Aspects of the hydrologic cycle and related salinity in the Belka valley, Western Australia

Abstract

Factors involved in increasing salinity, which has followed clearing in the Western Australian wheat belt, have been investigated in a typical valley. Field and laboratory studies show that salinity is associated with a three-component hydrologic system involving surface, soil, and aquifer waters. The amounts of surface and soil water have increased after clearing. The third component, which is not thus affected, consists of a confined and continuous fine-textured aquifer which extends under most of the area and which has its intakes adjoining rock outcrops. This aquifer is the major repository for water and salt in the landscape, and salinity of overlying soils results where capillary contact with the surface occurs in the valley bottoms. The increase in volume of surface water does not lead directly to increased salinity, but rather, ultimately, to a removal of salts from the system via the main drainage lines. Increased soil water, however, serves to affect salinity in two ways. Firstly, it increases the area and duration of capillary contact between the confined aquifer and the soil surface in valley floors. Secondly, it leads to the development of seepage spots in the coarse-textured soils on valley sides, thus resulting in the formation of saline patches. The main part of the salt in the landscape has accumulated through atmospheric accession.