ABSTRACT
The globally widespread phenomenon called dryland salinity occurs where there is the combination of a store of salt in the soil and a rising water table. The rising water mobilizes the stored salt upwards and also down slope where it may form salt seeps and enter streams.
Water tables rise when a greater proportion of the rainfall than before enters the soil. Such increase in recharge to the water table occurs when vegetation becomes more sparse, due, for instance, to overgrazing or to clearing of deep-rooted perennial forests or woodlands for agriculture. The reason why shallow-rooted, sparse or short vegetation increases recharge is that the shallower roots harvest less water, the smaller leaf area permits less transpiration and together with reduced leaf area, less interception of rainfall (evaporation from wet leaves) occurs.
To reclaim dryland salinity, a revegetation strategy is required that will discharge sufficiently more water to lower the water table to a safe level. Several major issues in forming such a strategy are addressed. The quantity of water which needs to be discharged to lower the water table to a required level must be estimated, and the combined evaporative discharge from transpiration and rainfall interception must be measured using candidate species. Of similar importance are location of 206vegetation in the landscape and choice of species. Extent of revegetation, cost of revegetation, and lead time to reclamation need to be determined. Several examples of successful reclamation are given.
