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%.
