Abstract:
Now a days the sign of climate change and its impact is revealing on different natural and man-made systems, in one or other ways. Accordingly, this impact is significant on the water resource
system. This study mainly deals with assessment of the reservoir performance under climate
change impact on the Megech reservoir which is found in Lake Tana Sub-Basin, using the
reliability, resilience and vulnerability indices.
To evaluate the impact of climate change, climate change scenario of evapotranspiration and
precipitation were developed for three period (base, short term and long term) using output of
CMIP5 with RCP for RCP4.5 emission scenarios and they are used to develop the future climate
change scenario. A hydrological model, HBV, was used in order to simulate the current and future
inflow volume to the reservoirs. The performances of the model were assessed through calibration
and validation process and the result shows NSE 0.72 during calibration and 0.69 during validation
at the gauge station.
The projected future climate variable shows an increasing trend .Tmax 0.23
o
c and 2.73
o
cin short
and long term respectively and Tmin 1.68
o
c and 2.13
o
c in short and long term respectively and but
precipitation also shows decreasing by 0.84% and 1.2% in short and long term respectively.
Relative to the current condition, the average annual open water evaporation for Megech reservoir
will increase by 1.01% and 1.03% in short and long term respectively. Relative to the current
condition, the simulated future period average annual inflow volume shows a decrease of 1.15%
and 1.58 % in the period of 2021 -2030 and 2061-2070 respectively from the base period.
On average, the time based reliability of Megech reservoir shows a value of above 90 %. However,
the resilience shows value less than 50% in the two periods. This shows that, the reservoir needs
long time to recover itself from failing to meet the demand. The dimensionless vulnerability, below
50% in all period. This Shows that the Reservoir have no shortage of Flow to meet the Demand in
all periods.
A reservoir simulation model, MODSIM, was used to simulate the amount of release potential of
the reservoirs and to determine the reservoirs operation rule curve. The future period average
annual Release will decrease by 1.2% and 1.19% for both short and long term in comparison to
the base period.
