point source sewerage was being
discharged directly into the wetland from an overflowing manhole just below the R41 Road. Based
on increased greening of the grass surrounding the discharge point it is assumed that this
sewerage has been discharging into the channel for some time. Increased sediment transport and
discharges from the slimes dams are also assumed to have a negative effect on water quality.
Additional impacts include flow impoundments in several dams upstream of the wetlands along the
routes and impoundment caused by road crossings, and cultivation extending into the
unchannelled valley bottom wetland.
As a result of the impacts discussed above, both valley bottom wetland systems assessed were
found to be seriously modified (PES category E).
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 19
Figure 3-5. Black and White Aerial Photograph of the area surrounding Canal 1 and mining-associated impacts affecting the wetlands in the 1950’s.
Figure 3-6. Map showing the PES classification of water resources within the vicinity of Canal 1.
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 20
Figure 3-7. Photographs showing impacts observed within the vicinity of Canal 1 (Clockwise from top left: Earthworks along and within the channel, sewerage discharge into the channel, accumulation of precipitates in the unchannelled valley bottom wetland originating from upstream mining activities, channel erosion and alien invasive species encroachment.)
3.2.2 Canal 2
Canal 2 was considered Largely to Seriously Modified (D-E). The impacts included:
Sedimentation. Historical mining has resulted deposition of sediments within the valley
bottom. Deposited sediments have been colonised by monospecific stands of Phragmites,
thus restricting biodiversity.
Increased runoff and flows. Old mine dumps store large quantities of water which are
slowly released into adjacent wetlands. As mine dumps are removed from the
Witwatersrand, this storage capacity is lost and increased volumes are being released into
adjacent wetlands.
Channelisation and erosion. Increased flows have resulted in vertical erosion of the wetland
to form a deeply incised channel within the valley bottom. This results in greater movement
of water out of the wetland area, with reduced lateral connectivity and a gradual drying of
adjacent seepage areas. In addition, channels have been constructed within the wetland,
downstream of the R41, restricting the wetland area.
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 21
Infilling and earthworks. Soil has been deposited within the valley bottom wetland, either as
a result of dredging, or as a result of soil stockpiling. Where soil has been deposited along
the channel margins, seepage areas have developed.
Water quality. The water quality has been critically compromised in this system.
Surcharging sewers were observed, algae were prevalent and the odour of sewage effluent
was evident throughout the system. In addition, seepage from adjacent mining areas and
tailings dams are likely to have affected water quality.
Alien vegetation. Alien vegetation was prevalent and included, amongst others, Acacia
mearnsii, Kikuya Pennisetum clandestinum, Bidens pilosa, Tagetes minuta, Eucalyptus sp.
and Cortaderia selloana. The latter two species were particularly evident on mine
sediments.
Solid waste was abundant and included old tyres dumped within the valley bottom wetland.
Road construction. A road has been constructed within the wetland, south of the R41.
Figure 3-8. Map showing the PES classification of water resources within the vicinity of Canal 2.
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 22
Figure 3-9. Photographs showing impacts observed within the vicinity of Canal 2, including impacts to water quality, infilling and mining.
3.2.3 Canal 3
Canal 3 was considered, for the most part, to be Largely to Seriously Modified (Category D-E), with
the southern canalised section considered Critically Modified (Category F). Impacts included:
Canalisation. The lower reach of the valley bottom wetland on site has been bulldozed in in
its entirety, with a deep trench constructed to channel water through. There was no
vegetation observed and erosion of exposed banks and stockpiles was evident.
Impoundments and berms. There is a dam and a railway crossing upstream of the eastern
branch of the wetland. There is a berm that has been constructed across the wetland,
separating it from the upper catchment to the north.
Channel incision. The dam and railway have resulted in constriction of flows, this causing
vertical erosion within deepening channels.
Sedimentation. The area is bounded by industrial and mining activities, with mine dumps in
various stages of being removed. The mine dumps have resulted in large quantities of
sediments having been washed into the adjacent wetland. Deposited sediments have been
colonised by Phragmites. Sedimentation has been exacerbated by informal mining
activities immediately upstream of the site.
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Increased volumes and velocities of flow. The constriction of flows to a small channel (or
canal in the lower reach) has caused accelerated, concentrated flows. Under natural
conditions, flows would have been diffuse over a large area. Increased flows have also
resulted from increased stormwater runoff within an urban context, as well as unregulated
discharges from upstream dams.
Water quality. The water quality has been seriously compromised by stormwater effluent
(including sewage effluent from surcharging or open sewers), seepage from adjacent
tailings dams and sediment (causing increased turbidity). There is also a small cemetery
within the subcatchment which may have water quality implications
Infilling and road construction. The wetland area has been severely restricted by infilling
and construction of roads.
Alien vegetation. Alien vegetation was prevalent and included, amongst others, Acacia
mearnsii, Solanum mauritianum, Pennisetum clandestinum, Bidens pilosa, Tagetes minuta,
Eucalyptus sp. and Cortaderia selloana.
Figure 3-10. Map showing the PES classification of water resources within the vicinity of Canal 3.
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 24
Figure 3-11. Photographs showing impacts observed within the vicinity of Canal 3, including canalisation, water quality impacts, sedimentation and mining.
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 25
3.3 Functional Importance and EIS
As part of the water resource of South Africa, wetlands are considered to be important ecosystems
and according to the GDARD Requirements for Biodiversity Assessments (2012) all wetlands must
be considered sensitive. However, this assessment looks specifically at the importance and
sensitivity of the wetlands in question relative to other wetlands rather than comparing them to
other ecosystem types. The findings of the assessment indicate that all the valley bottom wetlands
on site are of Moderate ecological importance and sensitivity. The factors influencing the
assessment of the wetlands’ include the following:
An assessment of the Gauteng Biodiversity Conservation Plan database indicates that the
majority of the site for Canal 1 falls within areas highlighted as being either “Irreplaceable”,
“Important” or “Ecological Support Areas”, primarily due to the presence of suitable habitat
for the Orange List plant species Gnaphalium nelsonii (Rare), which occurs in seasonally
wet grassland. It is anticipated that the presence of the rocky ridges also plays a significant
role in the importance attributed to this area.
The wetlands occur within the vegetation unit Soweto Highveld Grassland (Mucina &
Rutherford, 2006) which is currently listed as Endangered.
All the wetlands surveyed, although seriously impacted and changed from their assumed
reference state, provide habitat suitable for the support of biodiversity within the area, and
as the wetlands form corridors of natural or near natural vegetation relative to the
surrounding land uses, therefore provide important areas for migration of species within the
larger landscape.
The functions typically attributed to valley bottom wetlands, including biodiversity
maintenance, flood attenuation, erosion control, sediment trapping, and nitrate and toxicant
removal are expected to be performed by all the wetlands surveyed, albeit in a limited
capacity in certain cases. The functionality of the wetlands and their influence on the water
quality and quantity downstream contributes to the importance of these wetlands within this
landscape. It should, however, be noted that the extremely poor water quality within the
wetlands exceeds the wetlands’ capacity to trap sediments and remove pollutants, although
some water quality improvement is expected to occur.
The hillslope seepage wetlands along Canal 2 and 3, as well as the canalised section of the valley
bottom wetland at site 3, were considered of Low/Marginal Ecological Importance and Sensitivity.
Biodiversity was low to extremely low within these wetlands and they are likely to play a minor
small role in moderating the quantity and quality of water within the adjacent and downstream
channels.
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 26
4 Aquatic Assessment – Findings
4.1 Sampling Sites
Figure 4-1. Aquatic Sampling Sites Upstream and downstream of the proposed Canals – Canal C1 (top), C2 and C3 (bottom).
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 27
The locality and description of aquatic sampling sites is given in Figure 4-1 and Table 4-1. All
wetland systems sampled may, under natural conditions, have been non-perennial in nature but
are now considered to be perennial as a result of the high volumes of urban stormwater they
receive.
Table 4-1. Locality and description of aquatic sampling sites along Canals 1, 2 and 3.
Coordinates Description Aquatic components
sampled
C1A 26° 9'59.27"S
27°50'5.61"E
Canal 1, upstream of the proposed
canal within the Klip River
Water Quality, Diatoms,
SASS5, Fish
C1B 26°10'53.47"S
27°49'16.98"E
Canal 1, downstream of the proposed
canal within the Klip River
Water Quality, Diatoms,
SASS5, Fish
C1 26°10'37.01"S
27°49'4.28"E
Tributary of the Klip River which joins
with the Klip River immediately
downstream of Canal 1
Water Quality, Diatoms,
SASS5, Fish
C2 26°11'32.64"S
27°57'17.03"E
Canal 2, upstream site within a tributary
of the Klip River
SASS5, Fish
C2A 26°11'49.80"S
27°57'9.05"E
Canal 2, upstream site within a tributary
of the Klip River
Water Quality and Diatoms
C2B 26°12'9.65"S
27°57'1.26"E
Canal 2, downstream site within a
tributary of the Klip River
Water Quality and Diatoms
C3A 26°11'19.19"S
28°11'31.73"E
Canal 3, upstream site within the
Elsburgspruit
Water Quality, Diatoms,
SASS5, Fish
C3B 26°11'43.93"S
28°11'22.33"E
Canal 3, downstream within the
Elsburgspruit
Water Quality, Diatoms,
SASS5, Fish
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 28
4.2 Water Quality
4.2.1 On-Site Water Quality
The in situ water quality results are presented in Table 4-2. These results are important in assisting
with the interpretation of biological results because of the direct influence water quality has on
aquatic life forms. However, this provides only a snapshot view of conditions at the time of
sampling and does not provide information on long term trends. It also depends on the accuracy
and calibration of field instruments.
Table 4-2: In situ water quality recorded during the August 2013 survey
Site pH DO* (mg/ℓ) EC** (μS/cm) TDS*** (mg/ℓ) Temp (°C)
6.5 –9.0 >5.0 <1540 <1000 5 – 30
C1 7.5 7.8 390 254 12
C1A 8.6 7.4 200 130 14
C1B 7.5 6.6 600 390 11
C2A 7.8 2.3 550 358 19
C2B 7.4 0.7 500 325 12
C3A 7.5 5.1 480 312 18
C3B 7.4 4.8 760 494 13 * Dissolved Oxygen; ** Electrical Conductivity; *** Total Dissolved Salts; Target Water Quality Range
4.2.1.1 pH
The pH of natural waters is determined by both geological and atmospheric influences, as well as
by biological activities. Most fresh waters are usually relatively well buffered with a pH range from 6
to 8 (Davies & Day, 1998), and most are slightly alkaline due to the presence of bicarbonates of
the alkali and alkaline earth metals (DWAF, 1996). The pH target for fish health is presented as
ranging between 6.5 and 9.0, as most species will tolerate and reproduce successfully within this
pH range (Alabaster & Lloyd, 1982). According to the South African Water Quality Guidelines for
Aquatic Ecosystems the pH values should not be allowed to vary from the range of the background
pH values for a specific site and time of day, by > 0.5 of a pH unit, or by > 5 %, and should be
assessed by whichever estimate is the more conservative (DWAF, 1996).
The pH measurements recorded at all sites during the survey were alkaline and of no concern to
the aquatic biota as they fell within the Target Water Quality Range.
4.2.1.2 Electrical Conductivity (EC)/ Total Dissolved Solids (TDS)
Electrical conductivity (EC) is a measure of the ability of water to conduct an electrical current
(DWAF, 1996). This ability is a result of the presence of ions in water such as carbonate,
bicarbonate, chloride, sulphate, nitrate, sodium, potassium, calcium and magnesium, all of which
carry an electrical charge (DWAF, 1996). Many organic compounds dissolved in water do not
dissociate into ions (ionise), and consequently they do not affect the EC (DWAF, 1996). Electrical
conductivity (EC) is a rapid and useful surrogate measure of the Total Dissolved Solids (TDS)
concentration of waters with a low organic content (DWAF, 1996). For the purpose of interpretation
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 29
of the biological results collected during the August 2013 survey, the TDS concentrations were
calculated by means of the EC using the following generic constant (DWAF, 1996):
TDS (mg/ℓ) = EC (mS/m at 25 °C) x 6.5
If more accurate estimates of the TDS concentration from EC measurements are required then the
conversion factor should be experimentally determined for each specific site and for specific runoff
events (DWAF, 1996). According to Davies & Day (1998), freshwater organisms usually occur at
TDS values less than 3000 mg/ℓ. Most of the macroinvertebrate taxa that occur in streams and
rivers are sensitive to salinity, with toxic effects likely to occur in sensitive species at TDS
concentrations > 1000mg/ℓ (DWAF, 1996). According to the South African Water Quality
Guidelines for Aquatic Ecosystems, the TDS concentrations should not be changed by > 15 %
from the normal cycles of the water body under unimpacted conditions at any time of the year
(DWAF, 1996).
All the recorded TDS values fall within the South African Target Water Quality Range Guidelines
(TWQR) at the time of sampling and don’t appear to be a limiting factor to the aquatic biota (Table
4-2). No trends were identified.
4.2.1.3 Dissolved Oxygen (DO)
The maintenance of adequate Dissolved Oxygen (DO) is critical for the survival and functioning of
aquatic biota as it is required for respiration by all aerobic organisms. Therefore, DO concentration
provides a useful measure of the health of an ecosystem (DWAF, 1996). The median guideline for
DO for the protection of aquatic biota is > 5 mg/ℓ (Kempster et al., 1980). The amount of oxygen
that can be dissolved in water is influenced by the temperature, as the temperature of the water
increases, so the concentration of dissolved oxygen decreases (Davies & Day, 1998).
Three sites were found to have DO concentrations that were lower than the guideline values of > 5
mg/ℓ (Table 4-2). These sites were C2A, C2B, and C3B, with site C2B being extremely low with a
DO concentration of 0.7 mg/ℓ, while site C2A was moderately low and site C3B was just below the
guideline value. These low values have a limiting effect on the aquatic biota, making the site
unfavourable for fish if present. The remaining sites were found to be adequate and would not
have a limiting effect on the associated aquatic ecosystems (Table 4-2).
4.2.1.4 Water Temperature
Water temperature plays an important role in aquatic ecosystems by affecting the rates of chemical
reactions and therefore also the metabolic rates of organisms (Davies and Day, 1998).
Temperature affects the rate of development, reproductive periods and emergence time of
organisms (Davies and Day, 1998). Temperature varies with season and the life cycles of many
aquatic macroinvertebrates are cued to temperature (Davies and Day, 1998).
The water temperatures for the August 2013 survey were considered to be normal seasonal
temperatures for these freshwater aquatic systems and thus would not have a limiting effect on
aquatic biota (Table 4-2).
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4.2.2 Laboratory Analyses of water quality
Results of the laboratory analyses of water quality are shown in Table 4-3. The site downstream of
Canal 3 (C3B) has clearly been seriously contaminated. Salinity and pH are well beyond guideline
limits and are likely to severely limit the survival of aquatic biota downstream of this site. Salts
include extremely high sulphate levels, as well as sodium and calcium, strongly suggesting mining-
related impacts. The site upstream of canal 3 (C3A) has relatively good water quality but appears
to have high nutrient levels (nitrates) possibly from sewage effluent in urban stormwater.
Sites associated with canal 1 have relatively good water quality. The tributary (C1 trib) appears to
be receiving high nutrient loads, possibly from sewage effluent. The sampling site downstream of
canal 1 (C1B) has slightly elevated salt levels, including sulphates, suggesting some mining
impacts to this system.
Sampling sites along canal 2 had elevated salt and alkalinity (calcium carbonate) levels that may
be limiting to some aquatic biota.
Table 4-3 Water quality results for aquatic sampling sites. DWAF TWQR and limits are shown to the right. Red shading indicates exceedances, orange indicates levels of concern and yellow indicates elevated levels.
4.2.3 Diatoms
The Ecological Categories for the Council for Geoscience Canal Project sites based on diatom
species composition recorded in July 2013 are summarised in Table 4-4 below. The most
impacted sites appear to be C2A and C2B which are heavily impacted by wastewaters (principally
nutrients, organics and electrolytes) and therefore have been assigned an Ecological Category E
(Bad quality). Diatom communities at Sites C1 and C1B fall into a category C/D (Moderate quality)
with some signs of disturbance from urban and industrial wastewaters. The Ecological Category of
the water quality at Sites C1A and C3A is uncertain due to discrepancies surrounding the ecology
of the dominant taxon Achnanthidium minutissima which may be found in clean waters as well as
impacted waters. However, there are signs of nutrient and organic inputs at Site C3A and C1A.
Water quality at Sites C1A and C3A were therefore considered to be an Ecological Category of D
(Poor quality) due to nutrient, organic and electrolyte enrichment from surrounding land use
activities. Site C3B was considered to be Category D (Poor quality)
Analyses in mg/ℓ (Unless specified
otherwise)C1A C1B C1 (trib) C2A C2B C3A C3B
DWAF
1996
Ecosyste
ms
DWAF
1996
Domestic
Use
DWAF
1996
Agriculture
DWAF
1998
General
Limit
pH – Value at 25°C 7.5 7.5 7.5 7.1 7.2 7 10.5 6.0 - 9.0 6.5-9* 5.5-9.5
Electrical Conductivity in mS/m at 25°C 27.5 52.6 18.9 40.1 42 24.2 225 150 150
Total Dissolved Solids (Calculated) 150 317 121 257 269 155 1 440 450 1000#
Total Alkalinity as CaCO3 60 80 36 128 124 36 96 50-100 20-100*
Chloride as Cl 20 25 21 32 41 21 94 100 600*
Sulphate as SO4 44 137 13 31 33 32 1 121 200 1000#
Fluoride as F <0.2 <0.2 <0.2 0.2 0.2 <0.2 0.2 0.75 1 2# 1
Nitrate as N 0.7 1.4 19 <0.9 <0.9 21 <0.9 2.5 6 0.05*/100# 15
Nitrite as N <0.1 <0.1 0.1 <0.1 0.1 0.1 0.2 6 10# 3
Free & Saline Ammonia as N <0.2 3.1 <0.2 2.9 <0.2 0.2 7.5 200
Sodium as Na (Dissolved) 14 22 20 25 26 14 160 100 70#
Potassium as K (Dissolved) 2.7 4.7 1.8 5.2 4.5 5.1 15.1 50
Calcium as Ca (Dissolved) 21 59 10 31 34 16 381 32 1000#
Magnesium as Mg (Dissolved) 8 12 3 13 14 9 4 30 500#
* Aquaculture # livestock w atering
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 31
Table 4-4. Ecological Classification for the Council for Geoscience Canal Project Sites in July 2013 based on diatom species composition recorded at each site.
Table 4-5. List of dominant diatom species occurring at the Council for Geoscience Canal Project sites, expressed as a percentage of the total sample.
% of sample
Taxa C1 C1A C1B C2A C2B C3A C3B
ACHNANTHIDIUM F.T. Kützing 16
Achnanthidium saprophilum (Kobayasi et Mayama) Round 17.5
Achnanthidium minutissima Kützing 14.5 73 13 90
Fragilaria biceps (Kützing) Lange-Bertalot 11.5
Fragilaria capucina Desmazieres var.capucina 8
Fragilaria capucina Desm. ssp. rumpens (Kütz.) Lange-Bert. 8.5 19.5
Gomphonema lagenula Kützing 6 15.5
Gomphonema parvulius Lange-Bertalot & Reichardt 6 9
Navicula cryptocephala Kützing 17.5
Nitzschia intermedia Hantzsch ex Cleve & Grunow 17.5
Nitzschia pura Hustedt 53
Nitzschia palea (Kützing) W.Smith 5.5 73 74 5.5
Planothidium frequentissimum(Lange-Bertalot) 52.5 9
At Sites C1, C1A and C1B diatoms were sampled within moderate flowing waters hence the use of
the diatom software package OMNIDIA to infer water quality conditions at this site was applicable.
Index values were calculated in OMNIDIA for epiphytic diatom data (i.e. diatoms attached to
submerged vegetation) (Lecointe et al. 1993). In general, each diatom species used in the
calculation of the index is assigned two values; the first value reflects the tolerance or affinity of the
particular diatom species to a certain water quality (good or bad) while the second value indicates
how strong (or weak) the relationship is. These values are then weighted by the abundance of the
particular diatom species in the sample. The general water quality indices (integrating impacts
from organic material, electrolytes, pH and nutrients), used in the assessment, are:
- the Specific Pollution sensitivity Index (SPI), one of the most extensively tested
indices in Europe; and
- the percentage of (organic) pollution tolerant valves (%PTV)
Samples from Sites C1 and C1B are of relatively good water quality with very little organic content
in the system. At these sites Fragilaria capucina (Table 4-5), which is found in circumneutral to
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 32
alkaline, oligo- to mesotrophic waters with moderate electrolyte content, was dominant. From our
extensive database that includes sites in numerous mining areas, this taxon is also associated with
contaminated waters as a result of mining. Therefore it is likely that the water quality at these sites
is of an Ecological category C (Moderate quality). At Site C1, dominant species Fragilaria biceps
points to elevated inorganic nutrients and moderate electrolyte content.
The ecological water quality for Site C1A is also relatively high with negligible organic content in
the system. This is reflected by prevalent taxon Achnanthidium minutissima, a species generally
found in waters with low to moderate pollution levels and high oxygen content (Slàdecek, 1986;
Leclercq and Maquet, 1987; Prygiel and Coste, 2000). Studies have also revealed A. minutissima
to develop abundant populations at sites contaminated with mining effluent (Deniseger et al., 1986;
Genter et al., 1987; Medley and Clements, 1998; Ivorra et al., 1999, Gold et al., 2002, 2003,
Cattaneo et al., 2004, Ferreira da Silva et al., 2009). The other dominant taxon present is Fragilaria
capucina which as discussed above has been found in mine impacted waters. Due to the
discrepancies surrounding the ecology of A. minutissima, conclusions on water quality at this site
cannot be inferred.
The diatom software programme OMNIDIA is a tool to assess the health of moderate flowing
waters and is not applicable to slow flowing waters as was found at Sites C2A, C2B, C3A and
C3B. Analyses of diatoms were therefore based on measures of relative abundance and species
composition (i.e. assemblage patterns) to infer baseline water quality conditions at these sites.
Diatom assemblage patterns at Sites C2A, C2B, C3A and C3B suggest the following
(remembering that ‘pollution indicators’ used to determine anthropogenic stress in moderate
flowing, freshwater systems may be equally tolerant to the natural stressors that accompany
stagnant/slow flowing waters with naturally elevated nutrient/salinity levels):
At Sites C2A and C2B there was an extremely high abundance of taxon Nitzschia palea
(Table 4-5) which is found in highly eutrophic, organic-rich and very heavily polluted to
extremely polluted waters with moderate to high electrolyte content. For this reason the
water quality at these sites can be assigned an Ecological Category E (Bad quality).
Recorded at Site C3A Achnanthidium minutissima was prevalent (Table 4-5), - see
discussion above regarding the disparities of A. minutissima’s ecological characteristics.
Other taxa present suggest minor nutrient and organic inputs. Due to the discrepancies
surrounding the ecology of this taxon, conclusions on water quality at this site cannot be
inferred.
At Site C3B, the overall diatom species composition is dominated by pollution tolerant
species, occurring in weakly alkaline, eutrophic, moderately electrolyte and organic-rich
waters tolerating critical levels of pollution, such as Nitzschia pura, Nitzschia intermedia
and Navicula cryptocephala (Table 4-5). The water quality at this site can be assigned an
Ecological Category D - E (Poor to bad quality).
4.3 Habitat Integrity
Photographs of canal 1 sampling sites are shown in Figure 4-2, while photographs of sampling
sites along canals 2 and 3 are given in Figure 4-3. The results of the Habitat Integrity Assessment
are shown in Table 4-6.
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 33
The downstream Canal 1 sites (C1B) was considered to be in the best condition in terms of aquatic
habitats. The greatest impacts observed at this site included channel incision and erosion as well
invasion by alien trees (black wattle and Eucalyptus). However, most marginal and instream
habitats were intact, thus providing a diversity of habitats, and the reach was considered Category
C (Moderately Modified) in terms of aquatic habitats.
The site downstream of Canal 3 (Site 3B) was considered to be critically modified (Category F) in
terms of the availability and suitability of aquatic habitats. This reach lies immediately downstream
of a canal and flows have been seriously impacted. All marginal habitats have been eroded away.
In addition, water quality is likely to have been impacted by upstream mine dump reclamation
processes.
All other sampling sites were considered Largely to Seriously Modified (Category D-E). The major
impacts included:
channel modification and bed modification (largely as a result of informal mining at C1A
and canalization at C3B). Erosion has left the channel with little instream and riparian
habitat, with only shallow exposed areas.
water quality impacts as a result of sewage discharge into urban stormwater. Site C2A had
a large amount of visible pollution, with a distinct odour or raw sewerage. General habitat
availability for aquatic biota was limited. Dissolved oxygen levels were low at both C2 sites.
water quality impacts due to mining activities were likely at C3B.
flow changes as a result of high volumes of urban stormwater entering wetlands were most
notable along canals 2 and 3 but affected all sites.
channel incision as a result of erosion from urban stormwater runoff was evident at C3A
and C1 (trib).
Table 4-6. Results of the Index of Habitat Integrity Assessment
INSTREAM HABITAT INTEGRITY C1A C1B C1 (trib) C2 C3A C3B
WATER ABSTRACTION 5 5 5 2 0 5
FLOW/HYDROLOGICAL MODIFICATION 11 11 15 20 10 21
BED MODIFICATION /SEDIMENTATION 15 8 11 11 8 15
CHANNEL/STRUCTURAL MODIFICATION 12 8 18 16 11 15
WATER QUALITY 10 8 10 20 15 20
INUNDATION 3 3 3 5 5 8
EXOTIC MACROPHYTES 8 5 8 5 5 8
EXOTIC FAUNA 0 0 0 0 0 0
RUBBISH DUMPING 5 4 8 2 7 7
Total Score D C D E C E
RIPARIAN/MARGINAL INTEGRITY C1A C1B C1 (trib) C2 C3A C3B
VEGETATION REMOVAL 21 8 10 3 7 20
EXOTIC VEGETATION 5 12 12 15 8 14
BANK EROSION 22 10 18 15 12 16
CHANNEL MODIFICATION 11 6 20 20 15 19
WATER ABSTRACTION 5 5 3 3 3 2
INUNDATION 0 0 0 0 0 8
FLOW/HYDROLOGICAL MODIFICATION 15 8 18 16 12 21
WATER QUALITY 8 5 9 15 8 12
Total Score F C E F D F
Estimated Overall PES E C D E D F
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 34
Figure 4-2. Photos taken upstream and downstream of sampling sites along Canal 1, from top to bottom: C1, C2A, C2B
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 35
Figure 4-3. Photos taken at aquatic sampling sites C2A and C2B (top row), C3A (second row) and C3B (bottom row)
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 36
4.4 Aquatic Macroinvertebrates
The SASS5 results are shown in Appendix B and summarized in Table 4-7.
Diversity of aquatic macroinvertebrates was extremely low. This was partly in response to the
limited availability of habitats as all sites were considered to essentially be channeled valley bottom
wetlands and are therefore not expected to have a high diversity of aquatic habitats. C1B was
considered to be an exception as it had a higher relative diversity of habitats.
The maximum number of taxa sampled was seven (canal 1 sites). No individuals were recorded
from site C3B, largely due to an absence of habitats but possibly also due to water quality impacts
and significant flow modifications. The upstream site along (C3A) fared slightly better with five
taxa, including two species of baetid mayfly, indicating some sensitivity to changes in water quality.
Clearly, impacts to habitats and water quality are critical between C3A and C3B.
The highest diversity was recorded along Canal 1 (C1A and C1B) as well as C3A. This is reflected
by the higher SASS scores at these sites. However, the average sensitivity of the taxa to water
quality, as reflected by the ASPT, was generally low at all sites, with the exception of C3A.
All sites were therefore considered to be Seriously to Critically Modified for aquatic
macroinvertebrates (E-F) with only site C3A reflecting moderately modified conditions (Category
C). Site C1B, while having a relatively high diversity in response to the higher availability of
suitable habitats at this site, had an absence of sensitive taxa, suggesting that water quality
impacts have affected the macroinvertebrate assemblage. Site C1B was considered Largely
Modified (Category D) for aquatic macroinvertebrates.
Table 4-7. Summary of SASS5 Results for canal sites in July 2013.
C1A C1B C1 (trib) C2 C3A C3BStones 2 3 2 3 1 4
Marginal vege 2 3 3 2 3 1
Sediment 4 2 1 1 2 1
7 7 4 2 5 0
29 30 12 3 25 0
4.1 4.3 3.0 1.5 5.0 0.0
E/F D E/F E/F C E/F
SITE
Average Score per Taxon
TOTAL No. SASS TAXA
SASS Score
Biotopes Sampled (Rated 1-5)
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 37
4.5 Fish
Only one fish species (Barbus anoplus) was recorded from site C1A during the August 2013
survey (Table 4-8, Figure 4-4). No other fish species or B. anoplus individuals were found at any of
the other six sites sampled. Barbus anoplus is a moderately tolerant species that has adapted to
rivers in the Highveld. Typically it can withstand natural fluctuations in flow and water quality
throughout the year.
Table 4-8: Fish results from the August 2013 survey
Species Common name
IUCN Status Intolerance
rating
Site
C1 C1A C1B C2A C2B C3A C3B
Barbus anoplus
Chubbyhead Barb
Least Concern 2.6 0 5 0 0 0 0 0
Number of individuals 0 5 0 0 0 0 0
Number of species 0 1 0 0 0 0 0
Based on the assessment of the three canals, it was found that there was a limited diversity and
abundance of fish, with only one fish species present in the canal situated in Durban Roodepoort
Deep (C1A). Based on these results, the FAII index could not be applied.
Figure 4-4: Barbus anoplus collected at site C1A
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 38
5 Impact Assessment and Management
Recommendations
5.1 Impact Assessment
Canalisation is expected to have an impact on the behaviour, distribution and retention of water in
the landscape. The impermeable layer will prevent lateral and vertical connectivity with the beds
and banks, thus limiting wetland functions (such as water quality improvement and flood
attenuation). Canals tend to concentrate flows spatially and temporally, resulting in higher volumes
and velocities causing greater erosive forces. Seasonal hydrological patterns may also be
‘smoothed out’ resulting in stable water levels. These impacts are summarised below.
Impacts of the canals were considered in terms of site-specific impacts as well as impacts to
downstream reaches which may still be intact in terms of biotic integrity. For this reason,
downstream reaches of canal 1 were considered most sensitive in terms of aquatic ecosystem
integrity and is therefore also most at risk to disturbance.
Construction Phase Impacts
5.1.1 Increased sediment movement off the site
During construction, exposed soil areas resulting from vegetation clearing will be susceptible to
erosion. Currently, reed beds within the valley bottom system are facilitating the deposition of
sediment. Their removal, both during and after construction, will result in significantly increased
sediment loads reaching downstream ecosystems. This impact will be greatest within C1 which
shows the least amount of sedimentation downstream, largely because there are fewer tailings
dams feeding eroded sediments into the system. Sediment loads will be deposited downstream
within the Klip River where they will augment the, currently limited, Phragmites reed beds. C2 and
C3 drain indo extensive existing reed beds and, in addition, there is a dam located downstream of
C3.
Mitigation measures
Construction activities should take place during low flow period, it is suggested that a temporary
diversion is constructed to limit the extent of impact; possible piping may be recommended for the
short term during construction as further excavation may disturbed a wider area. This temporary
diversion will serve to provide dry areas for construction. It is suggested that engineers evaluated
and provide alternative options for temporary diversions that can be considered in terms of
minimising impacts. Gravitation flow is preferred so as to avoid any pumping which may cause
further impacts to aquatic ecosystems.
5.1.1 Loss of Vegetation, habitats and biota
Removal of vegetation for construction will result in the loss of riparian and wetland habitats, with
an associated loss of fauna, including small mammals and amphibians that migrate along riparian
margins (e.g. water mongooses, duiker). Stream diversions may cause further loss of aquatic fish
and macroinvertebrates.
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 39
Mitigation measures
It will be difficult to mitigate this impact in the short term. However in the long term the system will
reach equilibrium and species will adapt in terms of utilising the canal for migration. The designs of
the canals may need to be enhanced to maximise the potential for recolonisation and restoration of
aquatic species. This is discussed more fully in Section 5.2 (recommendations) of this report and
could include using irregular surfaces to create different flow regimes, the creation of pool habitats
to encourage sedimentation and colonisation by marginal vegetation such as reeds.
Operational Phase Impacts
5.1.2 Decline in Water Quality
Urban wetland systems typically contain high nutrient levels due to stormwater runoff, which
usually contains high levels of nutrients, organic material, bacteria, sediment and salts. Mining
activities have exacerbated the salt loads in receiving wetlands. Typically, algae proliferate under
these conditions. Wetlands can play a significant role in trapping sediments and nutrients.
Canalisation and the removal of reed beds within the active channel and banks will cause a
decrease in the capacity of wetlands to improve water quality and facilitate sedimentation. This
impact is likely to be more significant for a concrete-lined system than a reno mattress lining.
Mitigation measures
The proposed configurations of the canal consist of a thick Reno mattress lining including stone
rapped with bidim. These irregular surfaces, together with the intentional creation of pool habitats,
will slow flows and encourage deposition of sediments. These sediments will be colonised by
wetland plants, notably Typha, which will encourage further depositional zones. Deposited
sediments will contain various pollutants which will effectively be removed from the water column
and oxidised over time. Lateral wetlands and drainage areas that feed into the main canal should
be restored and maintained as this will help to maintain water quality.
5.1.3 Loss of habitats and biodiversity
All habitats and biota within the canalized wetlands will effectively be lost in a short term provided
that the configuration of the design is changed to enable some form of an engineered habitat type
to form. it is known that stream beds and banks provide diverse habitats (e.g. cobbles, marginal
vegetation, riffles, pools, etc.), trap organic matter and slow water down, thus providing suitable
food, shelter and habitat conditions to support plants, invertebrates, birds, mammals and fish. In
addition, no water or nutritional interchanges can occur between sediments within the banks and
stream bed and the water column, affecting nutrient cycling. Canals are therefore usually devoid of
life particular hard engineered however there is potential to retain life in bio engineered canals This
affects animals higher up in the food chain, such as birds and mammals as food and habitats are
rendered unavailable. This impact will be permanent and highly significant should a concrete lining
be used. Reno mattresses will result in the temporary loss of habitat and biota but there may be a
small measure of recovery over time, mainly by grasses and reeds. (Riparian trees are likely to be
lost. However, most trees were alien invasive vegetation so this impact is considered to be minor.)
Mitigation measures
It will be difficult to mitigate for this impact in the short term. However in the long term,
recolonisation will occur and a new equilibrium will be reached. It is acknowledged that complete
bio-engineered canals will not be possible in this case as the objective of these canals is to be fully
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 40
sealed so as to prevent ingress to underground workings. However, there are opportunities to
modify the physical structure for the deliberate creation of habitats (e.g. roughened surfaces to
create a diversity of flow patterns, creation of pools, etc.) which can then be colonised by aquatic
plants and animals. The creation of ‘habitat nodes’ and the rehabilitation of downstream reaches
could be considered. These opportunities are discussed more fully in Section 5.2.
5.1.4 Reduced water retention and flood attenuation
Canalisation will result in reduced lateral drainage between the channel and banks as well as
vertical interchanges with shallow groundwater, although the latter are expected to be limited. This
will increase the volumes and velocities of storm flows. However, this impact may be limited in
channelled valley bottom systems.
Mitigation measures
The design of the canals should include irregular surfaces (reno mattresses), with a series of
dissipaters, as well as the deliberate creation of pools. This will encourage sedimentation and
recolonisation by wetland plants which will further retard flows and increase the flood/stormwater
attenuation capacity of the canal.
5.1.5 Increased erosion and sedimentation
Canals tend to concentrate flows. Higher volumes result from decreased seepage of water from
the channel into the banks, beds or evapotranspiration by riparian trees, while velocities increase
as a result of decreased ‘roughness’ of the substrate and margins. This results in erosion and
scouring immediately downstream of the canal outlet. In addition, where water backs up at the inlet
of the canal, scouring can occur during storm events. Where sediments are deposited they are
colonised by monospecific stands of reeds and may alter the suitability of benthic habitats for
aquatic biota. Overall biodiversity is thus reduced.
Mitigation measures
The designs of the canals should include scour protection and energy dissipaters. Energy
dissipaters at inlets can be constructed using rock masonry, while outlets will require constructed
dissipaters. In addition, as indicated above, the configuration of the canal should consider surface
roughness with the creation of pools and other flow retarding mechanisms to ensure that flows at
the outlet mimic natural conditions. This will encourage colonisation of wetland plants which will
further retard flows and increase the flood/stormwater attenuation capacity of the canal
5.1.6 Altered flow regime
Flow rates and volumes can be altered by the altered channel morphology (e.g. meanders), the
loss of lateral and vertical connectivity with beds and banks and the loss of surface ‘roughness’
which would normally slow flows. As such, storm flows may be more pronounced and low flows
may be less frequent within downstream reaches. This may impact on certain biota with specific
flow requirements. It is understood that the design of the canals will cater for 1:2 or 1:5 year storm
events.
Mitigation measures
The design of the canals should include irregular surfaces (reno mattresses), with a series of
dissipaters, as well as the deliberate creation of pools. This will encourage sedimentation and
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 41
recolonisation by wetland plants which will further retard flows and increase the flood/stormwater
attenuation capacity of the canal.
5.1.7 Loss of access to local communities
C1 is being used by the local community for cattle grazing and watering, as well as informal
mining. These are social considerations and were not assessed as part of this study.
Mitigation measures
It is suggested that the community should be informed about alternative water resources within the
subcatchment.
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 42
Table 5-1 Impact Rating Table pre and post mitigation measures
Impact Magnitude Duration Scale Probability Significance Magnitude Duration Scale ProbabilitySignifican
ce
Sedimentation and erosion (Construction Phase) High Short term Regional High High Moderate Short term Regional HighLow-
Medium
Removal of vegetation and loss of habitats High Permanent Local Defini te High Moderate Permanent Local Defini te Medium
Decline in Water Quality Moderate Long term Regional High Medium Moderate Long term Regional Medium Medium
Loss of habitats and biodiversity High Permanent Local High High Moderate Permanent Local High Medium
Reduced water retention and flood attenuation Moderate Long term Local Medium Medium Low Long term Local MediumLow-
Medium
Increased erosion and sedimentation Moderate Long term Local High Medium Low Long term Local Medium Low
Altered flow regime High Long term Regional High Med-High Moderate Long term Regional MediumLow -
Med
PRE MITIGATION POST MITIGATION
Construction Phase Construction Phase
Operational Phase Operational Phase
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 43
The most significant impacts relate to the loss of habitats and biota within the canal itself, as well
as potential loss of habitats downstream as a result of flow changes and water quality changes.
However, these impacts should be weighed against the impacts associated with ingress and
subsequent decant of contaminated mine water. As such, the cumulative impacts are considered
to be positive, assuming that decant can be significantly delayed. This assumes that the mitigation
measures given below are effectively implemented to reduce impacts to downstream reaches,
particularly within the Klip River catchment.
5.2 Recommendations and alternative approaches:
While the construction of the canals is not likely to further degrade the biotic integrity of aquatic
ecosystems along the canal routes due to the already degraded state, the design of the canals
should consider impacts to downstream reaches which may still be intact. As such, mitigation
should aim to minimise impacts to downstream reaches.
It is recommended that the configuration of the canals within them must be re-engineered with the
following guiding principles:
• The hydrology should mimic the pre-development hydrology in terms of flow rates and peak
discharges as far as possible
• The functionality of the wetlands needs to be restored where possible, particularly with
respect to flood attenuation and water quality improvement.
• Sediments should be managed at their point of origin.
However, the following limitations apply to the project:
1. The feasibility of widening the canal to retard flows is limited.
2. The canal is required to be sealed with an impermeable layer to meet the objectives of the
project and therefore bio-engineering opportunities are somewhat limited.
A number of interventions can be used to satisfy these principles.
5.2.1 Consideration of alternative designs
The current design proposes a uniform bed design canal with a thick crushed rock layer (Reno
mattress). In order to enable some habitat formation within the canal it is recommended that
alternative creative design be considered as follows where feasible:
Opportunities of creating irregular features, including pools, with a series of erected
dissipaters within the canal, will assist with reduction of flow velocities. It will also
facilitate deposition of sediments which will be recolonized by wetland plants, this
retarding flows further, improving water quality and increasing biodiversity in the
long term.
Inlets and outlets should be protected with construction rock masonry at the inlet
and erected energy dissipaters at the outlet to reduce erosion.
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 44
5.3 Specific environment management programme for the proposed canals
5.3.1 Minimise disturbance due to stream diversions
It will be necessary to isolate the construction areas to create dry working conditions. This will
require temporary diversions or coffer dams which cause highly significant impacts to aquatic
ecosystems. It is therefore essential that construction take place during the dry season (May-
September).
Furthermore, where flows are low enough, it is recommended that partial isolation by coffer dams
or full isolation by gravity-driven flume pipes be used over short distances (100-150m). These may
be suitable for C2 and C3. These structures must however be designed to take into account
changes in flow velocity which could cause erosion and scour. Such structures should be regularly
inspected for leaks, damage or blockages. Energy dissipating structures and erosion protection
measures are required at outlets. Flooding of working areas should be avoided as this could lead
to contamination of downstream reaches and the period of isolation should be kept to a minimum.
Where flows are too high and a temporary stream diversion is unavoidable, it should be designed
by a competent person and should consider the following:
Where possible, construction should be staggered so that a series of shorter diversions are
progressively used, rather than a single, long diversion.
The selected route should pose the least possible risk to aquatic ecosystems.
The natural hydrology should be mimicked as far as possible. Gradient, water depth,
velocity, channel cross-section and alignment, sediment transport and bed material must
replicate natural conditions as far as possible. Energy dissipating structures (reno
matresses) will assist in slowing flows, as will maintaining that existing channel width.
Erosion Protection measures must be used at inlets and outlets, as well as within the
diversions. The slope of the banks should not be greater than 1 in 2 to ensure bank
stability.
Line the bed and banks of the diversion (e.g. geotextile or reno mattresses) to prevent
erosion and to retard flows.
Create pool habitats as depositional zones.
Soil stockpiles should be located away from the banks of the diversion to prevent erosion of
sediments into the channel.
Upon completion of the canal, diversions should be infilled, re-landscaped and revegetated
so as to prevent preferential flow paths from forming within the historical diversion.
5.3.2 Limit the use of concrete
It is strongly recommended that reno mattresses be used instead of concrete to line the canals.
Reno mattresses will add ‘roughness’ to slow flows and will still allow for some colonization by
plants and animals, thus allowing for the retention of some natural wetland processes and
functions, such as decomposition, shelter for invertebrates during flood events, habitat for
burrowing animals, etc.
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 45
5.3.3 Maintain the natural flow regime
It is recommended that the canal be designed according to the1:5 – 1:10 year storm event. This
will ensure shallower, more spread out flows over the canal surface, thus having a greater chance
of being slowed down by the underlying substrate. This will reduce the impact to flow-sensitive
ecosystems downstream of the canals, as well as disturbance to habitats as a result of erosion and
sedimentation downstream of the outlet. The 1:2 year design is likely to result in faster flows as
well as overtopping and lateral erosion of banks.
5.3.4 Minimise erosion at canal inlets and outlets
It is important that a solid structure be constructed at the inlet and outlet of the canal so that
erosion under the reno-mattress does not occur as suggested in the above sections. This may
eliminate surface flow if water is not captured correctly. Culverts should be if sufficient capacity at
canal inlets to ensure water is not significantly backed up, as this may create erosion.
Additional measures should include:
ensuring a gradual slope downstream of the outlet
rock masonry, rip rap basins and reno mattresses at inlets and outlets to attenuate flows
and protect banks against erosion
stilling basins or engineered energy dissipators
Increasing the roughness of the canal to slow flows prior to being discharged at the outlet.
5.3.1 Stormwater Management
A detailed stormwater management system must be developed, that clearly indicates volumes and
velocities entering and being discharged from the canal. This may include lateral inlets along Canal
1. If lateral inflows are not accounted for, erosion on the sides of the canal may occur,
compromising its integrity.
With regard to Canal 1, off-channel attenuation facilities would reduce peak flows and would also
improve water quality prior to it entering the main canal. These could include dry attenuation
ponds, depressions, grassed swales and reeded ‘wet’ detention ponds which should be reeded to
facilitate removal of sediments, together with associated nutrients and other pollutants. An
example is illustrated in Figure 5-1. It is further recommended that, where possible, further
developments within the local subcatchment be limited or managed (e.g. golf courses or playing
fields rather than hardened urban surfaces) so as to maximise infiltration rather than encourage
runoff into the adjacent canals where erosion can result.
5.3.1 Create habitats
It is further suggested, where feasible, that the canal could be widened in sections to create habitat
‘nodes’. Wider areas will slow flows and create deposition zones in pool-like areas, which will later
become colonized by reeds and associated biota. These ‘habitat nodes’ could potentially be
constructed with concrete to allow dredging, if necessary. This would apply mainly to Canal 1
which is 2.4 km long and therefore stands to lose the most habitat diversity and wetland function.
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 46
Figure 5-1. Example of stormwater attenuation facilities used along the Mhluzi River in Middelburg, Mpumalanga. This approach could be applied to lateral inflows into Canal 1.
5.3.1 Minimise sedimentation
Construction should take place during the dry season to reduce erosion and minimise flows that
may need to be diverted to allow for construction. All practical steps must be taken to minimise
earthworks and to reduce erosion from soil stockpiles, which should be located outside of wetland
areas. Sediment traps and detention ponds must be used to trap sediments that may be washed
into adjacent watercourses. The impacts associated with mining and slimes dams should be taken
into account my constructing berms that will trap sediments before they reach watercourses.
5.3.2 Minimise water quality impacts
All practical steps must be taken to prevent or reduce run-off of stormwater into the wetlands,
especially dirty stormwater from the construction sites, as cement and hydrocarbons will pollute the
river. No wash water or water that is in any way contaminated by construction or other materials
should be passed into natural watercourses. A construction phase Environmental Management
Programme should be compiled and implemented, such that it clearly addresses inter alia the
above activities, as well as appropriate locations for construction camps, vehicle storage and
parking areas, ablution facilities and waste management , such that these do not impact on
sensitive or otherwise important terrestrial or wetland areas. Toilet facilities should be located
outside of wetland areas. Artificial wetlands created downstream of canal sites could be
considered to offset the functional loss of wetlands on site. These could be constructed off-channel
within drainage lines, in consultation with a wetland specialist.
5.3.3 Habitat continuity
Wetlands provide habitat corridors for many mammals (e.g. otter, water mongooses), birds and
amphibians. It is recommended that a buffer of 30 metres be applied to ensure habitat continuity. It
is also recommended that security fencing be passable by small mammals (e.g. mongooses,
duiker).
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 47
5.3.4 Manage Waste
Regular housekeeping must ensure that solid wastes generated during construction are disposed
of appropriately, and not left on site. Tyres and petroleum products should be treated as
hazardous waste and disposed of at a registered disposal facility.
5.3.5 Minimise Disturbance to Wetland Areas
The disturbance footprint must be kept to a minimum; a construction corridor must be delineated
prior construction and fenced off. All construction related activities should be kept within this
servitude. Activities within wetland areas must be minimised. Activities that do not need to take
place within the wetlands, such as mixing of concrete, storage of equipment, washing of vehicles,
sanitation facilities, etc., should be located outside of wetland areas. Wetland areas that fall
outside the development footprint should be cordoned off and considered no-go areas.
5.3.6 Manage Spills
Emergency spill kits should be available in the event of a spill of oil or diesel, and oil and diesel
should be stored off-site. Cement and fines should be prevented from entering watercourses.
Vehicles and machinery should be well maintained so as to minimise leaks. No vehicle washing
should take place in watercourses
5.3.7 Alien vegetation
Invasion by alien invasive trees should be managed. In particular, black wattle seedlings should be
hand pulled in the seedling phase so as to reduce eradication costs at a later stage.
5.3.8 Rehabilitation
After construction, disturbed areas should be rehabilitated by smoothing out disturbed surfaces
and reseeding with indigenous vegetation. • Diversions should be infilled, re-landscaped and
revegetated so as to prevent preferential flow paths from forming within the historical diversion.
Rehabilitation should include management of invasive alien vegetation, in particular, wattle
seedlings which can be hand-pulled while they are still small.
5.3.9 Maintenance and Monitoring
Maintenance: It is important that the canals are maintained regularly so that they don’t become
damaged or blocked. Excessive amounts of debris may block longitudinal flow.
Monitoring: It is recommended that ongoing monitoring should be conducted during the
construction and operational phases, including:
Turbidity and suspended solids, especially during the construction phase
Visual inspections for erosion or blockages
Assessment of habitat integrity, including vegetation recovery
Assessment of colonisation by alien vegetation
It is further recommended that habitat integrity and water quality (particularly in terms of nutrients
and salts) be monitored downstream of the canals to ensure that no impacts to downstream
reaches occur.
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 48
It is recommended that monitoring be conducted weekly during the construction phase and
monthly for the following least three years. Thereafter annual surveys should be conducted. Any
problems detected during monitoring should be addressed in a clearly documented and auditable
manner.
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 49
6 Conclusion
Based on this assessment, it can be concluded that the current state of the wetlands and
watercourses associated with the three canals is largely to critically modified based on the habitat
integrity, aquatic macroinvertebrates, fish, diatoms and water quality assessed. The streams
concerned are first order streams located in urban /industrial areas and as a result are highly
impacted. In general, aquatic habitats and biota associated with canal 1 fared slightly better than
canal 2 and 3 wetlands, particularly in terms of water quality, biotic diversity and habitat integrity.
Construction of the canals is therefore not likely to significantly impact on the already degraded
biotic integrity of the surveyed wetlands. However, impacts to the downstream reach need to be
considered, particularly with regard to Canal 1 which is the longest, the most sensitive and stands
to lose the most in terms of wetland function and integrity.
Impacts associated with canalisation of a watercourse are mainly associated with habitat loss, loss
of biota and accelerated flows. Flow retarding structures (e.g. rocks, vegetation, bends and
meanders) are replaced by smooth, straight surfaces. Water quality may decline due to the
removal of vegetation that formerly encouraged settling out of sediments and the trapping/cycling
of nutrients and toxins. This however, should be weighed up against the positive impacts
associated with reduced ingress and delayed decant of AMD water.
A number of recommendations have been made to mitigate the abovementioned impacts. The
main recommendations include:
Creative design of the canal to allow for depressions and erected dissipaters as well as
limiting the use of cement/smooth surfaces (e.g. use reno mattresses instead)
Consideration of designing for the largest storm event possible (1:5 – 1:10 year events) to
prevent overtopping and erosion
Carefully designed inlet, outlet and culvert structures to reduce erosion/scouring as
discussed in the above section
Use energy dissipaters downstream of the outlet to avoid erosion within the downstream
reach
Creation of habitat nodes at intervals along the canal
Minimise erosion during construction (e.g. build in winter)
Rehabilitation, maintenance and monitoring of disturbed areas around the canal
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 50
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8 Appendix A: Diatom Results
List of diatom species and associated abundances at the Coucil for Geoscience Canal Project
sites in July 2013.
Taxa C1 C1A C1B C2A C2B C3A C3B
Achnanthidium affine (Grun) Czarnecki 0 4 0 0 0 0 0
ACHNANTHIDIUM F.T. Kützing 0 0 64 0 0 0 0
Achnanthidium eutrophilum (Lange-Bertalot)Lange-Bertalot 0 0 0 4 8 0 0
Achnanthidium macrocephalum(Hust.)Round & Bukhtiyarova 0 0 14 0 0 0 0
Achnanthidium saprophilum (Kobayasi et Mayama) Round & Bukh. 0 0 70 0 0 0 0
Achnanthidium minutissima Kützing v.minutissima 58 292 52 10 0 360 0
Amphora veneta Kützing 0 0 0 10 0 0 0
Brachysira neoexilis Lange-Bertalot 0 0 0 0 0 0 4
Cyclotella meneghiniana Kützing 0 0 0 0 0 0 6
Craticula molestiformis (Hustedt) Lange-Bertalot 0 0 0 4 0 0 0
Cymbella turgidula Grunow 1875 in A.Schmidt 0 0 2 0 0 0 0
Eunotia bilunaris (Ehr.) Mills var. bilunaris 0 0 0 0 4 0 0
Eunotia minor (Kützing) Grunow in Van Heurck 0 4 0 0 0 2 0
Encyonema minutum (Hilse in Rabh.) D.G. Mann 0 0 0 0 0 4 0
FALLACIA A.J. Stickle & D.G. Mann 0 2 0 0 0 0 0
Fragilaria biceps (Kützing) Lange-Bertalot 46 0 0 0 0 0 0
Fragilaria capucina Desmazieres var.capucina 32 0 0 4 0 0 0
Fragilaria capucina Desm. ssp. rumpens (Kütz.) Lange-Bert. ex Bukht. 0 34 78 0 0 0 0
Fragilaria ulna (Nitzsch.)Lange-Bertalot var.acus (Kütz.) 0 2 0 0 0 0 0
Frustulia vulgaris (Thwaites) De Toni 4 4 0 0 0 0 0
Gomphonema auritum A.Braun ex Kützing 0 0 0 0 2 0 0
Gomphonema exilissimum(Grun.) Lange-Bertalot & Reichardt 0 4 0 0 0 0 0
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 54
Taxa C1 C1A C1B C2A C2B C3A C3B
Gomphonema lagenula Kützing 0 0 24 4 62 2 0
GOMPHONEMA C.G. Ehrenberg 0 0 0 0 2 0 0
Gomphonema parvulum (Kützing) Kützing var. parvulum 2 0 6 12 12 8 0
Gomphonema pseudoaugur Lange-Bertalot 0 0 0 2 0 0 0
Gomphonema parvulius Lange-Bertalot & Reichardt 0 24 36 0 0 0 0
Luticola mutica (Kützing) D.G. Mann 0 0 2 0 0 0 0
Meridion circulare (Greville) Agardh var.constrictum (Ralfs) 14 8 0 0 0 0 0
Nitzschia acidoclinata Lange-Bertalot 2 0 2 0 0 2 0
Nitzschia acicularis(Kützing) W.M.Smith 0 0 0 0 0 0 2
Nitzschia amphibia Grunow f.amphibia 0 0 0 2 0 0 0
Navicula antonii Lange-Bertalot 0 0 0 0 0 0 2
Navicula arvensis Hustedt var.maior Manguin 0 0 0 0 0 0 2
NAVICULA J.B.M. Bory de St. Vincent 4 0 0 0 0 0 0
Navicula capitatoradiata Germain 0 0 2 0 0 0 0
Navicula cryptocephala Kützing 2 6 10 0 9 0 70
Navicula gregaria Donkin 0 0 0 0 0 8 0
Navicula heimansioides Lange-Bertalot 0 2 0 0 0 0 0
Nitzschia frustulum(Kützing)Grunow var.frustulum 0 0 0 4 0 0 0
Nitzschia intermedia Hantzsch ex Cleve & Grunow 2 0 0 0 0 0 70
Nitzschia pura Hustedt 0 0 0 0 0 0 212
NITZSCHIA A.H. Hassall 2 0 4 0 0 0 0
Nitzschia linearis(Agardh) W.M.Smith var.linearis 6 0 2 0 0 0 2
Nitzschia nana Grunow in Van Heurck 0 0 4 0 0 0 0
Nitzschia palea (Kützing) W.Smith 10 2 22 292 296 10 22
Nitzschia recta Hantzsch in Rabenhorst 0 2 0 0 0 0 0
Copyright © 2013 Wetland Consulting Services (Pty.) Ltd. 55
Taxa C1 C1A C1B C2A C2B C3A C3B
Navicula rhynchocephala Kützing 0 4 0 0 0 0 0
Navicula symmetrica Patrick 2 0 0 0 0 0 0
Navicula veneta Kützing 0 0 0 12 4 2 4
Nitzschia valdecostata Lange-Bertalot et Simonsen 0 0 2 0 0 0 0
Navicula zanoni Hustedt 0 0 0 2 0 0 0
PINNULARIA C.G. Ehrenberg 0 0 2 0 0 0 0
Planothidium frequentissimum(Lange-Bertalot)Lange-Bertalot 210 6 0 36 0 0 0
Pinnularia subbrevistriata Krammer 2 0 0 2 0 0 2
Surirella angusta Kützing 0 0 0 0 0 2 0
Sellaphora pupula (Kützing) Mereschkowksy 0 0 0 0 1 0 2
Sellaphora seminulum (Grunow) D.G. Mann 2 0 2 0 0 0 0
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9 Appendix B: SASS5 Results
C1A C1B C1 (trib) C2 C3A C3BStones 2 3 2 3 1 4
Marginal vege 2 3 3 2 3 1
Sediment 4 2 1 1 2 1
7 7 4 2 5 0
29 30 12 3 25 0
4.1 4.3 3.0 1.5 5.0 0.0
SASS5 Taxon
SASS5
Sensitivity
Score*
Turbellaria 3 1
ANNELIDA
Oligochaeta (Earthworms) 1 1 1
Hirudinea (Leeches) 3
CRUSTACEA
Potamonautidae* (Crabs) 3 1
Atyidae (Freshwater Shrimps) 8
HYDRACARINA (Mites) 8
EPHEMEROPTERA (Mayflies)
Baetidae 1sp 4 A
Baetidae 2 sp 6 B B
Baetidae > 2 sp 12 A
Caenidae (Squaregills/Cainfles) 6
Leptophlebiidae (Prongills) 9
ODONATA (Dragonflies &
Damselflies)
Coenagrionidae (Sprites and blues) 4 A
Lestidae (Emerald
Damselflies/Spreadwings) 8
Aeshnidae (Hawkers & Emperors) 8 1
Gomphidae (Clubtails) 6
Libellulidae (Darters/Skimmers) 4 A
HEMIPTERA (Bugs)
Belostomatidae* (Giant water bugs) 3
Corixidae* (Water boatmen) 3
Gerridae* (Pond skaters/Water striders) 5 A
Hydrometridae* (Water measurers) 6
Naucoridae* (Creeping water bugs) 7
Nepidae* (Water scorpions) 3
Notonectidae* (Backswimmers) 3
Pleidae* (Pygmy backswimmers) 4
Veliidae/M...veliidae* (Ripple bugs) 5 1
TRICHOPTERA (Caddisflies)
Hydropsychidae 1 sp 4
Cased caddis:
Hydroptilidae 6
Leptoceridae 6 A 1
COLEOPTERA (Beetles)
Dytiscidae* (Diving beetles) 5
Noteridae* 5
Gyrinidae* (Whirligig beetles) 5 A
Haliplidae* (Crawling water beetles) 5
Helodidae (Marsh beetles) 12
Hydraenidae* (Minute moss beetles) 8
Hydrophilidae* (Water scavenger
beetles) 5
Limnichidae (Marsh-Loving Beetles) 10
DIPTERA (Flies)
Ceratopogonidae (Biting midges) 5 1
Chironomidae (Midges) 2 B A C A B
Culicidae* (Mosquitoes) 1
Dixidae* (Dixid midge) 10
Empididae (Dance flies) 6
Ephydridae (Shore flies) 3 1
Muscidae (House flies, Stable flies) 1
Psychodidae (Moth flies) 1
Simuliidae (Blackflies) 5 A 1 A A
Syrphidae* (Rat tailed maggots) 1
Tabanidae (Horse flies) 5
Tipulidae (Crane flies) 5
GASTROPODA (Snails)
Ancylidae (Limpets) 6
Sphaeridae 3
Unionidae (mussels) 6
Lymnaeidae* (Pond snails) 3 A
Physidae* (Pouch snails) 3
Planorbinae* (Orb snails) 3
Thiaridae* (=Melanidae) 3
SITE
Average Score per Taxon
TOTAL No. SASS TAXA
SASS Score
Biotopes Sampled (Rated 1-5)
top related