Barros R., Isidoro D., Aragüés R. 2012. Three study decades on irrigation performance and salt concentrations and loads in the irrigation return flows of La Violada irrigation district (Spain). Agric. Ecosyst. Environ. 151: 44-52. Three study decades on irrigation performance and salt concentrations and loads in the irrigation return flows of La Violada irrigation district (Spain) R. Barros, D. Isidoro, R. Aragüés* Centro de Investigación y Tecnología Agroalimentaria de Aragón (CITA), Diputación General de Aragón (DGA), Unidad de Suelos y Riegos (Unidad Asociada EEAD-CSIC), Avenida Montañana 930, 50059 Zaragoza, España. *Corresponding author. Tel.: +34 976716357; fax: +34 976716335. E-mail address: raragues@aragon.es (R. Aragüés). ABSTRACT Irrigation district salt balances identify the main sources and sinks of salts and quantify salt loads in irrigation return flows. Salt balances were performed in La Violada Irrigation District during the 80’s (1982-1984), 90’s (1995-1998) and 00’s (2006-2008) decades. Total Dissolved Solids (TDS) and loads in irrigation return flows were related with changes in irrigation performance and infrastructures during these decades. TDS increased linearly to increases in Irrigation Consumptive Use Coefficient (ICUC) (P < 0.01), and decreased with increases in Drainage Fraction (DRF) (P < 0.001). The salt balances revealed that 82% of the exported salts originated from soil gypsum dissolution. Annual salt yields in return flows were high and similar in the 80’s and 90’s (about 19.3 Mg/ha year), and halved in the 00’s (9.9 Mg/ha year) due to comparable reductions in irrigation and drainage volumes derived from a better irrigation