Murrumbidgee River

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To show different flow options, choose one of the options below to show you on the map the changing inundation.

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Scenario: selected_flow at Wagga Wagga - Current flow limit

Legend

Upper limit of inundation extent for flow option¹

More typical inundation extent for flow option²

Embankment/levee

Reference gauges³

Modelling currently being undertaken

A legend for the topographic basemap used on this map can be accessed via this link

Details

Please select a scenario from the above for specific details

This option is for a flow limit of selected_flow at Wagga Wagga, which is the current flow limit (base case).

The mapping shows the following extents:

upper limit of inundation for this flow limit option (light blue)¹
an inundation extent more typically experienced when these higher environmental flow deliveries are made (dark blue)²

These extents show the inundation outcomes for the flow options being investigated vary depending on catchment conditions and would be less than the modelled upper flow limit in most cases.

¹The upper limit inundation extent assumes catchment conditions are wet (with low infiltration and evaporation losses) and flows are held at this level for an extended duration, substantially greater than the normal duration environmental flow releases would occur. Environmental flow releases causing this inundation extent across the full length of the river system would be infrequent or rare.

²The more typical inundation extent shows an inundation extent more frequently experienced under this flow limit option, under more typical catchment conditions and environmental flow release durations.

Flow rates and gauge heights

Estimated flow rates and gauge heights for the upper limit inundation extent across this project area are shown in Table 1, below.

Table 1: Flow rates and gauge heights

Frequency, timing and duration

The proposed frequency of managed environmental flows under the Reconnecting River Country Program (i.e., higher flows greater than 22,000 ML/d and up to the upper flow limit) would vary over time depending on water availability, climate and ecological conditions.

Over the long-term, it is anticipated these higher environmental flow deliveries would occur on average about four to five years per decade, comprising some smaller events and some larger events up to the flow limit.

Flows would include some new events and some events extending the duration of existing unregulated events using water for the environment. They would not occur during extreme wet conditions when there is elevated flood risk.

Most of these higher environmental flow deliveries would occur from August to October. Occasionally, and when conditions are appropriate, deliveries might occur slightly earlier in May to July, or extend slightly later into November.

Deliveries extending into November would be infrequent and would mostly involve adding to an existing unregulated flow event to improve environmental outcomes or manage hypoxic blackwater risk.

The duration of these higher environmental flow deliveries would be up to five days at the peak flow rate (in some years this would be the upper flow limit; in some years smaller flows would be delivered) and would be followed by a gradual reduction in flows back to background flow levels.

Inflows from tributaries upstream of Wagga Wagga

Environmental water releases from Burrinjuck Dam will continue to consider inflows from the Tumut River (including Blowering Dam releases), together with inflows from unregulated tributaries such as Jugiong Creek and Tarcutta Creek, to ensure the agreed flow limit at Wagga Wagga is not exceeded during environmental releases.

Assumptions regarding Billabong Creek flows

Managed environmental flows in the Murrumbidgee River associated with these flow limit options would contribute flows into Yanco Creek and subsequently into Billabong Creek via Colombo Creek. Managed environmental flows reaching Billabong Creek through Colombo Creek would be small relative to flows coming from the Billabong Creek catchment upstream of Colombo Creek.

The Billabong Creek catchment upstream of Colombo Creek would remain the primary contributor of high flows in Billabong Creek. However, there is potential for these managed environmental flows to coincide with high flows coming from the Billabong Creek catchment.

The modelling allows for up to a 2,300 ML/d contribution from the unregulated Billabong Creek upstream of Colombo Creek (including via the Nowrannie Creek anabranch), which is approximately in the 90th percentile flow during the period from August to October when managed environmental flow deliveries would occur.

This allows for managed environmental flow deliveries under a variety of conditions while noting that managed environmental flow deliveries would not occur during extreme wet conditions when there is elevated flood risk.