Increases in salinity, a measure of the quantity of dissolved minerals in freshwater, result from land-use changes, agricultural irrigation drainage, lake evaporation and seawater intrusion, usually most severe in arid and semi-arid regions (Vengosh 2003). Excess salinity renders the water unfit for many human uses, and most freshwater organisms have limited salinity tolerance (UNEP 2016e).
Salinity problems persist at various degrees in rivers throughout Africa, Asia and the Pacific, and Latin America, affecting agricultural irrigation as a result of accumulation of naturally occurring minerals in irrigation water, as well as industrial water uses (Foster et al. 2018; Annex 9-1), with surface-water salinization being a major issue in Central Asia. Saline water intrusion into coastal aquifers can result from over-abstraction and mismanagement, as well as sea level rise. Apart from sodium, waters with elevated levels of magnesium are emerging examples of water quality deterioration leading to environmental and food security constraints in several irrigation schemes (Qadir et al. 2018).
