Salt is a naturally occurring mineral that forms in a number of ways. It is a product of rock weathering, especially marine sedimentary rocks. It is picked up by wind blowing over the oceans and carried inland as salt laden moisture. Dispersed salt on the soil surface can be concentrated by the action of the wind. These salt deposits are buried over million of years, but can later be exposed by erosion or the salt can be mobilised by groundwater.

Salt is a natural part of some landscapes, for example, in inland salt pans, brackish streams, coastal salt marshes and naturally saline soils. However, where human activities such as vegetation clearing, cropping, and housing development have disturbed natural ecosystems and changed the hydrology of the landscape, the movement of salt into rivers and on land is accelerated. This is affecting the natural environment, reducing the viability of the agricultural sector and damaging infrastructure.

Salinity is a dynamic process with the potential for the movement and accumulation of salts to change over time and as a result of land use and management practices.

The processes of salinity vary at different scales such as individual sites, regions and whole river catchments, so the impacts can be close to or distant from the cause, depending on the landscape and groundwater characteristics.

The impacts of salinity depend on factors such as the susceptibility of the landscape, land use practices, the type of salt, length and frequency of wetting and drying cycles, the salt concentration in the landscape and the amount of water available.