Grange Lakes

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