Integrated Modeling of the Water–Food–Ecosystem Nexus in the Upper Main Catchment under Future Climate and Socioeconomic Scenarios

Understanding the complex interplay between hydrology, agricultural productivity, and ecosystem health is critical for sustainable catchment management under future climate and socioeconomic change. The Upper Main Catchment in Bavaria is a productive rainfed agriculture region with efficient sectoral water allocation and established cropping systems. This balance may be increasingly threatened by projected changes in temperature, precipitation patterns and water availability under future climate scenarios. Rising irrigation demands, coupled with shifts in crop phenology and soil nutrient dynamics, could intensify pressure on water resources and ecological stability. As such, this calls for integrated, forward-looking assessments to capture the dynamic interlinkages between water, food and ecosystem entities across diverse future pathways.

The present study employs a coupled modeling framework using the Soil and Water Assessment Tool (SWAT+) and the Water Evaluation and Adaptation Planning (WEAP) model to evaluate the water-food-ecosystem nexus under climate-driven socioeconomic scenarios. The framework is applied under three Shared Socioeconomic Pathway (SSP) scenarios, SSP126, SSP370 and SSP585, using bias-corrected climate projections from five Global Climate Models (GCMs) sourced from the ISIMIP3b dataset. A historically calibrated SWAT+ model simulates streamflow, percolation, crop yield, irrigation water demand and nitrate dynamics under 15 future scenario combinations (3 SSPs × 5 GCMs). WEAP simulations assess how much of the estimated irrigation demand can be met, allowing evaluation of unmet demands across sectors and time periods.

Scenario-specific projections are used to assess increase in irrigation demand and shortfalls, yield variability and soil nitrate accumulation. By integrating SWAT+-simulated demands with WEAP allocation outcomes, the study identifies spatial and seasonal mismatches between crop water requirements and available supply. Trade-off analysis highlights how future changes in water availability affect agricultural productivity and nitrate loading risks, revealing tensions between maximizing yield and maintaining environmental sustainability. Scenario-driven differences reveal potential stress hotspots, in both spatial and temporal scales. The ensemble spread across GCMs and SSPs underscores the uncertainty associated with climate projections, highlighting the need for resilient strategies for a range of plausible futures. The findings provide a critical evidence base to support integrated water, agriculture, and ecosystem management in Bavaria.