Factors contributing to salinity

The occurrence of salinity depends on several factors, the most important being the:

characteristics of the landscape
climate
effects of human activities.

An understanding of water movement associated with the salt-affected area is needed to determine the likely extent of any salinity problem. The sources of these salts are:

rainfall, which carries low concentrations of salts that have accumulated in landscapes over thousands of years
weathering and erosion of surface rocks
groundwater that has soaked through sediments and sedimentary rocks that originally formed in salty marine environments.

The amount of salts which accumulate in soil depends on the properties of the soil and rainfall. For example, clay soils (which occur extensively in inland Queensland) generally have the highest levels of salt.

Common landform features associated with salinity:

Basalt form
Catena form
Alluvial fan
Catchment restriction (artificial)
Catchment constriction (natural)
Alluvial valley
Dams

Basalt form

Both seepage and watertable salting can occur where:

basalt overlies less permeable rock
regions of variable permeability occur within the basalt
basalt is in contact with adjacent formations.

Catena form

Discharge areas can occur in the lower slope or at break-of-slope positions, where soils or geologic features restrict water movement. Lower slope soils may be sodium or salt affected.