Seawater intrusion impacts on groundwater and soil quality in the northern part of the Nile Delta, Egypt

Seawater intrusion (SI) is thought to be a significant threat to groundwater and soil quality in arid costal ecosystems, causing a reduction in freshwater availability and soil productivity. This study investigated the effects of seawater intrusion on soil and groundwater quality in the Nile Delta region at 16 sites located at distances of 5–45 km from the coast. We found that groundwater and soil quality were significantly affected by seawater intrusion. Results from the investigations indicated that: (1) the salinity and alkalinity of groundwater and soil pore-water decreased with increasing distances towards the inland, and showed significant positive correlations for EC, SAR, Na⁺ and Cl⁻ by 0.80, 0.46, 0.78 and 0.66 respectively offshore (45 km); (2) there were significant positive correlations between salinity and alkalinity of both groundwater and soil pore-water inland up to 15 km distance from the coast;(3) mixing ratio values (F%) of seawater and groundwater were 9.30 to 37.56% in different sites, recording a maximum value close to the sea (5 km), while a minimum value was observed offshore (45 km); and (4) increasing seawater intrusion had negative impacts on the quality of groundwater and soil up to 15 km from the sea, providing the possibility of exploiting irrigated land in Nile delta up to 15 km from the Mediterranean sea.