Impact of CO2 Gas Leakage on Anomalous Groundwater Level Fluctuation in Northern Aquifers of Hamadan Province

There are a number of aquifers in the northern half of Hamadan province that, deepening of water wells into the bedrock resulted in CO2 leakage into the aquifers. Groundwater level data near gas charged water wells indicating abnormal behavior in groundwater level fluctuation. Comparison of observation well hydrographs, variance inflation factor and field evidence in the gas charged and background areas shows that the observed abnormal behavior in water level fluctuation is not influenced by rainfall and groundwater pumpage variables. Due to high pH buffering capacity in the aquifers and decrease of PCO2 correlation with pH and TDS in the gas charged waters compared to the background ones, the main factor for increasing salinity in the gas charged waters is the intrusion of deep saline water with gas into the aquifers. In fact, the deepening of the wells into the bedrock, by lowering hydrostatic pressure, causes gas-rich saline water to enter the aquifer. As wells begin pumping during the irrigation season, the aquifer recharge rate by saline water exceeds the discharge rate of the wells, resulting in elevation of groundwater levels around the gas charged wells.