Salinization of groundwater during 20 years of agricultural irrigation, Luxor, Egypt

Groundwater salinization is a global problem accounting for 11-30% of the world's irrigated areas. Luxor region in Upper Egypt is one of such areas affected by salinity. Multivariate statistics indicate that groundwater is affected by intermixed processes; mineralization (salinization), fertilization, domestic wastes, and meteoric recharge. Temporal change in salinity and hydrochemical facies during 1997-2017 revealed aquifer salinization, due to the dissolution of salts from overlain saline soil and marine deposits underneath as well as up-coning of deep saline water. Increasing salinity over time was statistically documented, exhibited temporally high significant differences (P < 0.05), where salinization consumed a quarter of the aquifer during 20 years. Evolution of water facies from less mineralized Ca-Cl, Mg-Cl to highly mineralized Na-Cl species explains the salinization process over time. Elevated content of Na and Cl is associated with the dissolution of marine sediments and saltwater intrusion. The shift from silicate weathering into evaporation dominance confirmed the saltwater intrusion. As a result, groundwater has a high degree of salinity, is not suitable for domestic and other uses. On other hand, fertilization and domestic sewage are probably responsible for the high NO₃^- and Cd content. Over 80% of Cd exists in mobile species facilitates Cd-plant uptake indicating an alarming environmental situation. Cd mobility is closely related to elevated salinity and chlorinity, allowing competition with major ions and forming of soluble complexes. The present approach will improve the uncertainties of environmental interpretation, as an initial step for aquifers management in reclaimed lands.