Aquaculture Groundwater Resource Atlas - Groundwater temperature

Because groundwater is stored underground it is generally a constant temperature throughout the year. Groundwater is warmer in the north of the state, and becomes warmer with increasing depth.

Shallow groundwater isotherms

Shallow groundwater is around 18 degrees Celsius along the South Coast, and rises to 31 degrees Celsius in the Pilbara and Kimberley. This reflects the mean annual surface temperature.

The temperature increase with depth depends on the nature of the rocks and on the heat flow in that particular area of the Earth's crust. In the Perth Basin, geothermal gradients range from about 2 degrees per hundred metres in sandstones, to about 5 degrees per hundred metres in shale. With a knowledge of the surface temperature, and the thicknesses of the rock types at a particular location, the temperature at any depth can be predicted.

In the Carnarvon Basin, artesian water flowing from the Birdrong Sandstone reaches temperatures of between 32 and 80 degrees Celsius, depending mainly on the depth. Geothermal gradients in the mainly shale confining beds above the Birdrong Sandstone range between 5 and 7 degrees Celsius per hundred metres.

Further information on groundwater temperature in Western Australia is given by Bestow (1982).

The rate of cooling or warming of the groundwater as it is pumped into open ponds will depend on the rate of pumping and the residence time in the aquaculture pond as well as the air temperature.

[Please note that the groundwater temperature referred to in the Water & Rivers Commission's groundwater WIN database may refer to temperatures in the laboratory during analysis of the water sample, not in the field.]