Irrigation water quality used in paddy-rice fields in the Tejo River Basin and its consequences

The irrigation water quality is crucial to ecosystems services, soils preservation, and crops’ development. Paddy-rice culture is highly implemented in the lower Tejo river basin and its tributaries (Almansor and Sorraia) alluviums, using irrigation waters with diverse types (ditches, water supply system, water reservoir, water canal, and rivers runoff) and irrigation abilities (C1S1–C4S4 by Wilcox classification). The factorial analysis Principal Components Analysis was used as a multivariate statistical method to understand the relations between water quality variables and their location in the irrigated area. The location of the higher irrigation water mineralization is in the Southern section of Lezírias area, where paddy-rice crops’ implementation prevails. As paddy-rice is considered a salts sensitive crop along with the considerable salinity supply through irrigation, sustainability and crop continuity concerns start to arise. The preservation of natural resources is mandatory to maintain agriculture practices in this highly productive but highly sensitive region. Increasing salinity in soils can force to adaptation measures, namely the blending of irrigation waters or the shift for more salinity tolerant cultures.