Monitoring regional groundwater flow and contaminant transport in Southern Punjab, Pakistan, using numerical modeling approach

摘要

A three-dimensional groundwater flow model was developed using Visual MODFLOW to characterize the groundwater regime and simulate groundwater flow behavior in Multan District of Pakistan from 1962 to 2015. The multi-layered model was calibrated in which arsenic concentration was used as a point source for solute transport modeling in the flow domain. The model calibration indicated a close agreement between the simulated and observed head values achieving residual mean value of 0.1 m and a correlation coefficient (R) value of 0.9 during the steady-state condition. The study revealed a gradual rise in groundwater levels from 1972, i.e., at a rate of about 0.08 m/year followed by a gradual decline after 1990 at a rate of about 0.39 m/year likely due to overexploitation of groundwater. The other reasons of depletion of the aquifer may include lesser natural recharge due to reduction in canal command area and increasing water demand and pumpage due to growing urban/rural development. The findings of contaminant transport modeling depicted flow path representation of arsenic movement mostly towards the rivers in the model domain. Overexploitation of groundwater needs to be controlled for effective development of groundwater resource, and proper purifying/filtering techniques have to be adopted to ensure safe groundwater use in the area.