Land and Stream Salinity

Abstract

Soil salinity and salinity in water supplies are two major problems facing agricultural production in many arid and semi‐arid regions of the world. Salt, in varying concentrations, occurs naturally in both soils and aquifers. However, salinity problems usually result from man's interference with natural processes and disturbance of the hydrologic balance. For example, the clearing of trees in southwestern Australia and the breaking of native sod on the Great Plains of North America for wheat cropping have reduced evapotranspiration. At the same time, over irrigation in dry regions concentrates dissolved salts in the soil profile, while irrigation return flows add to downstream salinity problems. These problems are of great economic significance, and opportunities are being sought for improved drainage and for interception and disposal of saline groundwater. However, these structural solutions are capital‐intensive and quite expensive to say the least. The most cost‐effective measures, but also the most challenging, are in the areas of improved on‐farm water management to reduce losses, modified cropping patterns, selected retirement of marginally productive lands, and basin‐wide water resource management with regard to both quantity and quality objectives.