17.3 Leakage to groundwater
a. Groundwater models
The Department of Water use the Perth Regional Aquifer Modelling System (PRAMS) Version 3.4 and Peel–Harvey Regional Aquifer Modelling System (PHRAMS) to estimate the natural water movement to and from the groundwater store within the Perth region.
As shown in the following figure, PRAMS estimates groundwater movement for the area north of Mandurah. PHRAMS estimates groundwater movement for the Peel–Harvey area south of Mandurah. The volumes reported in this account refer to the natural water movement that occurs within each model area within the Perth region boundary.
Map of groundwater model areas relative to the Perth region boundary
b. Supporting Information
This line item volume (0 ML) represents the volume of groundwater recharge from drains, rivers and storages within the Perth region during the 2011–12 year.
Groundwater recharge was estimated for the Perth region using PRAMS and PHRAMS; however, the estimated groundwater recharge from surface water is zero for both model areas.
Assumptions, limitations, caveats and approximations
Both models assume that all flows between the groundwater store and rivers and drains comes from the aquifers, hence recharge from surface water is zero. This assumption is consistent with measured and simulated discharges. Wetlands were considered to be part of the water table aquifer, hence any groundwater recharge from wetlands was not considered.
Both models were initially developed for the purpose of estimating and assessing the impacts of changes in climatic conditions and varying extraction rates on the aquifers, not for the purposes of preparing water accounts. These models have since been modified to also provide data for water accounting.