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

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41Figure 4.7: Groundwater recharge Map of Africa (From Döll et al., 2002)4.2.4. INTERCEPTIONThe vegetation cover significantly affects interception. Much of the total annual rainfall receivedby the forest never reaches the forest floor. Instead it is intercepted retained on vegetation for ashort duration, absorbed by plants, or evaporated from the canopy. Therefore, vegetation servesas a bridge between the gap of rainfall and infiltration into the soil. Interception is very muchassociated with vegetation and varies with the forest type as shown by the result of this analysis(Fig 4.8). Generally, the values range from 0 mm to 1077mm/yr. The average is 104mm/yr.Regions of the tropical rainforest have the highest values. The result shows that the evergreenbroadleaf forest typically intercepts as much as 400-700mm/yr of the total annual precipitation.The desert regions of the Sahara, the horn of Africa and Southern Africa intercepts very little orno rainfall throughout the year. Values of between 0 and 120mm/yr of rainfall are interceptedhere. Interception by forest cover is more significant to water balance computation than othervegetative covers as they tend to intercept more rainfall.
30° 30° 10° 10° 30° 50° 30°42Inyear0 - 11 - 1010 - 5050 - 100100 - 200200 - 500500 - 1100No Data70°(mm)10° 10°NWE3000 0 3000 6000 MilesS10° 10°Figure 4.8: Interception Map of Africa30° 30° 10° 10° 30° 50° 70° 30°4.2.5. SOIL EVAPORATIONEvaporation is the process whereby liquid water is converted to water vapour then removed fromthe evaporating surface. The annual values of the simulated soil evaporation are shown on (Fig4.9). The trend shows higher values of 100mm to about 500mm per year for arid regions of theSahara, eastern Africa and the Namib and Kalahari deserts of southern Africa compared to therest of the continent.This trend is not surprising because these areas are characterized by:• Very high daily and seasonal temperature variations,• Low relative humidity,• High evaporation intensity,• Strong dry winds, and,
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 24 and 25: 233.3.1. TOPOGRAPHY AND SLOPEThe to
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: 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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