Abstract

The aim of this study was to assess the impact of land use / land cover changes on the hydrological process in the central valley basin of Ethiopia, from 1985 to 2018 and evaluate historical land use/land cover change using satellite image. Satellite images were classified by supervised classification technique with maximum likelihood. SWAT model were used to simulate hydrological processes in the watershed. The result of the study shows that barren lands, agricultural and settlement lands were expanded by 7 and 64%; whereas, forestlands, water bodies, shrub and grasslands were declined by 13, 57 and 41% respectively over the past three decades. The calibrated and validated SWAT model used also showed that there has been good agreement between simulated and observed streamflow on monthly basis. Streamflow evaluation due to LULC change influence showed that mean monthly simulated streamflow was increased by 10.84% between the years 1985 and 2003, also increased from the year 2003 to 2018 by 9.3% in wet months; whereas, decreased by 8.23 and 11.4% between 1985-2003 and 2003-2018 in dry months. Therefore, hydrological process of the watershed was highly influenced by LULC changes and it requires integrated watershed management techniques.

Key words: Digital image processing, Gis, hydrologic process, landsat image.