Turner, J., Rosen, M., Milligan, N., Sklash, M., and Townley, L. (1993), Groundwater recharge studies in the Kalgoorlie region. Minerals and Energy Research Institute of Western Australia, Report No.98, 276pp.

The report describes results obtained from research into the rates of groundwater recharge to hypersaline paleochannel aquifers in the eastern goldfields region of Western Australia. The groundwater resource in the region is of crucial importance to the mining industry as a source of water primarily for gold and nickel ore processing.

A range of techniques was employed in the investigation. These include measurement of the natural abundance of environmental isotopes such as oxygen-18, deuterium, carbon-13, carbon-14, chlorine-36, sulphur-34, uranium 234/238 and strontium 87/86 in the groundwaters. The measurements were used to estimate groundwater residence times and determine the interrelation of groundwaters in the paleochannel aquifers to those in fractured rock aquifers and salt lake environments. The systematic trends in groundwater salinity over the region were interpreted in terms of the processes of groundwater recharge, discharge and groundwater flow through the paleochannel aquifers using a distributed parameter model. The relationship of differences in hydraulic head between the paleochannel aquifers and saturated, low conductivity clay formations that bound the producing aquifers were investigated at specific field sites in the region.

Numerical modelling was used to evaluate the resource potential of the system. Results showed that groundwater storage in overlying clay layers was significant in comparison to the aquifers and that depressurisation of the aquifer causes delayed leakage from the overlying clays. Dewatering of the aquifer and saturated clay occurs under gravity drainage. A preliminary dimensional analysis, based on the numerical model of one section of paleochannel, was used to develop a generic paleochannel model that could be used to determine the time to economic dewatering and commandable groundwater resources of other paleochannel aquifers in the study region.

Evaporative discharge from the system via salt lakes was shown to account for a substantial proportion of the natural recharge to the paleochannel aquifers, the remainder discharging eastward from the paleochannel system. Under the assumption of a hydraulic steady state, the recharge rate was estimated to represent a replenishment rate of < 1.0% per year of the estimated groundwater storage in one section of paleochannel. The recharge rate, determined by the different methods, all show that recharge is less than 10% of the annual abstraction rate in this same section of paleochannel.