Water Resource

Permanent URI for this collectionhttps://etd.hu.edu.et/handle/123456789/71

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    HYDROLOGICAL RESPONSE OF CLIMATE CHANGE ON WEYB RIVER WATERSHEDS: THE CASE OF BALE MOUNTAINOUS AREA, ETHIOPIA
    (Hawassa University, 2019-04-18) NESHA BAHMUD USHI
    The hydrological regimes and cycles within a certain watershed can be changed by the global climate variability and change. This change adversely impacts on environmental sustainability,water resources, agriculture and ecosystems. The current study investigates the hydrological impacts of climate change in essence, changes in precipitation and temperature over the Weyb river watershed. It is based on a sample of Coupled Model Inter comparison Project version 5 (CMIP5) downscaled over the Africa-Coordinated Regional climate Downscaling Experiment (CORDEX) domain by a Rossby Centre regional atmospheric model version 4 (RCA4) output, under RCP 4.5 and RCP 8.5 scenarios. Variance scaling and linear transformation bias correction methods was used to develop the simulation output of RCA4 regional climate model with high correlation to the observed data. ArcSWATmodel was used to generate future water availability in the basin. The bias corrected data were then used as input to the SWAT model to simulate the corresponding future flow regime in Weyb river watershed which is calibrated daily at R2 = 0.6,ENS = 0.5, and validated daily at R2 =0.58,ENS 0.57. The future projections are made for three time periods; 2020 (2010-2039),2050 (2040-2069) and 2080 (2070-2099). Results revealed that future predicted both temperatures, and precipitation revealed a statistically significant (at 5% significant level) increasing trend in the forthcoming periods as perceived by MannKendall test.Trend analysis with test using Mann Kendall (MK) and Sen's slope non-parametric test was applied to detect significant trends on the climate parameters and stream flow for future periods using XLStat software. The level of statistically significant trend was selected at α = 0.01,α = 0.05andα = 0.1level of significance. The annual mean daily stream flow revealed an increase, possibly, in the ranges 9.16-23.39% (RCP8.5), and 3.97-20.30% (RCP4.5). The result revealed that the maximum and minimum temperatures increase for all the two scenarios in all future time horizons. Rainfall change for all the two RCPs scenarios were variable. Results also revealed that a decrease of stream flow in all months on the dry season this might cause water shortage in the lowland region, and greater increase of stream flow in an intermediate and rainy seasons this might cause flooding to some flood prone region of the basin. A significant conclusion from the study is that changes in rainfall have larger effects on stream flow.The use of integrated hydrological modeling in impact assessment and the inclusion of other factors that cause imbalance in the stream flow should be enhanced in the Weyb watershed
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    IMPACT OF CLIMATE CHANGE ON THE GROUNDWATER HYDROLOGY OF LAKE ZIWAY WATERSHED, ETHIOPIA
    (Hawassa University, 2022-10-23) MIERAF ABEBE DONKA
    Climate change poses uncertainties to the supply and management of water resources. The relationship between the changing climate variables and groundwater is more complicated and poorly understood. Groundwater resources are related to climate change through the direct interaction with surface water resources, such as lakes and rivers, and indirectly through the recharge process. The impact may be worse for developing countries like Ethiopia because of their economies are strongly dependent on basic forms of natural resources. This thesis presents the likely impact of climate change on groundwater hydrology of Lake ziway watershed located in the Rift Valley basin of Ethiopia, The RCP scenarios of types 4.5, and 8.5 were used for the climate projection from the CORDEX Africa domain from CMIP5. The RCM of RCA4 was used to generate future possible local meteorological variables in the study area. These data were used as input to the Soil and Water Assessment Tool (SWAT) model to simulate the corresponding future streamflow Variability in the Ziway watershed. SWAT-CUP, a program for calibration and uncertainty was utilized for uncertainty analysis. The two projected time periods for this study were the 2040s, and 2070s. In the Lake Ziway watershed, there exists a climate change in the study period of 1989-2019. Since, there is a significant change from the base period to the projected time periods, therefore there would exist a climate change impact for the projected time periods under both scenarios in the Lake Ziway watershed. Therefore, climate change shows a significant decreasing impact on the groundwater flow of Lake Ziway watershed, which in turn affects the level of Lake Ziway significantly