Modeling Coupled Impacts of Soil Salinity and Hydroclimatic Stress on Irrigation Demand

A transformation towards sustainable agriculture requires accurate tools to assess how environmental constraints limit food production. However, agricultural productivity faces increasing pressure from the interconnected issues of soil salinization and water stress. As climate conditions become more extreme, rising temperatures intensify evapotranspiration (ET) and crop water stress, while soil salinization further reduces soil moisture availability, particularly in arid and semi-arid regions. Despite these challenges, global agricultural models have historically lacked the capacity to quantify the specific impact of salinity on irrigation requirements at an operational scale.

To bridge this gap, this work advances the waterCROP agrohydrological model by integrating a new modeling layer that accounts for salt build-up in the root zone and its feedback on crop water availability. This represents one of the first operational attempts to simulate irrigation demand under distinct soil salinity conditions at the global scale. The enhanced framework improves the representation of soil-water-plant interactions by (i) simulating more realistic actual crop ET, (ii) estimating irrigation water demand under varying salinity levels, and (iii) incorporating up-to-date agricultural datasets across staple crops (wheat, rice, maize, soybean) and salt-sensitive crops (broadbean, cabbage, potatoes, tomatoes).

Simulations were conducted at a 5 arc-minute resolution (approximately 9×9 km at the Equator) for years centered on 2000 and 2015. Globally, maize and soybean show blue water demand (BWD) increases of 6 - 10 %, but locally BWD can increase up to 50% over this period, highlighting areas of particularly high water demand growth. This operational approach provides a refined, quantitative assessment of BWD, offering essential data to support sustainable land management strategies in the face of increasing climate and salinity pressures.