Towards a dynamic representation of irrigation in land surface models

Water use for irrigation has a critical impact on hydrology, ecology, and agricultural productivity. The irrigation water use is determined by (1) the irrigation water volume required per unit irrigated area and (2) the extent of irrigated land. At large scales, the required water volume per unit irrigated area is usually estimated by calculating soil water balances and quantifying the volume of water supply needed to ensure that crop evapotranspiration is at the potential level or at a level minimizing drought impacts on crop yield. Little information is available about the dynamics in the extent of irrigated land, mainly due to the limited observations and investigations at large scales. To fill the above research gap and to test for factors impacting interannual variability in irrigation extent, this study is going to develop a database with 1990-2020 annual irrigated cropland extent for Europe/Eurasia, a region with relatively well data availability, at sub-national resolution. Relationships between annual irrigation extent and factors potentially impacting variabilities in the irrigated area will be tested by using process-based models. The new annual irrigation database will be applied in Community Land Model to quantify differences in dynamics and trends of irrigation water use across the region compared to the use of the current static data products. Consequently, we will analyze the impact of climate variability on the extent of irrigated crops, irrigation water requirements, and irrigation water use. This study will be fundamental for better understanding and qualifying the human impacts on the natural environment and society under climate change, so as to support future scenario forecasts and decision systems, particularly in improving irrigation management.