Perth

Groundwater discharge into the sea from each aquifer for the two model regions during 2009-10 are given below. This is the net volume of groundwater discharge into the sea that occurred from the water table aquifers.

Data source

Western Australian Department of Water: PRAMS Version 3.4 and PHRAMS groundwater models.

Data provider

Western Australian Department of Water.

Method

This line item refers to the net annual volume of lateral outflow from the three primary groundwater stores (water table aquifers and the underlying aquifers - Leederville and Yarragadee) within the Perth region to the ocean. These lateral flows were derived for the Perth region (the area between Gingin and Mandurah) and the Peel-Harvey region (the area south of Mandurah) using the PRAMS and PHRAMS models, respectively. Both models apply a constant head at the coastline in order to estimate the volumes flowing through each boundary over the reporting period. It should be noted that for the Peel-Harvey area, the PHRAMS model assumes that the estuary inlets along the coastline form part of the boundary.

Uncertainty

Ungraded.

Approximations, assumptions, caveats/limitations

• PRAMS and PHRAMS models calculate lateral flow between the ocean and the modelled areas. Both use a constant head at the coastline of zero (given the level of 0.0 m AHD (Australian Height Datum) is mean sea level).
• Flows from the estuaries within the PHRAMS modelling area were estimated and included in the reported amount. That is, the estuary systems in the Peel-Harvey area were considered part of the ‘coastline’ boundary. These estuary systems are relatively minor in the area north of Perth and, therefore, were not considered in the PRAMS model.
• Both models were initially developed to estimate and assess the impacts of changes in climatic conditions and varying extraction rates on the aquifers, not to prepare water accounts. These models have since been modified to also provide data for water accounting.