Modelling irrigation scheduling to analyse water management at farm level, during water shortages.

The area under irrigated corn has significantly increased in the Charente river basin during the last 10 years. Corn water requirements are maximum in the summer, the period with low water flows and highest environmental vulnerability. Periods of water shortage during which irrigation is temporarily forbidden occur frequently. To reduce water demand, specific water saving policies are required. This paper investigates irrigation management strategies at farm level during water shortages. A computer programme called IRMA is used to represent the farmer's decision making process. The model was calibrated and validated using information collected through a detailed monitoring of irrigation and farming practices of three representative farms during two irrigation seasons. The accuracy of the model was good; the difference between measured and simulated cumulative water volume used was slightly less than 8.5%. Analysis of daily simulated water demand shows that farmers have adopted different strategies to deal with water shortages, depending on the physical and socio-economic characteristics of their farms. The application presented in this paper stresses the potential of the proposed approach, if used on a larger farm sample, to compare the expected impact of different water management policies on water demand and irrigation practices at the farm level.