A water-energy-food-carbon nexus optimization model for sustainable groundwater development in the lower Ain river basin

Groundwater management within the water-energy-food-carbon (WEFC) nexus is inherently interdisciplinary, particularly in regions with significant groundwater-surface water interactions. Effectively balancing trade-offs and synergies among nexus components is critical for socio-economic and environmental sustainability. This study presents an integrated many-objective simulation-optimization (S-O) framework to address WEFC nexus management challenges in the lower Ain River basin (LARB), a typical alpine basin with intensive agricultural activities and river-aquifer (R-A) interactions.

The approach integrates a transient groundwater flow model (MODFLOW) to simulate the flow budget and R-A exchanges. These outputs inform the optimization process, which employs the NSGA-III metaheuristic algorithm to evaluate conflicting objectives, including groundwater supply, agricultural yield, energy consumption, and total carbon emissions from agricultural practices. The Pareto optimal front generated by this framework highlights sustainable withdrawal scenarios that minimize environmental degradation while balancing competing objectives. Three scenarios were developed to enhance decision-making based on nexus trade-offs, R-A exchanges, and carbon emissions. Results demonstrate that the optimized solutions achieve improved nexus outcomes, significantly reducing total carbon emissions while maintaining water supply and agricultural productivity. This many-objective S-O framework offers a robust tool for managing the WEFC nexus in river basins characterized by groundwater-dependent agriculture and complex R-A interactions, supporting sustainable resource management and climate resilience.