Groundwater Potential Zones Assessment and Mapping using Integrated Geospatial Techniques and Multi-Criteria Decision Analysis (MCDA) for the Bale Zone, Genale-Dawa Sub-Basin, Oromia, Southeastern Ethiopia

Eshetu M and Alemu M

Published on: 2024-05-18

Abstract

Groundwater is one of the most crucial natural water supplies because it continuously directly or indirectly supports many domestic, agricultural, and industrial activities but is now being degraded due to various causes. Even though the dryness of deep and shallow groundwater resources is due to LULC, climate change, and groundwater exploitation failures, a limited research-based study and a lack of documented baseline information that supports multi-planners, decision-makers, investment, and management options are the main research gaps in the Bale Zone, Genale-Dawa sub-basin. Therefore, this study aimed to assess and map the factors that determine groundwater potential and produce a groundwater potential zone map for the Bale Zone, Genale-Dawa Sub-Basin. Accordingly, in this study, ten (10) factors affect groundwater potential at varying degrees, namely: rainfall, geomorphology, LULC, lithology, soil texture, slope, elevation, topographic wetness index, drainage, and lineament density. Criteria weights and rankings were assigned based on expert opinion, literature review, and field survey experience, using the Analytical Hierarchy Process (AHP) and ArcGIS 10.3 software to map potential groundwater zones. The results show that thematic factors such as rainfall, geomorphology, LULC, lithology, soil texture, slope, topographic wetness index, elevation, drainage density, and lineament density affect groundwater potential with weight values of 24.2%, 18.7%, 10.7%, 13%, 7.9%, 6.9%, 3.8%, 3.8%, 5.4%, and 5.7%, respectively, in the study area. Maps of groundwater potential zones are classified into five categories: very low 366,001.80 ha (24.36%), low 249,151.07 ha (16.58%), moderate 271,817 ha (18.09%), high 278,343.13 ha (18.53%), and very high 337,194.06 ha (22.44%) for the Bale Zone and the Genale-Dawa Sub-Basin. The low to very low groundwater potentiality has been seen on the map at different distances due to the presence of hills and steep slopes, rock outcrop surfaces, clay soil textural class, low rainfall areas, very high drainage density, low lineament density, and bare land. The validation analysis revealed a 91% agreement, which confirms the very good agreement between the groundwater inventory data and the developed groundwater potential zone. The groundwater potential zone assessment and map of the current research results serve as baseline information for planners, decision-makers, and adopters of sustainable management options to identify suitable sites for groundwater exploration and as an as an initial for further studies. Further studies, detailed water chemistry surveys, geophysical surveys at potential drilling sites, and grade analysis should be recommended.