Evaluating the time lag of the drop in groundwater level compared to the occurrence of subsidence using vulnerability analysis in the Tasuj Plain aquifer

Subsidence in the plains due to the over-exploitation of groundwater resources is one of the problems facing most of the country's plains. The drop in the water table of aquifers is the triggering factor for subsidence occurrence. However, due to the complexity of the nature of the problem, subsidence may not start immediately after the drop in the water table. In this study, a step has been taken in the direction of understanding the time lag in the water table drop in the occurrence of subsidence. The aquifer of Tasuj plain, as the study area, is located north of Lake Urmia in East Azerbaijan province. The amount of subsidence has been quantified by the INSAR technique in a differential manner in the plain. The research results also identify the vulnerable areas of this aquifer against subsidence. Due to the dynamic nature of the water table drop, which leads to the dynamics of the vulnerability results, the correlation of the vulnerability results with the INSAR results was calculated using the ROC curve and it was observed that the highest correlation was related to the water table drop two years ago of subsidence records. The subsidence occurs with a two-year time lag compared to the drop in the water table.