Abstract
Potential implications of rainfall variability along with Land Use and Land Cover Change (LULC) on stream flow have been assessed in the Black Volta basin using the SWAT model. The spatio-temporal variability of rainfall over the Black Volta was assessed using the Mann-Kendall monotonic trend test and the Sen’s slope for the period 1976–2011. The statistics of the trend test showed that 61.4% of the rain gauges presented an increased precipitation trend whereas the rest of the stations showed a decreased trend. However, the test performed at the 95% confidence interval level showed that the detected trends in the rainfall data were not statistically significant. Land use trends between the year 2000 and 2013 show that within thirteen years, land use classes like bare land, urban areas, water bodies, agricultural lands, deciduous forests and evergreen forests have increased respectively by 67.06%, 33.22%, 7.62%, 29.66%, 60.18%, and 38.38%. Only grass land has decreased by 44.54% within this period. Changes in seasonal stream flow due to LULC were assessed by defining dry and wet seasons. The results showed that from year 2000 to year 2013, the dry season discharge has increased by 6% whereas the discharge of wet season has increased by 1%. The changes in stream flows components such us surface run-off (SURF_Q), lateral flow (LAT_Q) and ground water contribution to stream flow (GW_Q) and also on evapotranspiration (ET) changes due to LULC was evaluated. The results showed that between the year 2000 and 2013, SURF_Q and LAT_Q have respectively increased by 27% and 19% while GW_Q has decreased by 6% while ET has increased by 4.59%. The resultant effects are that the water yield to stream flow has increased by 4%.
Highlights
Assessing temporal trends and their spatial distribution pattern of precipitation remains a difficult task owing to their complex and non-linear nature in different regions
We discussed the spatio-temporal trend of rainfall and land use practices in their impacts on the Black Volta river discharge through the Soil and Water Assessment Tool (SWAT) modeling
Mann-Kendall trend test showed that 61.4% of the rain gauges (8 stations over a total of 13) presented an increased precipitation trend whereas the rest of the stations showed a decreased trend
Summary
Assessing temporal trends and their spatial distribution pattern of precipitation remains a difficult task owing to their complex and non-linear nature in different regions. It is an important step for water resource projects in a basin. Rainfall distribution in Ghana, and West Africa in general, is influenced by the moist south-west monsoon and the dry north-east trade wind. Rainfall variability has a large influence on a water resource project. The eco-hydrological processes that influence the evolution of the surface ecosystem, depend on the spatio-temporal patterns of the precipitation and evapotranspiration (Oguntunde et al, 2006) [1]. Land use and cover are changing fast in basin due to population growth and economical activities development in the basin
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