Evaluation of Groundwater Potential Zone Using Geospatial Techniques, The Case of Muger Sub-Basin, Upper Blue Nile Basin, Ethiopia.

Abstract

Groundwater potential assessment is the process of measuring, collecting, and analyzing relevant parameters on the quantity of groundwater resources for the better development and management of water resources. There is limited information about the occurrence, distribution, recharge, discharge, and factors that affect groundwater protection site selection. Finding a systematic approach is required to minimize this knowledge gap. Therefore, the main objective of this study is to evaluate and delineate the groundwater potential zone in Muger catchment, Upper Blue Nile, and evaluate the effect of the land management factor of the area on the distribution of groundwater potential, using geospatial techniques. Eight multi-influencing elements such as, land use land cover (LULC), DEM, rainfall, geology data, soil type, drainage density, slope, and lineament density, are used to develop groundwater potential. The land use land cover (LULC) image of 2022 was generated from a land satellite and classified using the ERDAS Imagine 2015. The Analytical Hierarchy Process (AHP) is used to estimate the weight of the parameters based on their relative value and percent of influence on groundwater potential and recharge. The consistency ratio for the weights assigned to each parameter was found to be 0.0785, which is less than 0.1, indicating that the weights assigned to each parameter are appropriate. A knowledge base ranking of 1 to 5 was assigned to each layer based on the importance of each layer for groundwater potential. Using the raster calculator feature of ArcGIS software, all the theme maps were combined to produce a composite groundwater potential map of the research area. Based on its groundwater potential availability rank and class, the created groundwater potential map has four ranks: 2, 3, 4, and 5. Its classes are Low, Moderate, High, and Very High, respectively. The groundwater potential zone (GWPZ) area coverage of the study area was identified as very high (2.79%, or 192.92 km2 ), high (73.79%, or 5114.08 km2 ), moderate (23.14%, or1600.054 km2 ), and low (0.0867%, or 5.99 km2 ). The validity of the identified groundwater potential maps was done, by cross-checking with the existing borehole data collected from the catchment, as evidenced by the prediction accuracy was 71.42%. Reflects that the method applied for the present study produced significantly reliable and precise results. In addition to GWPZ evaluation the effect of land management factor on GWPZ was evaluated. Thus, based on the slope value (>30%) of LULC in the study area was changed from agricultural land to vegetation area (351 km2 ). Due to this change of LULC, the groundwater potential zone of the study area increased by (0.44% or 30.14 km2 ) to a good groundwater potential area. This implies that the groundwater potential zone of the catchment was influenced by land management practices, and the method is effective in doing such an investigation.