Chloride balance of some farmed and forested catchments in southwestern Australia

Abstract

Loss of chloride in streamflow (salt flow) from forested catchments in southwestern Australia is only slightly greater than the total annual input (salt fall) from rain and dust. However, salt flow from catchments in which a significant area of the forest vegetation has been cleared for farming is much larger and exceeds salt fall by up to 690 kg/ha yr, or a factor 21. The net loss of Cl is interpreted to result from decreased storage in catchment soil water. Removal of the forest vegetation is estimated to have increased groundwater discharge of whole catchments by amounts ranging from about 1 to 13 cm 3 /cm 2 yr. From present rates of groundwater discharge, characteristic times for equilibration of Cl input and loss on farmed catchments are estimated to range from 30 to 400 years. In equilibrium the salty streams draining farmed catchments would yield water with Cl concentrations acceptable for drinking.