Application of geophysics to saline reclamation of farmland in W.A.

Abstract

Salinity is a serious problem in farmlands of Western Australia where the agricultural land lost due to salinity is estimated at over 300 000 hectares while the annual increase in salt land is in excess of 25 000 hectares. Using a multidisciplinary approach, geophysics is applied to economically establish the geology and hydrology that control the salinity, and then hydrological and engineering solutions are implemented for the land reclamation. In 1984, a Cranbrook property of 1297 hectares had 240 hectares of salt-affected land although when the property was purchased in 1967 there was no evidence of water-logging or salinity. Magnetic and electrical sounding surveys indicated a series of dyke formations which obstructed the main ground-water system causing an increase in pressure in the system. This is one of the major causes of salinity in Western Australia. Prior to agricultural development, the groundwater system was in equilibrium. However, with clearing of native vegetation and replacement with species that use less water, it has caused a hydrological imbalance, resulting in the accumulation of salt in the top 2 metres of soil. The engineering and hydrology solution consisted of water pumping and gravity feed. After 2 years the salt-affected land has been reclaimed to top production.