Murrumbidgee dams rising as BoM forecasts wet Spring

Murrumbidgee dams rising as BoM forecasts wet Spring

28 August 2020

WaterNSW is monitoring rising storage levels at the two major supply dams for the Murrumbidgee valley, as the Bureau of Meteorology (BoM) forecasts ongoing wet conditions for the region over Spring.

Burrinjuck Dam on the Murrumbidgee River sits at 82% of capacity, up from 46% just weeks ago, having received 430,000 megalitres of inflow in August – the dam’s fourth highest monthly total in 10 years.

Blowering Dam on the Tumut River, which feeds into the Murrumbidgee, is at 72%, and the BoM is predicting wetter than average conditions from September to November.

In the August of 2016, prior to the September 2016 spill, Burrinjuck was at 89% of capacity, while Blowering was 83%.

WaterNSW is working with the BoM to monitor weather forecasts and assess the need to commence making minor airspace releases from Burrinjuck Dam especially.

The Burrinjuck catchment in particular is saturated from repeated rain events, and highly responsive as a result, with inflows peaking at a rate of approximately 100,000 megalitres per day following rain in mid-August.

Major tributary flows downstream of dams have also been a feature of recent rainfall, including large volumes flowing in the Jugiong and Tarcutta creeks, and to a lesser extent the Goobarragandra River.

WaterNSW executive manager of system operations, Adrian Langdon said the wet catchments, rising storage levels and weather forecast have prompted WaterNSW river operations personnel to prepare for the possibility of a spill.

“While there is no cause for alarm, the ongoing rain events – especially over the Burrinjuck catchment – are generating large inflows and we are monitoring the situation carefully,” he said.

“We work very closely with the BoM so we have access to the nation’s best weather forecasting, and we will use that information to help us decide whether to make flood mitigation pre-releases in the event of a significant rain forecast.

“As dam managers we are mindful that we cannot make releases to create airspace capacity to absorb inflows without a high degree of certainty that the anticipated inflows will replace those releases, and therefore not impact adversely on long term water security.

“The other consideration is that we don’t want to exacerbate a flood-prone river system downstream of the dam by adding water to the existing, naturally-occurring tributary flows.

“Conventional wisdom has it that all the water in the river originates from the dam – especially during a flood event – but this overlooks the major contribution of downstream tributaries.

“Without Burrinjuck Dam to capture the extensive inflows of recent weeks from its upstream catchment the Murrumbidgee valley would already be experiencing flooding.”

For more information on WaterNSW storages visit: www.waternsw.com.au

Media contact – Tony Webber 0428 613 478.

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