The effect of irrigation on glacier evolution in High-Mountain Asia

Over the past century, global irrigation extent has expanded nearly fivefold, increasing from approximately 63Mha in the early 1900s to over 306Mha today. This growth has been particularly pronounced in Asia, which accounts for roughly 85% of current global irrigation withdrawals. Irrigation, as one of the most impactful land management practices, substantially influences regional climate by altering precipitation patterns and cooling surface air temperatures. These meteorological changes raise important questions about how irrigation-driven weather modifications might affect glaciers in High Mountain Asia (HMA). This study investigates the impact of irrigation expansion on glaciers in HMA using simulations from the Irrigation Model Intercomparison Project (IRRMIP). IRRMIP provides historical climate simulations (1901-2014) under two contrasting scenarios: (1) the Irr-scenario, representing real-world irrigation trends, and (2) the NoIrr-scenario, modeling a world with irrigation extent fixed at early 20th-century levels. These scenarios are then used as inputs for the Open Global Glacier Model (OGGM) to assess the effects of irrigation expansion-induced climate changes on glaciers. Our results reveal that irrigation expansion had an important impact on glacier changes in HMA. Without irrigation expansion, glaciers would have lost considerably greater volume loss over the 1985-2014 period compared to the real-world case with irrigation expansion. This outcome discovers the buffering effect of irrigation on glaciers in HMA, partially offsetting climate-induced glacier loss and underscores the interconnection between human land management and cryospheric systems.