Change in recharge of aquifers under several cropping systems due to climate change. Consequences on land use at territorial level
Résumé
Climate change will produce a decrease in rainfall over French territory, especially in western France. Cropping systems pattern is a key factor in water resources management at catchment basin level. In the frame of the ANR French project ―Climator‖, we have undertaken an analysis of the relationship between rainfall and the annual supply of water to the aquifers under several cropping systems and ecosystems. This was performed through crop modelling using agroclimatic data provided either by measurements at 12 experimental sites in France (1971-2000) or by using regionalised outputs of the French climatological model Arpege (2021-2050 and 2071-2100). The simulations highlight the important differences in aquifers recharge between cropping systems (rainfed vs irrigated but also winter vs spring crops and annual crops vs perennial vegetation). For the 12 sites, they also give an estimate of the decrease with time of the annual recharge under each cropping system (at least 2/3 of rain decrease). In the driest locations, that decrease may lead to a partial change in cropping systems pattern in order to match the total water demand at catchment level. Such change could be devoted either to increase annual recharge when irrigation water is pumped from large aquifers or to reduce summer water demand when irrigation water comes from rivers. Both cases are illustrated.
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