Frank Leon Lehmann Water quality of the Swakoppoort Dam, Namibia Master’s Thesis under supervision of Dr. Christoph Külls Freiburg im Breisgau, December 2010 Frank Leon Lehmann Water quality of the Swakoppoort Dam, Namibia Supervisor: Dr. Christoph Külls Co-Supervisor: Prof. Dr. Klaus Kümmerer Master’s Thesis under supervision of Dr. Christoph Külls Freiburg im Breisgau, December 2010 Declaration of Authorship I, Frank Leon Lehmann, declare that this thesis titled, “Water Quality of the Swakoppoort Dam, Namibia” and the work presented in it are my own. I confirm that the work was made independently and only on the use of indicated resources. (Frank Lehmann) Freiburg im Breisgau, 15th of December 2010 Table of Contents Table of Contents List of Figures ........................................................................................................................... I List of Tables ............................................................................................................................ V Abbreviations .......................................................................................................................VII Acknowledgements ............................................................................................................. IX Abstract .................................................................................................................................... XI Zusammenfassung ............................................................................................................ XIII 1 Introduction .................................................................................................................... 1 1.1 Objectives .................................................................................................................................. 2 1.1.1 Research question ...................................................................................................... 2 1.1.2 Research needed ........................................................................................................ 2 1.2 State of the Art ........................................................................................................................ 2 2 Theoretical background .............................................................................................. 5 2.1 Physical and physio-chemical water Parameters .................................................... 5 2.1.1 Temperature and lake stratification .................................................................. 5 2.1.2 Oxygen in surface waters ........................................................................................ 6 2.2 Major Ions ................................................................................................................................. 6 2.3 Iron and Manganese ............................................................................................................. 7 2.4 Dissolved organic carbon (DOC) ..................................................................................... 7 2.5 Anorganic nutrients .............................................................................................................. 8 2.5.1 Nitrogen compounds ................................................................................................ 8 2.5.2 Phosphate ...................................................................................................................... 8 2.5.3 Sulphate .......................................................................................................................... 9 2.6 Eutrophication and algal blooms in lakes .................................................................. 9 2.7 Heavy metals ......................................................................................................................... 11 2.8 Phenol and Formaldehyde .............................................................................................. 12 2.9 Excursion: Isotopes of H2O ............................................................................................. 12 3 Study area ...................................................................................................................... 15 3.1 Climate ..................................................................................................................................... 17 3.2 Geology and soils ................................................................................................................. 18 3.3 Windhoek’s water supply ................................................................................................ 20 3.3.1 Groundwater supply .............................................................................................. 21 3.3.2 Surface water supply .............................................................................................. 21 3.3.3 Reclaimed water supply ....................................................................................... 22 3.4 The Swakoppoort Dam ..................................................................................................... 25 4 Methods .......................................................................................................................... 29 4.1 Field Methods ....................................................................................................................... 29 4.1.1 Sampling plan ............................................................................................................ 29 4.1.2 Sampling and equipment ..................................................................................... 34 4.2 Analytical methods ............................................................................................................. 35 5 Results ............................................................................................................................ 37 5.1 Oxygen and Temperature ................................................................................................ 37 5.1.1 Sampling group “Klein Windhoek” .................................................................. 37 5.1.2 Sampling group “Otjiserva surface” ................................................................. 37 5.1.3 Sampling group “Otjiserva wells” ..................................................................... 37 5.1.4 Sampling group “Boreholes” ............................................................................... 38 5.1.5 Sampling group “Swakoppoort Dam” ............................................................. 38 5.1.6 Summary ..................................................................................................................... 38 Table of Contents 5.2 pH and Conductivity .......................................................................................................... 40 5.2.1 Sampling group “Klein Windhoek” .................................................................. 40 5.2.2 Sampling group “Otjiserva surface” ................................................................ 40 5.2.3 Sampling group “Otjiserva wells” .................................................................... 40 5.2.4 Sampling group “Boreholes” .............................................................................. 40 5.2.5 Sampling group “Swakoppoort Dam” ............................................................. 40 5.2.6 Summary ..................................................................................................................... 41 5.3 Major ions .............................................................................................................................. 43 5.4 Iron (Fe) and Manganese (Mn) ..................................................................................... 45 5.4.1 Sampling group “Klein Windhoek” .................................................................. 45 5.4.2 Sampling group “Otjiserva Surface” ................................................................ 45 5.4.3 Sampling group “Otjiserva wells” .................................................................... 45 5.4.4 Sampling group “Boreholes” .............................................................................. 46 5.4.5 Sampling group “Swakoppoort Dam” ............................................................. 46 5.4.6 Summary ..................................................................................................................... 46 5.5 TKN, DOC, UV254 (Nutrients) ....................................................................................... 48 5.5.1 Sampling group “Klein Windhoek” .................................................................. 48 5.5.2 Sampling group “Otjiserva surface” ................................................................ 48 5.5.3 Sampling group “Otjiserva wells” .................................................................... 49 5.5.4 Sampling group “Boreholes” .............................................................................. 49 5.5.5 Sampling group “Swakoppoort Dam” ............................................................. 49 5.5.6 Summary ..................................................................................................................... 50 5.6 Nitrogen compounds ........................................................................................................ 52 5.6.1 Sampling group “Klein Windhoek” .................................................................