Dryland Salinity

From Dry Tropics Wiki
Jump to: navigation, search

Dryland Salinity develops in catchments in response to changes in the hydrological balance brought about by clearing and the replacement of native perennial grasses with annual pastures, crops or weeds. Reduced water use with the loss of trees and other perennials increases groundwater recharge. In many landscapes, this increase in recharge will cause water tables to rise. Once the water table rises to within a few metres of the surface, salt dissolved in groundwater will begin to accumulate in the soil profile and may affect the health of native vegetation and agricultural plants. Salty water may be directly discharged into streams or gullies where they intersect the water table.

The time taken for salinity to be expressed and the ways in which it is expressed vary with geology, climate and landform (National Land and Water Resources Audit 2001). Local flow systems, in which groundwater moves over distances of hundreds of metres to a few kilometres, are relatively responsive to changes in land use and management. Salinity may take many decades to develop in region scale groundwater flow systems and are much less responsive to management interventions. While there are few outbreaks of dryland salinity in the region, much larger areas are considered to be at risk. The Department of Natural Resources and Mines (2001) produced a salinity hazard map for the Burdekin catchment (Roth et al. 2002). It highlights a number of salinity hotspots including the Cape River and Campaspe River catchments and parts of the upper catchment of the Suttor River.