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Groundwater and the environment in Gippsland

Groundwater and the environment in Gippsland

Groundwater interacts with the surface environment where it occurs at or near the surface. The upper aquifers across this region occur at or near the surface and so they interact most closely with surface water environments such as rivers, coastal lakes, wetlands and other Groundwater Dependent Ecosystems (GDEs). The middle aquifers are thought to discharge to the Gippsland Lakes and nearby wetlands. In the highlands, rivers and streams receive baseflow from the lower aquifers and basement where these outcrop at the surface.

Where is groundwater most likely to interact with the environment?

To see where groundwater is most likely to interact with the environment in this region visit our Gippsland region map and select the 'Environment' layer from the drop down box in the top right corner.

What do we know?

Coastal lakes and wetlands

Coastal lakes and internationally recognised wetlands near the Gippsland Lakes are thought to receive saline discharge from shallow groundwater.

Several recent studies have also suggested that the middle aquifers discharge into the Gippsland Lakes around the southern parts of Lake Wellington, Lake Victoria and Lake Reeve. It is also thought that nearby significant wetlands such as Dowds Morass, Sale Common, Heart Morass and Clydebank Morass rely on discharge from the middle aquifers caused by upward pressure.

There is also potential for the saline water from the Gippsland Lakes to enter the middle aquifers if pressure or groundwater levels fall below lake level. However to date no firm conclusions can be drawn from the available data.

The middle aquifers discharge mainly to the limestone and marl aquitard beneath the Gippsland Lakes and along the coast. It is thought that these aquitards provide habitat for cave ecosystems.

Rivers and streams

Most rivers in Gippsland receive baseflow from groundwater. Studies have shown the importance of groundwater to the flows of the Avon, Mitchell and Tarra Rivers.

The Avon and Mitchell Rivers interact with groundwater in the sand and gravel alluvium of their floodplains.  During low flow periods these rivers gain groundwater and during floods they recharge the alluvial aquifers. Groundwater pumping also can impact river and stream levels, particularly during dry years. It is estimated that groundwater pumping near the Mitchell River at Wy Yung during dry summers could reduce the river flow by up to 13%. This happens with very little lag time because the bores being pumped are close to the river and the groundwater moves quickly through the sand and gravel aquifer.

The Tarra River near Yarram is thought to be affected by declines in regional groundwater levels in the lower sand aquifer. It is estimated that the average annual baseflow in the Tarra River is 13% or 5ML/day less now than it was in the 1950s when records started. A new observation bore has been drilled near the Tarra River to better understand the relationship between surface water and groundwater in that area.

The highlands

Spring flows from the basement contribute to rivers across the highland areas in the north and east. Some of these river ecosystems such as the Thomson, Mitchell, Woonangatta, Snowy, Bemm and Genoa Rivers are in very good condition and are listed as ‘Heritage Rivers’.

The high number of farm dams located along the spring fed streams near Thorpdale in the Strzelecki Ranges indicates groundwater interaction. It is likely that many of these dams are fed by springs that flow even throughout the dry months. 

How do we manage this?

When assessing licence applications for new entitlements and the trading of existing entitlements Southern Rural Water takes into account the needs of the environment. With licence applications for bore construction, no new bores are permitted immediately adjacent to streams or rivers.

Learn the basics

To find out about how groundwater supports surface water features such as lakes and rivers visit our How does groundwater interact with the environment page.

To find out about who manages groundwater visit our Who manages groundwater page.

Page last updated27th May 2015
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