Exploration of Strategic groundwater in fractured and karstic rocks in order to supply of drinking water for Myaneh and Tark in the condition of water crisis

Abstract

Water resources in fractured formation are significant due to their high spatial distribution and efficient quality. They have a considerable role in supplying drinking and industry water. However, dual-porosity characteristics of fractured rocks complicate the nature and behavior of water flow (Frederick et al., 2017). Remote sensing (RS) and geographic information system (GIS) are used for satellite image processing to determine groundwater resources of fractured formation. Analytic hierarchy process (AHP) and fuzzy logic method can be employed for a final and mutual decision making regarding multivariate processes and better problem management (Jankowski et al., 2008; Jelokhani et al., 2015). This study evaluates areas with groundwater potential in fractured formation units of Germi Chai, Miyaneh, (northwest of Iran) to determine resources for supply drinking water. Germi Chai basin with an area of 926 km2 located at the northeast of Miyaneh (East Azarbaijan), at the southern slopes of Bozgush Mountains. Average annual temperature of this area is 32 to -18C°. Based on 19-year precipitation data, average annual precipitation is 319 mm. The highest and lowest parts of the basin are located with 3090 and 1200 m height above mean sea level in southern parts of the basin. Landsat 8 satellite images (with OLI-TIRS sensing, 11 bands in 2017/07/19) were provided and processed in ENVI 5.2 software. Nine main parameters were regarded to determine area with potential overlaying the layer maps that were used to produce groundwater potential zoning map. After determining criteria weights in Expert Choice Software using AHP method, fuzzy and objective maps are produced in Arc GIS. At first, all the maps were converted to fuzzy maps using fuzzy membership function. Then, they were overlapped by the weights which are determined by AHP method. After preparing the related data layers in determining groundwater potential of fracture formation, some potential detection methods are used, such as SUM, AHP, Weighted Overlay, and Fuzzy Gamma. In the all methods, 9 data layers were merged together both in reclassify and fuzzy modes. The results of all 4 methods were compared together and reclassified in order to produce the final map. For accuracy evaluation of the final potential detection map, the location of springs and wells were projected on the map and their compatibilities with high potential areas were evaluated. “High” and “very high” zones with 34 springs are considered to have the highest water resources potential and discharge volume. The results of this study indicated that areas with high permeability of rocks, and also areas with high fracture density, bearing high groundwater potential as well. These results indicated that 80.09% of springs are compatible with “high” and “very high” potential areas. “Very high” potential areas with 67.06% discharge have the highest significance groundwater resources. About 61.3% of “very high” potential areas are related to conglomerate geological unit. Moreover, 17.8 and 9.2% of them are related to northeast pyroclastic rocks and northwest karst areas of the basin. Other geological units make 11.7% of “very high” potential area with highly tectonic weathered andesite. Therefore, future researches will be necessary to use geophysical studies as a tool to determine the precise point of abstraction in “high” and “very high” potential areas.