Lower Vet River Water Quality Situation Analysis with Special Reference to the OFS Goldfields CEHerold • WV Pitman • AK Bailey • I Taviv Report to the Water Research Commission by Stewart Scott Incorporated WRC Report No 523/1/96 Disclaimer This report emanates from a project financed by the Water Research Commission (WRC) and is approved for publication. Approval does not signify that the contents necessarily reflect the views and policies of the WRC or the members of the project steering committee, nor does mention of trade names or commercial products constitute endorsement or recommendation for use. Vrywaring Hierdie verslag spruit voort uit 'n navorsingsprojek wat deur die Waternavorsingskommissie (WNK) gefinansier is en goedgekeur is vir publikasie. Goedkeuring beteken nie noodwendig dat die inhoud die siening en beleid van die WNK of die lede van die projek-loodskomitee weerspieel nie, of dat melding van handelsname of -ware deur die WNK vir gebruik goedgekeur of aanbeveel word nie. LOWER VET RIVER WATER QUALITY SITUATION ANALYSIS WITH SPECIAL REFERENCE TO THE OFS GOLDFIELDS FINAL REPORT to the WATER RESEARCH COMMISSION bv C E Herald (Project Leader) W V Pitman A K Bailey and I Taviv STEWART SCOTT INCORPORATED (Consulting Engineers) P O Box 784506, Sandton, 2146 WRC Report No. 523/1/96 ISBN 1 86845 233 6 ACKNOWLEDGEMENTS The research in this report emanated from a project funded by the Water Research Commission and entitled: "Lower Vet River water quality situation analysis with particular reference to the OFS Goldfields". The Steering Committee responsible for this project, consisted of the following persons: Mr H M du Plessis Water Research Commission (Chairman) Mr A G Reynders Water Research Commission Mr F P Marais Water Research Commission (Committee Secretary) Mr S A P Brown Department of Water Affairs and Forestry Mr F C van Zyl Department of Water Affairs and Forestry Dr J van der Merwe Department of Water Affairs and Forestry Dr A Kuhn Department of Water Affairs and Forestry Mr H P J Pretorius Department of Water Affairs and Forestry Mr P J J Basson Department of Water Affairs and Forestry Mr G Quibell Department of Water Affairs and Forestry Prof F D I Hodgeson Institute for Ground-water Studies, U.OFS Dr V E Cogho Trans-Natal Collieries Ltd Mr N Rossouw Division of Water Technology, CSIR Dr C E Herold Stewart Scott Incorporated (Project Leader) Mr A K Bailey Stewart Scott Incorporated Mrs I Taviv Stewart Scott Incorporated The financing of the project by the Water Research Commission and the contribution of the members of the Steering Committee is acknowledged gratefully. This project was only possible with the co-operation of many individuals and institutions. The authors therefore wish to record their sincere thanks to the following: Department of Water Affairs and Forestry, in particular Dr J van der Merwe and Mr H P J Pretorius for information regarding pollution sources, Messrs H Pretorius and F Viviers for information regarding the Sand-Vet GWS Scheme, Mr SAP Brown for guidance regarding water quality management policy and the report structure, Dr A Kuhn, for advice regarding the appV"L... «.' «u= j.n.. water ^uaiity Guidelines, Mr F C van Zyl for organisation of the public information meeting held in Welkom, Mr J Schutte for providing hydrological and water quality records, Messrs H Keuris and B du Plessis for the re-evaluation of weir discharge tables; Department of Nature Conservation, in particular Mr J Hardy for information regarding water quality requirements for the natural environment; Welkom Municipality, in particular Messrs R Spies and P Bezuidenhout for water use data; Virginia Municipality, for water use data; AB0O29.1 2 Senekal Municipality/ in particular Mr R Botha, for water use data; Bultfontein Municipality, in particular Mr C de Jager, for water use data; Henneman Municipality, in particular MrJWK Scholtz, for water use data; Hoopstad Municipality, for water use data; Theunissen Municipality, in particular Mr R Franken, for water use data; Winburg Municipality, in particular Mr T D Botha, for water use data; Goldfields Water, in particular Mr A J Dippenaar, for water supply and water quality data; Harmony Gold Mine, in particular Mr R Zorab and A Uys for the provision of information regarding water use water quality data; Freegold Mines, in particular Messrs D Bell, A Howard and J R Rossouw for the provision of information regarding water use and water quality data for mines in the Freegold group; St Helena and Unisel Gold Mines, in particular Messrs H Laycock, Smuts and Townsend for the provision of information regarding water use water quality data; Oryx Gold Mine, in particular Messrs H Dodds, Visser, A van Niekerk and M van der Merwe for the provision of information regarding water use wateT quality data; Beatrix Gold Mine, in particular Messrs J Vollenbroek and M Meijer for the provision of information regarding water use water quality data; H J Joel Gold Mine, in particular Messrs P Russel and H Opperman for the provision of information regarding water use water quality data; Soils and Irrigation Research Institute, in particular Dr Dries van der Merwe for advice regarding irrigation soils in the lower Vet catchment; University of the Orange Free State, Institute for Ground-water Studies, in particular Professor F D I Hodgeson for ground-water data; SRK, in particular Messrs G Murray and R McNeil for water quality data; The irrigation farmers who provided valuable information in response to the questionnaire. AB0Q29.1 (i) TABLE OF CONTENTS Page EXECUTIVE SUMMARY ES.l 1. INTRODUCTION 1.1 2. OVERVIEW OF WATER USE 2.1 3. PROVISIONAL WATER QUALITY USER REQUIREMENTS 3.1 4. POLLUTION SOURCES 4.1 5. ASSESSMENT OF EXISTING MONITORING SYSTEMS 5.1 6. NATURALISATION OF STREAMFLOW 6.1 7. HYDRO-SALINITY MODEL CALIBRATION 7.1 8. ESTIMATION OF TDS LOADS 8.1 9. EVALUATION OF SALINITY STATUS 9.1 10. CONCLUSIONS 10.1 11. RECOMMENDATIONS 11.1 APPENDIX A MAPS APPENDIX B ; TERMS OF REFERENCE FOR THE VET RIVER WATER QUALITY SITUATION ANALYSIS APPENDIX C WATER BALANCE FOR THE OFS GOLDFIELDS APPENDIX D STATISTICAL SUMMARY OF OBSERVED WATER QUALITY DATA APPENDIX E : SAND RIVER AND SAND RIVER CANAL EC GRAPHS APPENDIX F : HYDRO-SALINITY MODELLING: STATISTICS AND GRAPHS OF RESULTS AB0029.1 EXECUTIVE SUMMARY AIM The main aim of the study is to evaluate the surface water salirtity status of the Lower Vet River catchment and identify the main factors affecting the status. MOTIVATION The major water quality management goal of the Department of Water Affairs and Forestry (DWA&F) is to maintain fitness for use of the country's water resources on a sustained basis. Attainment of this management goal requires the setting of source water quality objectives. The water quality situation analysis is the first step in the process of setting these objectives. The DWA&F is in the process of setting water quality objectives for water sources on a prioritised basis. Owing to the water quality problems being experienced, the Lower Vet catchment was given a high priority and selected as one of the first sources for the setting of water quality objectives. TERMS OF REFERENCE Scope The Vet River catchment is shown in Fig. 1. The main focus of the study was on that portion of the catchment influenced by pollution sources in the OFS Goldfields mining area. The water quality situation analysis was confined to the study of Total Dissolved Salts (TDS) and its main inorganic constituents in the surface water. Only data available up to the end of September 1992 was included in the analysis. Hence subsequent changes in the water quality status will not be reflected. Specific tasks The specific tasks included in the study are summarised as follows: • determine water quality requirements for recognised users; • document sources of pollution; • assess existing water quality monitoring systems; • patch and naturalise hydrological records; • estimate diffuse source salt loads; and • evaluate the present water quality status of the catchment. The main findings of the study are discussed under the report chapter headings in the following sections. ES.2 %& TOWN CATCHMENT BOUNDARY JT] MINING AREA P5 PRIMARY STUDY AREA SECONDARY STUDY AREA FLOW GAUGE C4HOO4 {BLOEMFONTEIN Z6-E 27*E Fig. 1 : Map of Vet River catchment WATER USE (Chapter 2) There is a high degree of inter-dependence between the different water users in the OFS Goldfields region. The following is an overview of water use and water balances in the study area. Water supply The main suppliers of water are the Sand-Vet Government Water Scheme (GWS), which draws water from Allemanskraal and Erfenis Dams, and Goldfields Water, which draws most of its raw water from the Vaal River. A number of towns abstract water from local water sources. The Sand-Vet GWS provides water mostly for irrigation use, part of which is supplied direct from the canals and part from the lower Vet River. It is only the latter part that could be affected by pollution emanating from the OFS Goldfields area. Of the towns supplied from the Sand-Vet river system, only Hoopstad, adjacent to the lower Vet River, is likely to be affected by pollution sources in the OFS Goldfields region. The main crops irrigated from the Sand-Vet system are wheat, maize, fodder crops, potatoes, other vegetables, ground-nuts and sunflowers. Several contradictions and deficiencies were found in the water use data for the Sand-Vet GWS. The most serious of these is the apparent large under-estimation of the actual irrigation supply from the canals. AB0Q29.1 ES.3 Effluent discharge Most of the purified sewage effluent generated in the study area is re-used by local mines and to irrigate parks, gardens and sports fields.