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    STREAMFLOW RESPONSE TO CLIMATE CHANGE ON TIKUR WUHA SUB WATERSHED, RIFT VALLEY BASIN, ETHIOPIA
    (Hawassa University, 2018-10-23) BROOK LEGESE DADHI
    Climate changes alter regional hydrologic conditions and results in a variety of impacts on water resource systems. Such hydrologic changes will affect almost every aspect of human well-being. Simulation models of watershed hydrology and water quality are extensively used for water resources planning and management. This study aims to assess the streamflow response to Climate Change on Tikur Wuha Sub-watershed, Rift Valley Basin of Ethiopia. In the study the daily hydro-meteorological data values for the baseline period of 1981-2005 were used. Historical Representative Concentration Pathway (RCP) data along with observed data of precipitation and temperature were used for extraction and bias correction using CMhyd tool. After evaluation of bias correction methods using residual plot, and RMSE, MAE and RE, the downscaled climate data such as, RCP4.5 and RCP8.5 scenarios was used for the future period assessment. Soil Water Assessment Tool (SWAT) models were used to assess the streamflow response to Climate Change. Calibration and validation of the model output were performed by comparing simulated streamflow with corresponding measurements from the Tikur Wuha outlet for the periods of 1992-2001 for calibration and 2002-2005 for validation using SWAT-CUP(SUFI-2). The model calibration and validation results shows a good agreement with the observed flow with the coefficient of determination 0.79 and 0.86, and a Nash Sutcliffe efficiency was 0.56 and 0.64, respectively. The result of projected temperature reveals a systematic increase in all future time periods for both RCP 4.5 and RCP 8.5 scenarios, and for all considered period whereas the projected result of precipitation was inconsistent throughout all future time periods and for both RCP 4.5 and RCP 8.5 scenarios. The dynamically downscaled daily climate variables (precipitation and temperature) were used to simulate future projections of streamflow. Streamflow projections for future time periods showed that mean annual streamflow may increase by 15.43, 23.48, and 25.42% in 2020s, 2050s, and 2080s, respectively, from the baseline period for RCP 4.5 scenario, whereas for RCP 8.5 scenario, it will be expected to increase by 29.58, 34.20, and 38.72% in 2020s, 2050s, and 2080s, respectively. The model simulations considered only future climate change scenarios assuming all spatial data constant. Therefore, future study need to consider impact of land use/cover change on the sub-watershed for future sustainable development plan.
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    SOIL LOSS RISK ASSESSMENT UNDER CLIMATE CHANGE AND MANAGEMENT PRACTICES: A CASE OF NERI WATERSHED, OMO-GIBE BASIN, SOUTHWESTERN ETHIOPIA
    (Hawassa University, 2019-10-22) ABEBE HEGANO HEMACHO
    Soil erosion is one of the biggest global environmental problems resulting in both on-site and off site effects. Climate change is expected to affect soil erosion based on a variety of factors, including a direct impact on soil loss by increasing precipitation amounts and erosive power. Neri watershed was chosen for this study. The objective of study is to assess soil loss risk under climate change and anticipated management practices. Revised Universal Soil Loss Equation model was applied by integrating bio physical and remote sensing data. Model parameters were computed from available data. Three Representative concentration Pathway scenarios (RCP2.6, RCP4.5 and RCP8.5) and management practices considered for estimation of annual soil loss rates. The resultant annual soil loss map under baseline condition shows the mean and total of 9.955t/ha/yr- 1 and 0.46m t/yr respectively. Estimates suggest that out of the total (46546 ha), about 32.7% % of the total area exceeded the tolerable limit and 67.3%% of the total area were below tolerable rate. The future soil loss rates are higher than the baseline period if no management actions are taken. Under no- management action scenario, the predicted the incremental rate of soil loss from (21.95%) for RCP8.5 (2051-2080) followed by 4.57% RCP4.5 (2021-2050) to insignificant decline (-0.75%) for RCP2.6 (2021-2050) compared to baseline period whereas, the other two predicted reduction. Moreover, inclusion of comprehensive management may result much higher reduction in soil loss over baseline and future condition of no action. The maximum reduction by 41.2% of its soil loss due to climate change is predicted RCP8.5 (2051-2080). The resultant soil loss map of baseline period was used in prioritization of intervention areas based on soil loss tolerance. Among eleven (11) sub-watersheds, eight and ten administrative kebeles out of nineteen are above the tolerable limit. However, watershed as planning unit, taking the proportion of soil loss to area, seven sub watersheds were identified as areas of intervention. To ensure sustainable resource use, management practice like contour cropping system complimented with terraces in agricultural fields and with giving special attention through strong policy measures to climate change, erosion minimization in non-agricultural land use classes were needed. Finaly, the study indicates a need for further study to understand the land suitability that consider the climate change
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    ASSESSING THE IMPACTS OF CLIMATE CHANGE ON STREAMFLOW UNDER CMIP6 CLIMATE PROJECTION IN THE UPPER OMO GIBE RIVER BASIN, ETHIOPIA
    (Hawassa University, 2023-03-25) LEMLEM GETNET MOLA
    Climate Change is projected to have an impact on future streamflow in various watersheds. This study examined the impacts of climate change on streamflow in the Upper Omo River Basin using a Soil and Water Analysis Tool (SWAT). Projected climate variables (precipitation and temperature) ensemble of 5 Global Circulation Models (GCMs) were obtained from the World Climate Research Programme (WCRP), downscaled by the SDSM4.2 model and applied under the Shared Socioeconomic concentration pathways (SSP2-4.5) and (SSP5-8.5) scenarios. The downscaled SSPs data cannot be directly used to the hydrological model (SWAT) to simulate flow so, Distribution Mapping bias correction method was selected for this study. SWAT was calibrated and validated before it was used for simulation purpose. The performance measures R2 and NSE for calibration (2000-2013) and validation (2014-2019) were 0.79 and 0.71 and 0.86 and 0.85 respectively. Mann Kendall (MK) trend testing was used to determine if a change is statistically significant and to detect trends in temperature and precipitation. According to RCP4.5 and RCP8.5, the emission scenarios predicted significant increasing temperature, but significant decreasing precipitation. Streamflow was simulated for two consecutive periods from 2020 to 2045 and from 2046 to 2071 for both scenarios and compared with the base period from 2000 to 2019 to explore the impact of climate change on Streamflow. The results indicated that the basin is likely to experience increased temperatures and altered precipitation patterns, whereas overall annual flow was projected to be significantly decreasing under SSP2-4.5 and SSP5- 8.5 emission scenarios in the mid and near future. These changes are likely to have major implications for water resources management in the region, particularly for agriculture, hydropower generation, and ecosystem services. The findings suggest the need for adaptive measures to address these impacts, including improved water management strategies and increased investment in climate-resilient infrastructure.
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    IMPACT OF CLIMATE AND LAND USE LAND COVER CHANGE ON STREAMFLOW: A CASE STUDY OF YADOT RIVER WATERSHED, GENALE DAWA BASIN, ETHIOPIA
    (Hawassa University, 2021-12-15) ABAY MUSTEFA ABDULE
    Both climate and land use land cover (LULC) change are the main factors that influence hydrological regimes by altering the magnitude of ground water recharge and river flow. Thus, for predicting future stream flow both climate and LULC changes projection should be accounted. In this study, Cellular Automata (CA)-Markov in IDRISI software was used to predict the future LULC scenarios and the ensemble mean of three regional climate models (RCMs) in the coordinated regional climate downscaling experiment (CORDEX)-RCM daily precipitation and temperature for Ethiopia under RCP 4.5 (medium emission scenarios) and RCP 8.5(higher emission scenarios) were used for the future climate scenarios. Power transformation and variance scaling method were used to correct bias the RCMs outputs, with respect to the observed precipitation and temperature. The separate and combined impact of climate and LULC change on stream flow was analyzed using SWAT hydrological model. The calibrated and validated for stream flow simulation using SWAT-CUP with a method of SUFI2.The performance of the model was assessed through calibration and validation process and resulted R2 = 0.8 and ENS = 0.73 during calibration and R2 = 0.83 and ENS = 0.77 during validation on monthly base simulation. The results of the ensemble mean of the three RCMs (CCLM4.8, RACMO22T and EC-EARTH) output show parallel precipitation and temperature increasing trends in the future under RCP4.5 and RCP8.5 scenarios but vary on monthly basis. The increases in mean annual maximum and minimum temperatures are higher for higher emission scenarios than medium emission scenarios. The LULC results showed that both in the past and future period, agricultural and settlement are significantly increased while forest land and scrub/bush lands continuously declined conversely grass/range lands and wood land show decline in the past and increased from 2015 to 2035 and again decreased from 2035 to 2055 in the future period. The past LULC caused an increased mean annual flow by 1.26%, and wet season flow by 2.68% but dry season flow decreased by 2.22% while the future LULC 2015 to 2055 will cause mean annual flow increased by 1.19%, and wet season flow by 2.9% but by decreased for dry season flow by 3.14%. The mean annual flow is projected to increase under both climate and combined scenarios by 7.63% (8.13%) and 5.76% (6.26%) in the near (2021-2050), while in the midterm (2051 – 2080) flow increased by 5.76% (6.26) and 6.07% (6.72%) at the outlet of the watershed under RCP4.5 and RCP8.5 scenarios, respectively. Generally, results of future stream flow projection indicated that the combined change of climate and LULC have relatively higher than the climate changed alone. Such studies enhance better understanding of the various impacts of climate and LULC change scenarios on stream flow, which can be used for better adaptation and mitigation of water resources management problem in the watershed by Appling different water and soil conservation measures.
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    IMPACT OF CLIMATE CHANGE ON SURFACE WATER AVAILABILITY IN THE MOJO RIVER CATCHMENT
    (Hawassa University, 2018-10-23) ERGETIE TILAYE WONDMAGEGN
    Climate change is likely to have severe effects on water availability in Ethiopia. The aim of the present study was to assess the impact of climate change in the Modjo River, Upper Awash Basin. The Statistical Downscaling Tool (SDSM) was used to downscale the HadCM3 (Hadley centre Climate Model 3) Global Circulation Model (GCM) scenario data into finer scale resolution. The Soil and Water Assessment Tool (SWAT) was set up, calibrated and validated. SDSM downscaled climate outputs were used as an input to the SWAT model. The climate projection analysis was done by dividing the period 2011-2099 into three time windows with each 30 years of data. The period 1980-2010 was taken as the baseline period against which comparison was made. Results showed that flow volume may decrease in the 90-year period (2020, 2050 and 2080) this decrease may. in seasons .Kiremit(2020,2050 and 2080) -94.36%,- 43.38% and -49.31% in A2a respectively and -97.21% (2020) and -97.51% (2080) and negligible in 2050 for B2a scenario and Belg seasons should a decrease and is -92.12% and - 80.035 in 2020 for A2a and B2a scenario respectively. In 2050 it should an increase is+3.87% for A2a and negligible for B2a and for 2080 it is -55.54% and -64.94% for A2a and B2a respectively that expected to show the larger share in decreased flow volume for both scenario and in Bega season may a decrease in 2080 for A2a by -54.46% , in B2a may decrease by - 67.33% in 2020 and negligible for 2080s while for A2a in 2020 and 2050 it may increase by +43.29% and +13.995 respectively when one observe annual flow for both scenarios (2020,2050 2080) it may decrease by-47.73,-8.51% and-53.10 %respectively in A2a scenario and - 81.52%,thechange negligible and -30.33% respectively in B2a scenario. Overall, it appears that climate change will result in an annual decrease in flow volume, ranges for A2a -8.51%-to - 47.73% and from -30.33% to-81.52% for B2a scenarios
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    THE EFFECT OF CLIMATE CHANGE ON URAN DRAINGE: CASE OF BISHOFTU CITY DRAINAGE
    (Hawassa University, 2018-07-14) ABREHAM AMDE GEBRESELASSIE
    Climate change is a reality that planners and designers of drainage infrastructures must consider. Therefore, the risk should be investigated and quantified properly. The objective of this thesis is to investigate the effect of climate change on Urban Drainage having the case of Bishoftu city drainage. Projection of the future climate is done by using CMIP5 climate model outputs of RCP4.5 and RCP8.5 scenarios and downscaled daily rainfall and temperature data of CMIP5. The future climate projection analysis was done by partitioning the coming 50 years in two periods which are (2020-2040) and (2051-2070) and the 1994-2013 is taken as the base line period. These climate scenarios data were bias corrected for serving as input to the SCS for impact analysis. Using Easy fit software, the rain fall data was fitted to Gumball distribution for the quantile estimation. The quantile estimation of 2, 5, 10, 25, 50 and 100 years return period for the site were found to be 47.818, 60.043, 68.137, 78.363, 85.95, 93.481, 110.884 and 118.365. Respectively. The study area which are Kalhiwet church area and the market area water shed area of the drainage design was done. The hydrologic analysis of rain fall run off is computed by using modified SCS method and the hydraulics parameter is computed by 4.2 Hydraulic tool box software for the two catchment area with RCP4.5 and RCP 8.5 Scenarios of the two time horizon of 2030s and 2060s. Finally the design discharge amount is change in Market area by RCP 4.5 in 2060 is change by 63.3% and Minimum 18.64% in RCP 4.5Average design discharge, channel width and depth will increase up to 60.8% Max and 16.9% Min , 29.9% Max and 6.05% Min, and 20.21% Max and 6.7% Min depth is changed in KHC respectively. And for the design discharge of market area Max 63.3% and Min 18.64%, the width of channel is changed by 31.16% Max and 8.17% Min, and also the depth of the channel 32.22% Max and 9.09% Min also change. Therefore, the consideration of climate change on drainage is important
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    ASSESSMENT OF CLIMATE CHANGE IMPACT ON SURFACE WATER RESOURCE IN WOSHA WATERSHED, RIFT VALLEY LAKES BASIN, ETHIOPIA
    (Hawassa University, 2024-10-16) ELSAE WARE GIDESA
    Climate 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.
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    ANALYSIS AND CHARACTERIZATION OF HYDROLOGICAL DROUGHT UNDER CLIMATE CHANGE IN HAMASSA WATERSHED, RIFT VALLEY BASIN
    (Hawassa University, 2024-07-20) REDIAT LEGESE SIME
    Hydrological 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 watershed
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    ASSESSMENT OF CLIMATE CHANGE IMPACT ON STREAM FLOW OF GIDABO SUBBASIN, RIFT VALLEY BASIN, ETHIOPI
    (Hawassa University, 2022-08-10) YIDIDYA TSEGAYE ALEMU
    Climate 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