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

Abstract

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