The Use of Isotope Hydrology to Characterize and Assess Water Resources in South(ern) Africa TT 570/13 The Use of Isotope Hydrology to Characterize and Assess Water Resources in South(ern) Africa in South(ern) Resources Water and Assess Characterize to Hydrology of Isotope Use The TT 570/13 Tamiru Abiye (Editor) TT 570/13 THE USE OF ISOTOPE HYDROLOGY TO CHARACTERIZE AND ASSESS WATER RESOURCES IN SOUTH(ERN) AFRICA Tamiru Abiye Report to the Water Research Commission by School of Geosciences, University of the Witwatersrand Contributors: Balt Verhagen Carl Freese Chris Harris Craig Orchard Eddy van Wyk Gideon Tredoux Jennifer Pickles Julius Kollongei Liang Xiao Mannie Levin Michael Butler Roger Diamond Seraphine Grellier Siep Talma Simon Lorentz Tamiru Abiye Vincent Chaplot Yongxin Xu WRC Report No TT 570/13 November 2013 Obtainable from Water Research Commission Private Bag X03 Gezina, 0031 [email protected] or download from www.wrc.org.za The publication of this report emanates from a project entitled The use of isotope hydrology to characterize and assess water resources in South(ern) Africa (WRC Project No. K5/1907) DISCLAIMER This report has been reviewed by the Water Research Commission (WRC) and approved for publication. Approval does not signify that the contents necessarily reflect the views and policies of the WRC nor does mention of trade names or commercial products constitute endorsement or recommendation for use. © WATER RESEARCH COMMISSION 2 THE USE OF ISOTOPE HYDROLOGY TO CHARACTERIZE AND ASSESS WATER RESOURCES IN SOUTH (ERN) AFRICA Environmental isotopes are routinely employed world-wide in the study of groundwater and surface water, as they provide unique information on transport and interconnectivity of water resources and reservoirs. The term environmental isotope embraces the measurement of isotope ratios of the elements making up the water molecule and of substances dissolved in water that could give rise to hydrogen and oxygen. These are subject to environmental processes and undergo changes, for example during evaporation. Water in specific environments, thus, obtains isotopic labels that are transported and can be traced along the flow pathway. The sustainable development and management of groundwater resources requires an accurate assessment of their occurrence, availability, sustainability and vulnerability to deterioration. Environmental isotope studies have been shown to provide important information useful in the effective management of water resources in different parts of the World. The overall contribution of this project will be to raise awareness of environmental isotope hydrology as a useful tool in the assessment of water resources at different spatial scale both at local and catchment level. Generally, the project focuses on previously executed studies as well as newly undertaken investigations which will advance the understanding of the selected individual studies. Where further information has been gathered since the original investigation, interpretations on the capability of isotopes in water resource assessment have been re- interpreted. In particular, the involvement of students in this endeavour exposed them to the analytical disciplines, approaches and methodology of isotope hydrology as well as to the concepts, models and feel involved in the interpretation and integration of the isotope data. The main objectives of the project were: • To identify past studies and to undertake new studies suitable for demonstrating the contribution of isotope hydrology to an enhanced under-standing of the systems studied • Through re-assessment of isotope data to re-interpret former conclusions and identify data gaps, where new study areas are identified, to gather all necessary isotope, hydro geochemical and hydrogeological data, and produce the required conceptual and numerical framework highlighting the role of isotopes • To gather all necessary isotope, hydro geochemical, hydrogeological and geological data, and produce the required conceptual and numerical framework highlighting the role of isotopes • Develop course material on the discipline of isotope hydrology. This project has involved a complex work programme with the participation of many individuals and institutions executing different studies. The main method focuses on identifying completed and on-going isotope related project in different institutions. In some cases new isotope application projects have been identified. In the pre-project phase, a team of researchers were brought together in the light of individual interest, activity, potential contribution to the aims of the project such as existing or previous studies, knowledge of potential study areas etc. The team has identified nine existing and two new projects that form this report. 3 4 Table of Contents THE USE OF ISOTOPE HYDROLOGY TO CHARACTERIZE AND ASSESS WATER RESOURCES IN SOUTH (ERN) AFRICA ................................................................................................................................................................. 3 APPLICATION OF ISOTOPE TECHNIQUES TO TRACE LOCATION OF LEAKAGE FROM DAMS AND RESERVOIRS .. 9 APPLICATION OF ISOTOPE TECHNIQUES TO TRACE POLLUTION IN MONITORING BOREHOLES OF WASTE DISPOSAL SITES .................................................................................................................................................. 24 OXYGEN AND HYDROGEN ISOTOPES RECORD OF CAPE TOWN RAINFALL AND ITS APPLICATION TO RECHARGE STUDIES OF TABLE MOUNTAIN GROUNDWATER.............................................................................................. 38 TOWARDS A MANAGEMENT MODEL FOR THE EXPLOITATION OF GROUNDWATER FROM THE TAAIBOSCH KAROO GRABEN, LIMPOPO PROVINCE .............................................................................................................. 53 RAINFALL AND GROUNDWATER ISOTOPE ATLAS .............................................................................................. 83 CORRELATIONS BETWEEN RAINWATER AND GROUNDWATER GEOCHEMISTRY SIGNATURES WITH REFERENCE TO EPISODIC RAINFALL EVENTS IN SEMI-ARID ENVIRONMENTS, SOUTH AFRICA ....................... 102 KALAHARI GROUNDWATER ISOTOPE SYNTHESIS ............................................................................................ 111 ENVIRONMENTAL ISOTOPE CONTRIBUTION TO A MULTI-DISCIPLINARY GROUNDWATER RESOURCE ASSESSMENT IN EASTERN BOTSWANA ........................................................................................................... 123 ISOTOPE AND CHEMICAL FEASIBILITY OF GROUNDWATER IN GORDONIA AS A SOURCE FOR A LOCAL RETICULATED SUPPLY ...................................................................................................................................... 133 SURFACE WATER AND GROUNDWATER INTERACTION IN THE UPPER CROCODILE RIVER BASIN .................. 141 PROGRAM DEBUGGING AND APPLICATION THROUGH CASE STUDIES........................................................... 165 USE OF ISOTOPES IN CATCHMENT HYDROLOGY, VEGETATION UPTAKE AND NON-POINT SOURCE POLLUTION ANALYSES ......................................................................................................................................................... 170 APPENDIX A: HILLSLOPE RESPONSE ANALYSIS FOR THE WEATHERLEY CATCHMENT ..................................... 201 APPENDIX B: RAINFALL – RUNOFF EVENT ISOTOPE RESPONSES, WARTBURG CATCHMENT ......................... 203 5 Acknowledgements The authors wish to thank the Water Research Commission for funding this project and the following Steering Committee members: Shafick Adams Water Research Commission Stephan Woodborne CSIR Eddy van Wyk Department of Water Affairs now Golder Adam West University of Cape Town Henk Coetzee Council for Geoscience Gideon Steyl University of the Free State Accompanying CD 1. Isotope Hydrology References 2. Isotope Hydrology Teaching Material 3. MSExcel Box Model and Guidelines 6 TASK LEADERS 1. Prof. Balt Verhagen, School of Geosciences, University of the Witwatersrand, Johannesburg. Email: [email protected] 2. Mr. AS Talma, P.O. Box 72906, Lynnwood Ridge, 0040, 138 Genl Louis Botha Avenue, Lynnwood Ridge, Pretoria, Email: [email protected] 3. Dr. Mannie Levin, P. O. Box 1731, Faerie Glen, 0043, Waterpoort Street 986C, Faerie Glen, Pretoria, Email: [email protected] 4. Mr. Michael Butler, iThemba LABS, Environmental isotope group, Private Bag 11, Wits 2050, Johannesburg. Email: [email protected] 5. Prof. Chris Harris, University of Cape Town, Dept of Geological Sciences, Rondebosch, Cape Town, Email: [email protected] 6. Prof. Tamiru A. Abiye, School of Geosciences, University of the Witwatersrand, Johannesburg. Email: [email protected] 7. Prof. Yongxin Xu, University of the Western Cape, Groundwater Group, Dept. of Earth Sciences, Cape Town, Email: [email protected] 8. Prof. Simon Lorentz, University of KwaZulu-Natal, School of Bioresources Engineering and Environmental Hydrology, Scottsville P O Box X01, Pietermaritzburg. Email: [email protected] 7 8 APPLICATION OF ISOTOPE TECHNIQUES TO TRACE LOCATION OF LEAKAGE FROM DAMS AND RESERVOIRS M Levin and B Th Verhagen EXECUTIVE SUMMARY Dams and reservoirs are vital to the sustainability of a large part of the world's population for water supply, irrigation, flood protection and hydropower. The two biggest concerns regarding dam leakage are safety or economic impact. Dam leakages have led to disasters is cases where dam walls collapsed. Dam leakage can cause a big