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    ASSESSING THE IMPACT OF LANDUSE/LAND COVER CHANGE ON STREAM FLOW AND FUTURE PREDICTIONS OF LANDUSE/LAND COVER CHANGES OF BELES SUB-BASIN, UPPER BLUE NILE BASIN, ETHIOPIA
    (Hawassa University, 2023-08-22) TSEGA MOGES
    Landuse and land cover change drives changes that limit availability of products and services for human, and it can undermine environmental health. Studying impact of landuse/land cover changes on the stream flow is very important for proper basin management. Hence this study investigated the past and potential future land cover changes, and the impact of the past on the stream flow of Beles Sub-Basin using using the Soil Water Assessment Tool (SWAT). To analyze the change that in the study area, satellite images were downloaded for 1987, 2002, and 2019 years and processed using ERDAS Imagine 2014. Then using supervised image classification, the satellite images were classified to agriculture, wetland, forest, shrub land, and urban land. Accuracy assessment was done, and overall accuracy of 86.25%, 88.7% and 87.9%, were achieved for the classified images of 1987, 2002 and 2019 respectively. The net changes of landuse/land cover of the study area from 1987 to 2019 indicated that forest, shrub land and wet land decreased by 4.73%, 10.59%, and 1.10%, respectively, while Agriculture, and Urban, increased by 14.18%, and 2.24%, respectively. The future LULCs of 2035 and 2055 were projected by IDRISI (CA Markov method), and the result indicated an increase of Agriculture 10.94%, Urban 44.04%, where as forest -12.63%, shrub land -11.35%, and wetland -43.61% decreased. Ten parameters identified to be sensitive for the stream flow. Model calibration was carried out using observed stream flow data from (1989-2010) and The validation was performed from (2011-2019). Both results showed good match between measured and simulated stream flow data with R 2 and ENS achieved 0.80, 0.74 for calibration and 0.64, 0.78 for validation respectively. Due to LULCC, the mean annual Stream flow increased by 3.04m3 /s from 1987-2002, and, 2.83m3 /s from 2002-2019 and seasonal flow increased by 12.05m 3 /s, and 5.49m 3 /s in the wet season, while increased and decreased by 2.13m 3 /s and -2.78m 3 /s respectively in the dry season. The surface runoff increased, while groundwater flow decreased from 1987 to 2002 and from the year 2002 to 2019 the mean monthly stream flow increased by 23.29m3 /s for the wet months while for the dry months decreased by 6.31m3 /s. The Stream flow change to different predefined study years indicates LULCC has significant impacts on the stream flow of the study area. To mitigate LULCC, local and national officials in the Beles Sub-Basin should be invited to develop and implement scientific and suitable planning and management plans
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    IMPACT OF LAND USE/LAND COVER DYNAMIC ON HYDROLOGY REGIME: A CASE STUDY IN THE UPPER BARO BASIN, GAMBELLA, SOUTHWEST ETHIOPIA
    (Hawassa University, 2019-03-11) Tewodros getu engida
    The principal driving forces for land use/land cover change(LULCC) are rapid increases of population and forest clearing. Those are important factors that influence the hydrological condition of a catchment. Land use/land cover change can also result in change of flood frequency, increase peak flows, base flow, and annual mean discharge. To reverses such kind of problems, assessment of hydrological condition in relation to LULC and finding solution at a watershed level is necessary. The objective of this study was to assess the impacts of LULC change on the hydrology of Upper Baro Basin using Soil and Water Assessment Tool model. The LULC change analysis was performed by using supervised classification method using ERDAS imagine 2014. The accuracy of the classified maps was assessed using error matrix of each selected period. Consequently, 92.14%, 94.63% and 95.63% were found for LULC classification of 1987 ,2002 and 2017 study years, respectively. The result show that there was a drastic decreased of grass land by15.64 % and an increase of agricultural land and settlement by 18.01% and 13.01%, respectively over period. SWAT model was adopted to perform simulation of the main hydrological component in order to finding the effect of LULCC using in 1987,2002 and 2017 and also calibration, validation and uncertainty analysis were performed using sequential uncertainty fitting (SUFI-2). The result showed that there was a reasonable agreement between observed and simulated streamflow with coefficient of determination (R2) and Nash-Sutcliffe efficiency values 0.87 and 0.76 for calibration periods 1990-2002 and 0.77and 0.72 for validation period of 2003 to 2010 respectively. Further, the model was predicting the impact of LULC change on streamflow for period 1987,2002 and 2017. Evaluation of hydrologic response unit (HRU) due to LULCC showed that mean monthly streamflow was increased by 35.8% in wet months and decreased by 21.05% in dry months between the years 1987 and 2002. While betwee 2002 and 2017, it was increased by 47.1% and 3.49% for wet and dry months, and the year 2017 and 1987, it was increased by 82.9% and 15.54% for wet and dry months respectively. InVEST model was used to assess the total soil loss potential for each LULCC, these result show that increased from 276462.8 in 1987 to 391741.2 ton/year in 2017 and the mean annual soil loss was also increased from 67.67ton/ha/year in 1987 to 70.84ton/ha/year in 2017. The trend of soil loss and sediment export indicates that an increase in LULCC. Deforestation and soil erosion problems need to be give attention urgently to maintain the stability and resilience of the ecosystem
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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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    ASSESSING THE EFFECT OF LAND USE LAND COVER CHANGE ON STREAM FLOW AND SEDIMENT YIELD: THE CASE OF ROBIGUMERO WATERSHED, UPPER BLUE NILE BASIN, ETHIOPIA
    (Hawassa University, 2024-07-26) KASAHUN TADESSE MARE
    Land use and land cover change significantly affected global water yield and sediment yield. The population within the Robigumero watershed experiences periodic increases that are attributable to changes in land use and land cover patterns occurring over both a spatial and temporal scale. Therefore, this study mainly focused on assessing LULC change and analyzing its impact on stream flow and sediment yield in the Robigumero watershed. For this study, spatial and hydro-meteorological data were used as model input. ERDAS Image 2015 was used to assess land cover classification and accuracy. SWAT model was used to simulate stream flow and sediment yield in monthly time steps. The model predicted stream flow with R2 values of 0.89 and 0.77, NSE values of 0.87 and 0.76, and PBIAS values of -2.3 and -5.1 during calibration and validation periods, respectively. Similarly, the model predicted sediment yield with R2 values of 0.80 and 0.75, NSE values of 0.80 and 0.74, and PBIAS values of -7.1 and 0..9 during the calibration and validation periods, respectively. During the study period from 1994 to 2021, the Robigumero watershed experienced substantial LULC change, with agricultural land and built-up area increasing by 18.6% and 160.8%, respectively, while forest, grassland, and shrubland cover decreased by 12.7%, 10.4%, and 40%, respectively. The calibrated model predicted results showed that on the watershed outlet point, mean annual stream flow increased by 4.64 m3 /s, and mean monthly stream flow increased by 0.86 m3 /s during the wet season and decreased by 0.14 m3 /s during the dry season from 1994 to 2021. Similarly, annual sediment yield increased by 5.5 t ha- 1 .yr-1 , with seasonal yields increasing by 4.84 t ha-1 .yr-1 during the wet season and 0.49 t ha- 1 .yr-1 during the dry season. Spatially, nine subbasins (43.3%) of the catchment revealed sediment yield-critical areas; from these, 24.02 t ha-1 yr-1 of sediment was generated. Implementing terracing, filter strips, and contouring in the critical subbasins demonstrated sediment yield reductions of 71.1%, 46.3%, and 51.9%, respectively. The findings of this study indicate that annual and wet season stream flow and sediment yield increased, while dry season stream flow was reduced. The change in stream flow and sediment yield is a direct result of the significant change in land use and land cover in the watershed. This suggests soil and water resource development in the catchment needs urgent regulation by the LULC and should be given priority to sediment reduction measures