Water Resource

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

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    IMPACT OF LAND USE LAND COVER CHANGE ON HYDROLOGIC RESPONSE: THE CASE OF DEME CATCHMENT, OMO-GIBE RIVER BASIN, ETHIOPIA
    (Hawassa University, 2021-10-24) MULUKEN ISRAEL BIRRU
    Hydrologic modeling was conducted for each LULC map in three time periods (1999, 2010, 2018) in the Deme catchment using the SWAT model. Changes in streamflow and its components between three simulations by using the LULC map of 1999, 2010, and 2018 were related to the changes of LULC to quantify the impact of LULCC. The data used for analyses were streamflow of Deme catchment, satellite imageries of 1999,2010, and 2018, Digital elevation model, and meteorological data. LULC classification was carried out by using ERDAS imagine2014. Five types of LULC were identified in the Deme watersheds such as agricultural land, grassland, bushland, built-up area, and forest. The LULCC analysis depicted that there was an expansion of agricultural land and the built-up area in the catchment. Agricultural land was increased by 29.96% and 36.78% from 1999-2010 and 2010 -2018 respectively. The built-up area was also increased by 80.41% and 148.47% during the first and the second period respectively. The other LULC classes showed a continuous decrement in all periods. The performance evaluation result depicted that the SWAT model can be used for the analysis of the impact of LULCC on streamflow of the Deme catchment. During calibration, the value for NSE, R2, and PBIAS was 0.80, 0.75, and -1.2 respectively. During validation, the value for NSE, R2, and PBIAS was 0.74, 0.70, and -7.3 respectively. The LULCC had impacted the magnitude of streamflow and its components. During the driest season, mean monthly streamflow has decreased by 16.71% and 37.81% during the first and second periods respectively. But in contrast during the wettest month, the mean monthly streamflow has increased by 12.79% and 25.16% during the first and second period respectively. The contribution of mean annual surface runoff increased by 11.63mm and 15.94mm from 1999- 2010 and 2010 to 2018 respectively. While lateral flow decreased by 6.47mm and 9.96mm in both periods. Similarly, shallow groundwater recharge decreased by 3.77mm and4.67mm during the first and second periods. The decrease in lateral flow and shallow groundwater recharge and increase in surface runoff was related to the expansion of agricultural land, and built-up area, as well as decrement of forest, bushland and grass land. Therefore, Deme watershed requires the application of appropriate watershed management options to minimize the undesirable impacts on water and land resources.
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    PHYSICAL IRRIGATION POTENTIAL ASSESSMENT FOR SURFACE IRRICATION: A CASE STUDY IN CHEMOGA WATERSHED, UPPER BLUE NILE BASIN, ETHIOPIA
    (Hawassa University, 2020-10-11) KASSANESH MELKAM MENGISTE
    Assessment of available land and water resources for irrigation is essential for planning their use, to utilize limited resources efficiently and for the sustainable production of crops and food security of the ever increasing people in developing countries like Ethiopia. The study was mainly focused on assessing the available land and water resources potential for surface irrigation of Chemoga Watershed. This was done by using Geographic Information System (GIS)-based Multi Criteria Evaluation (MCE) tools, a hydrological Soil and Water Assessment Tool (SWAT) model, and a Crop Water and Irrigation Requirements Program of FAO (CROPWAT) model. GIS was used to map the land suitable for surface irrigation based on slope, soil, land use /land cover, and river proximity. SWAT model was used to estimate the water availability, and CROPWAT model calculate the reference crop evapotranspiration, effective rainfall, net and gross irrigation water requirement of crops. Potentially suitable land for surface irrigation development was evaluated by selecting six crops (barley, wheat, bean, maize, onion, and potato). The result of the overall weighted analysis for these factors gave about 25462.08 ha (71.4 %) of the Watershed land considered as high to moderately suitable whereas 10427.53 ha (28.6 %) were not suitable for surface irrigation. The SWAT model was calibrated and validated from the available hydro metrological and spatial data. Model performance result showed in between the observed and simulated stream flow with coefficient of determination (R2) and Nash-Sutcliffe efficiency (ENS) values 0.86 and 0.7 for calibration, and 0.74 and 0.63 for validation, respectively and indicated a good performance of the model in simulating the hydrology. The annual average simulated stream flow was evaluated and 36.2 m 3 /s. The water demand required by the selected crops was 228.18m3 /s/ha. From the total available suitable land, only 12376.03 ha can be irrigating with the available water
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    HYDROLOGICAL RESPONSES TO CURRENT AND PROJECTED LAND-USE/LAND COVER CHANGES OF THE WELMEL RIVER WATERSHED, GENALE DAWA BASIN, ETHIOPIA
    (Hawassa University, 2021-03-27) SOLOMON ESHETE AYALEW
    Land use/land cover change is one of the important concerns in many regions of the world. It is recognized that dramatic LULC change can significantly impact regional climate, ecosystem stability, water balance, stream silt up, socioeconomic practices, and biodiversity. The main objective of this study was to assess the hydrological responses to historical and future Land Use/Land Cover Change at basin and sub-basin levels of the Welmel River watershed, which is located in the Genale-Dawa Basin South Eastern Ethiopia using hydrological SWAT model. The study analyses the historical LULC change between the years 1990, 2005 and 2020 and the future year of 2035 and 2050. The hydrological responses to LULC changes in the Watershed were analyzed using the historical and future LULC maps. Images were processed using ERDAS Imagine 2014 and CA-Markov chain model was used for the prediction of the LULC map of 2035 and 2050. Discharge data from 1990 to 2006 and 2007 to 2014 were used for calibration and validation respectively with three years of warm-up period and climate data from 1990 to 2020 time period. The main finding of this study revealed that the coverage of agriculture/settlement increased by a rate of change of 6.85km2 /year, while forestland was declined by the rate of change of 9.16km2 /year over the last 31 years between 1990 and 2020. In the coming 31 years (by 2050), if the current trend of LULC change continues, agriculture/settlement land is expected to increase by the rate of change of 6.73km2 /year, while forestland is expected to diminish by a rate of change of 8.78km2 /year. As a result of LULC change, surface runoff has increased by 25.32% while lateral flow, groundwater flow, water yield, evapotranspiration and percolation declined by 19.91%, 17.17%, 2.38%, 0.36% and 17.17% respectively between 1990 and 2020. If the current rates of LULC change continue, surface runoff is expected to increase by a relative change of 18.47% while lateral flow, groundwater flow, water yield, evapotranspiration and percolation are expected to decline by 26.84%, 17.51%, 2.09%, 1.91% and 17.47% respectively by 2050. Average annually, surface runoff in all 29 sub-basins has increased by 39.90mm and groundwater flow decreased by 34.57mm. The average annual stream flow increased with a relative change of 6.18% from 1990 to 2020 and is expected to increase by 12.69% by 2050. The average wet annual flow from 1990 to 2020 increased by 10.21%, while the average dry annual flow decreased by 6.34%. The average wet and dry annual stream flow is expected to increase and decline by 19.67 % and 6.86% respectively in 2050. Therefore, the Woredas in and around the Welmel River Watershed and the Bale Mountains National Park should integrate to design and implement a proper strategy for protecting and managing the existing forest and woodlands in addition to rehabilitating the degraded areas to maintain the hydrological balance of the watershed.
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    ASSESSMENT OF WATER BALANCES USING SWAT MODEL AND AGRICULTURAL WATER DEMAND ANALYSIS OF GIDABO RIVER CATCHMENT, RIFT VALLEY BASIN, ETHIOPIA
    (Hawassa University, 2020-07-18) CHALA TADESSE
    To use water resources sustainably, it is important to understand the quantity of water resource spatially and temporally. The work presented here attempts to model water balance of one of Gidabo sub-watershed of Ethiopian Rift Valley Basin using the Soil and Water Assessment Tool (SWAT. Statistical model performance measures, the coefficient of determination (R2 ) and Nash-Sutcliffe Efficiency (NSE) were used to evaluate the correlation between the observed and simulated monthly stream flow. The result shows an acceptable performance of SWAT model in simulating the watershed hydrology as evidenced by the NSE value of 0.79 and R2 value of 0.80 at calibration (using data from1990-2009) and NSE = 0.71 and R2 =0.82 at validation (using data from2010- 2014). In terms of water balance components, the long-term annual precipitation is found to be in the magnitude of 1435.58 mm; whereas the surface runoff; total water yield; and actual evapotranspiration, are estimated as 62.20; 1189.73, and 228.40 mm respectively. In order to link the water balance estimation with the local agricultural water demand, wheat and potato are selected for they are common crops for irrigation in the watershed. While taking the month of March, which is the month of maximum agricultural water demand (11.6 m 3 /s), the watershed is found to be water-surplus as indicated by the water availability of the critical month (12.22 m3 /s) to be higher than the demand. This research implies that the use of models in supporting decisions related to water resources development and management is paramount important to understand how the system functions