Little Ruaha River catchment
(6370 Km2) in the Southern Agricultural Growth
Corridor of Tanzania (SAGCOT), is one of the country’s most significant
waterways due to its ecological composition and economic value. Regardless of
its ecological and economical value, the regional hydrologic condition has been
tremendously affected due to land uses alteration, influenced by different
socio-economic factors. This study aimed to understand the associated impacts
of the present Land Use Land Cover (LULC) change on the surface runoff and
sediment yield in the Little Ruaha River Catchment. Hydrological modelling
using Soil and Water Assessment Tool (SWAT Model) was done to quantify the
impact of land use and land cover dynamics on catchment water balance and sediment loads. The calibration and
validation of the SWAT model were performed using sequential uncertainty
fitting (SUFI-2). The results showed that, for the given LULC change, the
average annual surface runoff increased by 2.78 mm while average annual total
sediment loading increased by 3.56 t/ha, the average annual base flow decreased
by 2.68 mm, ground water shallow aquifer recharge decreased from 2.97 mm and a
slight decrease in average annual ground water deep aquifer recharge by 0.14
mm. The model predicts that in the future, there will be a further increase in
both surface runoff and sediment load. Such changes, increased runoff
generation and sediment yield with decreased base flow have implications on the
sustenance flow regimes particularly the observed reduced dry season river flow
of the Little Ruaha River, which in turn cause adverse impacts to the biotic
component of the ecosystem, reduced water storage and energy production at
Mtera Hydroelectrical dam also increasing the chances of flooding at some times
of the year. The study recommends land use planning at the village level, and
conservation agricultural practices to ameliorate the current situation.
Developing multidisciplinary approaches for integrated catchment management is
the key to the sustainability of Little Ruaha River catchment.
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