Development of Water Allocation and Utilization System for Koka Reservoir under Climate Change and Irrigation Development Scenarios (Case Study Downstream of Koka Dam to Metahara)
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Date
2016-11
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Addis Ababa
Abstract
The subject of climate changing is one of the central issues facing the atmospheric sciences
community today. The most profound effect of such changes may be by altering in hydrologic
cycles and changes in regional water availability, within a context of increasing water scarcity;
climate change threatens to worsen the current supply-demand imbalance. This Study was
conducted in Upper Awash Catchment in the Central Rift Valley of Ethiopia, to assess the
consequences of climate change and irrigation expansion on current and future water use
practices of koka reservoir release for its downstream irrigations water use schemes using a
WEAP model. Records of hydrology, meteorology, and irrigation water supply for the study area
have been statistically tested and arranged as an input data source to fit the model.
Meteorological and grid climatic data were corrected with multi-regression and distribution
mapping (DM) method respectively and the two data were also correlated with each other. The
demand and the supply for the baseline and the future development activities of the area were
compared in climate change and irrigation expansion scenarios. This thesis analyses first the
model calibration, validation and its statistical measure were seen and the result shows that it is
very good and the model can simulate the current and the future scenarios. The results of this
analysis revealed that the reservoir capacity fluctuating between the minimum operating level
and the maximum outflow level; as the result unless the minimum flow requirements are
maintained, the future irrigation demands are unmet in more or less. For the climate change
scenario, the volume of reservoir evaporation in the baseline period was 404.5Mm3 and for the
coming first and second 35 years the volume of evaporations are 421.4 and 426.8Mm3
respectively. While compared with the baseline period, in the first 35 year the reservoir
evaporation increased by 16.9Mm3 and 22.3Mm3 for the coming two 35 years. The irrigation
expansions scenario indicated that from the total 947.7Mm3 demand of irrigation for the current
existing command areas, the supply delivered was 946.7Mm3. The planned irrigation expansions
demand for the future time period is 1659.1Mm3 and the supply delivered 1649.3Mm3. Relating
the future with the baseline period the demand and the unmet were increased by 711.4 Mm3 and
8.9Mm3 respectively. It is necessary that more detailed water resource assessment should be
done, including sustainable abstractions.
Keywords: Koka reservoir, climate change, irrigation development, water allocation and WEAP.
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Keywords
Koka reservoir, Climate change, Irrigation development, Water allocation and WEAP model