Development and Application of Distributed Hydrological Model for the Central and Southern Catchments in the Eastern are Mountains of Tanzania

Eastern are mountains (EAMs) catchments have experienced significant flow reductions since late 1970s, and due to varied physiography and hydro-climatic conditions the available hydrological networks are not well enough for sound assessment of water resources. Various sources attributed the flow reductions to land use and land cover changes in the catchment over the years. In this study the effects of catchment cover changes were studied together with the hydrological behavior of the of the EAMs catchments. Distributed and physics based hydrological model and empirical and conceptual models were developed using results of remote sensing GIS technology and hydro- metrological data. The results of the study showed no significant impact on the simulated flow a due to the effect of land cover changes. For example, using a scenario land cover changes in some 8.34% of the catchment area, a change in annual flow to the extent of only 4.7% was observed which nearly 84% was attributed to ground water flow alone. The research also indicated that parameter reductions and use of catchment characteristics in hydrological model development improved the efficiency of hydrologic variables predictions. This research further demonstrated that streamflow reductions in the studied area were attributed to valley bottom cultivation through current abstractions at the valleys are not documented but indicative of creating soil moisture deficit with high loss of water by evaporation. The developed hydrological models are suitable tools for environmental modeling and wider applications are recommended for comprehensive understanding of the hydrological processes of tropical catchments.