Rivers carry dissolved salts from exposed saline shale formations, surface salt deposits (eg salt lakes), and saline springs and seeps, into the sea. Farmers withdraw groundwater and surface flows for irrigation water, which percolates through the soil and leaches more salts into the stream or basin. Saline water tables can be drawn up by the depletion of freshwater, further adding to soil salinity. Each subsequent use of the water adds to its salinity until the water becomes too salty for human use. Salinization of rivers and inland seas is also disruptive to their natural ecosystems.
About 2 million hectares of agricultural land in southern Western Australia is already affected by salinity, and a further 4 million hectares is threatened.