Lake Urmia, the largest in the Middle-East, is located in the northwest of Iran. The lake has been dramatically desiccating during the last two decades, mainly as a result of human-induced agricultural development, which remarkably accounted for diminishing of surface and subsurface inflows to the lake. This research focused on the mountainous area of Aji-Chay river basin, the largest basin supplying the lake, determining different groundwater potential zones, GWPZ, over the area. In order to indicate the zones, Multi Criteria Decision Making, MCDM, techniques in the frame of Geographical Information System, GIS, were utilized. Accordingly, GIS thematic layers of precipitation, lithology, landform, density of lineaments and faults, slope, land curvature, and stream density were quantified based on the direct field observations, geological maps and Remote Sensing. Among available MCDM techniques, Entropy, Analytical Hierarchy Process, and Fuzzy techniques were comparatively employed, utilizing spring and exploitation wells as validation tools. Results showed that, Entropy based MCDM techniques was slightly more accurate than the rests. Since impermeable intrusive and extrusive igneous rocks of low fracturing are abundantly cropped out over the area, the high and very high GWPZ were estimably negligible. The resultant map of GWPZ can be adopted to site any new exploitation water wells in the region, indeed. However, the prospective karst and hard-rock groundwater has to be considered as substitution of current drinking water supply of low quality in the villages and rural areas. Because, any further exploitation cannot be amenable for such a basin, feeding one of the most precious UNESCO Biosphere Reserve.
Keywords: karst and hard-rock groundwater potential zone, Entropy, Analytical Hierarchy Process, Fuzzy, Lake Urmia