Water Resource

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    MODELING OF SURFACE WATER RESOURCES FOR WATER ALLOCATION: A CASE STUDY IN UPPER GIDABO WATERSHED, GIDABO SUB BASIN, ETHIOPIA
    (Hawassa University, 2023-10-28) TAMIRAT SHUKE KITAWA
    The processes of population increase, urbanization, industrialization, and dependency ratio has resulted in a rapid demand increase for water resources in the developing world. Water managers in the watershed of the developing world face the increasingly difficult task of allocating the limited water resources among competing users for fulfilling their demands due to difference in available resources and water demand increment. Water resources management has limited in the Upper Gidabo watershed and there is traditional water allocation are vastly practiced. This was due to lack of sufficient awareness about available water resources and management in watersheds. Understanding the potential and use of surface water in upper Gidabo would help to increase the productivity of Agriculture and other sectors, to improve the traditional water management system. Therefore the objective of this study was to Modeling of surface water resources for water allocation under developed scenarios for maximizing overall benefits without compromising ecological requirements in the Upper Gidabo watershed in Gidabo sub basin. To achieve the aim of this study soil and water assessment tool (SWAT) model was used to determine the available surface water resources of the watershed after sensitivity analysis, calibration and validation of the model by SWAT_CUP sufi-2 algorithm. The simulated result revealed that the total average surface water potential from the watershed was 773.5 MCM annually during the study period (2021). Both the calibration and validation result for Aposto and kolla gauging station showed a good performance with a value of R2 and NSE of 0.83 and 0.65 for calibration and 0.81 and 0.6 for validation in Aposto and 0.79 and 0.62 for calibration and 0.78 and 0.61 for validation in Kolla gauging station, respectively. After this Water Evaluation and Planning (WEAP) model was used to assess water demands. To assess irrigation water requirement of the sixteen (16) crop types CROPWAT 8.0 software was used. After assessing the currently existing demands Different scenarios were also developed to determine the future water demand, and unmet demand from overall time period of 2021-2050, This scenarios namely: reference, population growth and increased water demand scenario was established to determine increasing demands under increasing human as well as Livestock population, agricultural areas and different industrial activities. The current (2021) utilization is about 110.4 MCM for consumptive use and non-consumptive (EFR) use, For EFR 10% considered from available flow to maintain ecological functioning and water resource development in the watershed. The current demands fully met with available flows and for scenarios the assessed total annual water demand may be expected to be 126 MCM, 195.1 MCM and 341.8 MCM for the reference, high population growth, and increased water demand scenarios, except increased water demand scenario the other scenarios is met fully, It is appropriate to shape more effective policies and regulations in the area for effective water resources management in reducing water shortage and achieving downstream water needs in the future
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    QUANTIFYING SURFACE WATER AVAILABILITY AND DEMAND ANALYSIS IN THE POORLY GAUGED CATCHMENTS OF JEMMA SUB-BASIN, ABBAY/UPPER BLUE NILE BASIN, ETHIOPIA
    (Hawassa University, 2023-10-28) SAMUEL ABABU FARIS
    The socioeconomic activities and environmental changes with respect to the spatiotemporal variation of streamflow in the catchment intricates the supply and demand management system. Assessment of the surface water potential and demand analysis at a sub-basin level was aimed at estimating escalating demands of the catchments and meeting the society's needs without causing potential negative consequences on the ecological balance of the catchments. To quantify the surface water availability of the catchments, the soil and water assessment tool (SWAT) model was used after the sensitive analysis, calibration, and validation of the model was done by SWAT-CUP. The annual total demands was anlysed in water evaluation and palanning (WEAP) model after the surface water potenial was quantified. Different‘’what if” scenario was developed to forecast future water demand, supply requirement, and unmet demands in 2022-2035. The model showed the mean annual flow depth in Beressa and Robigumer catchments was 174.4mm and 166.91mm, respectively and contirbutes to 37MCM and 149.05MCM surface water potential, respectively. From the mean annual precipitation recieved in the Beressa and Robigumer catchments, 48% and 43% was lost through evapotransipiration, respectively. The model performace showed satisfactory result with a value of 0.89(R2 ), 0.87(NS), and 0.76(R2 ), 0.74(NS) in calibration, and 0.71(R2 ), 0.70(NS), and 0.72(R2 ), 0.66(NS) in validation in the Beressa and Robigumer catchments, respectively. The CROPWAT 8.0 model was used to determine the irrigation water requirement of selected crops. The total consumptive water demand in 2022 was 11MCM(29.7%) and 8.1MCM(5.4%) of the total surface water potential of the Beressa and Robigumer catchments, respectively. The total water demand in projected irrigation area scenario was 125.64MCM(84.05%) of the surface water potential of the Robigumer catchment in the year 2035. The EFR was significant parameter to maintain the ecological balance of catchments. In the two last scenarios the total water demand were beyond the surface water potential of the Beressa catchment. To mitigate the future water stress and scarcity in the catcments, dopting rainwater harvesting, other potential sources, and integrated water resources management options are importannt
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    MODELING WATER RESOURCES USING WEAP MODEL FOR EFFECTIVE WATER MANAGEMENT: A CASE STUDY IN LEGEDARA RIVER CATCHMENT, SNNPR, ETHIOPIA
    (Hawassa University, 2017-10-27) HENOK MEKONNEN ARAGAW
    Water is the life blood of all living things yet its availability and management is not well understood and quantified at the catchments scale. Legedara River catchment water resources availability is not well known since the catchment is ungauged and also the water demands within the catchment is not quantified and properly allocated. This study attempted to model the water resources of Legedara river catchment in SNNPR for effective water management through scenario analysis using WEAP model.Hydro-meteorological, spatial, and water demand data were the basic inputs to the model. FAO-Rainfall-Runoff (Simplified Coefficient) method was used to estimate runoff of Legedara River catchment by transferring calibrated model parameters from gaugedWaleme River catchment. However, before transferring calibrated model parameters different procedures were done, since selection of representative catchment, modeling of gauged catchment and calibration and validation. Catchments areal rainfall and reference evapotranspiration are estimated by Thiessen Polygon method and Penman Monteithmethod respectively. Domestic, industrial and environmental water requirements were estimated using WEAP model. Current situation of water demands for the selected water users were simulated. Five different scenarios for future water demands were developed and in addition to these climate scenario was developed and evaluated. During the model setup, all demand sites were assigned equal priority. As a result of parameter derivation hydro meteorological Waleme River catchment is almost similar to Legedara River catchment. The model calibration and validation results were found satisfactory for the gauged catchment (ENS = 0.81; R2 = 0.86 and RVE = -2.64% for calibration and (ENS = 0.77; R2 = 0.81 and RVE = - 7.73% for validation). The water balance components of Legedara River catchment were estimated and mean annual values of rainfall and reference evapotranspiration found to be 1316.42mm and 1142.07mm, while the actual evapotranspiration and runoff constitutes; 538.78mm and 778.65mm respectively. The modeling result revealed that, all the selected demand sites satisfied fully in the current situation and for reference scenario, scenario one, two and four, even though the remaining river flows for the months of December, January and February were almost zero after deduction. However, the result of catchment water resources and demands showed that at the last year of scenario three (2040), there will be a 26.71MCM, i.e., 36.17%, reduction in the total annual flow of Legedara river catchment.Moreover, it was found in the catchment that it is having unmet demands in scenario three. Nonetheless, it was shown that environmental flow requirement of 14.77MCM will be fully delivered at the outlet of Legedara River catchment. Hence, no absolute scarcity of water would develop. In scenario five, the simulating value showed that, increase and decrease of current mean monthly rainfall values by 10% and 5% have an impact on increase or decrease of catchment runoff.Further researches on groundwater availability were also suggested to meet the unmet demands
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    SURFACE WATER AVAILABILITY AND SCENARIO BASED DEMAND ASSESSMENT OF THE KELETA RIVER WATERSHED, AWASH RIVER BASIN, ETHIOPIA
    (Hawassa University, 2020-10-25) MEHIRET HONE FISHA
    The ever-increasing world population, changes in the living standard and consumption pattern, and the rapid expansion of irrigation agriculture exert a lot of pressure on water resources. Irrigation, the major water user, relies mostly on surface water from the Awash River and its tributaries and it is very important to assess surface water potential at this basin. This study was conducted at Keleta River Watershed, which is found in the Upper Awash River Basin of Ethiopia. The main objective of this study was to assess the surface water availability and scenario-based water demand assessment in the Watershed using the Soil and Water Assessment Tool (SWAT) and Water Evaluation and Planning System (WEAP) models. The SWAT and WEAP models were used to estimate the surface water availability and scenario base users’ water demands in Keleta River Watershed, respectively. The SWAT model was calibrated and validated using observed streamflow data to get reliably predicted streamflow values. The model performance was evaluated employing two error indices called Nash-Sutcliffe efficiency (NSE) and coefficient of determination (R2 ). The results showed that the mean annual precipitation, actual evapotranspiration, and potential evapotranspiration were 831.1, 451.4, and 1180.4 mm, respectively in Keleta Watershed. The estimated surface runoff available from the entire catchment was 124.50 million cubic meters (MCM), which was equivalent to 165 mm depth of mean annual runoff. The assessment of water demand was done based on the current and projected future scenarios. The identified sectors of water users in the watershed were irrigation, livestock, domestic (rural and urban), public and industrial demands. The scenarios evaluated what would be the water demand if the population growth rate is 4% and the Irrigable area increases by 5% annually in the coming 25 years until 2045. The results showed that irrigation was found the highest water consumer among the demand sites whereas the lowest was observed in the public demand site, which consumed 42.22 and 0.63%, respectively from the total demand. The predicted water demand increases by 83.55% in 2045 while the unmet demand increases from the current volume of 0.25 MCM to 7.65 MCM due to the expansion of the irrigable area as compared to the reference scenario. Generally, the result indicated that the water demand as well as the unmet demand increases in the Kelata watershed. The study shows that the water demands in January, February, March, and April were found to be high as the supply was found to be low during the same months. This indicates the temporal variation of supply and demand in the Watershed. Water harvesting structure and groundwater development should be conducted to supplement this water deficit