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House of Assembly - Fifty-Second Parliament, First Session (52-1)
2010-09-14 Daily Xml
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Grievance Debate

MURRAY RIVER WEEDS

Mr WHETSTONE (Chaffey) (15:42): My grievance is directed to the Minister for the River Murray. Many of the problems facing the River Murray and the impact that these problems have had on the communities which rely on the river have been well documented and well publicised. There are quite a lot of these problems, and one such problem is aquatic weeds.

For a decade now, and perhaps much longer, invasive weeds have been building up in the river and now present a real threat to regional tourism, navigation, water quality and, quite possibly, human lives. There are two species of aquatic weed involved—the Elodia canadensis (an exotic species commonly called Canadian pond weed) and Hydrilla verticillata (a species native to Asia, North America and Australia).

The invasion of these weeds has been insidious because, like the European carp, the problem is mostly happening out of sight. However, the extent of these weeds is now becoming quite clear. They are everywhere. They have spread along the river from Lock 6 at Murtho to Lock 1 at Blanchetown. It is understood that this may well have been a result of low river inflows, allowing higher concentrations of nutrients to build up in the weir pools. The weeds appear to have thrived in these conditions, and two weeks ago I saw for myself the extent of the problem at the invitation of some constituents who live along the river.

The location of these weeds can often be found by looking for patches of floating duckweed, which sometimes anchors itself to the Canadian pondweed and the Hydrilla. Today, there are patches of this anchored duckweed covering most of the breadth of the main river channel, although it does not reveal the true extent of the other weeds. Reach below the duckweed with a hook and you will drag up large clumps of this invasive weed.

At one point during our short trip to the river, we were forced to stop and clear away the weeds which fouled the propeller and stopped our travel. The major concern I have is that, in the warmer weather, someone will go for a swim or come off their water ski, become trapped in these weeds and drown. There have already been some close calls reported, and I understand that in New Zealand there have already been some drowning deaths associated with that same weed.

On my trip we saw a dead kangaroo, which obviously had become caught in the weed trying to cross the river. Another important concern is the impact that the weed will have on river traffic, particularly houseboats and tourism. Not all patches of weeds will be readily visible, so there is a real risk of inexperienced boating tourists getting into difficulty; this, of course, has the potential to diminish the tourism experience in the region, as does the prospect of unsightly patches of weeds spreading across the river.

More than ever, the Riverland is relying on tourism for the local economy, and any possible impediment to regional tourism, such as these weeds, must be addressed. The weeds also present a potential threat to water quality. They appear to inhibit natural water flow, which could possibly lead to the build-up of toxic blue-green algae. It is my understanding that the South Australian Murray-Darling Basin Natural Resource Management Board has investigated the problem, as well as having the weeds positively identified and establishing the extent of the infestation. What remains is for the state government to acknowledge the problem, to develop a solution and to act.

In New South Wales and on Lake Burley Griffin in Canberra, these weeds are controlled by mechanical harvesting. This method also involves collecting the clippings to ensure that they are not scattered across the water body and thereby spread the infestation.

I strongly urge the government to investigate this and other methods of effective control before these weeds become more than a problem than they already are today.

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