Modelling of Drainage and Hay Production over the Crau Aquifer for Analysing Impact of Global Change on Aquifer Recharge

Changes in climate and land use affect water resources and agricultural production. It is important to document these changes and to provide prospective scenarios for improving knowledge and tools that will help stakeholders to anticipate their impacts and propose adaptations. The recharge of the aquifer in the Crau plain mainly depends on the irrigation, in excess, of grassland producing high quality hay. The sustainability of this system is challenged by possible decreases in water availability from the Durance River, the main water source for irrigation, and the decrease in irrigated grassland surfaces. We implemented a modelling system combining the STICS crop model, used in a distributed mode, and the MODFLOW aquifer model for analysing the evolution of hay production, aquifer recharge and water level in the aquifer. The modelling system was implemented for several scenarios concerning climate and land use evolutions, as well as water availability for irrigation, in a close future (2025-2035). The main results showed that the level of the aquifer is seriously threatened by a decrease in irrigation level, either because of a reduction of irrigated grassland surfaces, or because of a limitation of water availability for irrigation. Conversely, the hay production (in term of quantitative yield) would be enhanced by the increase in temperature, even in situation of reduction of irrigation.