Impact of Land Use Land Cover Dynamics on Stream Flow: A case of Borkena Watershed, Awash Basin, Ethiopia

Abstract

Land use and land cover in recent decades have changed ecosystems more rapidly and extensively than in any comparable period. Land used land cover (LULC) change is one of the major factors that affect the watershed response. The LULC change analysis was performed by using supervised classification method in ENVI software. The study results showed that the watershed experienced significant LULC change from 1986 to 2016. During the study period, most parts of the grass land, cultivation land, and shrub land were changed to build-up area and bare Land. The LULC map shows an increase of buildup area and bare Land by 3.6% and 5.9% respectively over the last 31 years. The SWAT model was used to assess the impact of LULC change on stream flow for the period 1996 to 2016. The result showed that there was a good agreement between observed and simulated stream flow with a coefficient of determination (R) and NashSutcliff efficiency (N_ef) values of 0.81 and 0.79 for calibration, and 0.75 and 0.74 for validation periods, respectively. The evaluation of the SWAT hydrologic response unit (HRU) due to LULC change between the years 1996 and 2016 showed that monthly stream flow was increased by 5.4 m³ /s in wet season and decreased by 0.5 m³/s in dry season from 1996 to 2016. Understanding the effect of LULC change on stream flow is crucial for knowledge-based decision making in the development of water resources projects.