Scenario-based modeling of water yield under future climate conditions using the InVEST model (Jajrud watershed, Iran)

The increasing intensity of climate change and the accelerated urban expansion of cities in recent years have posed significant challenges to water resources in semi-arid regions such as the Jajroud watershed, located east of Tehran. This study applies a two-stage framework to assess the impact of future climate change on the basin’s water yield. In the first stage, historical and future climate conditions were examined using observational data and the results of the CMIP۶ General Circulation Models (GCMs). The LARS-WG model was used for downscaling and bias correction, and the MRI-ESM۲-۰ model was selected as the best-performing GCM based on statistical criteria. In the second phase, the Water Yield model from the InVEST suite was used to estimate the spatial distribution of water yield under present (۲۰۲۴) and future (۲۰۴۰) conditions, using climate projections under scenarios SSP۲-۴.۵ and SSP۵-۸.۵. Model inputs included precipitation, reference evapotranspiration (ET₀), root-limiting depth, plant-available water, land use/cover, and a GIS-based biophysical table. Results indicate that water yield increased from approximately ۸۰ MCM in ۲۰۱۴ to about ۱۱۰ MCM in ۲۰۲۴, mainly due to higher recent precipitation. However, future projections reveal a strong decline, with total water yield decreasing to about ۶۰ MCM under SSP۲-۴.۵ and further dropping to ۴۴ MCM under SSP۵-۸.۵ by ۲۰۴۰, representing nearly a ۶۰% reduction compared with current conditions. Besides climatic drivers, land-use changes—especially expansion of built-up areas and reduction of vegetation cover—further intensify water loss by limiting infiltration and increasing evaporation.

کلیدواژه ها:

Water resources planning ، Climate Change ، CMIP۶ scenarios ، MRI-ESM۲-۰ model ، Jajrud basin