Estimation of soil erosion in the Pangani basin upstream of Nyumba ta Mungu reservoir

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University of Dar es Salaam
The Universal Soil Loss Equation (USLE) was used to estimate soil erosion in the Pangani Basin upstream of Nyumba ya Mungu reservoir located to the North-Eastern part of Tanzania using data from reconnaissance surveys such as Geo-referenced soil, land use and topographic maps. The R-factor (rainfall Erosivity) was estimated using empirical equation proposed by Wischmeier and Smith et al, 1978 as rainfall intensity data was insufficient to evaluate average annual R by usual procedures, using data from three rainfall recording gauges. The K-factor (soil erodibility) was determined using data derived from Physiography map of Tanzania (De E.PAUW, 1984). The LS-factors (slope length and steepness) were determined from a digital elevation model (DEM) of the basin. The C-factor (crop and management) was determined from the land use and farming system maps, obtained from the Institute of Resource Assessment (IRA) and Ministry of Agriculture (Mlingano Soil Research Service) respectively. The P-factor (Soil conservation practice) was taken to have a value of 1, for the whole basin, with the assumption that the entire population in the basin does not practice the soil conservation programs. A raster-based Geographic Information System (GIS) was used to calculate soil loss and volume of sediments deposited into Nyumba ya Mungu Reservoir over years. The results obtained from soil loss models (equations) using GIS in the upstream of Nyumba ya Mungu reservoir were compared to measured amount of sediments deposited into reservoir by echo-sounding technology. The result obtained from this study indicates that the mean potential soil erosion in the basin is 24 t/halyr. And about half of this average erosion finds its way into Nyumba Mungu Reservoir. Generally, there is a need for detailed research to determine appropriate USLE parameters.
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Soil erosion, Pangani basin, Nyumba ya Mungu, Reservor
Ndomba, P. M. (2001) Estimation of soil erosion in the Pangani basin upstream of Nyumba ta Mungu reservoir, Masters’ dissertation, University of Dar es Salaam. Available at (