WATER sent downriver to South Australia through the Murray-Darling system is wasted and an extra 450 gigalitres should be kept upstream, interstate crossbenchers argue.

Pauline Hanson’s One Nation – which holds a crucial bloc of four senators – have joined Liberal Democrat David Leyonhjelm in calling for a halt on that water being delivered to SA.

They also want the controversial Wellington weir built and Lower Lakes flooded with seawater.

In federal Parliament yesterday, the group appeared with irrigators to say that the water would be wasted through evaporation and sending it downriver would cause devastating floods in other states.

They want to see a weir built at Wellington and barrages lifted to flood the Lower Lakes with salt water. That would save evaporation and deliver freshwater where it’s needed, they say.

Senator Leyonhjelm said the 450GL part of the Murray Darling Basin Plan “should not proceed” and that he and One Nation will seek to find a way a way to block it.

Minister Ian Hunter says the SA Government will continue to fight for the MDB plan.

“Vast amounts of water are being sent down the river and ending up in the Lower Lakes in SA where it’s being evaporated,” he said.

“The question is whether evaporated water from the Lower Lakes is good for the environment. There’s quite a lot of opposition to any changes to that in SA based on the misconception that if it doesn’t go to SA, somehow or other SA will be adversely affected.”

The Murray plan aims to deliver an extra 3200GL to the system, but a controversial 450GL component is considered “optional” by some if delivery adversely affects upstream communities.

The Federal Government is talking about alternative ways to deliver environmental outcomes.

SA Water and the River Murray Minister Ian Hunter said delivering the water was not “optional”, but was legislated for as a way to protect wetlands.

“One Nation’s comments show they don’t understand the MDB plan, unlike the many Australians who depend on it for their livelihoods or rely on it for critical human needs,” Mr Hunter said.

“The SA Government will continue to fight for the Murray Darling Basin Plan to be delivered on time and in full.”

Along with One Nation climate change sceptic Senator Malcolm Roberts, Senator Leyonhjelm and irrigators say environmental outcomes can be achieved in other ways.

Yesterday they released a report into the socio-economic affects of the plan in NSW, which found that communities would be hurt without enough water – particularly in another drought – and that irrigators’ viability was at risk.

A tearful NSW farmer, Louise Burge from Deniliquin, showed reporters pictures of her flooded property, saying politics had cause the “nightmare” of environmental flows that cost them up to $400,000 in crops.