Water for McDonalds delayed

The North Central Catchment Management Authority (CMA) has delayed a planned wetland watering in the north of the state on the back of the prolonged blue-green algae (BGA) outbreak in the Murray River system.

The North Central CMA planned to deliver a partial fill to McDonalds Swamp north east of Kerang in April, to promote a high diversity of winter habitats for waterbirds and frogs and provide conditions conducive to native plant germination in the following spring.

North Central CMA Environmental Water Manager Andrew Sharpe said BGA levels were still high and the window of opportunity to deliver enough water through the irrigation network to benefit the targeted plants and animals has almost passed.

"The water is delivered through irrigation channels, and with no evidence that BGA levels will drop by the May 15 irrigation season closure, we have had to delay the flow till spring," he said.

"McDonalds Swamp is close to two Ramsar-listed wetlands and acts as an important ecological link in a highly modified landscape.

"We have spoken with Goulburn Murray Water about other delivery options, but off-season maintenance works have ruled them out."

Mr Sharpe said the planned partial fill in autumn was to be followed with a top-up in spring and would be compared with previous spring-only fills, to understand how the ecology responds during different seasons

"The plan now is to deliver environmental water to McDonalds Swamp in late-winter/ early-spring, which will still use about the same amount of water overall," he said.

"BGA occurs naturally in creeks, rivers and wetlands, but it can be toxic to animals, including waterbirds, and humans, and if blooms suddenly collapse they can severely deplete oxygen levels in the affected waterways.   

"We consulted two independent wetland ecologists about the risks of delivering BGA-affected water to wetlands and both indicated that while it would not definitely cause problems, there was a risk to existing environmental values.  

"If BGA blooms die off or collapse quickly they can cause very low dissolved oxygen concentrations.  If that happened in McDonalds Swamp it would limit plant germination and not meet the intended environmental watering objectives.  

"These risks are more pronounced in wetlands than rivers because there is no capacity to increase through flow to flush the system if BGA does cause environmental problems."