Application of GIS in water balance estimation : case study : Busitema sub catchment.

Abstract

The demand for water is increasing with growing population and industrialization. Water supply is considered to be one of the key factors for rapid development and urbanization. However, the over exploitation of water resources has resulted in a condition of un sustain ability and environmental degradation. Hence, the information on water balance studies will be helpful for the optimum utilization of water resources. The water balance was used for computing patterns of water availability to facilitate better management of available water resources. This was achieved through determining the net change in storage of water taking into account losses of runoff and evapotranspiration, Rates of evapotranspiration were determined using the Penman Monteith model to determine-rates of ETs for maize grains It, is one of the major crops grown in the area. Remote sensing and GIS, were used in formulating thematic maps of slope, land use, soil. Types and rainfall as factors that affect runoff, Runoff was determined using the- USDABCS:CN loss method and a transform method of SCS Unit Hydrograph through, running a simulation in HEC-HMS. The study was helpful indicating periods of surplus and deficit after calculation, of the change in storage. This study indicates that there is a maximum monthly deficit of 128 min in February which could be attributed to high rates of evapotranspiration and runoff and an average surplus of 36.99mm in Ju1y. The surplus indicated an increase in ground water storage. Periods of surplus and deficit are essential in 'assessing and evaluating the, status and' trends in water resources availability. Water balance studies are essential to the Local people as this will determine when to adjust their crop calendar basing on periods of surplus or deficit.