i' ""f - ~s..; -'·: ': The Ge,ohydrology of the Swartkops River Basin - Uitenhage Region, Eastern Cape Town LIMONT .GORDON ALEXANDER MACLEAR ' ·' BSc (Hons) Joint - GeologyCape & Geography Rhodes University,of Grahamstown .•,( .·'f Submitted in fulfilment of the requirements for the degree of MASTER OF SCIENCE ·~';.:·• i_" in the Department of Geological Sciences ~ ~.'·. Faculty of Science .. ..< University L···\ University of Cape Town March 1996 -· _,,; \' :;;. .. ~; ': "''. : _J ~~__._I.~ The copyright of this thesis vests in the author. No quotation from it or information derived from it is to be published without full acknowledgementTown of the source. The thesis is to be used for private study or non- commercial research purposes only. Cape Published by the University ofof Cape Town (UCT) in terms of the non-exclusive license granted to UCT by the author. University ,. ' i. ~ .. No Water.~:·~-.:~~ No Nothing ! National Water Conservation Campaign caption Department of Water Affairs and Forestry- 1995. ABSTRACT A hydrocensus of all groundwater users in the Swartkops River Basin was conducted in 1992 and 1993 to assess the occurrence and quality of groundwater in the Basin, as well as the characteristics of the various aquifers in the Basin. The extent of pollution of the groundwater reserves was noted. This specialist study was carried out to assist the Department of Water Affairs and Forestry in fonnulating a water quality management plan for the river basin, and was prompted by concern regarding the deteriorating water quality of the region. It was detennined that the only aquifer in the river basin which was severely polluted in places was the Swartkops River Alluvial Aquifer. Following recommendations arising from the initial survey, a groundwater monitoring network of shallow boreholes was installed in the alluvial aquifer in 1994 and groundwater sampling runs commenced in 1995. Groundwater occurs in the region in a shallow alluvial aquifer and a deeper fractured secondary aquifer. These aquifers are separated from one another by an impenneable, confining layer of Cretaceous sediments in the central and eastern parts of the study area, causing artesian conditions in places. The groundwater of the aquifers in the study area has a sodium-chloride character of low salinity in the western high-lying portion of the study area, with mineralisation increasing eastward, as aquifer lithology and distance from recharge sources change. The hydrochemical character of the groundwater is a function of the proximity of the basin to the sea, as well as connate conditions existing in the sediments of marine origin. It is sho~ that pollution of both the surface and shallow sub-surface water bodies is occurring, mainly in the industrial and residential areas of Uitenhage and Despatch. These polluted zones are not extensive when compared with the whole catchment area but have a definite effect on local conditions. Estimations of pollution load volumes are made based on hydraulic parameters derived from aquifer tests. This study represents an overview of the geohydrology of the Swartkops River Basin, thereby providing a reference tool for water-resource management purposes in the region. It includes a unique study on the geohydrology of the Swartkops River Alluvial Aquifer and the extent of pollution of this aquifer, as well as a detailed account and discussion on the historical and present factors affecting variations in groundwater flow and artesian conditions in the area. A summary of suggested aquifer management practices is given to ensure the long-tenn sustainability of the groundwater resources of the river basin. SAMEV ATTING 'n Hidrosensus van al die grondwater-verbruikers in die Swartkopsrivieropvangsgebied is in 1992 en 1993 uitgevoer om die bestaande grondwatergehalte en -voorkoms in die gebied, sowel as die eienskappe van die veskillende waterdraers te bepaal. Die omvang van besoedeling van die grondwaterbronne is aangeteken. Die spesialiteitstudie, uitgevoer om die Departement Waterwese en Bosbou met die opstel van 'n watergehalte bestuursplan vir die rivierkom behulpsaam te wees, is deur kommer rakende afuemende watergehalte in die gebied gemotiveer. Dit is vasgestel dat alleenlik die alluvialewaterdraer noemenswaardig by plekke besoedel is. 'n Grondwatennoniteringsnetwerk van vlak boorgate is in 1994 gei"nstalleer, na aanleiding van aanbevelings atkomstig van die oorspronklike hidrosensus, en monitering is in 1995 begin. Grondwater kom in die gebied voor in 'n vlak riviergruisafsetting en 'n dieper genate sekondere waterdraer. Hierdie waterdraers word deur 'n ondeurlaatbare laag Kryt afsettings van mekaar geskei, met gevolglike artesiese toestande. Die grondwater van die waterdraers is 'n natriumchloried tipe, van goeie gehalte in die westelike hoerliggende gedeelte van die studiegebied, terwyl 'n toename in mineralisasie ooswaarts merkbaar is. Die hidrochemiese eienskappe kan gekoppel word aan veranderings in die waterdraende fonnasies asook die konnaatwater wat in die afsettings voorkom. Dit is bewys dat plaaslike besoedeling van oppervlak- en grondwater hoofsaaklik in die industriele en residensiele gebiede van Uitenhage en Despatch voorkom. Hierdie besoedelingsones is in vergelyking met die totale opvangsgebied nie groot nie, maar het 'n merkbare uitwerking op plaaslike toestande. Beramings van besoedelingsladings, gebaseer op hidrouliese parameters afkomstig van waterdraertoetse is gemaak. Hierdie studie verteenwoordig 'n oorsig van die geohidrologie van die Swartkopsrivieropvangsgebied en vonn 'n waardevolle basis vir waterbronbestuur in die gebied. Dit sluit 'n unieke studie van die geohidrologie van die Swartkopsrivier alluviale waterdraer en besoedeling hiervan in. 'n Volledige beskrywing van die faktore wat grondwatervloei en artesiese toestande in die gebied bei"nvloed is ingesluit. 'n Opsomming van waterdraerbestuursstrategie om die grondwaterbronne van die rivierkom te beveilig is gegee. Frontispiece: Landsat thematic image of the Swartkops River Basin (bands 4-R 5-G 3-B, June 1990) ACKNOWLEDGEMENTS The following people and organisations are thanked for their contributions to this study: • Henk van Kleef (DW A&F Geohydrology Directorate - Port Elizabeth) for his thorough data collection during all stages of the study, and without whom this project would not have been possible. • All the residents in the study area - especially the farmers - who freely gave access to their land and co-operated by providing information on their groundwater abstraction points during the initial hydrocensus. • The Department of Water Affairs and Forestry (DWA&F) for financing the study through the University of Cape Town, as well as giving permission to publish the data obtained. • Werner Stadler (GIMS consultant to DWA&F - Cape Town) for his invaluable help in the map and data composition on Arc/Info GIS (Geographical Information System) and Rooseda Lippert (DWA&F Geohydrology Directorate - Cape Town) for her accurate digitising of the coverages. • Werner Vosloo (DWA&F Water Quality Management Directorate - Port Elizabeth) for his interest in the study and valuable inputs on aspects relating to water pollution and surface water quality. • Prof. Anton Le Roex (Dept. of Geological Sciences - UCT) for readily providing assistance with the "mixer" program used for the chemical optimisation study. • Drs. Phil Kempster (DWA&F - Institute for Water Quality Studies) and Peter Wade (Watertek - CSIR) for their advice on water chemistry. • My supervisors, Prof. James Willis and Dr. Martin Fey (Dept. of Geological Sciences - UCT) for accepting the project for consideration towards a Masters dissertation and their subsequent reviews of the drafts and advice. • Alan Woodford (DWA&F Geohydrology Directorate - Cape Town) and Jeff Jolly (Groundwater Consulting Services - Cape Town) for acting as mentors, providing guidance and reviewing the drafts. • The software package Groundwater for Windows Verl.l developed by the United Nations was used extensively for graphical data presentation and analyses. • And lastly, but most importantly, my parents for all their support and inspiration and my children for providing me with the will to go on! TABLE OF CONTENTS Section Page List of Maps .................................................................................................................................... iv List of Tables .................................................................................................................................. iv List of Figures ....................................................................................................................· ............ iv List of Equations ............................................................................................................................. v List of Plates .................................................................................................................................... v List of Orthophotos ..............................· ........................................................................................... v List of Appendices ........................................................................................................................... v Glossary .......................................................................................................................................... vi List of Abbreviations ........................... 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