18.1 Groundwater outflow to outside region
The volume presented in the water accounting statements (0 ML) represents groundwater flow across the Melbourne region boundary for the following processes:
- through fractured rock along the northern and north eastern boundary
- through major sedimentary and basalt aquifers at the western and eastern boundary.
The following figure shows the groundwater flow boundaries. In general, the dominant direction of groundwater flow in the Melbourne region is from the recharge area in the fractured rock aquifers in the north, northwest and northeast towards Port Phillip Bay and Western Port in the south.
Groundwater flow boundaries
Port Phillip Catchment Management Authority groundwater model (Department of Sustainability and Environment 2010b), hydraulic conductivity and aquifer thickness; Victorian Department of Environment and Primary Industries bore locations, groundwater level data and aquifer attribution.
The estimation of groundwater inflow to the outside region across the Melbourne region boundary is explained by groundwater observations in the region and the assumptions in the following section.
Assumptions, limitations, caveats and approximations
Groundwater inflow across the Melbourne region boundaries is assumed negligible on an annual basis based on the fact that the northern and northeast boundaries represent a groundwater divide. Groundwater flow along the landward boundary of the region is thought to be minimal (Department of Sustainability and Environment 2010a). A small amount of cross-boundary flow is likely in the Kinglake area due to the concentration of abstractions from the Kinglake groundwater management area immediately to the north of the Port Phillip catchment management authority boundary.
Groundwater outflow to outside region across the Melbourne region boundary is assumed negligible on an annual basis based on the following fact that the groundwater flow direction in the western part of the region is approximately parallel to the region boundary. It is assumed that there was no significant flow across the boundary.
The uncertainty estimate was not quantified.