Stakeholder notification: River fresh flow

Current information for landholders, local councils, recreational river users and other stakeholders about a plan to deliver a low level ‘river fresh’ along the Murrumbidgee River and Yanco Creek systems in winter 2021.

River Red Gums (Eucalyptus camaldulensis), Murrumbidgee River

July/August 2021 - Murrumbidgee and Yanco Creek systems

What is a ‘river fresh’ flow?

It is a ‘pulse’ or ‘fresh’ of water for the environment that will flow at a level within the river channel.

Why is it being done?

To improve the health of wetlands along the mid and Lower Murrumbidgee river.

During the drought years (2002–10 and again from 2018–20), hundreds of wetlands along the Murrumbidgee River that normally connected to the river remained dry. As a result, these wetlands suffered and are in need of regular inundation to help them recover.

These wetlands provide critical breeding and foraging habitat for native fish, waterbirds, frogs and other fauna. They support native wetland plants which help to improve water quality and help to produce zooplankton, insects and crustaceans which are important for juvenile fish. This water delivery will also help to move nutrients and carbon back into the river. Doing this during winter when the water is cooler may also reduce the chance of hypoxic blackwater which can cause mass fish kills in summer.

Whilst most of the wetlands were inundated in the 2016 floods, and a smaller subset inundated in 2017 during a water for the environment event, most have since dried out or water levels have dropped to low levels. Ongoing monitoring of these sites indicates that many contain native fish, including golden perch and long and short necked turtles. This flow will help reconnect these wetlands and allow for native fish movement back into the river.

A reconnection flow will also control unwanted red gum encroachment and build up the aquatic vegetation following the 2016 and 2017 flows.

Whose water is it?

Commonwealth environmental water holdings, The Living Murray and NSW Environmental Water Allowances.

How much water will be released and for how long?

The planned total volume will be up to 250 gigalitres (GL) and this will depend on allocation levels for 2021–22 water year and operational conditions. Depending on conditions, the duration of the event is planned to be similar to that indicated in the table below.

Releases would be made during low base flow periods (minimum required flows in the river) and when little to no rainfall is forecast.

What level will the flow reach?

The environmental water releases are targeted to reach a river level of 4.3 metres (or 25,000 ML/d) at Wagga Wagga. This is far below the minor flood level of 7.3 metres, and marginally higher than the previous ‘reconnection flow’ levels in 2017 of 4.2 metres at Wagga Wagga.

A flow height of 4.3 metres is known to be of minimal inconvenience to a small number of landholders with river frontage.

If heavy rainfall is predicted during or shortly after the planned release of environmental water, the event may be postponed or immediately ceased, so as to minimise the chances of exceeding river levels of 4.3 metres at Wagga. However, it is possible this height may be reached or exceeded due to other river operations or heavy local rainfall within normal river flow variations.

When will it happen?

Current planning has scheduled the water delivery to commence around mid-late July 2021. Expected travel times and river levels for Gundagai, Wagga and downstream locations are shown in the table below.

Stakeholders will be notified once the commencement of water delivery has been confirmed.

If this water delivery event is cancelled, stakeholders will be notified as soon as this decision is made via email and SMS.

Will it affect me?

If you have land or infrastructure (e.g. pumps) that are normally affected by rising Murrumbidgee River levels, you could be affected. However, as the proposed release is well below the minor flood level, effects are expected to be minimal.

See Table 1 for predicted river heights at specific gauge locations.

The Department of Planning, Industry and Environment has consulted with riparian landholders to identify and address potential effects of these flows.

The department and partner agencies continue to work with landholders to address any concerns about these flows.

If you think you may be affected by the proposed river fresh flow please contact the department as soon as possible.

Landholders who lease areas or agist areas of their floodplain property should forward this information on to their tenants.

Who is responsible for the event?

The department manages and plans environmental water allocations in New South Wales and is the lead agency for this environmental flow event. WaterNSW manages water orders, deliveries and operates the river for all water users.

Partnering agencies include the Commonwealth Environmental Water Office, The Living Murray, WaterNSW, DPIE-Water and Riverina Local Lands Services.

How will I be notified if the flow is occurring?

Department staff will manage the pre-event communications and WaterNSW will take over during the release phase. Communication will continue for the duration of the event through the provision of regular event updates to website, local media and contact lists, or via direct calls to the department. 

Together we will provide regular communication updates to:

  • landholders/managers: Landholders or stakeholders who wish to be kept informed of the planning and delivery of this environmental water should contact us as soon as possible – see below
  • local councils: to ensure infrastructure such as roads or drainage systems are being monitored for potential effects.
  • project partners: to ensure all partners are aware of the details of the proposed event and that potential risks are identified and managed within a risk management strategy.
  • SES: will be notified by the department prior to any releases as a courtesy and preventative measure. However, as the proposed flow (4.3m) is below the minor flood level (7.3m) at Wagga, it is not anticipated that the SES will be involved in flow-related operations.
  • public information: Media releases will be issued to local newspapers and radio stations to inform the wider Murrumbidgee community of the environmental water release and the objectives of the flow. Regular event updates will be posted on the department’s website.

Where do I get more information?

If you would like to be informed via SMS or email on progress of planning and implementation of the proposed Murrumbidgee ‘river fresh’ flow then please send an email to:

James Maguire
Senior Environmental Water Management Officer – Murrumbidgee
NSW Department of Planning, Industry and Environment

Phone (02) 6022 0604

Email james.maguire@environment.nsw.gov.au

Predicted river heights for proposed 2021 Murrumbidgee River Fresh event

Location

Height (m)

Max Discharge (ML)

Peak Duration

(days)

Travel time from Burrinjuck

Gundagai

 

4.1 to 4.4 1

22,400 to 25,300

5-6

1.5 days

Wagga

 

4.0 to 4.32

22,600 -24,900

5-6

2 days

Narrandera

 

4.8 to 5.1

17,600-19,800

5-6

5 days

Yanco Creek Offtake

3.4 to 3.6

1,700 to 1,900 3

6-7

6 days

Darlington Point

 

4.4 to 4.9

16,700 to 20,400

6-7

7 days

Carrathool

 

4.6 to 4.9

13,700 to 15,100

7-8

10 days

D/S Hay Weir

 

5.4 to 5.8

12,400 to 14,100

8-9

12 days

D/S Maude Weir

 

5.6 to 5.9

12,000 to 13,000

9-10

13 days

D/S Redbank Weir

 

5.3 to 5.6

8,100 to 9,000

9-10

15 days

D/S Balranald Weir

5.1 to 5.4

7,100 to 8,000

10-12

18 days

1 similar to the river levels observed on 25 June 2021, following catchment rainfall event

2 0.5m lower than river levels observed on the 26 and 27 June 2021, following catchment rainfall event

3 the current DPIE-Water approval specifies environmental flow levels up to 2600ML/day at the Yanco Creek Offtake (YCO), however, with the proposed low target level at Wagga, the predicted peak YCO flow is unlikely to exceed 1900ML/day.

Note: The actual river heights and flow durations may vary slightly from the above estimates as a result of ‘other river operations’ which are not related to the delivery of this environmental water event – these may include base irrigation demand and weir pool levels.

Note: D/S - downstream from