Securing low flows in the Mount Lofty Ranges
Producing premium food and wine from South Australia’s Mount Lofty Ranges is a state priority – and it needs water.
The State Government is committed to this priority and is also striving to get the balance right to make sure that while productivity is optimised, the region’s environmental health is also preserved.
The Securing Low Flows project focuses on how water is stored and diverted from watercourses for use on farms. Dams are important because they provide water security, but they have changed the pattern and amount of water flowing through the Mt Lofty Ranges. Low flows have been largely impeded and parts of some catchments go without flow for long periods of time.
What is the Securing Low Flows project?
The Securing Low Flows project is a key element of water management policy in the Mt Lofty Ranges. It aims to give the 74 catchments across the Mount Lofty Ranges small amounts of water at critical times in the seasonal cycle, while maintaining current water allocations. Under the program low flows below certain threshold flow rates will be required to pass downstream of some dams and diversions in order to maintain catchment health.
Keeping the environment sustainable whilst maintaining productivity is a balancing act that can be achieved by allowing water to flow downstream at the right times, and in the right amounts. This can be done in a way that maintains water allocations and will benefit both water users and catchment health.
What are low flows?
Low flows are all flows below a certain threshold flow rate which are required to pass downstream of dams in order to maintain catchment health.
Low flows are naturally occurring, small flow events which originate from rainfall or ground water discharge; coloured in blue in the graph below low flows are a small proportion of total flows, but are part of the flow pattern most impacted by farm dams and diversions. Under current conditions, these flows are delayed until dams fill and overflow later in the flow season.
The threshold flow rate is calculated for each dam and is based on local runoff conditions for the management zone, multiplied by the size of the catchment area upstream of the dam.
Why are low flows important to catchments?
Low flows play a key role in determining the health of aquatic habitats. Although small in volume, low flows provide a continuous or intermittent flow over the bottom of channels, providing connectivity between aquatic refuges, and refreshing in-channel pools during the drier seasons. Low Flows help maintain water quality by flushing nutrients and pollutants that accumulate. They provide and maintain aquatic refuges during dry periods, and support the life cycle of water dependent plants and animals. Low flows help to maintain vegetation alongside river banks which protects them from erosion. Changes to flow patterns impact the whole river system including terminal wetlands and estuaries.
Why is securing low flows a shared problem?
Water in the Mount Lofty Ranges is a shared resource. Downstream water users often share water which originates from upstream neighbours. The combined impact of dams and water diversions across catchments has significantly altered the natural pattern and amount of flow, contributing to a decline in waterway health. Securing environmental flows will require all water users to work together to ensure the long term health and function of catchments on which they rely.
When and where are we likely to see benefits?
Improving the health of waterways will take time. The Securing Low Flows project aims to achieve a range of short term and long term responses including: a longer flowing period and maintenance of permanent pools, improved diversity of water bugs, recolonization of water dependent plants, improved stability of watercourses and healthier native fish populations.
Each catchment is unique and the benefits of restoring low flows are expected to vary across catchments. A number of threats impact waterway health, and existing water demands are much higher in some areas. As a result, the environmental benefits will depend on the current conditions of watercourses, other localised threats, and the rate at which management actions are adopted. Restoring low flows is a critical step in the progress towards improving catchment health.
Why is the project happening?
Dams are important because they provide security of supply. But the combined impact of dam development across the Mount Lofty Ranges impedes flow – and parts of the catchments go without flowing water for longer periods of time.
With dam interceptions effectively lengthening the time that catchments go without water, the no-flow period is getting longer and catchment health is declining. We know this because water quality is decreasing, watercourse pools are drier for longer, water dependent vegetation and fish are disappearing and plants and animals are struggling to reproduce and survive.
Low flow trial sites
Eleven trial sites have been established to demonstrate practical ways to pass low flows around farm dams in the Eastern and Western Mount Lofty Ranges.
Eastern Mount Lofty Ranges sites: Paris Creek, Mount Barker, Bugle Ranges and Mount Jagged
Western Mount Lofty Ranges sites: Oakbank, Biggs Flat, Myponga and Back Valley
Marne Saunders: Springton, Eden Valley, Keyneton
These sites are being monitored to:
- demonstrate how different types of low flow solutions work in a range of different ‘on-farm’ settings and in different types of catchments
- confirm how accurately the required low flows are being passed around the trial dams
- understand how the provision of low flows will affect water availability for landholders
- explain how the provision of low flows creates healthier creek lines downstream of the trial dams.
Who is involved?
The project will involve some landholders in the Eastern Mount Lofty Ranges, Western Mount Lofty Ranges and the Marne Saunders Prescribed Areas. See the project area map for more information.
The project is managed as a partnership between the Adelaide and Mount Lofty Ranges and South Australian Murray-Darling Basin Natural Resources Management (NRM) boards and the Department of Environment, Water and Natural Resources.
How will the community be involved?
Local knowledge and community views are fundamental to inform the planning to secure low flows. As far as possible we want to develop tailored solutions with landholders which recognise the differences between catchments. Establishing a strong working relationship between the broader community, peak industry groups, NRM boards and the department is also vital.
Securing Low Flows is a long-term program which will begin slowly, dealing with areas of highest priority first.
Recent engagement with landholders in Clare Valley has provided some insights as to how landholders are living and working with active low flow devices on farm dams.
Read our case studies:
Community low flows design library
The SA Murray-Darling Basin NRM Board funded a design competition crowd-sourcing ideas from farmers, inventors, engineers, entrepreneurs and designers to propose new ways to secure low flows around dams and watercourse diversions in the Mount Lofty Ranges.
Entrants contributed their know-how to build on the existing range of low flow designs. You can view the designs in the Community low flows design library.
Want more information?
Department of Environment, Water and Natural Resources, Adelaide and Mt Lofty Ranges Natural Resources Management Board and South Australian Murray-Darling Basin Natural Resources Management Board.