River Aquifer Interaction in Lower Gandak Command Area in Bihar, India

In this paper, the quantification of the interaction of aquifer and river during various stages of river Gandak has been carried out. A groundwater flow model, MODFLOW, has been used to quantify the interaction of river Gandak and the adjacent aquifer in all months of the year. The model has been calibrated with the observed water level data of the existing wells. Calibrated model was used to simulate the groundwater flow in the study area and the flows from river Gandak to adjacent aquifer and vice-versa. Results show that the river Gandak is recharging adjacent aquifer during the months May to October and again during January to February. In the months March, April, November and December aquifer is contributing water to Gandak River. It was found that the quantity of inflow/outflow from river Gandak is proportional to the difference of water level in river and aquifer. Further, a relationship for the interaction of Gandak River and adjacent aquifer has also been developed to find the aquifer recharge with rise in river stage in the study area.