Experimental studies on gas-clogging characteristics during groundwater artificial recharge

Groundwater artificial recharge has been widely used to effectively utilize abundant rainfall in rainy seasons for managing a number of environmental problems such as seawater intrusion and depletion of spring flow caused by groundwater overexploitation. However, physical clogging (including suspended solid clogging and gas clogging) is an important factor that may negatively affects efficiency of groundwater artificial recharge. To tackle the problem of gas-clogging (i. e., a large amount of bubbles contained in artificial recharge water), an indoor device for conducting column experiments is designed. A column is filled with sand of multiple layers, and the hydraulic conductivity of each sand layer is estimated based on the Darcy's law to investigate the processes and mechanisms of gas-clogging development. The laboratory results show that, due to gas clogging, hydraulic conductivity is not a constant but a temporal function of exponential decay. The results also show that gas clogging mainly occurs in the upper layer(0-30 cm)of the sand column, and that the clogging rate decreases gradually with depth. The results suggest that, to reduce the negative effects of gas clogging on efficiency of groundwater artificial recharge, it is necessary to occasionally pause recharge and to conduct degassing during the recharging processes.