The Application of Multiple Correspondence Analysis Method to Irrigation Water Quality in Tejo Alluvial River Plain

Abstract

The lower Tejo river basin is an important crop production area in Portugal. The mild climate, diverse water sources and availability along with flat and fertile land areas provide the condition to a highly productive region. Although the historically rainfed cultures installation since the eighteen century, irrigated cultures, such as rice, started to gradually occupy the region in the beginning of the twentieth century. Nowadays, rice cultivation prevails in the area, which requires reliable sources to fulfil water demand for this culture. Paddy-rice fields installation in Tejo tributaries alluvium, such as Sorraia and Almansor rivers, directly supply those parcels in the vicinity. Nevertheless, the largest production area is installed in Lezírias de Vila Franca de Xira, located in Tejo alluvium plains. Such area requires large amounts of water during crop season, from April to October, mainly withdrawn from Tejo river. The Tejo estuary proximity and its salinity influence along with demand peak during summer compromise water quality which, in a long term, can cause salinization and alkalinization of soils. Rice is a light salinity tolerant culture, which is adapted with the current water quality, but the region faces serious sustainability challenges if a shift for some other crop type occurs, as happened in the past. Multiple Correspondence Analysis was used as a statistical method to assess water quality in the region. Water management, driven with water quality allocation by crop and soils requirements can be an answer to minimize permanent soil damages achieving natural resources sustainability in the long term.