Goulburn-Murray Water (GMW) has identified residual traces of imazapyr, an active ingredient contained in herbicides used to control the aquatic weed arrowhead, in some sections of irrigation channels in the Murray Valley, Shepparton, Central Goulburn and Rochester areas.
The levels of residue detected mean the water cannot be used on-farm in the identified channel sections.
As a precautionary measure, we are contacting customers who are supplied from these sections of the channel to inform them they will be delayed from accessing water beyond the traditional start of the irrigation season on 15 August 2015.
GMW has started a flushing regime and will retest the water.
The total volume of water used to flush the channels is minimal and will not impact customers' irrigation water allocation.
Our ongoing testing and monitoring program will determine when customers can access water from these sections of channels and we will communicate with them accordingly.
The active ingredient detected was likely part of a spraying program to control arrowhead weed, determined as suitable following GMW trials. Imazapyr is widely used with confidence around the world for crop protection situations. There is no risk to humans.
GMW goes through rigorous environmental and health regulatory processes when it uses herbicides. GMW only uses herbicides that are approved for use by the Australian Pesticides and Veterinary Medicines Authority (APVMA) to ensure the risk to humans, animals and aquatic life and the environment are acceptable.
Arrowhead plagues channels in these regions and significantly impacts on GMW's ability to deliver water as it chokes channels and traps sediment.
Controlling weeds in channels and good stewardship are high priorities at GMW.
In April 2015, GMW notified all customers along these channels in advance of applying the treatment. They received follow-up letters in June and July. These letters informed customers to source an alternative supply of water during this time.
Demand for irrigation water is low at the moment and we are working with customers to understand their future water needs.
For more information, landholders can call 1800 013 357.