Delineating Groundwater Potential Zones Using RS,GIS,and Multi-criteria Decision-making Analysis

Recently,the exploration of groundwater has increasing,and became fundamental to supports the multiple demands of water supply for drinking and agricultural fields,particularly in the regions that suffering surface water shortage.Geographic Information Systems（GIS）and remote sensing（RS）,are intensive tools for the performance and analysis of spatial datum associated with groundwater source control.Potential groundwater equipping in the igneous rocks field demands lineaments analysis for proposing the suitable locations.Digitally processed color composites and panchromatic images of different satellite images were taken to generate thematic maps.The study area located in southern part of the Gedaref State eastern Sudan,including four local municipalities;El Faw,El Rahad,El Qalabat,and El Quresha.The hydrogeological situation of the study area is represented by two water resources:1)Annual surface water resources including the seasonal storage basins of El Rahad river and its tributaries and 2)Groundwater,which represents the main water resource in the area.Geomorphologically,the flood plain in the alluvial areas is a more dynamic and complex than all other present geological features.The river meandering and migration was studied to understand the geomorphology of El Rahad River;in which the Digital Shoreline Analysis System（DSAS）tool of the geographic information system（GIS）was used.In this case,six different dates in the past 45-years of the shoreline changes that happen in（1972,1981,1990,2000,2008,and2017）;were investigated.The lineaments analysis was conducted by using the high spatial resolution Sentinel-2A and the ALOS PALSAR-DEM images for detecting and mapping the groundwater to understand its potentiality in the granitic area.On the other hand,the integrated approach of（RS）,（GIS）,and Electrical Resistivity Tomography（ERT）techniques were adopted to estimate the groundwater potential in the sandstone,alluvium and basaltic zones.In this case,the hydrological thematic layers of the geomorphology,slope,geology,land use,lineaments,and drainage were produced.Subsequently,the weighted overlay technique in the Arc GIS was used for each thematic layer and normalized utilizing the multi-criteria decision making（MCDM）technique.The obtained results of this integration were then cross-checked with boreholes data and other interpreted data of electrical resistivity.Beside the GWPZ locating,the GIS interpolation tool was used to obtain the spatial distribution of groundwater quality parameters and drinking water quality index（DWQI）in the study area.The outcomes of the lineament’s interpretation in the granitic area are shown as the lineament’s density map;thus,the high density of the lineaments are related to the positive occurrence of groundwater.Therefore,from this analysis,the proposed potential groundwater localities were suggested.The final output of the GWPZ in the sandstone,alluvium and basaltic layers were classified by four GWPZ,named as:very good,good,poor,and very poor.The DWQI investigate that the groundwater in the study area was controlled by sodium and bicarbonate ions that defined the composition of the water type to be Na HCO₃.The investigation concluded that the Sentinel-2A and ALOS-DEM images;both are capable of extracting lineaments.Therefore,this has confirmed the contribution of using these data in groundwater delineation and locating a sustainable water supply for underground boreholes and hand-dug wells.However,the Sentinel-2 image reflects the superiority in the lineament’s quantity and distributions than the ALOS-DEM data.The study of El Rahad river morphology was reported for the first time the river meandering and migration in the study area.The obtained results from river meandering and change showed that the meandering changes have a wide range of migration.The extracted lineaments were indicated that the morphology of the lineaments was governed by four fracture orientation systems（East-West,North-South,Northeast-Southwest,and Northwest-Southeast）.These research results are beneficial to the water resources managements decision-makers in locating the suitable positions of new production wells for their target areas.The process and findings of this study also could be used for improving plans for potential utilization of the groundwater resources in other regions of the same geological,hydrogeological and environmental conditions.This study has added significantly and useful information at a detailed scale to the existing hydrological and geological information in the study area.