A GIS Based Water Balance Study of Africa - Physical Land Resources

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233.3.1. TOPOGRAPHY AND SLOPEThe topographical data used in this study for characterizing the horizontal hydrologicalcharacteristics of the land surface are derived from the HYDRO1k geographic databasedeveloped by the US Geological Survey's EROS Data Center in cooperation with the UnitedNations Environment Programme/Global Resource Information Database (UNEP/GRID) locatedin Sioux Falls, South Dakota USA. The slope data layer describes the maximum change in theelevations between each cell and its eight neighbors. The slope is expressed in integer degrees ofslope between 0 and 90.The elevation of the study area varies from below sea level to 5825m above sea level. Theaverage is approximately 651m (Fig 3.1). The slope varies from 0 to 44 percent with average0.80 percent (Fig 3.2).30° 30° 30° 10° 10° 30° 50° 70°10° 10°10° 10°Topography(m)Below sea level0 - 100100 - 250250 - 500500 - 10001000 - 15001500 - 20002000 - 2500>2500No DataNWE3000 0 3000 6000 MilesSFigure 3.1: Topographic Map of Africa30° 30° 10° 10° 30° 50° 70° 30°
30° 30° 30° 10° 10° 30° 50° 70°10° 10°24Slope of Topography0 - 0.5 ( % )0.5 - 11 - 1.51.5 - 22 - 55 - 77 - 10>10No DataNWE3000 0 3000 6000 MilesS10° 10°Figure 3.2: Slope Map of Africa30° 30° 10° 10° 30° 50° 70° 30°3.3.2. SOILThe soil map of major soil types in the area of study came from the United Nations’ FAO1.5,000,000 Digital Soil Map of the World. The soil code system that WetSpass uses is based onthe soil texture triangle developed by the United States Department of Agriculture (USDA).USDA soil classification takes into account the percentages of clay, silt and sand in the soil.Soils dominated by fine textures are classified as clay. Those with intermediate textures loam,coarse texture soils are sand. The original soil map consisting of 4904 soil classes based on FAOnomenclature were reclassified to the USDA soil system (Fig 3.3). We must admit here thaterrors of misclassification could have occurred during this painstaking and laborious process,however, without undermining one’s determination to achieve maximum accuracy the outcomeof such minor error will be minimal taking into account the 1km by 1km pixel size. The soil
Page 5 and 6: 4LIST OF FIGURESFigure 1.1: Flowcha
Page 7 and 8: 6SUMMARYNkezeah, A.J., 2010. A GIS
Page 9 and 10: 81.2. OBJECTIVE OF THE RESEARCHThe
Page 11 and 12: 101.4. ORGANISATION OF THE REPORTTh
Page 15: 14independent water balances. Thus
Page 18 and 19: 17c is the vegetation coefficient [
Page 20 and 21: 19GROUNDWATER RECHARGERecharge refe
Page 22 and 23: 21CHAPTER 3MATERIALS AND METHODS3.1
Page 26 and 27: 25textural types were dominated by
Page 29 and 30: 283.3.4 PRECIPITATION INPUT DATAThe
Page 31 and 32: 30° 30° 30° 10° 10° 30° 50°
Page 33 and 34: 32CHAPTER 4RESULTS AND DISCUSSION4.
Page 35 and 36: 30° 30° 10° 10° 30° 50° 30°3
Page 37 and 38: 30° 30° 10° 10° 30° 50° 30°3
Page 39 and 40: Figure 4.5: Annual average Runoff M
Page 41 and 42: 30° 30° 10° 10° 30° 50° 30°4
Page 43 and 44: 30° 30° 10° 10° 30° 50° 30°4
Page 45 and 46: 70°(mm)444.2.6. TRANSPIRATIONTrans
Page 47 and 48: 46areas of Cental-West Africa. The
Page 49 and 50: 48variations of these components ar
Page 51 and 52: 50CHAPTER 5CONCLUSION AND RECOMMEND
Page 53 and 54: 52REFERENCESAlemaw, B.F., and Chaok
Page 55 and 56: 54Stone, D.B., Moomaw, C.L., Davis,

A GIS Based Water Balance Study of Africa - Physical Land Resources

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