• Loddon Herald

Flows enhance biodiversity

By PAUL HAW


LAKE Boort filled approximately once in three years when the Loddon was unregulated.

And it is hard to believe the lake used to be a heavily timbered red gum swamp - most were drowned in the 1850s after continually flooded as a result of Mr Godfrey from Boort Station redirecting a large amount of the flow from the Loddon in 1845.

Many of the dead red gums were removed during the two world wars and sent to Melbourne to produce charcoal gas.

Lake Boort was full of water until 1995, the latter years were filled mostly from channel outfall. All wetlands around Boort were kept full artificially for breeding of ibis and ducks.

Since, channel outfall has ceased to save water for irrigation. Regulation and the effects of climate change means Lake Boort is expected to only fill one in 15 years, therefore, it desperately needs environmental flows.

Ecologist Damien Cook recently recorded 200 native plant species in the Lake Boort Reserve, many are listed as rare and endangered.

Lake Boort has a rich Aboriginal history - at least 50 cooking mounds around the perimeter, some are up to 10 metres wide.

The reserve also contains the highest concentration of scarred trees in Australia, possibly the world, carved with stone tools. After the last flood in 2016, we donated over 1000 red gums to the reserve, they propagated the seedlings after collecting the seed locally. Volunteer groups helped plant out as the water receded in early 2018.

The best performing red gums are now over four metres tall, all planted out on the bed of the lake. It has been discovered that the weeds are not growing under the new trees. This will make the lake less of a fire hazard.

If the lake was left to its own demise, it would eventually return to a red gum forest.

With the next flood or environmental flow it will be important to plan a revegetation program well. This is just as important as environmental water.

The only concern that I have is in autumn, when the environmental water is planned to arrive, the channel supplying Lake Boort is at capacity supplying water to irrigators leaving little water to partially fill the lake.

The Lake Boort reserve is just over 400 hectares. Every 100mm rise takes 400 megalitres to fill. It also takes about 400 megalitres to wet the bed of the lake before it starts filling. The capacity of Lake Boort is approximately 6000 megalitres.

It will also be important to erect a European Carp exclusion fence to stop the fish entering to help establish aquatic plants. Yando swamp is a good example of what can be done with carp exclusion, revegetation and environmental flows.

North Central Catchment Management Authority must work with the Little Lake Boort Committee. The committee prefers to lower the lake level to carry out maintenance, ensuring that the salinity level stays low. There would be enough water to raise Lake Boort at least 100mm.

Autumn is the correct time to place water as it will control winter weeds, such as mustard weed. The lake bed has already been transformed and has a high level of native plants which thrive being flooded.

In 1913, the level of Lake Boort was raised considerably, making it too deep for aquatic plants.

The Boort West of Loddon Salinity Management Plan lowered the level in 1996 by 300mm. The level could still be lowered more to its natural level.

Most people are looking forward to an environmental flow which will enhance the bio-

diversity significantly, bringing many species of birds and plants for people to enjoy. Lake Boort is already receiving quite a high number of visitors studying Indigenous history.



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