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Subject: search.filters.subject.SWAT Model

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    MODELLING THE IMPACT OF LANDUSE/LAND COVER CHANGE ON THE STREAM FLOW OF UPPER GUDER RIVER CATCHMENT USING SWAT, ABBAY BASIN, ETHIOPIA
    (Hawassa University, 2021-10-23) TAKELE DUFERA TASGARA
    Water resources are a critical component of any type of socio-economic development all over the world. Due to extensive agricultural practices, the LU/LC change was the cause of streamflow changes. The main objective of this research was to model the impact of landuse/land cover change on the streamflow of Upper Guder River Catchment using the SWAT model, by using meteorological data in the period between 1989 -2018. Upper Guder River Catchment was one of the catchment of the headwaters in the south Abbay Basin. In this study, the impact of LU/LC change 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 landuse/land cover maps from Landsat TM, TM, and ETM+ acquired in the years 1989, 2002, 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 1989-2018. During the study period, forest land, and shrub and grassland decreased by 6.48% and 4.23% respectively while Agricultural land and Built-up area increased by 8.04% and 2.69% respectively. Using three land cover maps, three SWAT model setup were run to evaluate the impacts of landuse/land cover changes on the streamflow of the study catchment. The performance of the SWAT model was evaluated through sensitivity analysis, calibration, and validation by using SWAT-CUP. Statistical measures like coefficients of determination and Nash–Sutcliffe were used to evaluate the model and it resulted in 0.84 and 0.74 for calibration and 0.83 and 0.72 for validation respectively. During the study periods, the simulation result indicated that streamflow increased in the wet season and short rainy season streamflow by 10.04% and 5.25% respectively, while decreasing by 6.60% in the dry season. The Surface Flow (SURQ) increased by 5.73% while Groundwater Flow (GWQ) decreased by 2.26% due to the increment of Agricultural land. The model results showed that the streamflow characteristics changed due to the landuse/land cover changes during the study period. The catchment was sensitive to past LU/LC change, so it needs an effective integrated participatory approach for catchment management.
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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
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    MODELING HYDROLOGICAL RESPONSES TO LAND USE AND LAND COVER CHANGE IN MEGECHA RIVER CATCHMENT OMO-GIBE BASIN, ETHIOPIA
    (Hawassa University, 2023-10-26) BEAKAL YISEHAK ASHENGO
    Land use/ land cover change has been one of factors responsible for altering the stream flow of the watershed on the Megecha River Catchment OMO-GIBE basin leading to impacting river flows. The study mainly focused on to evaluate the impact of land use land cover change on streamflow. Land use change detection was done using remote sensing techniques and the maps were processed through maximum likelihood algorithm of supervised classification using ERDAS Imagine 2014 and ArcGIS 10.4 software. A physical based, semi –distributed hydrological model, SWAT was used to investigate the impact of land cover change on streamflow, of Megecha River Catchment OMO-GIBE Basin. From the land cover change analysis result it was found that there has been a substantial decline of sparse and moderate forest, grass land, bare land and water body. The cropland in the watershed increased from 68.80% in 1996 to 71.13 in 2016. Similarly shrub land and settlement shows increase. This is mainly because of the population growth that caused the increase in demand for new agricultural land and rural settlements which in turn resulted shrinking on other types of land use and land cover of the area. Results have revealed that there is substantial increase in surface runoff volume from 94.34mm to 125.97mm for the LULC map of year1996 and 2016 respectively. The model evaluation statistics for stream flow provided a very good result since NSE >0.75 and R2 >0.75. The change in LU/LC ensued in augmented stream flow and in which the expansion of agriculture has also resulted an increase of surface run off, but decreased the ET of river catchment. Therefore, curving the trends of LU/LC towards increasing vegetation covers is very important so as to reduce the seasonal flow and surface runoff, on the other hand to increase ground water flow. One way of increasing vegetation cover in the river catchment is through controlling the expansion of agriculture at the expense of other land covers and improving the productivity of existing farm lands through the provision of improved production inputs and livelihood diversification