Salinization of groundwater in arid zones

Abstract

Natural pollution of surface and groundwaters by inorganic salts (mostly chlorides and sulphates of Na, Mg and Ca) in arid zones is a consequence of the dry climate and the extensive irrigation practices in agriculture. Salts, accumulated in the soil profile after evaporation of the water phase, are redissolved either by fluctuation of shallow groundwater or leached down by fresh irrigation water applied on the soil surface. This results in a continuous increase in groundwater salinity and deterioration of its quality. In alluvial regions, groundwaters with a total dissolved solids concentration as high as 46,000 mg 1 −1 can be found. In desert oasis areas, layering of relatively fresh water (TDS 500–3500 mg 1 -1) above the saline groundwater (TDS 7,000–12,000 mg 1 −1) can occur. Vertical distribution of groundwater quality within the same aquifer shows pronounced zonation. Methods of water salinization control and utilization of saline water resources to supplement the existing water supplies in arid countries are discussed.