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Monitoring of environmental watering in the Murrumbidgee River - early results

Commonwealth Environmental Water Office, 2012

Scientists have been monitoring water quality and biodiversity in the Murrumbidgee River since June 2011, when more than 160 gigalitres of environmental water was released into the river.

The large-scale release, which included 109 gigalitres of Commonwealth environmental water, was intended to enhance connectivity between the river and its wetlands.

A report on the team's early findings supports that the release has improved connectivity across the system, with benefits for aquatic animals and water quality. It will be followed by a final report mid 2012.

The research, supported by Commonwealth Environmental Water, is led by Dr Skye Wassens from Charles Sturt University.

In this interview, Dr Wassens explains how connectivity supports fish breeding and can reduce the risk of blackwater events.

Podcast transcript

Interviewee: Dr Skye Wassens

Interviewer: "Scientists studying ecological responses to environmental watering in the Murrumbidgee River have released a report on their early findings.

The research, supported by Commonwealth Environmental Water, is led by Dr Skye Wassens from Charles Sturt University.

As Dr Wassens explains, connecting rivers with wetlands creates nursery environments for fish breeding."

Dr Wassens: "Wetlands for fauna are almost like little nurseries. When the water goes into them a lot of native fish are able to move in from the river, which isn't that productive, into these wetlands where there's lots of food and it's nice and warm and quite still.

So they're able to breed in there and produce often quite large numbers of little larval fish and those fish are then able to sort of grow up to a reasonable size before returning to the rivers.

So that's why these flows become really important for a whole range of species, for frogs and turtles and fish, because they create little nursery habitats and actually allow them to breed. And that's why we often need repeat flows over a few years or through the season so that we can let those little fish get back into the river after they've grown up a bit and we can allow that movement. "

Interviewer: "As well as supporting fish movement, flows of environmental water can generate movement of organic matter with benefits for water quality."

Dr Wassens: "There can be a whole lot of effects of river regulation on water quality and probably one of the most problematic impacts of river regulation, that reduces the frequency of flooding into wetlands and into these little creeks, is you get a build up of organic matter that starts to build up from trees and various things. And that can create what people call blackwater events or low oxygen events. And they occur if a wetland hasn't been frequently flooded so in a way environmental water can be used to reduce the risk of blackwater events by keeping a more normal flooding frequency and not allowing that organic matter to build up at such a high level.

You almost have to think of flooding the same way as we might think of doing controlled burning or reduction burning in that you're using water to reduce the build up of this organic matter on the floodplains so that when you do have a big natural flood you're not getting all of that matter just getting washed into the river. So it becomes a bit of risk management to use environmental water to reduce that risk of blackwater event in the long term. "

Interviewer: "The researchers are continuing to monitor the river's response to environmental watering and will make recommendations on the timing and scale of future releases based on their research."