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Environment

Environment

Grange Lakes

This summer has been the hottest summer in recorded history for metropolitan Adelaide, and is the driest summer we have experienced in 33 years. The City of Charles Sturt has not received more than 5mm of rain since mid to late December 2018. The AMLRNRMB has not been able to release any water into the Torrens River system since Tuesday 8 January 2019.

This extreme weather pattern highlights how our urban environment adapts and changes in response to periods without rainfall.

This has resulted in both the Torrens River and the Grange Lakes stormwater system becoming almost completely dry. We have taken the opportunity to remove approximately 2,300 cubic metres of silt from the system which has resulted in some small ponds which provide water to the flora and fauna that inhabits the area. This system is primarily ephemeral – meaning it is intended to hold stormwater during winter and dry out when water is not available.

Environmental Flows occur at the discretion of the AMLRNRMB and are to address algal bloom and maintain water quality in the Torrens Lake which Council has then been able to divert into the St Clair and Port road Wetlands and Grange Lake system. These releases are strictly controlled by water quality testing undertaken by the EPA and SA Water and occur only where necessary.

Unfortunately this summer, there has not been justifiable reason to release water and the Torrens River and Grange Lakes system has dried. Our wetlands are also drying in the current drought conditions.  

In order to look after the Grange Lake system, even in dry periods, we commenced excavation using the long reach excavator during March to remove sediment and maintain areas of flora to protect the system’s environment. We maintain vegetation within the Grange Lakes System for both amenity and habitat purposes and this vegetation has adapted to the ephemeral conditions associated with the Lakes. We continue to monitor both planted and invasive species (such as the commonly known Typha) to balance the amenity of the reserve and Lakes system.

During dry periods, our birds will seek refuge in alternative water bodies, such as Fresh Water Lake, Cooke Reserve and the Port Road Wetlands.  Wetland birds rely on wetlands and waterways for survival and have evolved numerous adaptations to these environments. Each bird species has its own requirements for food, shelter and breeding sites which influence its use of the wetland.

For further information on the Grange Lakes System and the investigations we intend to make for the future of the system, please read our FAQs below or contact our Customer Contact team. We understand the importance of the Grange Lakes to our residents, and we look forward to the cooler months bringing much needed rain into the system.

Please read our Frequently Asked Questions:

Why has council not excavated while the system is dry? - accordion - Grange Lakes

Why has council not excavated while the system is dry?

The City of Charles Sturt normally plans to excavate sediment in parts of the system after an environmental flow is undertaken. Environmental flows are events strictly managed and controlled by the AMLRNRMB and aim to mimic natural flow patterns in the Torrens, South Para and Onkaparinga rivers. The timing and volume of flows is carefully planned to try and mimic what would have happened under pre-development conditions. There will be periods of no flows, low flows and high volume flushes, as would have happened under natural conditions. This summer period, only one environmental flow has occurred due to a lack of water across the whole system. Environmental flows, are usually carried out during the summer period when the Blue Green Algae in the Torrens Lake reaches levels significantly impacting human health. Given the lack of water, Charles Sturt is planning to excavate during March.

Why have we not started removing sediment yet? - accordion - Grange Lakes

Why have we not started removing sediment yet?

The City of Charles Sturt normally plans to remove sediment in parts of the system after an environmental flow is carried out further upstream. This summer period, no environmental flow has occurred due to a lack of water across the whole system. Since March 2019 we have taken the opportunity to remove approximately 2,300 cubic metres of silt from the system which has resulted in some small ponds which provide water to the flora and fauna that inhabits the area.

Why is the system dry? - accordion - Grange Lakes

Why is the system dry?

Metropolitan Adelaide, including all areas of the City of Charles Sturt, has not received more than 5mm of rain since mid to late December 2018. As a result, the s AMLRNRMB has not been able to release any water into the system since Tuesday 8 January 2019. This summer has been the hottest summer recorded in South Australia.

It has also been driest summer in the last 33 years. This extreme weather pattern highlights how our urban environment 'adapts and changes in response to periods without rainfall.

It is however important to recognise the history of our urban area and the impact of changes we have made to our environment. Prior to urban development, the West Lakes and Grange area hosted a natural wetland associated with the River Torrens. Formerly, the river flowed northwest toward the Port River, but the sediment picked up in the uplands choked the channels and the Torrens was diverted to the west migrating laterally before eroding its present channel, creating swamps, marshes and, notably, the ‘Reedbeds’ behind the sand dunes which front the coast, before draining north to the Port River or south to the Patawalonga.

During the first century of settlement, considerable time and money was expended on attempts to control the river and the problems it posed, especially for the areas west of the city. A direct outlet to the sea was excavated through the coastal sandhills at West Beach, channels were straightened and cleared, and the flood danger mitigated with the construction of dams, and especially the Torrens Dam (or weir) west King William Road in the city in 1881, behind which was formed the Torrens Lake.

Since these management techniques were implemented, natural flows have changed and the increase in urban development has required the management of stormwater. This has resulted in the construction of the Grange Lakes stormwater system, which collects stormwater from the Henley Fulham catchment. This system is primarily ephemeral – meaning it is intended to hold stormwater during winter and dry out when water is not available. To further provide environmental benefits and improved amenity during periods where the system is dry, Charles Sturt and the AMLRNRMB have worked collaboratively to install a diversion pump in the River Torrens – with an associated licence which allows us to divert 350ML. into the Grange Lakes System in conjunction with a release of water (‘Environmental flow’) from the Torrens Lake.

Environmental flows are required to maintain river health. Whilst volume of flow is important, it is also important that flows occur at the right frequency, right time of year and for the right length of time in order to sustain ecological health. Further information can be found here:

https://www.naturalresources.sa.gov.au/adelaidemtloftyranges/water/managing-water/water-courses/environmental-flows

What are we doing about the rubbish? - accordion - Grange Lakes

What are we doing about the rubbish?

We have sent crews into the area to remove rubbish along the dry sections of Grange Lakes. If you have concerns in a particular area please contact out customer service team and raise a Customer Request.

What are we doing about the sediment? - accordion - Grange Lakes

What are we doing about the sediment?

We are excavating areas during March.

What are we doing about the lack of water? - accordion - Grange Lakes

What are we doing about the lack of water?

We are in a holding pattern until water is released from the Torrens Lake or until a natural rainfall event occurs. We have no other water available to us. We do continue to work closely with the AMLNRMB to understand when an environmental flow is to occur, so we may divert the maximum amount of water available to us and replenish the Grange Lakes system.

What are we doing about the flora? - accordion - Grange Lakes

What are we doing about the flora?

We maintain vegetation within the Grange Lakes System for both amenity and habitat purposes. Much of the vegetation has established over the years and adapted to the ephemeral conditions associated with the Lakes. We continue to monitor both planted and invasive species (such as the commonly known Typha) to balance the amenity of the reserve and Lakes system.

What are we doing about the Fauna? - accordion - Grange Lakes

What are we doing about the Fauna?

During dry periods, our birds will seek refuge in alternative water bodies, such as Fresh Water Lake, Cooke Reserve and the Port Road Wetlands.  Wetland birds rely on wetlands and waterways for survival and have evolved numerous adaptations to these environments. Each bird species has its own requirements for food, shelter and breeding sites which influence its use of constructed and natural water bodies.

What are we doing about feeding plans? - accordion - Grange Lakes

What are we doing about feeding plans?

Feeding birds too much artificial food may not provide adequate nutrition which can lead to health problems. An example is the feeding of bread to ducks. This might seem like a treat but it lacks nutrients that they would normally obtain from their natural diet of insects and fish.

Problems can arise if the adult birds raise their young on this diet as the juvenile birds can suffer from brittle bones. Feeding bread to birds (even ducks!) can cause problems with their digestive systems as the bread ferments in their stomachs and honey/water mixes do not provide the complex sugars that a bird would get from the nectar of a flower. Further, processed meats are high in salts, fats and preservatives. Magpies fed items like fritz have been shown to have high cholesterol.

We recommend you don't feed birds artificially but preferably plant up your garden to attract birds, as it is much healthier for birds to glean natural food from your garden. If you feel you must feed the birds, small amounts of seed or salad greens are advised.

Should we remove the gum trees? - accordion - Grange Lakes

Should we remove the gum trees?

Concerns have been expressed around the potential for trees to die or drop branches as a result of the extreme weather. We will undertake a general assessment of the trees within the Grange Lakes corridor to determine if this is a concern and further action required.

Why have we not cleaned the area?

Once the area had dried out, we had team walk the length of the area and clean any rubbish found. If you have particular issues please contact us and we will attend ASAP.

Why was no action taken after report? - accordion - Grange Lakes

Why was no action taken after report?

A decision was made by Council in November 2016 (CL 28/11/2018 Item 6.153) as per the below:

3. That Council accepts the pump infrastructure donated by the AMLNRMB to assist with Grange Lakes environmental flows.

4. That Council support the diversion of River Torrens water through the Grange Lakes system at times of the environmental flows as determined by the AMLNRMB.

Unless the water is made available by State agencies we are unable to act on these recommendations. In its developed state, without the opportunity for diversion, the Grange Lakes system is ephemeral – meaning that it will dry out when rainfall and stormwater is not channelled into the system.

Why have we not done any sediment removal in summer? - accordion - Grange Lakes

Why have we not done any sediment removal in summer?

During summer we expect to have up to 4 environmental flows, we intended on starting the sediment removal after the last flow but prior to any major winter rain event. As the flows have not occurred we have commenced sediment removal.

Why does the rubbish come back up the drain? - accordion - Grange Lakes

Why does the rubbish come back up the drain?

West Lakes is a tidal lake and this causes backflow up the drain, added to this the trash collectors require pressure from outgoing water flow to hold the rubbish within them. Please let us know if an excessive amount of rubbish is within the drain and if safe we will have it removed.

Send us a request

When are we going to remove the rubbish from the northern section of concrete drain? - accordion - Grange Lakes

When are we going to remove the rubbish from the northern section of concrete drain?

Sweepers will be cleaning the concrete section in the first and second week of March.

Are the Trash collectors working at the entrance to the lake? - accordion - Grange Lakes

Are the Trash collectors working at the entrance to the lake?

Yes, the drainage team inspect the trash collectors frequently throughout the year and notify of any damage. It is important to understand that during extreme rain events water can bypass the collection system to allow flow, this is to minimise flooding within the catchment.

Why don’t we clean the concrete section more frequently? - accordion - Grange Lakes

Why don’t we clean the concrete section more frequently?

The drainage team assess the condition of all drains and priorities which drains we will clean at which times including which year. This is assessed throughout the year as different rain events create changes in sedimentation levels.

What can I do as a resident? - accordion - Grange Lakes

What can I do as a resident?

If anyone has any specific requests they should be logged through our customer care team.

These requests can also be logged by an app which includes photos that assists greatly to plan the correct teams to the specific issue.

http://www.charlessturt.sa.gov.au/MyLocalServicesApp

Contact page

http://www.charlessturt.sa.gov.au/requests

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