Hydraulic Engineering
Permanent URI for this collectionhttps://etd.hu.edu.et/handle/123456789/69
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Item ASSESSMENT OF CLIMATE CHANGE IMPACT ON SURFACE WATER RESOURCE IN WOSHA WATERSHED, RIFT VALLEY LAKES BASIN, ETHIOPIA(Hawassa University, 2024-10-16) ELSAE WARE GIDESAClimate change (CC) and Land Use/Land Cover (LULC) changes present significant threats to global water resources and socio-economic systems. This study aimed to evaluate the impact of climate change and LULC changes on the availability of surface water resources in the Wosha watershed, located in the Rift Valley Lakes Basin (RVLB) of Ethiopia. The available water resources were assessed using the Soil and Water Assessment Tool (SWAT), a semi-distributed, physically-based hydrological model. Calibration and validation of computed stream flow were conducted using SWAT-CUP with the SUFI-2 algorithm. Bias-corrected data from three climate models output from Coupled Model Intercomparison Project Phase 6 (CMIP6) models such as CANESM5, MIROC6, and NESM3 were used to assess baseline (1985-2014), mid-term (2041- 2070), and long-term (2071-2100) periods under the Shared Socioeconomic Pathways (SSP2 4.5 and SSP5 8.5) climate scenarios. The SWAT model's performance was robust, achieving R² values of 0.88 and NSE values of 0.75 during calibration, and R² values of 0.83 and NSE values of 0.72 during validation for monthly simulations. The projections indicate that both rainfall and temperature will increase under SSP2 4.5 and SSP5 8.5 scenarios in the mid-term period, with a temperature rise of 1.2°C expected under SSP5 8.5. Precipitation is also expected to increase by 1% to 10% in the long term for both scenarios. Therefore, the primary objective of this study was to assess the impact of climate and LULC changes on the availability of surface water resources in the Wosha watershed. The results underscore the importance of understanding surface water availability and mitigating the impact of climate change to ensure future water resources for the region.Item ANALYSIS AND CHARACTERIZATION OF HYDROLOGICAL DROUGHT UNDER CLIMATE CHANGE IN HAMASSA WATERSHED, RIFT VALLEY BASIN(Hawassa University, 2024-07-20) REDIAT LEGESE SIMEHydrological drought occurs when there is an extended period of significantly reduced water availability, leading to depleted water sources and severe impacts on ecosystem and communities. Water scarcity caused by prolonged periods of reduced rainfall due to climate change can lead to the natural disaster of drought. However, little has been done so far on hydrological drought under climate change in Hamassa watershed. This study aimed to analyze and characterize hydrological drought under climate change in the Hamassa watershed, Rift Valley Basin, Ethiopia. Hydrological data (1992-2015), meteorological data (1992-2022), future climate data 2030-2090), spatial data, DEM, land use land cover, and soil were collected. CMhyd software package was used for bias correction of the climate data. The hydrological model soil and water assessment tool (SWAT) was used for hydrological analysis. The simulation result was calibrated and validated using the SWAT calibration uncertainty procedure (SWAT-CUP). Standard precipitation index (SPI) and stream flow drought index (SDI) are used to decide drought conditions in a watershed and to identify drought-prone areas in the watershed. Temperature projections for both the near and long term indicate an increase compared to the current period under both RCP2.6 and RCP8.5 scenarios. Meanwhile, precipitation projections suggest a decrease for the periods 2040-2060 and 2061-2072 under both RCP2.6 and RCP8.5 scenarios. The standard precipitation index (SPI) and stream flow drought index (SDI) results showed that the watershed experiences mild (-0.5- -0.999), moderate (-1- -1.49), severe (-1.5- -1.99), and extreme (≤ - 2) drought events. Droughts are projected to occur in the periods 2040-2060 and 2061-2072 under both RCP2.6 and RCP8.5 scenarios. Sub-watersheds 7, 8, 9, 10, and 11 showed high vulnerability to severe and extreme drought. Drought-mitigating structures are needed to mitigate drought in the watershedItem ASSESSMENT OF CLIMATE CHANGE IMPACT ON STREAM FLOW OF GIDABO SUBBASIN, RIFT VALLEY BASIN, ETHIOPI(Hawassa University, 2022-08-10) YIDIDYA TSEGAYE ALEMUClimate changes alter regional hydrologic conditions and result in a variety of impacts on water resource systems. Such hydrologic changes will affect almost every aspect of human well-being. The goal of this thesis is to assess the impact of climate change on the hydrology of Gidabo subbasin located in the Rift Valley basin of Ethiopia. The RCP scenarios of types 2.6, 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 Gidabo subbasin. SWAT-CUP, a program for calibration and uncertainty was utilized for uncertainty analysis. The three projected time periods for this study were the 2040s, 2060s, and 2090s. The time series generated by RCM of RCA4 driven by MIROC5 indicate a significant increasing trend in maximum and minimum temperature values and a decreasing trend in precipitation for all RCP emission scenarios in Measso station for all time periods. The hydrologic impact analysis made with the downscaled temperature and precipitation time series indicates variation in an increasing and decreasing trend for the three RCP scenarios at different periods respectively. The model output shows that there may be a mean annual, seasonal, and mean monthly decrease in stream flow volume for all RCP scenarios in the Projected time periods in the future. It also shows most of the projections are within the uncertainty bandwidth of 95PPU