Features, Projects, Sustainability, Water & wastewater

Flooding the forest

The Murray-Darling Basin Authority has brought together local companies to save the Hattah Kulkyne National Park. The area relies on natural flooding to keep the river system healthy. When dry conditions persisted the MDBA used Australian pumps to artificially raise water levels – creating the ideal conditions for the river to flourish.

The demands of the task required Tocumwal-based Batescrew Pumps & Valves Australia to use seven pumps, each 32 metres long, capable of churning 1600 litres of water per second. Their combined power can shift 1050 mega litres every day into the  creek-lake system, simulating the natural, cyclical flooding that sustains the ecosystem.

For such a demanding task model 24/30, 2-stage Axial flow and driven pumps were selected for the job. With 300kw variable speed electric motors and a 745 rpm capability the pumps peaked at a 85% efficiency.

The pumps are automatic and capable of variable rates of water flow. This is controlled from the G. M. Water Flow Office in Mildura.

The motors are set above FLOOD water level and connect to the impellers at the bottom. This means that the pump can work when the river is at any level. Once the motors are on the pumps can supply water straight away  without any priming. The 77 tonnes of pump machinery is supported by 56 300-350mm diameter steel piles, installed by Hunter Piling, Newcastle. An additional row of piles surround the pumps to protect the asset from any trees or houseboats. The pumps were designed, manufactured, and tested in Tocumwal, NSW and the castings for the impeller assembly took place in Melbourne.

The junction of the Chalker Creek and the Murray River was the spot chosen for the project. This allows for the water to be pumped from the Murray River, through concrete lined discharge steel pipes into a junction box, where it is then diverted into a 2100mm diameter pipe that feeds it the last 300m to the Chalker Creek. Flood gates manufactured by AWMA Cohuna ensures that no water ends up flowing back into the Murray.

The “Electricals” were designed and   installed by Ladd Electrical of Melbourne. The solar panels provide power to the SCADA system and essential controls. Inside the shed the electric starters, dynamic filters, variable speed drives, SCADA system Human Machine Interface (HMI) and electric urn are stored.

Principal Contractor Comdain Infrastructure managed the overall project including Occupational Health and Safety Concerns. Logistical challenges came to light during the installation process because the building site was in a remote forest area.  Changing weather conditions meant that over the six months of construction, semi trailers of supplies had to be dragged through swampy bog or over cracked, dry ground in 46 degree heat.

To protect surrounding trees and grassland, extra expense and planning went towards minimising the harmful environmental impact of the project. Rather than felling trees and powering the pump station with overhead wires, 5.2km of underground HV cable carrying 2100kw was laid down. An expensive way to wire a pump, but one that saved 26 hectares of native forest.

The construction required the use of two 100-tonne cranes supplied by Sunraysia Crane & Rigging. The steel work was completed by Sunstone Industries while GHD Melbourne Office did the design and modelling work. In total the project saw to the completion of three major structures including diversion gates further down river at the forest’s edge. These should maximise the impact of the project by increasing water supply to the river lakes over a greater area.

Access to the area was denied to the public during major construction , but the track had to remain open to fire authorities.

The Murray-Darling Basin Authority expects this solution will have long-term positive effects on the ecological health of the river catchment, the beauty of which can now continued to be enjoyed for years to come.

Background

After years of drought one of Australia’s largest environmental works projects was initiated to secure a sustainable future for this iconic system of freshwater lakes with the use of pump technology.

The package of works included the construction of a permanent pump station, regulators and environmental levees, which will be used to return a more natural and healthy pattern of flooding to the lakes.

“The beautiful Hattah Lakes system needs both wet and dry periods to be healthy, but river regulation and a changing climate have reduced the frequency and extent of natural floods and the environment has suffered as a result,” Mallee Catchment Management Authority (CMA) Board Chairperson Sharyon Peart explained.

“By constructing these works, it is now possible to top up natural floods to increase water levels in the lakes system or, when river flows are not able to naturally reach the lakes, water can be pumped into the system to maintain watering regimes.”

The Hattah Lakes system is part of the 48,000 hectare Hattah-Kulkyne National Park, 60 kilometres south of Mildura. The 18 kilometre Chalka Creek connects the lake system to the Murray River, with the lakes supporting populations of River Red Gums and Black Box communities, as well as many threatened and rare native plants and animal species. These works will deliver water to the twelve lakes that are Wetlands of International Importance under the Ramsar convention.

The Mallee CMA coordinated the environmental works construction project, on behalf of the Murray Darling Basin Authority and the Victorian Department of Environment and Primary Industries, and in partnership with Parks Victoria.

Funding was provided through The Living Murray program, which is a joint initiative funded by the New South Wales, Victorian, South Australian, Australian Capital Territory and the Commonwealth Governments, coordinated by the Murray–Darling Basin Authority. Construction works were undertaken by Goulburn-Murray Water.

The works will deliver water and achieve environmental benefits that would be normally require a natural flood with river flows of nearly 100,000 megalitres a day over a number of months. The works will make it possible to achieve the environmental outcomes of a natural flood while the river is operating at normal flow levels (approx 5 to 10,000 ML/Day), without any impact on other river users.

Environmental water to be delivered to the lakes will come from a number of sources, including The Living Murray, the Commonwealth Environmental Water Holder and the Victorian Environmental Water Holder.

“Using environmental water effectively and efficiently has always been the top priority at Hattah Lakes,” Ms Peart said.

“The Hattah Project is a good example of how environmental works and measures can offer a more accessible and effective way to deliver Basin Plan environmental outcomes in wetlands and floodplains along the Murray.

“Using water more efficiently means environmental outcomes can be achieved without further significant economic impact on Basin communities.”

Future watering events at Hattah Lakes will be informed by water availability and ecological requirements.

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