Evaluation of alternatives for flood irrigation and water usage in Spain under Mediterranean climate

Abstract Evaluation of water management has been progressively more necessary to determine the availability of water resources, especially in the Mediterranean environment where competition for these resources is maximum. This work evaluates the irrigation management and evolution of hydric needs for the main crops implemented in the Ebro basin (Spain), through the monitoring of a pilot experimental basin between 1998 and 2012. This 15-year period comprehends changes in irrigation implemented by the Irrigation District as well as climate and agronomic variabilities of the region. Changes in water management (implementation of an on-demand irrigation system with annual water allowances and payment per surface and consumption, in opposition to an irrigation system in shifts) and crops contributed to reduce irrigation by 40% and drainage by 72%. This occurred due to better adjustments between the water volumes applied and the hydric needs of the crops, achieving flood irrigation efficiencies of 80%. However, small negative trends were detected in the water deficit evolution of corn and sunflower, which should be addressed and improved. Improvements in water management by farmers have enabled the increase of irrigation efficiency up to values found in pressurized irrigation systems, especially in initial stages of the irrigation campaigns. However, specific water deficit episodes were detected that should be remediated.