Improving irrigation–climate interactions in land surface modeling: Development, validation, and applications of the two-way coupled irrigation framework in CoLM

Human water management—particularly irrigation water withdrawal and use—strongly reshapes land–atmosphere interactions and modulates regional hydroclimate. Yet representation of irrigation processes in land surface and Earth system models remains limited, constraining our ability to assess water management–climate feedbacks at large scales. In this study, we advance the Common Land Model (CoLM) by developing a two-way coupled irrigation scheme that integrates irrigation demand, application, and water withdrawal processes. The new module estimates irrigation water demand based on soil moisture deficit, represents four major irrigation methods, and links irrigation water supply to multiple water sources by coupling CoLM with a river-routing model and a reservoir operation scheme. This framework explicitly resolves dynamic feedbacks between irrigation demand and water availability from runoff, streamflow, reservoirs, and groundwater.

Comprehensive evaluations over the United States show that the enhanced model realistically reproduces irrigation withdrawals, their spatial distribution, and water source proportions, consistent with reported state-level statistics. The new irrigation scheme substantially improves simulations of surface energy fluxes, near-surface temperature, river discharge, and crop yields for major crops. The improved CoLM has now been incorporated into the ISIMIP3 Water (global) sector model intercomparison project, providing a new tool for coordinated global assessments of human water management impacts.

Applications of the new framework further demonstrate its utility in predicting irrigation-induced climate effects and assessing agricultural water use and scarcity. Overall, this work provides an advanced representation of irrigation–climate–water interactions, offering new opportunities to investigate the co-evolution of climate, water resources, and agricultural production, and to support sustainable water management under a changing climate.