Many studies on rainfall variability had been used data at relatively in all resolutions, either global climate models (GCMs; e.g. Reason 1998; Goddard and Graham 1999; Cook 2000; Rautenbach and Smith 2001; Nicholson 2003) or monthly, seasonal to annual rainfall totals (e.g. Richard and Poccard 1998; Landman et al. 2001; Thiamand Singh 2002; Bartman et al. 2003). The identification of extreme rainfall is main function of scale, with the ability to highlight rainfall extremes increasing in step with the data resolution (Williams et al. 2007). An improved understanding of extreme daily rainfall at high spatial resolution is important, because of rainfall variability and extremes have impacts on society. We can see that developing countries suffer more from extreme rainfall events than developed countries because, being environmentally and socio economically vulnerable before the extreme event occurs, developing countries are more sensitive to such disasters. Mozambique, for example, experienced an extreme rainfall event associated with Tropical Cyclone Eline during 21’25 February 2000, resulting in severe flooding and displacing over a million people (Layberry et al. 2006). Evaluating and predicting the availability and accessibility of groundwater under changing boundary conditions is one of the central tasks in Integrated Water Resources Management (IWRM) because groundwater is a major drinking water resource and critical for irrigation in all parts of the world (Villholth, 2006; Holman, 2006). The objectives of IWRM namely to provide water in sufficient quantity and quality justifiably to different consumers and at the same time to maintain and guarantee a sustainable qualitative and quantitative status of the groundwater resource itself (Hiscock et al. 2002). A ‘good status’ of groundwater refers to its function in water supply (drinking water, irrigation water, industrial use, etc.) but also to its role as a long term reservoir to sustain aquatic ecosystems(wetlands) and to provide a source of discharge in dry periods.
GIS is an important technology for geologists (Baker and Case 2000). GIS has emerged as a powerful technology for instruction, for research, and for building the stature of programs (Openshaw 1991; Longley 2000; Sui and Morrill 2004).
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