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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

[email protected]

By:

Wetland Consulting Services (Pty) Ltd

PO Box 72295 Lynnwood Ridge Pretoria 0040 Tel: 012 349 2699 Fax: 012 349 2993 Email: [email protected]

REF: 2013/988

mailto:[email protected]

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

[email protected]

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: [email protected]

mailto:[email protected]

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

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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


........................................................................................................................................................ 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


........................................................................................................................................................ 21

Figure 3-9. Photographs showing impacts observed within the vicinity of Canal 2, including

impacts to water quality, infilling and mining. ................................................................................. 22


........................................................................................................................................................ 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).


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.


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


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.


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”.


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.


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.


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


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


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.


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.


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.


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.


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


Wetland 7.53 85.96

Canal 3

Hillslope Seepage Wetland 0.21 12.00


Wetland 1.01 57.71

Canalised Valley Bottom

Wetland 0.53 30.29


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.



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.



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.


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).


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 3-7. 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.


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 3-9. 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.


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 3-11. Photographs showing impacts observed within the vicinity of Canal 3, including canalisation, water quality impacts, sedimentation and mining.


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.


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).


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


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


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


SASS5, Fish

C3B 26°11'43.93"S

28°11'22.33"E

Canal 3, downstream within the

Elsburgspruit


SASS5, Fish


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


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).


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


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


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.


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


Figure 4-2. Photos taken upstream and downstream of sampling sites along Canal 1, from top to bottom: C1, C2A, C2B


Figure 4-3. Photos taken at aquatic sampling sites C2A and C2B (top row), C3A (second row) and C3B (bottom row)


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)


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


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.


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


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


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.


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


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.


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.


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.


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).


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.


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.


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


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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.


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



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



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


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)