Lake Gol Gol

Project Outline

To provide an allocation of water to Lake Gol Gol to help inform future management decisions and provide an interim respite to drought-impacted vegetation.

Objectives

  • Ground-truth the capacity of the Gol Gol Creek/channel system and determine its effectiveness in delivering environmental water to Lake Gol Gol.
  • Provide an emergency water allocation to severely drought stressed wetland vegetation communities within and fringing the Lake.

The project aimed to deliver ~2500 ML of water to Lake Gol Gol via Gol Gol Creek by gravity feeding and/or by pumping. This volume was anticipated to:

  • inundate approximately 77.5% of the lake bed;
  • extend to the inner circle of fringing River Red Gums falling within the 33.34 – 33.64 mAHD contour levels, and
  • achieve an average depth from 0.3-0.6 m.

This project provided an opportunity to determine the capacity of the Gol Gol Creek/channel and ground-truth past modelling. Information generated will be used to inform future management decisions for the wetlands.

Project Management

The project was initiated following enquiries from the community, in particular the Gol Gol Creek irrigators and the former Murray Darling Wetlands Ltd.

Management of the event was undertaken by the former Department of Environment, Climate Change and Water (now Office of Environment and Heritage) in conjunction with NSW Office of Water, the Gol Gol Creek irrigators and the former NSW Murray Wetlands Working Group.

The project was supported by the former Lower Murray Darling Catchment Management Authority and the local community.

Background Information

Gol Gol wetlands are large freshwater ephemeral systems comprised of Lake Gol Gol and Gol Gol Swamp. Located approximately 7 km north-east of Mildura, on the NSW-side of the Murray River, Lake Gol Gol is 494 ha in size and is situated north-east of Gol Gol Swamp.

Aerial view of Lake Gol Gol (14 December 2010)

Prior to development, the Gol Gol wetlands would have received floodwaters from the Murray River via Gol Gol Creek. Since the 1950s, a number of flow control structures have been installed along Gol Gol Creek. The Gol Gol wetlands have been disconnected from the Murray River for a number of years. The last significant flooding of Lake Gol Gol occurred during the 1974 and 1975 flood events. In 1990, the southern lobe of the wetland was flooded for experimental purposes.

In addition to the lack of flooding, the wetlands are subject to groundwater salinity issues caused primarily by the operation of the Mildura weir pool.

Recent investigative studies indicated that future rehabilitation projects should concentrate on Lake Gol Gol, over Gol Gol Swamp, due to its vegetation being in a comparatively better condition.

Water Volume and Source

A total of 2500 ML was allocated and the water used was sourced from unregulated flows declared in NSW within the Murray River between the Murrumbidgee Junction and Wentworth reach between October and December 2010.

Lake Gol Gol before watering event

After watering event; note positive response of overstorey and understorey vegetation

Project Outcomes

  • Water delivery into Lake Gol Gol was conducted between 6 October and 10 December 2010.
  • Between 2500 and 2600 ML of water was diverted into the Lake. Flow rates into the lake averaged 46 ML/d.
  • High water mark mapping indicated that the water level reached between the 33.5-34.0 mAHD level, which equates to approx. 77% of the lake bed surface.
  • Water quality readings were within accepted ANZECC ranges. Outbreaks of blue-green algae were noted during the project.
  • River Red Gum, Black Box and River Cooba trees have shown a positive response to the watering through growth of new foliage. Very little aquatic vegetation has been noted to date.
  • Up to 50 bird species were observed at the Lake, including a juvenile Sea Eagle (this species is not commonly found in this area).
  • Common carp (Cyprinus carpio) was the only species of fish found in the Lake following inundation.
  • Groundwater levels in some bore wells have risen but may not be solely attributable to the watering of Lake Gol Gol. Higher flows within the Murray River plus heavy rainfall events are likely to have contributed to elevated levels.
  • The watering event received local media coverage.

Photo credits: Paula D’Santos and Sascha Healy (OEH, Buronga)