Assessment of Groundwater Potential Zones in Baro Basin using GIS and Remote sensing

Abstract

Baro river basin, located in southwest of Ethiopia is the largest sub basin of Baro-Acoobo basin. For the proper utilization and management of groundwater resource in the basin, it required to know its spatial distribution. Hence, geographic information system and remote sensing techniques were used to analyze the groundwater system based on seven selected groundwater influence factors thematic maps. The thematic maps we used were geology, soil, lineament density, drainage density, rainfall distribution, slope and land use maps. Lineament and land use maps were prepared through the process of remote sensing techniques from Landsat TM imagery using ERDAS imagine and PCI Geomatica softwares. Other thematic maps were prepared using Arc GIS 9.3 from DEM and previous prepared soil and geology maps .for each maps weight value were estimated by using PriEst software after assigning weight value of domain effect by using pairwise comparison based on Saaty’s analytical hierarchy process. Finally thematic layers were integrated in Arc GIS 9.3 based on estimated weight values. In the basin, four groundwater potential zones were identified; namely: excellent, good, moderate and poor. Excellent groundwater potential zones are associated with areas of alluvial deposition, flat and sand dominant soil group of western part of the basin; north and eastern portion of basin have good and moderate potential zone. Poor potential zone is in areas of mountain which have steep slope and high drainage density in center of the basin. Groundwater recharge of the basin was also estimated using wetspass model. The model performs recharge estimation by using water balance method in single raster cell level. Wetspass model inputs are grid maps of elevation, slope, groundwater level, land use, soil and seasonal meteorological grid maps such as temperature, rainfall, potential evapotranspiration and wind speed. Wetspass model outputs include annual recharge, actual evapotranspiration, surface runoff and others. Estimated annual groundwater recharge reaches the highest amount of 465 mm/ year in center of basin and decreases to other areas of the basin.