Abstract:
This study presents distributed and lumped hydrological modeling approaches for the Kihansi river
catchment in south central Tanzania using the Soil and Water Assessment Tool (SWAT). The catchment
is source of water for the Lower Kihansi Hydropower Plant (LKHP) that supplies 25% power to the
national grid and the bio-diverse gorge eco-system in lower Kihansi Basin. In the distributed modelling
sub-watersheds were defined at the existing gauging stations. There are four upper sub-watersheds
and ten sub-watersheds located downstream. Three sub-watersheds of the river system were
separately modelled in a lumped approach. Subsequent parameterization of physically-based soil
parameters, landuse, and management files were defined. Four quantitative and two qualitative
evaluation criteria were used to evaluate the prediction performance of SWAT model. Model prediction
results using unoptimized parameter sets resulted poor modeling performance. Hence parameter
specification and optimization was necessary to ensure correct hydrological processes. Modelling
results using optimized parameter sets resulted better prediction of hydrological variables. Finally
correction factors were introduced for optimised parameters to facilitate future land cover change
studies.
