Numerical Modeling of Groundwater Dynamics and Management Strategies for the Sustainable Groundwater Development in Water-Scarce Agricultural Region of Punjab, Pakistan

Focusing on the Lower Bari Doab Canal (LBDC) command area, characterized by its heavy reliance on agriculture, this study addresses the critical issue of groundwater table fluctuations in response to diverse pumping scenarios. Herein, we comprehensively evaluated the dynamic interplay between crop water requirements and groundwater pumping within the expansive canvas of the LBDC, which is facing water shortages. Using the Penman-Monteith equation, we calculated annual average evapotranspiration for major crops-wheat, maize, cotton, rice, and sugarcane. Three-dimensional MODFLOW-based numerical modeling was used to analyze the dynamics of groundwater regimes. MODFLOW was calibrated from 2010 to 2020. Thereafter, we simulated water table changes under a 20% increase and decrease in groundwater extraction up to 2040s. Results revealed significant variations in water demands among these crops, with sugarcane requiring the highest average annual evapotranspiration at 1281 mm. Spatiotemporal analysis revealed substantial declines in the water table in the tail-end command areas, particularly Sahiwal and Khanewal where the decline was 0.55 m/year between 2010 and 2020. The upper reaches, such as Balloki and Okara, experienced milder declines. In considering management scenarios, a 20% increase in groundwater extraction up to September 2040 was projected to raise pumping to 4650 MCM/year. and decrease the net water balance to -235 MCM/year. Alternatively, a 20% decrease in groundwater extraction up to September 2040 could reduce pumping to 4125 MCM/year and increase the net water balance to 291 MCM/year. This study sheds light on major crop water requirements, spatiotemporal groundwater dynamics, and the implications of groundwater extraction in the LBDC command area. Scenarios presented here, encompassing increased and decreased groundwater extraction, offer invaluable guidance for policymakers and stakeholders seeking a balance between agricultural productivity and long-term groundwater sustainability.