Abstract:
This paper revises the hydrological drought under future climate change scenarios. The most part
of the study area is disposed to a drought; shared sources of water such as reservoirs, rivers and
groundwater for wells are in danger of running dry. An analysis of drought in Kessie basin based
on daily data from 1983-2012, in 11 stations over the study area were presented using SWAT
model. General Circulation Models (GCMs) which are considered as the most important tools for
estimating future climate change scenarios operate on coarse resolutions. Climate change
scenarios of precipitation and temperature were developed at Bahir Dar, Debre Markos and
Motta stations of the Basin for three periods namely; 2011-2040, 2041-2070 and 2071-2099 and
their respective changes were determined as deltas (for temperature) and as percentages (for
precipitation) from the base period values. The outputs of HadCM3 coupled atmosphere-ocean
GCM model for the A2 and B2 SRES emission scenarios were used to produce the future
scenarios. The study found that there is an overall increasing trend in annual temperature and
significant variation of monthly and seasonal precipitation from the base period level. These
changes of the climate variables were applied to SWAT hydrological model to simulate future
water availability. SWAT was calibrated with fifteen years of data (1985-1999) to assess the
possible impact of climate change in the Basin. Stream flow model efficiency by regression
coefficient and Nash-Sutcliffe was 0.713 and 0.664 for calibration and 0.83 and 0.62 in
validation respectively. The future climate variables as an output from the GCM model and
downscaled by the SDSM model and directly as an input to the SWAT model. As a result of the
average total annual flow at the outlet of the study area might decrease up 11.13% and 10.24%
for both A2a and B2a scenario respectively at 2013-2040 period, 14.43% and 23.46% for both
A2a and B2a scenario respectively at 2041-2070 and 27.15% and 22.11% for both A2a and B2a
scenario respectively at 2071-2099.The decrease in the future flow of 2013-2040 periods might
be unsatisfactory in some months to meet future demands for the water of the ever growing
population within and around the basin. The future possible volume of deficiency or hydrological
drought appears below the Q70
line, it indicates the hydrological drought. The study area of
drought was observed 313 months of 1044 for both scenarios.
