Impact of declining groundwater levels on river flows in the Ganga Alluvial plain-a case study of Gomti River, India

This study is carried out on the Gomti River Basin (GRB) in Uttar Pradesh, India - a sub-basin of Ganges, to understand if groundwater abstraction has affected the flow-regimes in the river. Gomti River is a tropical groundwater-fed alluvial river in which base flows form an important component of the overall flow. A large number of sampling points in the basin, i.e. data from 764 groundwater observation wells were computed separately for pre- and post-monsoon periods. The flow data from 1978 to 2015 is used to separate the base flow share from the river discharge. The results of the comparison of changes in groundwater depths and surface flow trends showed a decrease in groundwater levels in past years as well as an overall decrease in river flow. During the lean flow periods, the groundwater usage is highest in the basin, and base flow reduces due to which rivers are not able to meet the minimum flows requirements. This study suggests that river flow can be effectively restored by regulating the indiscriminate abstraction of groundwater in the basin and through promoting conjunctive use of surface and groundwater. The study also recommends that a component of groundwater recharge through water bodies should be included for base flow augmentation to maintain sufficient ecological flows in the river.