THE HYDROLOGY OF THE CONGO RIVER BASIN: A GIS-BASED HYDROLOGICAL WATER BALANCE MODEL

摘要

A GIS-based hydrological model, namely HATWAB - Hybrid Atmospheric andTerrestrial Water Balance (Alemaw, 2006), was developed to compute water resourceavailability, simulating its spatial and temporal distribution over the CRB. HATWAB modelsimulates the Integrated Moisture Convergence (C), soil moisture (SM), ActualEvapotranspiration (AET) and Runoff (ROF). The spatial distribution of the simulatedparameters shows a strong correlation with the rainfall pattern, especially in the high rain fedregion (Effective Rainfall >1100 mm/year), corresponding to the heart of the equatorial forestwhich extend between 5 and -5 degrees of latitude; whereas some disturbances are observed inthe lowest rain fed (Effective Rainfall <1000 mm/year) regions of the basin located the southeasternand the up-north part of the CRB. The Evapotranspiration Ratio (ETR) defines two mainclimatic regions, ETR close to 1 for region 1 and ETR < 7, with an intermediate zone between(07 < ETR < 0.8). The Annual average SM varies between 0 and 400 mm while the AET variesbetween 400 and 1700 mm/year with highest values on the water bodies. The total annual gridROF varies between 0 and 1400 mm. Swamps are characterised by 0 to 40 mm values whilehighest runoff (> 900mm) are computed on the rivers and lakes. The inland grid ROF variesbetween 50 and 900 mm per year with an average of 324 mm/year. The accumulated ROFcomputed final outlet reaches 44700m~3/second which is within an error margin of 5 % comparedto the observed discharge. The HATWAB model still proved its ability of simulating waterbalance for large scale basins such as the CRB if input data are available and well prepared atacceptable resolution.