Abstract:
Reservoirs are constructed and operated for multiple purposes and the application of
simulation models are efficiently analyze these multi-purpose reservoir’s operations. In
Ethiopia the optimization of hydropower potential is the first problem that face the existing
hydropower plants; due to poor reservoir operation policy, which leads to unwise use of
available water. Unlike most other reservoir; low operating policy of Koka reservoir is
critical and most common problem. The present research aims to satisfactorily simulate
and optimize the operation of multipurpose reservoir of Koka hydro power plant using
HEC-ResSim. The simulation approach indicates an improvement in the reservoir
operation in terms of increasing storage volumes, and ensuring reliable releases.
HEC-ResSim is one of the simulation models that can simulate reservoirs these contribute
a significant amount of water to the water resources system. This model search the space
of possible design variable values and identify an optimal operating policy for a given
system objective and set of constraints.
The input data used for the HEC-ResSim model; daily inflow, daily precipitation, water
level and monthly reservoir surface evaporation and Koka dam and reservoir physical
data. The Koka reservoir operation modeling has been done with inflow data of four
stations of Akaki, Hombole, Melka kuntrie, and Mojo; within twenty years (1996 - 2015)
time series data and the precipitation data at the reservoir surface (i.e Koka station) for
twenty years (1996-2015).
In this study the optimal, maximum and minimum guide curve level is determined. The
average optimal guide curve level is 107.88m, maximum guide curve level of 112.43m and
minimum guide curve level is 100.4m. The maximum releases from Koka reservoir and net
inflow to the reservoir; 5226.94m3
/s and 1968.07m3
/s respectively. The calibration and
validation of simulated verses observed values of R2=0.84 and 0.82 respectively and with
Nash-Stucliffe model efficiency of 0.81 this value shows the model was correctly simulate
the reservoir.
