<p>The evaluation of the available groundwater potential is critical for the development and management of groundwater resources. In this regard, GIS-based multi-criteria decision analysis (MCDA) plays a crucial role in prioritizing the groundwater potential of an area. In this study, the WetSpass-M and GIS-based MCDA models were used in an attempt to define the groundwater potential of Chamo Lake Basin (CLB), which is situated in the southern Main Ethiopian Rift (MER). The WetSpass-M model was used to simulate the water balance components, mainly the spatial variability of recharge (RCHG). The WetSpass-M model performance evaluated by Percent Bias was 11.84%, suggesting the applicability of the model. The long-term mean annual RCHG over the basin reveals remarkable spatial variability and varies from 39&#xa0;mm/yr in the rift floor to 497&#xa0;mm/yr in the highland. The simulated RCHG and other groundwater potential influencing thematic layers such as geomorphology, lithology, drainage density, and lineament density were examined using the GIS-based MCDA technique to delineate the GWPZs (groundwater potential zones) of the study area. Four GWPZs were identified in the CLB, namely very high, high, moderate, and low. According to the model result, 3.74% of the lake basin is identified as having a very high GWPZ, situated mostly in the western part, while 18.86% of the area is categorized as having a low GWPZ, found along the eastern part of the study area. The remaining 29.43% and 47.97% of the lake basin are identified as high and moderate GWPZs, respectively. The GWPZ results were validated against an independent set of groundwater inventory data (yields of wells and springs), showing 81% agreement. This integrated approach, combining the spatially distributed hydrological model WetSpass-M with GIS-based MCDA, offers an efficient and effective method for groundwater prospecting.</p>