Water Resource
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Item EVALUATING THE PERFORMANCE OF HEC-HMS AND SWAT HYDROLOGICAL MODELS IN SIMULATING THE RAINFALL RUNOFF PROCESS FOR DATA SCARCE REGION OF ETHIOPIAN RIFT VALLEY LAKE BASIN(Hawassa University, 2020-10-23) MOHAMMEDRESHID ABDALA ALIYESeveral physically-based and distributed watershed models have been developed to model the hydrology of the watershed. For a specific watershed, selecting the most suitable hydrological model is necessary to obtain good simulated results. In this study, two hydrologic models, Soil and Water Assessment Tool (SWAT) and Hydrological Engineering Centre–Hydrologic Modeling System (HEC-HMS), were applied to simulate streamflow in the Katar river basin, Ethiopia. The performances of these two models were compared to select the right model for the study basin. Both models were calibrated and validated with streamflow data of 11 years (1990- 2000) and 7years (2001-2007) respectively. Nash-Sutcliffe Error (NSE) and Coefficient of Determination (R2 ) were used to evaluate the efficiency of the models. The results of calibration and validation indicated that, for river basin Katar, both models could simulate fairly well the streamflow. SWAT gave the model performance with the R2 > 0.78 and NSE > 0.67; and the HEC-HMS model provided the model performance with the R2 > 0.87 and NSE > 0.73. Hence, the simulated streamflow given by the HEC-HMS model is more satisfactory than that provided by the SWAT modelItem STREAMFLOW RESPONSE TO CLIMATE CHANGE ON TIKUR WUHA SUB WATERSHED, RIFT VALLEY BASIN, ETHIOPIA(Hawassa University, 2018-10-23) BROOK LEGESE DADHIClimate 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.Item ASSESSING THE IMPACT OF LANDUSE/LANDCOVER CHANGE ON THE HYDROLOGICAL RESPONSE OF KOLA RIVER WATERSHED, SIDAMA REGION, ETHIOPIA(Hawassa University, 2021-10-23) NIGUSU MULETA ETANALanduse/land cover change is one of the major factors that affect the hydrological response of watersheds. Hence studying the impacts of past and future landuse/land cover changes on the hydrology of Watershed is very important for proper watershed management. This study investigated the past and potential future land cover changes and their impact on the hydrological response of the Kola River Watershed by using the Soil Water Assessment Tool (SWAT).To detect and analyze the change that had taken place in the study area, satellite images were downloaded for 1988, 1998, 2008, and 2018 years and processed using ERDAS Imagine 2014. Then by using the supervised image classification technique, the satellite images were classified to agriculture, agroforestry, built up pasture, land, and forest landuse the land cover types. Then accuracy assessment was done, and overall accuracy of 87.83%, 88.41%, 89.15%, and 91.76%, was achieved for the classified images of 1988, 1998, 2008, and 2018 respectively. The changes of landuse/land cover of the study area from 1988 to2018 indicated that Pastureland, Forest, and Agroforestry decreased by 69.55%, 40.86%, and 15.77%, while Agriculture, and Built-up, increased by 24.67%, and 23.9%, respectively. The future LULC of 2048 was projected by IDRISI (CA-Markov method) and the result indicated a continuous increase of Agriculture and Built-up areas as the other landuse land cover such as forest, pastureland and Agroforestry decreased. Model sensitivity analysis was made to choose the most sensitive parameters. Then, R2 and ENS achieved 0.87, 0.77 during calibration and 0.85, 0.74 for validation respectively. The model performance evaluation indicated that SWAT can be used for modeling the impact of historical and projected LULCC on the hydrological response of the study Watershed. As the investigation of 1988 to2018 shows, due to LULCC, the seasonal flow increased by 25.71%, 23.73%, and 19.96%in the first and, second rainy seasons, and short rainy season, while it decreased by 22.21% in the dry season respectively. The annual surface runoff and water yield increased and by 22.21%, and 3%, whereas evapotranspiration and lateral flow, decreased by, 6.21%, and 14.61% respectively. The future LULCC prediction of 2048 showed thatseasonal flow increased by 29.03%, and 28.08%, 14.6% in the first and second rainy season, and short rainy season and decreased by 19.3 in dry seasons. Generally, the investigation of hydrological response to LULCC by taking other data constantly at different predefined study years indicates LULCC has significant impacts on the hydrological response of the study watershed. Therefore to overcome the impact of LULCC, local and national policymakers should be invited to prepare and apply scientific and appropriate watershed planning and management, strategies in the Kola River WatershedItem HYDROLOGICAL RESPONSE OF CLIMATE CHANGE ON WEYB RIVER WATERSHEDS: THE CASE OF BALE MOUNTAINOUS AREA, ETHIOPIA(Hawassa University, 2019-04-18) NESHA BAHMUD USHIThe 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 watershedItem IMPACT OF CLIMATE CHANGE ON SURFACE WATER RESOURCE AVAILABILITY: A CASE STUDY IN WELMEL WATERSHED,GANALE-DAWA BASIN, SOUTH ETHIOPIA(Hawassa University, 2018-10-27) BERECHA DINSA CHAKAClimate change, nowadays, has significant impact on the water resource system of an area. This study was conducted for Welmel watershed, Ganale-Dawa river basin, Ethiopia, using Soil and Water Analysis Tool(SWAT) hydrological model and General Circulation Model (GCM) aiming at estimating the impact of climate change on water availability of the study area. By making proper calibration, precipitation and temperature outputs of HadCM3 coupled atmosphere-ocean GCM model for A2a (medium to high) and B2a (Medium to low) SRES emission scenarios were downscaled using the Statistical Downscaling Model (SDSM). The downscaled minimum temperature shows an increasing trend in all future time horizons for both A2 and B2 scenarios. The average annual minimum temperature will be 0.30 C change from baseline in 2020s (2014-2041).In2050s (2042-2069) of minimum temperature will be 0.65o C and also 0.63o C for A2 and B 2 scenario respectively. For the 2080s (2070-2099) periods the average annual minimum temperature will be increased by 1.3o C and 1.03o C for A2 and B2 scenario respectively. The downscaled maximum temperature scenario, on the other hand indicates that for most months there will be an increasing trend for both A2 and B2 scenario. The projected temperature in 2020s indicates that maximum temperature will rise by 0.232o C. In 2050s the increment will be 0.527o C and 0.53o C for A2 and B2 scenario respectively. The future precipitation of the study area is expected to annual average increase by 11.90% for A2a and 11.67% for B2aemission scenarios. The actual evapotranspiration will also increase by 3.64% for A2a and 3.75% for B2a respectively. The results obtained from this investigation indicate that there is significant variation in the seasonal and monthly flow. In the main rainy season (June-September) the runoff will be reduced by 12% in the 2080s. The result from synthetic (incremental) scenario also indicates that the catchment is sensitive to climate change. As much as 23% of the seasonal and annual runoff will be reduced if an increment of 2o C in temperature.Item WATER RESOURCE POTENTIAL INVESTIGATION OF LAKE HAWASSA WATERSHED BY USING A SOIL AND WATER ASSESSMENT TOOL (SWAT(Hawassa University, 2019-07-24) JUNDI YUSUF ABRAHIMUncertainties in information about fresh water resource potential have created a critical situation for many countries. Investigating spatiotemporal variability of water resources is, therefore, a critical initial step for water-resource management. Successful planning and management of water resources require the application of effective integrated water resources management (IWRM) models that can solve the encountering complex problems in these multi-disciplinary investigations. In this work, the water resources of Lake Hawassa watersheds were modeled using the Soil and Water Assessment Tool (SWAT), which is a continuous-time, semi-distributed, process-based model. The SWAT-CUP program was used for calibration/validation of the model with uncertainty analysis using the SUFI-2 (Sequential Uncertainty Fitting program) algorithm over the period of 1990- 2015 at one gauge station. Parameter transfer method was used from gauged (Tikurwuha) sub catchment to ungauged one. The performance of the SWAT model was evaluated through sensitivity analysis, calibration, and validation. Ten flow parameters were identified to be sensitive for the stream flow of the study area and used for model calibration. The model calibration was carried out using observed stream flow data from 1995 to 2010 and a validation period from 2011 to 2015 years. Both the calibration and validation results showed satisfactory match between measured and simulated stream flow data with the coefficient of determination (R2 ) of 0.71 and Nash-Sutcliffe efficiency (NSE) of 0.66 for the calibration, and R2 of 0.64 and NSE of 0.59 of the validation period. The results reveal that the annual blue-water potential (water yield and deep aquifer recharge) of Lake Hawassa Watershed is 854 million m3 , Whereas the green-water flow (actual evapotranspiration) (ET) is 629 million m3 and green water storage (soil moisture) is 82 million m3 . Watersheds located around Wondo-Genet yield more blue-water resources compared to watersheds at the western side. The model highlights the water potential of the catchment under current circumstances and gives an insight into its spatiotemporal distribution over the watershed. This study provides a strong basis for the forthcoming studies concerning better water-resources management practices, climate change, and water-quality studies, as well as other socio-economic scenario analyses in the region.Item ASSESSING THE IMPACT OF LU/LC CHANGE ON HYDROLOGICAL RESPONSE BY USING SWAT MODEL: A CASE STUDY AT DEDABA WATERSHED, ETHIOPIA.(Hawassa University, 2021-04-26) IBSA DIBO DEKOWater is a precious and finite resource and must be managed in sustainable way to meet human as well as environmental needs. Land use/land cover change has an impact for alteration of watershed hydrology. The watershed is undergoing land use change due to intensive cultivation andurbanization as a result of population growth which has an impact on hydrologicresponse of the watershed. This study quantified watershed runoff volume using SWAT modeland assessed the effect of land use/land cover change on the stream flow. In this study, the impact of LU/LCchange was carried out by using the Soil Water Assessment Tool (SWAT2012) model, which was integrated with GIS10.3 software. GIS and ERDAS IMAGINE2014 were used to generate LU/LCmaps from Landsat TM, TM, and OLI acquired in the years 1990, 2001 and 2018 respectively. The land cover maps were generated using the maximum likelihood algorithm of supervised classification. The classified maps were assessed using confusion metrics. The results of the analysis showed that the Agricultural land has expanded during the study period of 1990-2018. During the study period, forest land, and shrub and grassland decreased by 19.5% and 15.61% respectively while Agricultural land and Built-up area increased by 33..63% and 1.48% respectively. Using three land cover maps, three SWAT model setup were run to evaluate the impacts of LU/LC changes on the streamflow of the study watershed. The performance of the SWAT model was evaluated through sensitivity analysis, calibrationand validation by using SWAT-CUP. The Coefficients of determination and Nash–Sutcliffe were used to evaluate the model and it resulted in 0.87 and 0.73 for calibration and 0.82 and 0.68 for validation respectively. During the study periods, the simulation result indicated that streamflow increased in the wet season and short rainy season streamflow by 9.64% and 3.05% respectively, while decreasing by 5.6% in the dry season. The Surface Flow (SURQ) increased by 12.58% while Groundwater Flow (GW_Q) decreased by 14.83% due to the increment of Agricultural land. The study resultsshowed change in flow with change in land use/landcover, so it needs landuse planning and sustainable water resource managementItem SURFACE WATER AVAILABILITY AND SCENARIO BASED DEMAND ASSESSMENT OF THE KELETA RIVER WATERSHED, AWASH RIVER BASIN, ETHIOPIA(Hawassa University, 2020-10-25) MEHIRET HONE FISHAThe 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 deficitItem STREAM FLOW RESPONSE TO LAND USE/LAND COVER CHANGE-: (THE CASE OF GELANA CATCHMENT, RIFT VALLEY LAKE BASIN, ETHIOPIA)(Hawassa University, 2020-10-21) ENKU SIYOUM MENEBOWater resources are significantly affected by land use/land cover change (LU/LCC) at multiple spatial scales. This change is overwhelming in recent years globally. LU/LCC also aggravated in Gelana catchment within space and time. The main objective of this study was to detect the LU/LCC and investigating its effect on stream flow in the Gelana catchment, Rift valley Lake basin, Ethiopia. Spatio-temporal data were gathered and analyzed. Meteorological data from 1987 to 2018 and hydrological data from 1991 up to 2010 were used for characterizing the climate and used as model input. ERDAS 2014 was used to process preliminary data extracting, layer stacking, pan sharpening of images, image classification, and accuracy assessment for the Landsat image of 1988, 2003 and 2018. The Soil and Water Assessment Tool (SWAT) was used to perform stream flow simulation. The model was calibrated and validated on a monthly and daily time scale for a period of 1991 to 2005 and 2006 to 2010 during calibration and validation respectively. The accuracy of LU/LC classification was achieved by overall, user, producer accuracy and kappa coefficient. Results of the LU/LCC detection show that from the year 1988 to 2018 cultivation land increased by 39.7%, grass land increased by 3.7% and, the settlement area increased by 1.3%. While, mixed forest area and shrub land decreased by 38.3% and, 6.1% respectively. The model result depicts that the SWAT model run on a monthly time scale could able to capture the different response mode of the catchment well reasonably as evaluated through the coefficient of determination, Nash Sutcliffe efficiencies and PBAIS of 0.82, 0.77 and -9 during calibration and 0.76, 0.7 and -10.4 during validation respectively. From this study, it was perceived that, expansion of farming land and reduction of forest and shrub land affect stream flow volume of the catchment. The stream flow results indicated that 1-day and 7-day max flow increased in 4.3m3 /s, 5.1 m3 /s and 1-day and 7-day min flows were by 0.12m3 /s and 0.1 m3 /s respectively in comparing 1988 and 2018 simulation period. Beside the volume of annual flow increased by 0.94 m3 /s during from 1988 simulation period to 2018 simulation period. Moreover; past LU/LCC affects the wet season flow it increased in 1.56 m3 /s, and the dry season flow was decreased in 0.32 m3 /s in comparing 1988 and 2018 simulation period. The findings of this study indicate that water resources development in the catchment needs a proper understanding of the LU/LCC and its effect on stream flow. Thus, for sustainable water resources development, catchment interventions aiming at reducing high flows and increasing base flows are recommended.Item ASSESSMENT OF SURFACE IRRIGATION POTENTIAL: THE CASE OF GIDABO WATERSHED, RIFT VALLEY LAKES BASIN, ETHIOPIA(Hawassa University, 2019-03-07) AZEMERAW ALEMUEthiopia has immense potential in expanding irrigated agriculture. Irrigable land assessment is essential for the development of irrigated agriculture. The study was aimed at assessing land potential of Gidado watershed. Land suitable for irrigation development was determined with a GIS-based multi-criteria evaluation, which considers the interaction of various factors such as slope, soil, LULC, proximity to river and road. The Analytical Hierarchal Process (AHP) and ArcSWAT were used for analyzing the different factors by assigning weights and mapping of suitable potential irrigable areas and surface water potential of the study area was estimated using SWAT model respectively. The model was calibrated and validated from observed stream flow data at three monitoring sites within the watershed using the periods of 1993-2004 and 2005-2012 respectively by using SWAT-CUP program and Global Sensitivity Analysis (GSA) was used for identifying important model parameters. The irrigable land of the area was identified using weighted overlay analysis of the suitability parameters, thus the result indicated that 1138.31 km2 areas was classified suitable and 2042.19 km2 area was classified as not suitable for surface irrigation. During calibration and validation, the results of model performance indicators were in the acceptable range (R 2= 0.68, 0.73, 0.72), (NSE = 0.60, 0.63, 0.71) and (PBIAS=12.2, -9.0 and -14.0) for Gidabo, Kola and Bedessa rivers respectively which indicated that a good to very good agreement between observed and simulated values. And average surface water resource potential of the catchment estimated to be 86.36m3 /s or 223.86 MCM. However after analyzing 25 years river discharge and determined the water demand of the crop, 74390.89ha (23.39%) of the potential irrigable area was estimated and could be irrigated consistently with runoff from the river systems. For sustainable irrigation development, other suitability factors such as soil chemical properties, socio-economic, environmental issues, and distance from markets and town should be considered