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close this bookIrrigation-Induced Salinity - A Growing Problem for Development and the Environment (World Bank, 1993)
close this folderThe nature and impact of irrigation-induced salinity
View the document(introduction...)
View the documentNature of irrigation-induced salinity
View the documentAlkalinity: a related problem
View the documentEffects of salts on plants
View the documentEconomic impact of salinity
View the documentOff-site external costs

Off-site external costs

The impact of irrigation-related salinity is not restricted to the production areas alone. For example, the disposal of saline drainage water back into rivers have adverse effects on downstream riparians. Deason (1992) notes that many rivers, especially in arid regions reflect a progressive increase in salinity levels from their headwaters to their mouths. In some areas, such as the Colorado River Basin, the aquifers interrelated with the river are highly saline because of soluble salts in the aquifer fill material. The salts discharged to the river system from saline aquifers adversely affect downstream water users--irrigated agriculture, municipal and industrial consumers, and in some special cases, wildlife. In Pakistan, the disposal of saline drainage water from the state of Punjab, which involves the channelling of the drainage water through the Left Bank Outfall Drain that cuts through the state of Sind, has resulted in substantial political tensions between the two states (Smedema, 1992). In other regions, the effects are even felt across international borders. The increasing use of the Euphrates system by Syria and Turkey not only reduces the flow of the river to Iraq, but is also contributing to degradation of water quality (higher salinity) for the downstream riparian (Keenan 1992b). Similar problems are being encountered in Israel and Jordan with respect to the Jordan River and the United States and Mexico with respect to the Colorado River (Keenan 1992b; Schilfgaarde 1992). The following section discusses the extent of salinity problems in various countries in greater detail.