Salinization of groundwater (downward salinization) and of soils (upwards salinization) is one of the main desertification processes in arid and semiari dregions, especially in agricultural areas. Anthropogenic activities such asirrigation, water drainage, regulation of surface flow, modification of hydrographic networks, and construction of water reservoirs affect the stability andrhythm of natural processes and cause significant changes in ecology at localand regional scales. Negative consequences include upward secondary salinization, waterlogging, and increased mineralization of return drainageflow.
Although there is a pressing need to identify salt-affected soils, detection and monitoring of such areas have posed problems to remote sensing applications since most of the salts are featureless in the reflectivity portion of the electromagnetic spectrum. Different indirect methods need to be developed andtested. These could be based on detecting changes in soils (over differentseasons), vegetation status data, integration of thermal data, principal component analysis, and more.
Turkmenistan is one country that suffered severely from secondary salinizationdue to mismanaged irrigation schemes. Irrigation in Turkmenistan ismainly concentrated in oases, where water is diverted from several local riversand from a long system of canals. Water is lost at a considerable rate fromthe unprotected banks of the canals. This has caused massive waterloggingand salinization of the surrounding land. In undrained irrigated fields, dissolved salts are pushed deeper into the soil by the irrigation water, and at thefield margins, these salts spread to vacant lands. Figure  demonstrates remote sensing methods we have developed to detect and map different degreesof salinization in the Dashguz oasis in northern Turkmenistan.