Modeling The Water Balance, Reservoir Operation and Simulation Analysis for Cascaded Hydropower Plants: A Case Study of Upper Genale-Dawa River Basin
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Date
2019-06
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Addis Ababa University
Abstract
This research is intended to assure the equilibrium between energy production and
consumption from hydroelectric energy. Hydroelectric power plant development on GenaleDawa
River
basin
is,
a
part
of
development
plan
for
Ethiopian
energy
production.
Modeling
of
Water
balance
and
Reservoir
Operation
is
frequently
required
in
Hydraulic
engineering
for
reservoir
management
and to
control
fluctuation
of
water.
This
study
mainly
focuses on
water
balance
and
reservoir
operation
analysis
for
cascaded
hydropower
plants
in
the
Genale-Dawa
river
basin by using HEC-ResSim and HEC-HMS model. The stream flow generation were
estimated by using HEC-HMS model to enhance the water balance components at Genale
cascade reservoirs in the semi-ungauged parts of upper river basins. A Digital Elevation Model
(DEM) with 30 × 30 resolution of the study area was used to extract the physical
characteristics of watersheds using Arc-Hydro and the Geospatial Hydrologic Model
Extension HEC-GeoHMS. Then the HEC-HMS program was selected for this study, to attain
the water balance components of the basin due to its versatility, capability for flow generation,
automatic parameter optimization and its connection with GIS through HEC-GeoHMS.
HEC-ResSim (Hydrologic Engineering Center-Reservoir System Simulation) was used to
simulate the water allocation and operation of ongoing and planned reservoirs system in
Genale-Dawa River basin. It is capable of modeling any reservoir system and designed to
perform reservoir operation modeling at single or multi reservoir system. The performance of
the model has been evaluated through calibration and validation process. The HEC-HMS
model was calibrated and validated on a monthly time scale, with reference to Chena-Mansa
gauging station to estimate the flow from Genale-Dawa river basin using a time series dataset
of 16 years from 1990-2005. For calibration the model results in the performance criteria of
R
2
= 0.903, and NSE = 0.8926, and D = -0.0002%, and for validation performance criteria of
2
R
= 0.866, and NSE = 0.8447. Thus, HEC-HMS model has the ability to predict the water
potential of the basin.
Following the configuration, and application of HEC-ResSim model, the position of guide
curve was fixed at a minimum operative level for GD-3 and assigned at top of conservation
zone for GD-5, and GD-6 along with explicit system storage balance which is used to force the
upstream reservoir, GD-3, to fill first, allowing the downstream reservoirs, GD-5, and GD-6
to stay empty as long as possible when operating for flood control. The results of annual
average hydropower energy generated by the model from joint operation of the reservoirs
system is 4,311.25 GWh/year. The whole cascade power generation increment is 381.25
GWh/year and it is a 9.701% improvement over the current design which is 3,930 GWh/year.
Also, Combined reservoir system operation model is capable to store 517.13 million cubic
meter flood water resources annually which shows 16.75% total reduction of spill release over
the current design.
Description
Keywords
Arc-GIS, Arc-Hydro, HEC-GeoHMS, HEC-HMS, HEC-ResSim, Optimal Water Release, Storage Balance, Genale-Dawa River Basin