Upper Murrumbidgee Black Willow Survey 2008-09

The health of the Murrumbidgee River in its upper reaches is of particular interest to many organisations in the area and this includes the Upper Murrumbidgee Landcare Committee (UMLC) and associated network of Landcare Groups.

Supported by a NSW Environmental Trust Grant, the UMLC is currently working to reduce the threat to the river from invasive black willows. Black willows are a declared weed within the Cooma Monaro Shire due to its invasive nature and its impact on the environment.

Black willow leaves are the same green on both sides and the twigs reddish

Black willows can grow from seed and have increased in numbers alarmingly since their introduction into the catchment some fifty years ago. Black willows not only have the ability to become established along rivers but they can also spread to wet areas outside waterways such as culverts and beside dams.

Black willows grow at the expense of valuable native vegetation and may also contribute to other negative consequences along our rivers. Particular high risk areas for black willow are sand deposits within the waterway. The colonisation of these sand beds can lead to increased silting of the river and diversion of flow into riverbanks, potentially causing significant erosion.

Previous black willow control programs eradicated most, but not all, the black willows on the Murrumbidgee. The UMLC has received funding from the NSW Environmental Trust to survey the upper Murrumbidgee for the presence of black willows and to kill them once identified.

Assisting the UMLC are the Willow Warriors, a group of volunteers that enjoy river rafting and protecting the environment. They surveyed the river by raft from the Cooma Reserve to the ACT border and killed most small black willows around 18 months ago. Since then, low water levels prevented a similar program being undertaken above Cooma Reserve.

Instead, in a collaborative effort with the Upper Murrumbidgee Catchment Coordinating Committee (UMCCC), the river is being surveyed on foot by the UMCCC Willow Project Officer, Douglas Kerruish. So far, about half the river below the Tantangara Dam wall has been surveyed, with the heartening result of no black willows being located. Douglas completed the surveying of the final section of the river to Cooma Reserve in March 2009, with some surprising results.

After a few stops and starts a survey of the Murrumbidgee between Tantangara Dam and the Cooma pump house for the presence of black willows (S. nigra) has been completed! We would like to thank all the people who assisted for their time, expertise and hospitality.

We are pleased to say that no black willows were observed along the Murrumbidgee between Tantangara Dam and the Cooma pump house. This is not to say black willows are absent from the area as tributaries were not surveyed and black willows also have an ability to seed into seasonally wet off stream sites. It does however suggest that unlike lower down the catchment this type of willow is currently not a significant threat in the area. This may be a reflection of the current extent of the plant or it may mean the habitat in the upper headwaters is less suitable to black willows than elsewhere in the catchment.

Crack willow on the upper Murrumbidgee (photo: Douglas Kerruish)The dominant willow along the Murrumbidgee between Tantangara Dam and the Cooma pump house is crack willow (S. fragilis). This willow spreads by the dropping of branches into the stream that later put down roots. A common observation along the length of our survey is the build up of crack willow at the heads of gorges downstream of river flats.

For further information contact:

Tony Robinson 0409 776 705 or 6235 9334

Lynton Bond 6238 2368

Douglas Kerruish on 6205 2466.

This project is supported by the NSW Environmental Trust