Saltwater intrusion management in shallow and deep coastal aquifers for high aridity regions

Abstract

Study regionThe current study was applied on two extensive and important regional aquifers: the first is the shallow aquifer of Gaza coastal aquifer (GCA), Palestine and the second is the deep aquifer of the Nile Delta (NDA), Egypt. The two sites are suffering from high stress water resource and contamination by saltwater intrusion (SWI). SWI is natural phenomena that damage the fresh groundwater in two sites and increase the aquifer. Shallow and deep aquifer plays a natural role for keeping the quality of freshwater from SWI in costal aquifers. This study aims to compare different methods for aquifer protection from SWI by analyzing their efficiency using numerical groundwater models in the two sites. Study focusThe finite difference for density dependent groundwater flow model SEAWAT was used on two sites to investigate the extension of SWI without management (base case) and the four methods to control SWI. The numerical models were calibrated for the base case using the other studies and field data to simulate the intrusion in GCA and NDA. The investigated four methods focused on (1) subsurface physical barriers of Cut-off walls), (2) subsurface physical barriers of subsurface dams, (3) the hydraulic method including Treatment and Recharge of collected wastewater, Abstraction and Desalination of low salinity by brackish water, and (4) the land reclamation using earth fill method. New hydrological insights for the regionThe simulated results indicated for the base cases that the intrusion salt mass (NaCl) reached 6068 × 103 kg for GCA and 8863 × 1010 kg for NDA. Moreover, the percentage of aquifer salt mass was decreased and reached 17.60%;, 23.30%; 7.85% and 6.20% in for shallow aquifer while it reached 2.05%; 0.90%; 5.30% and 0.80% in deep aquifer for the physical subsurface dam of cut-off wall, subsurface dam, hydraulic method and land reclamation technique respectively. On the other side the control methods in shallow aquifers is more effective than the deep one. The subsurface barriers and land fill method isn’t effective for deep aquifer while the hydraulic of TRAD method has a positive effect on SWI in shallow and deep aquifers. The current study could be carried out around the world in different coastal hydrological groundwater thickness using the effective method to increase the mitigation of SWI and increase the fresh groundwater resources in coastal aquifers.