Evaluation vulnerability coastal aquifer by GALDIT index and calibration by AHP method

Background and objectives: Groundwater is one of the main sources of drinking water supply, agriculture, So the management of underground water table is very important. The change quality of groundwater resources in arid areas due to the discharge of water and reduce recharge causes have shortage problems and environmental crisis for aquifers in Iran. Extreme groundwater extract has disturbed the balance of saltwater and freshwater, resulting in significant saltwater intrusion in many parts of the aquifer. The most important factors controlling seawater intrusion were found to be the following: Groundwater occurrence (aquifer type; unconfined, confined and leaky confined); Aquifer hydraulic conductivity; Depth to groundwater Level above the sea; Distance from the shore (distance inland perpendicular from shoreline); Impact of existing status of sea water intrusion in the area; and Thickness of the aquifer, which is being mapped. The acronym GALDIT is formed from the highlighted letters of the parameters for ease of reference. Therefore, sustainable development is necessary to the constant demand of groundwater. In recent years, environmental assessments of groundwater resources have resulted in development of models that help identify the vulnerable zones.
Materials and Methods: In this study, investigated vulnerability of Astaneh- Koochehsfahan aquifer which is coastal aquifer located in Sefidrood Basin and adjacent to the Caspian Sea by GALDIT index. GALDIT index a new index model developed for the study of the effects of salt water intrusion into coastal aquifers is caused by irregular discharge. In other words, the use of index in this area has negative effects on the groundwater aquifers indiscriminate harvesting of salt water and beach analyzed.
Results: Initial survey results indicate that the index of negative impact on the vulnerability of the region's coastal areas. To check the calibration of the vulnerability utilized the correlation between the concentration of TDS, nitrate, chloride and sodium and the statistical analysis, the parameters for TDS calibration using Analytical Hierarchy Process(AHP) Using Software Expert choice was selected. TDS feature selection with salt and minerals found in sea water, which can have a direct impact on the effectiveness of the measure coast more vulnerable.
Conclusion: Using the weight of the different components of the model output for the region was estimated optimal and The final model showed that close to the beach bar vulnerability of groundwater to contamination than other areas of the aquifer. The result of hierarchical analysis showed a significant parameter sensitive measure the distance from the sea, and after calibration model GALDIT index showed a 30 percent drop in the risk of intrusion of sea water is salty.