PhD Theses

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Browsing PhD Theses by Author "Alexander, Augustina"

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    Impacts of land use/cover changes on the streamflow of kihansi river catchment
    (University of Dar es Slaam, 2010) Alexander, Augustina
    This study uses distributed and lumped hydrological model SWAT (Soil and Water Assessment Tool) to present the impact of landuse/landcover changes in the Kihansi river catchment in south central Tanzania. The Kihansi River catchment is ideal source of water for the Lower Kihansi Hydropower Plant (LKHP) and the bio-diverse gorge eco-system Kihansi Spray Toad (KST) in lower Kihansi gorge. The catchment is gradually encroached by agricultural activities taking part upstream with an increase change of about 19% from 1979 to 1995 affecting the natural surface run-off pattern. Spatial, rainfall, runoff and climatic data collected were used to setup the model. Sensitive parameters specified were optimized to ensure correct hydrological processes. Four quantitative criteria were adopted for measuring the efficiency of the model, among them are the Nash and Sutcliff efficiency criterion (NCE) and the Index of Volumetric Fit (IVF) which gave 58% and 103% during calibration and 89% and 54% in verification periods respectively. The sensitivity analysis study found out that the catchment hydrological regime is highly influenced by the catchment characteristics that are Land cover, Soil and Topography. The model uses two land cover maps of 1979 and 1995 to study the effect of LULC in stream low flows. The changes in land use/cover had no impact on total water yield, but it increases the surface runoff by 4% in the expense of base flow. The low flow indices Q50 and Q95 indicate a decrease of 4% and 8% respectively which if the change persist with the same trend in long run will affect the operation of the LKHP and so to the gorge eco-system (KST).