Investigating island groundwater salinity, using vulnerability index and numerical methods

Seawater intrusion is one of the major issues in Qeshm Island, which is the biggest island of the Persian Gulf. To investigate seawater intrusion in this island, a modified GALDIT index is used to map the vulnerability of the whole region. Considering the vulnerability map, two critical sections which have the highest vulnerability, one in the northeast and the other in the west side of the island, are chosen for detailed investigation. To achieve this goal, two numerical models, MODFLOW and SEAWAT are applied to simulate the groundwater flow and solute transport. The results show that the aquifer is in a dangerous level of threat of vulnerability and 15 km2 of the aquifer is in danger of being salinized. A comparison is made between MT3DMS and SEAWAT results, indicating that SEAWAT simulates seawater intrusion with more accuracy. It seems because of considering salt density in SEAWAT flow equations. The numerical simulation shows that the seawater is intruding on the island at a rapid rate.