Groundwater depletion susceptibility zonation using TOPSIS model in Bhagirathi river basin, India

Groundwater depletion zonation is the utmost necessity for preparing the sustainable groundwater management plan; thus, the present paper attempts to delineate groundwater depletion susceptibility zonation by bridging relevant physico-environmental factors in the Bhagirathi river basin (BRB). First, the groundwater status was assessed by detecting spatio-temporal trends in groundwater levels of 168 dug wells from 1996 to 2017 using innovative trend analysis (ITA) and classical Mann–Kendall (MK), or modified Mann–Kendall (mMK), and the magnitude of the slope was determined by Sen’s slope estimator. Subsequently, the technique for order preference by similarity to an ideal solution (TOPSIS) model has been used for modeling the groundwater depletion zonation using nine influencing parameters. The hastily increasing trend of GWD (slope 28.69–86.70 cm/year) in the monsoon season specifies the depletion of shallow groundwater, and groundwater withdrawal exceeds the groundwater recharge. Additionally, this increasing tendency has observed in the recent period, indicating the chances of water stress in the basin shortly. The TOPSIS model shows that most of the areas of the BRB are in the sub-critical zone (52.81%), followed by critical (34.79%), supercritical (5.66%), and replenish zone (6.73%). The groundwater depletion map can be adopted for sustainable groundwater management by planners. If proper water management techniques are not implemented, the shallow pumps for large-scale irrigation will not work in the future.