Drought and irrigation water demand: elements for thought

Abstract

This article reviews what is currently known in the field of water consumption for irrigation in France, which varies drastically in time and space. During the last ten years, irrigated surfaces have increased significantly, with some variations depending on the regions, in spite of the CAP reform. With 43% of irrigated area, corn remains the main irrigated crop. The knowledge of irrigated surfaces, satisfying from a statistical standpoint, remains inadequate to quantitatively estimate water samplings for irrigation, because of the important variability of the crops water requirement and of the limited knowledge of irrigation practices. The Cemagref has developed, at regional scale, a method for estimating the supply in irrigation water during a severe drought. The theoretical water requirements of corn, chosen as a reference crop, are assessed for the main production regions, using climatic data and soil characteristics, and by taking into account restriction practices by farmers during a lasting drought. On the basis of this work, it is possible to propose a system of monitoring and prediction analysis of water demand from farmers on a regional scale, in order to better assess the risks of inadequation between supply and demand - and therefore of conflicts between users -, and to set up more efficient management modes. This system will rely, among others, on a better understanding of the farmers' practices.