THE EFFECT OF FLOODS AND HIGH RAINFALL ON THE WATER QUALITY IN SELECTED SUB-AREAS OF THE UPPER VAAL CATCHMENT. Sonia Merolla Minor dissertation submitted in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE in ENVIRONMENTAL MANAGEMENT Faculty of Science University of Johannesburg Supervisor: Prof. J. T. Harmse September 2011 ABSTRACT The purpose of this study was to determine the effect of flooding and high rainfall on water quality at selected points along the Vaal River, Wilge River and Vaal Dam that make up part of the Upper Vaal Catchment Area. Four study sites were selected, three along a section of the Vaal River that flows from Standerton (site S-ST_NEW) through Villiers (site C-VV) into the Vaal Dam ( C-VD21). The fourth site is on the Wilge River at Frankfort (C-WF) and joins with the Vaal River at site C-VD21 in the Vaal Dam. For each of these four sites seven water quality parameters, namely Chemical Oxygen Demand (COD), conductivity, chloride, fluoride, orthophosphate, sulphate and faecal coliforms where used to determine if there is a change in water quality during flooding and high rainfall in a six year period from 2005 to 2011. This period included the 2006 and 2011 floods and the 2009 high rainfall period. The results of this study demonstrated two types of changes that flooding and high rainfall can cause, either a dilution effect or a concentrating effect. Dilution is caused by low runoff of a particular pollutant/contaminant with an increase in water volume while the concentrating effect is due to a much increased runoff of a particular pollutant/contaminant. Results were not consistent. However general trends could be observed at specific sites. As a general rule, dilution occurred in the following parameters: conductivity; chloride, orthophosphate, COD and faecal coliforms. The remaining water quality parameters, namely fluoride and sulphate showed a general tendency to increase in concentration during flooding and high rainfall. The effect of floods on the quality of the water using the Vaal Dam Reservoir Forum (VDRS) water quality guidelines for sites C-VV, C-WF and C-VD21 and the Sewage Works Compliance to general standard for site S-ST_NEW was also studied. In general, flooding and high rainfall had very little effect in changing water quality, in that parameter levels were not altered significantly enough to cause a change in water quality. However, in some circumstances water quality was reduced. The statistical two-tailed one-sample t-test and p-value for the most part did not yield any significant difference in water quality during flooding and high rainfall and the six- year average. i ACKNOWLEDGEMENTS It is with sincere appreciation and gratitude that I wish to acknowledge the following people and institutions for the great efforts and contributions that they made in assisting me with the completion of this dissertation • Prof. J. T. Harmse, my supervisor, for his guidance and support. • Mr Francois van Wyk, Catchment Manager, Rand Water for his time, effort and support during the completion of this study. • Rand Water, under the auspices of Mr Francois van Wyk, who supplied the raw data for water quality. • South African Weather Services, especially Coleen de Villiers, who supplied raw data for rainfall. • Mike Muller under the auspices of Statkon who assisted with using Excel Microsoft to plot graphs. • Last, but not least, I would like to thank my family and friends for their love, patience and moral support and in particular my friend Antonella for her advice and support. ii TABLE OF CONTENTS Page ABSTRACT…..…………………………………………………………………… i ACKNOWLEDGEMENTS……………………………………………………… ii LIST OF FIGURES………………………………………………………………. v LIST OF TABLES………………………………………………………………... vi ACRONYMS USED ……………………………………………………………… vii 1. INTRODUCTION……………………………………………………………….. 1 2. PROBLEM STATEMENT AND OBJECTIVES……………………………… 5 3. WATER QUALITY AND SUSTAINABLE DEVELOPMENT………………. 6 3.1. Sustainable development of water in South Africa………………………... 11 3.1.1. Water legislation and water management in South Africa………… 11 3.1.2. Effective and sustainable management of water quality in South Africa………………………………………………………... 15 3.2. Rand Water’s management and supply of good quality potable water……. 18 4. CLIMATE AND WATER RESOURCES OF SOUTH AFRICA……………... 22 4.1. Water availability and water quality in South Africa……………………… 25 4.2. Climate change and its effect on future water supply in South Africa…….. 29 4.3. Floods and their impact on surface water resources and water quality……. 33 5. WATER POLLUTION AND WATER QUALITY…………………………….. 36 5.1. Water pollution and its effects on sustainability in South Africa………….. 36 5.1.1. Sources of Water pollution in South Africa……………………….. 37 5.1.2. Water pollution problems in South Africa………………………… 39 5.2. Water quality parameters…………………………………………………... 42 5.2.1. Physical Properties – Conductivity………………………………………… 44 5.2.2. Chemical parameters………………………………………………………. 45 5.2.2.1. Chloride………………………………………………………….. 45 5.2.2.2. Fluoride…………………………………………………………… 46 5.2.2.3. Phosphate…………………………………………………………. 47 5.2.2.4. Sulphate……………………………………………………………48 iii 5.2.3. Organic Parameters - Chemical Oxygen Demand (COD)…………………. 49 5.2.4. Microbial Parameters – Faecal coliforms………………………………….. 50 6. THE STUDY SITE……………………………………………………………….. 51 6.1. Overview and Location of the Upper Vaal Catchment Area………………. 51 6.2. Description of the Upper Vaal Catchment Area…………………………... 52 6.3 Land use and water availability of the Upper Vaal Catchment Area……… 54 7. DATA COLLECTION AND METHOD OF ANALYSIS……………………... 55 7.1. Data Collection and Location of Sample Sites…………………………….. 55 7.2. Data Analysis………………………………………………………………. 58 7.3. Shortcomings of Data……………………………………………………… 61 8. RESULTS AND DISCUSSION………………………………………………….. 62 8.1. Effects of floods and high rainfall on conductivity………………………………... 64 8.2. Effect of floods and rainfall on the chemical component of water………………… 66 8.2.1. Chloride……………………………………………………………………..66 8.2.2. Fluoride…………………………………………………………………….. 70 8.2.3. Orthophosphate…………………………………………………………….. 72 8.2.4. Sulphate……………………………………………………………………..75 8.3. Effect of floods and rainfall on the Chemical Oxygen Demand of water…………. 77 8.4. Effect of floods and rainfall on faecal coliform count in water……………………. 80 8.5. Statistical Analysis…………………………………………………………………. 83 9. CONCLUSIONS AND RECOMMENDATIONS……………………………… 85 REFERENCE LIST………………………………………………………………. 89 APPENDICES…………………………………………………………………….. 97 iv LIST OF FIGURES Figure 1: The nineteen Water Management Areas of South Africa………………….. 14 Figure 2: Rand Water’s service supply area………………………………………….. 19 Figure 3: Rand Water’s bulk distribution sales for 2009/2010………………………. 19 Figure 4: The median annual rainfall of South Africa……………………………….. 23 Figure 5: The three driving forces and their effects on water resources on water resources in South Africa…………………………………………………... 26 Figure 6: Estimated water balance for major catchment areas for South Africa in 1996 and 2030……………………………………………………………… 27 Figure 7: The Conservation Status of the main South African Rivers……………….. 28 Figure 8: The Upper Vaal Catchment with surrounding Water management Areas (WMA) showing sub-areas and sub-catchments…………………… 52 Figure 9: Rand Water’s sample points for the Upper Vaal Catchment area…………. 56 Figure 10: South African Weather Services weather station locations that were used to obtain rainfall readings for this study…………………………………… 57 Figure 11: Total monthly rainfall and conductivity nitrate concentration for four sites along the Upper Vaal Catchment…………………………………………... 65 Figure 12: Total monthly rainfall and changing chloride concentration for four sites along the Upper Vaal Catchment…………………………………………... 69 Figure 13: Total monthly rainfall and changing Fluoride concentration for four sites along the Upper Vaal Catchment…………………………………………... 71 Figure 14: Total monthly rainfall and changing orthophosphate concentration for four sites along the Upper Vaal Catchment………………………………... 74 Figure 15: Total monthly rainfall and changing Sulphate concentration for four sites along the Upper Vaal Catchment…………………………………………... 76 Figure 16: Total monthly rainfall and Chemical Oxygen Demand (COD) for four sites along the Upper Vaal Catchment…………………………………………... 79 Figure 17: Total monthly rainfall and changing faecal coliforms count for four sites along the Upper Vaal Catchment…………………………………………... 82 v LIST OF TABLES Table 1: Annual rainfall distribution and climatic classification in South Africa…... 23 Table 2: Increase in Green House Gases since 1970………………………………... 29 Table 3: Pollution problems resulting from impacts of human activities on water resources…………………………………………………………………… 38 Table 4: Some of the parameters that can be used to measure the properties of water…………………………………………………………..………… 43 Table 5: Location of monitoring sites within the Upper Vaal Catchment…………... 53 Table 6: The water quality parameters used in this study for Upper Vaal Catchment………………………………………………………………….. 59 Table 7: Water quality guidelines used for the Upper Vaal Water Management Area………………………………………………………………………… 60 Table 8: Conductivity at the four sampling sites during the flooding/high rainfall periods……………………………………………………………………… 66 Table 9: Concentration of Chloride at the four sampling sites during the flooding/high rainfall periods ……………………………………………. 68 Table 10: Concentration of Fluoride at the four sampling sites during the flooding/high rainfall periods ..…………………………………………… 72 Table 11: