Mapping of groundwater potential zones using sentinel satellites (−1 SAR and -2A MSI) images and analytical hierarchy process in Ketar watershed, Main Ethiopian Rift

Abstract

AbstractGroundwater is an important natural resource for drinking and irrigation. Nevertheless, identifying potential sources in Ethiopia still presents a challenge in terms of time and costs for solving water scarcity problems and managing groundwater systems. To address these issues, this study combines optical and microwave remote sensing to identify groundwater potential zones in Ketar watershed, Ethiopia. Two Sentinel families, Sentinel-1A Synthetic Aperture Radar (SAR) and Sentinel-2AMulti-Spectral Instrument (MSI) images, were processed to derive a Digital Elevation Model (DEM) and thematic layers (lineament density, soil moisture, land-use/land-cover, drainage density, slope, and geomorphology) for the study area. Secondary data were used to produce geological units, soil texture, and rainfall thematic layers. These nine total layers were considered proxies to signify groundwater occurrence and analyzed in GIS environment with a consistency ratio (CR = 0.013). Since each proxy contributes differently to the occurrence of groundwater, the Analytical Hierarchy Process (AHP) technique was used to assign individual weights to each factor. These factors were reclassified based on standard criteria and aggregated using Weighted Linear Combination (WLC). Results of a weight comparison show that geological unit, rainfall, soil texture, slope and lineament density are the dominant factors controlling groundwater occurrence. The WLC classifies the area of potential groundwater zones into five classes: very low (607.64 km2), low (942.19), moderate (777.2), high (598.74) and very high (428.23). These zones were validated using 43 existing data points of boreholes, hand-dug wells, and springs and have a correlation coefficient of 0.93. The outcome of this study emphasizes the importance of integrated optical and microwave remote sensing in identifying potential groundwater zones with a better accuracy to address issues of water scarcity in Ethiopia.