Chapter 8 Hydrogeology October 2010 Republic of Botswana Makgadikgadi Framework Management Plan 2010 Table of contents List of Tables ................................................................................................................................................. 2 List of Figures ................................................................................................................................................ 2 List of Acronyms ............................................................................................................................................ 4 Acknowledgements ....................................................................................................................................... 5 1. Introduction .......................................................................................................................................... 6 2. Terms of reference - Hydrology Specialist ............................................................................................ 6 3. Approach-method and activities........................................................................................................... 8 3.1 Introduction ................................................................................................................................. 8 3.2 Topography of the Makgadikgadi and its catchment..................................................................... 10 3.3 Rainfall around the Makgadikgadi .............................................................................................. 17 3.4 Stream hydrographs for the Makgadikgadi catchment .............................................................. 21 3.5 Riparian systems and seepage points ......................................................................................... 26 3.6 Ephemeral lacustrine surface water ........................................................................................... 38 3.7 Pan surface morphology ............................................................................................................. 48 3.8 Pan chemistry .............................................................................................................................. 55 3.9 Groundwater ............................................................................................................................... 59 3.10 Mass Balance Estimation ............................................................................................................ 65 3.11 Water Take-Off ........................................................................................................................... 69 3.12 Water Conflict ............................................................................................................................. 69 3.13 Proposed monitoring program ................................................................................................... 72 3.14 Summary of Makgadikgadi wetspots .......................................................................................... 72 4. Major Findings for FMP ....................................................................................................................... 76 5. Follow up work .................................................................................................................................... 79 6. References .......................................................................................................................................... 81 Volume 2 Chapter 8: Hydrogeology 1 Makgadikgadi Framework Management Plan 2010 List of Tables Table 1: Global Digital Elevation Data ......................................................................................................... 10 Table 2: Icesat data is on average -4.8 m lower than SRTM and 1.6 m higher than ASTER ....................... 12 Table 3: Monthly weather station data made available to this project ..................................................... 18 Table 4: Mean monthly and annual rainfall figures for the Makgadikgadi ................................................ 19 Table 5: Stream gauge record for the Makgadikgadi.................................................................................. 21 Table 6: Catalogue of Landsat Data for the Makgadikgadi. ........................................................................ 26 Table 7: Most persistent and dynamic Makgadikgadi wetspots ................................................................ 43 List of Figures Figure 1: Okavango Catchment: Note the location of the Makgadikgadi in its eastern extension .............. 8 Figure 2: A proposed hydrological model for the Makgadikgadi .................................................................. 9 Figure 3: Quality of SRTM derived height against DGPS for the Gweta area ............................................. 11 Figure 4: SRTM and ASTER DEM heights plotted against 65000 Icesat Point heights covering the Makgadikgadi basin. ................................................................................................................................... 12 Figure 5: ArcGIS automated watershed and drainage generation for Makgadikgadi ................................ 13 Figure 6: Shaded SRTM with drainage and major contours ....................................................................... 14 Figure 7: Eastern Catchments and Watersheds .......................................................................................... 16 Figure 8: Location of weather station data provided to this project .......................................................... 18 Figure 9: Rainfall deviation from the mean (in mm) for selected stations NE of the Makgadikgadi from 1959-2008 ................................................................................................................................................... 20 Figure 10: Location of Stream gauges with DWA code in the Makgadikgadi Catchment and its main contributers the Boteti , Nata , Mosetse and Mosope Rivers .................................................................... 22 Figure 11: 1971-1999 Stream Records in MCM for Boteti (Blue), Mosupe (Green), Mosetse (Red) and Nata Rivers (Purple) .................................................................................................................................... 23 Figure 12: Monthly Flood in MCM .............................................................................................................. 24 Figure 13: Eastern Margin of pan. Riparian systems and dynamic pans and protopans ............................ 28 Figure 14: Surface dynamics at Nata, Ntwetwe, and Mosu Escarpment ................................................... 30 Figure 15: Micro-dams, dynamic proto pans, and Lake Xau desiccation ................................................... 32 Figure 16: Persistent surface water in lower the Boteti and deactivation of Mopipi dam ........................ 34 Figure 17: Significant and permanent riparian between 1970 and 2000 period........................................ 35 Figure 18: A flowing Lower Boteti, a filled Lake Xau and rim full Mopipi Dam in June 1979 as seen in Landsat MSS. ............................................................................................................................................... 36 Figure 19: Lower Boteti reaches Lake Xau, September 29, 2010 ............................................................... 37 Figure 20: 1980-2005 Time series for the Makgadikgadi ........................................................................... 39 Figure 21: MODIS Terra, 218 day image stacks .......................................................................................... 42 Figure 22: Preliminary pan water time series 2000-2009 derived from MODIS NIR record ...................... 44 Figure 23: Relative pan wetness and wetspot map as depicted in NIR (top) and MIR (Bottom) for 2000- 2009 period ................................................................................................................................................. 45 Figure 24: Example of MODIS derived Flood Count Map for Year 2000 .................................................... 47 Figure 25: Aeolian pan environment controlled by hydrological dynamics ............................................... 50 Figure 26: Hysplit model output ................................................................................................................. 51 Volume 2 Chapter 8: Hydrogeology 2 Makgadikgadi Framework Management Plan 2010 Figure 27: Downwind Bicarbonate Footprint at Makgadikgadi. Background sampled upwind (east of pan) .................................................................................................................................................................... 53 Figure 28: Downwind Uranium Footprint at Makgadikgadi. Background sampled upwind (east of pan) . 54 Figure 29: Piper plot depicting water chemistry for fresh river flood water and surface leaches, saline lake water for Sua pan and subsurface brine ............................................................................................. 56 Figure 30: Ion log concentration (mmol/L) plotted against Cl .................................................................... 57 Figure 31: Water quality in Makgadikgadi basin ........................................................................................ 58 Figure