1.1.6 Surface water – groundwater interactions


Interactions between streams and alluvial aquifer and between the alluvial and surficial Permian fractured rock aquifers, are considered to occur in both directions in the Hunter subregion. Different rules apply in water sharing plans (WSPs) for the regulated and unregulated parts of the Hunter River alluvium. In the unregulated portions the alluvium and surface water systems are considered highly connected and managed together as a single unit, while in the regulated portions the alluvium is simply a separate unit from other geological units.

Fluxes within the alluvial aquifer are river leakage, diffuse rainfall recharge and upward flow from fractured rocks. River leakage is around four times greater than rainfall recharge to the alluvial aquifer, while baseflow discharge to streams is around two-thirds of discharge from the aquifer. Digital filtering of daily hydrographs estimate that more than 50% of river flow is baseflow discharge from alluvial aquifers, however in low flows or specific locations it may be close to 100%. Both mining operations and river regulation affect the behaviour of water levels in the alluvial aquifer, and can alter the direction and magnitude of water exchange between the river, alluvial aquifers and fractured rock aquifers.

Last updated:
18 January 2019
Thumbnail of the Hunter subregion

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