Assessement of the Impacts of Pollution on Water Quality in the Calueque-Oshakati Canal in North-Central Namibia
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UNIVERSITY OF ZIMBABWE ASSESSEMENT OF THE IMPACTS OF POLLUTION ON WATER QUALITY IN THE CALUEQUE-OSHAKATI CANAL IN NORTH-CENTRAL NAMIBIA. By SHUUYA MATHEUS. KUUTONDOKWA A DISSERTATION SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTERS IN INTERGRATED WATER RESOURCES MANAGEMENT (IWRM) Faculty of Engineering Department of Civil Engineering JUNE 2008 Assessment of the impacts of pollution on water quality in the Calueque-Oshakati Canal in north- central Namibia. ABSTRACT North Central Namibia which is home to almost half of Namibia‟s estimated 2 million people, like the whole of Namibia is heavily dependent on water sources from neighbouring countries for secure water supplies. A good example is the Calueque- Oshakati Canal which was built to convey water to the Region from the Kunene River in Angola. Due to population expansion, traditional sources of water could no longer meet the water demand in the Region and they increasingly became susceptible to pollution and contamination. There are four water purification plants (Olushandja, Ombalantu, Ogongo and Oshakati) abstracting water from the Canal and distributing it to the surrounding villages and urban centres. The Canal is however exposed to pollution due to poor sanitation and other land use activities in the basin. The objective of this study was to assess the impacts of pollution on water quality and its subsequent effects on the water suitability for the various intended uses (Aquaculture, irrigation and potable use) and its implications on the water purification processes. Water samples were collected at four points along the Canal from February to April 2008 with the furthest sampling point upstream situated at the Canal entry into Namibia borders and furthest point down stream located at the end of the Canal. The following physico-chemical and biological parameters were determined: temperature, dissolved oxygen, pH, turbidity, total dissolved solids, sodium, Calcium, Magnesium, total hardness, Nitrate, and Escherichia coli. Water treatment plant performance data for the year 2006/2007 of the four water purification plants were obtained from NAMWATER with monthly average values of pH, turbidity, coagulants and chlorine used, and the cost of chemicals used. Jar tests were also carried out to confirm the impacts of pollution on water purification process. Water samples were collected at four points along the Canal from February to April 2008 with the furthest sampling point upstream situated at the Canal entry into Namibia and furthest point down stream located at the end of the Canal. Temperatures at all stations averaged between 24ºc and 26.7ºc, dissolved oxygen averaged between 3.9 and 4.7mg/l at all sampling stations, pH values averaged between 6.9 to 7.6, turbidity averaged 111NTU upstream and 243NTU down stream. Total dissolved solids concentrations were 43mg/l upstream and 68mg/l down stream, total hardness was 15mg/l as CaCo3 upstream and 24mg/l as CaCo3 downstream while nitrate concentrations both up stream and down stream were below 0.1mg/l. and E.coli averaged 4 Most probable number per 100ml (MPN/100ml) upstream and 42 MPN/100ml. Jar test results indicated that chemical dosages increased from upstream to down stream treatment plants, Olushandja, 16mg/l, Ombalantu 18mg/l, Ogongo 29 mg/l and Oshati 38mg/l. Despite the increase in parameters concentration from upstream to downstream, most parameter concentrations were within the permissible limits of NAMWATER standards and the WHO guidelines for drinking water and the water was found to be suitable for the various intended uses except, as a direct source of potable water. The jar test results shows that treatment plant further downstream use high dosages of coagulants to purify the water compared to those further upstream, this could be attributed to the cumulative impacts of pollution. MSc. IWRM Thesis by Shuuya. M. K June 2008 ii Assessment of the impacts of pollution on water quality in the Calueque-Oshakati Canal in north- central Namibia. DEDICATION This project is dedicated to my Mother. Thanks mom for always being there, keeping strong and keeping us all grounded. MSc. IWRM Thesis by Shuuya. M. K June 2008 iii Assessment of the impacts of pollution on water quality in the Calueque-Oshakati Canal in north- central Namibia. ACKNOWLEDGEMENTS First and for most I thank the Almighty Father for giving me the strength and wisdom during the work of this project. Secondly, thanks to Waternet for financing my studies. The author wishes to convey special thanks and appreciation to Eng. Z. Hoko for his assistance as the author‟s supervisor. He is thanked for his suggestions, constructive criticisms, advice, instruction and above all his patience. May the Almighty Father bless you always! I will always be thankful to Eng. C. Moyo for the assistance and advice on this study. In addition I will always be thankful to our working group of Grace Nkuli, Mavuto Chiimpantenga, Victor Kimey, Jacquiline Diaz and Hazel Mpande I really learned a lot from you guys, GOD BLESS YOU. This study could not have been possible if it were not for the assistance and material support from NAMWATER. To my brothers and cousins, thanks a lot for the immense moral support and for having me living off you during my studies. Your support and patience are not taken for granted. MSc. IWRM Thesis by Shuuya. M. K June 2008 iv Assessment of the impacts of pollution on water quality in the Calueque-Oshakati Canal in north- central Namibia. TABLE OF CONTENTS ABSTRACT...................................................................................................................ii DEDICATION ..............................................................................................................iii ACKNOWLEDGEMENTS .......................................................................................... iv TABLE OF CONTENTS............................................................................................... v LIST OF FIGURES ....................................................................................................viii LIST OF TABLES ........................................................................................................ ix LIST OF APPENDICES ................................................................................................ x ABBRIVIATIONS AND ACCRONYMS ................................................................... xi CHAPTER ONE ............................................................................................................ 1 1.0. INTRODUCTION .................................................................................................. 1 1.1. Background ......................................................................................................... 2 1.2. Problem identification......................................................................................... 3 1.3. Justification ......................................................................................................... 3 1.4. Study objectives .................................................................................................. 4 1.4.1. The specific objectives:................................................................................ 4 1.5. Scope of study ..................................................................................................... 4 CHAPTER TWO ........................................................................................................... 6 2. LITERATURE REVIEW .......................................................................................... 6 2.1. Fresh water availability from a global perspective ............................................. 6 2.2. Namibia‟s water resources .................................................................................. 6 2.3. Interbasin transfers (IBT).................................................................................... 6 2.4. Pollution Regulations and legal framework in Namibia ..................................... 7 2.5. Water pollution ................................................................................................... 8 2.5.1. Causes of water pollution............................................................................. 9 2.5.2. Natural processes affecting water quality .................................................. 10 2.6. Impacts of pollution on water quality ............................................................... 10 2.7. Impacts of water pollution on different water uses........................................... 11 2.7.1. Impacts of pollution on the water suitability for Agricultural use ............. 11 2.7.2. Impacts of pollution on the water suitability for Fisheries use .................. 12 2.7.3. Impacts of pollution on the water suitability for Potable use .................... 13 2.8. Physical, chemical and biological water parameters ........................................ 13 2.8.1. Temperature ............................................................................................... 13 2.8.2. Dissolved Oxygen ...................................................................................... 14 2.8.3. Water pH .................................................................................................... 14 2.8.4. Turbidity..................................................................................................... 15 2.8.5. Total dissolved solids................................................................................