Water and salt balance in an irrigated area of the Ebro River Basin (Spain)

Summary Water balance components (effective precipitation, diverted water, actual evapotranspiration and irrigation return flow) and salt balance components (TDS of precipitation, diverted water and irrigation return flow, and sources/sinks in the soil profile) of the Violada irrigation district (3,913 ha) located in the Ebro river basin were measured for the 1982 and 1983 hydrological years. The irrigation district discharges annually 73,000 t of salt into its receiving river. The gypsiferous character of the soils gives a saturated gypsum character to the leachate resulting in a fairly constant TDS of the irrigation return flow (coefficient of variation of 12% for the 1982 hydrological year). The salt load of this area is 18.8 t/ha due to the gypsum content of the soils and improper water management. This results in a mean annual irrigation application efficiency (JAE), calculated as the average actual evapotranspiration/diverted irrigation water ratio, of 0.67 for the 2 years studied. On-farm irrigation system evaluation tests were performed in order to evaluate uniformity of water application and irrigation requirements of the main crops. The results indicate that JAE can be improved by means of better irrigation water management (especially irrigation scheduling) and proper land levelling of the fields.Formerly Instituto Nacional de Investigaciones Agrarias, CRIDA-03