Salinity is the most important criterion for evaluating irrigation water quality because of the potential crop yield reductions resulting from using salty water that might prevent water uptake by plants. There are different causes, both natural and human, that can induce accumulation of salt in water resources. Irrigation can cause the mobilization of salts accumulated in soils and therefore provoke the salinization of water bodies. Intrusion of saline seawater in aquifers is another important cause of salinization of water resources in coastal areas. This intrusion is frequently due to excessive groundwater extractions for agriculture.
Major soil and water salinity problems have been reported in big irrigation schemes in China, India, United States, Argentina, Sudan and many countries in Western and Central Asia, where more than 16 million hectares of irrigated land are salinized. Globally, the extent of the problem is much higher with estimates of 34 million irrigated hectares salinized.
Leaching and drainage are required to maintain salt balance in the soil profile and to sustain crop yields in arid areas. However, this drainage needs to be carefully managed to prevent salinization of water bodies. Some drainage water management options include drainage minimization through water conservation, drainage water reuse, safe drainage water disposal or drainage water treatment.
Another crucial issue in coastal areas is the prevention of saline intrusions. Rising ocean levels, drought, and people’s increased use of water, specially for agriculture, all contribute to increased saltwater intrusion into freshwater bodies. Two main approaches taken in dealing with this problem are to: (i) reduce water extraction from groundwater in coastal areas and (ii) create salt water intrusion barriers through injection of water into aquifers.