Integration of remote sensing, geochemical modeling, and isotopic constraints for the detection of promising groundwater zones in arid regions. A study in Qena- Luxor area, Egypt

The renewable groundwater resources in Egypt are restricted close to the Nile River. In the study area, two major water bearings are near the Nile: The Quaternary and the Eocene aquifers. Remote sensing (ASTER DEM, Landsat-8, and Sentinal-1 InSAR images), geochemical modeling, and isotopic constraints (δ¹⁸O and δ²H) were employed and integrated with the GIS framework for delineating the low saline and sustainable groundwater zones. Remote sensing data indicates intensive structure lineaments in the middle-eastward part, spatially congruent with subsurface features deduced from radar satellites, facilitating hydraulic connections with the Nile water. The soil moisture index, land surface temperature, and salinity index in irrigated areas, reveal a strong association between in situ electrical conductivity values and satellite-derived spectral indices. The higher groundwater salinity in the middle eastern region coincided with high lineament density zones, and higher temperature zones, leading to increased rock water interaction that leads to groundwater salinization. The isotopic composition of the Quaternary aquifer ranges between −1.30 ‰ and +5.53 ‰ for δ¹⁸O, while δ²H ranges between −11.49 ‰ and +34.47 ‰. In the Eocene aquifer, δ¹⁸O ranges between −0.46 and +3.45 ‰, while the δ²H ranges between −3.16 ‰ and +23.50 ‰, indicating subsurface recharge from the Nile water. The simulation of the mass transport geochemical NETPATH model revealed mixing ratios from the Nile water ranging from 3.4% to 93.7%. Based on the results, the area is classified into four classes, class (1) represents samples of high conduit with Nile water (<50% mixing), class (2) represents samples of moderate conduit with Nile water (10–50% mixing), class (3) represents samples of low conduit with Nile water (<1–10% mixing), class (4) represents samples of water-rock interaction. The findings would be of great importance for delineating sustainable zones of the Nile Valley aquifers.