Hydro-economic basin impacts of extensive adoption of deficit irrigation by farmers: Are we overestimating water resources?

Abstract

Deficit irrigation (DI) is an agronomic practice in which the volume of irrigation water applied is below maximum yield requirements, usually during drought-sensitive growth stages. DI is often used when water is scarce, and farmers need to either reduce the irrigated area or reduce the water supply to the existing irrigated area. This research presents an agroeconomic model of field efficiencies and related losses to study the relationship between DI adoption and return flows (RF). Results show that RF are significantly overestimated when DI is widely adopted as there are no losses when relative irrigation supply (ν) is low. The hydrological impact at basin level has been illustrated for the Guadalquivir River Basin, showing that RF and water resources are substantially overestimated when constant efficiency values (an assumption common to many hydrological models) are used without including the impact of DI on RF.