As the nation's gaze focused on millions of dead fish in Australia's drought-stricken and empty Menindee Lakes, further south the Murray River was spilling over its banks.

While residents in far-west NSW were running putrid water out of their taps, those along the Murray despaired as huge volumes of water they could not use on their farms flowed right by them.

In the grip of severe drought, the sensitive connections between disparate parts of the 1.3 million square kilometre Murray-Daring Basin have been painfully exposed.

The corpses of millions of fish in Menindee are the most visible symbols of the Darling's woes, while in the Murray it's more subtle but no less serious.

The Barmah-Millewa forest is an internationally significant wetland, and through its centre runs the Barmah Choke, the Murray River's narrowest stretch.

The Barmah Choke restricts the flow of water down the Murray to 9,500 megalitres a day, and if more water is pushed through, it spills over the banks into the surrounding forest. ( ABC News: Peter Healy )

With no water coming down the Darling, and little flowing into the Murray's other tributaries, this short section of the river did the heavy lifting supplying water users in three states this summer.

Standing on the river banks, surrounded by ancient river red gums, ecologist Ian Davidson pointed out the visible tree roots extending into the water and large chunks of bank that had collapsed into the stream.

"When you've got the river being maintained at such high levels for such long periods of time, you don't have enough vegetation that's holding that clay and sand and levee together, so it's actually slumping in," he explained.

"This has the double-edge effect of actually making the channel itself wider but shallower so it's losing capacity for flow, and that's got major ramifications of course, downstream."

Serious erosion caused by high flows through the Choke have many worried the banks may burst in the future, which would mean less even less water could pass through this narrow section of the river. ( ABC News: Peter Healy )

The Murray-Darling Basin Authority (MDBA) told Landline the bank erosion was concerning, and a survey to determine the worst areas was underway.

The MDBA was looking for ways to shore up the banks, without further reducing the amount of water that can flow through the Choke.

With the largest storages, Hume and Dartmouth dams, sitting upstream of this section, and the majority of water users being downstream, the Barmah Choke is stuck in the middle.

Not only is it losing its capacity to carry the same volume of water, according to Victorian Government figures, but it is governed by rules three state governments developed in the 1960s.

Rules which may not suit the reality of an increasingly dry environment.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 1 minute 2 seconds 1 m 2 s The Barmah Choke restricts the flow of water down the Murray ( Trudi Arter and Clint Jasper )

Around 9,500 megalitres a day can enter the Barmah Choke, a tiny amount when anywhere between 7,000 to 12,000 megalitres a day has to cross the South Australian border.

In a 'normal' year, there is enough water in other storages, like the Menindee Lakes and Lake Victoria, as well as tributary rivers to supply towns and farms with water without pushing large amounts through the Choke.

But in January, when an extended heatwave saw demand for irrigation water from farmers in north-west Victoria peak, authorities had to issue warnings that the water they had ordered from upstream storages might not make it in time.

Following a deal last year, the MDBA can divert water around the Choke through the Mulwala Canal (above), but this summer huge volumes still flowed through the Barmah Forest. ( ABC News: Peter Healy )

Leap in irrigation development prompts plea for water caution

Large volumes of water that once raised crops of rice in the Riverina and dairy pastures in northern Victoria are now used to water an increasing area of almonds, citrus and grapes in north-west Victoria and South Australia.

"After the [Millennium] drought broke it really kicked in," Sunraysia farmer and Almond Board of Australia chair Neale Bennett said.

"That's mainly been because water was unbundled from land, and people have been able to shift it to different parts of the river."

Neale Bennett is one of a growing number of Sunraysia farmers worried that, if left unchecked, the amount of water demanded during the summer months will be more than the river is capable of supplying. ( ABC Rural: Clint Jasper )

Surging demand for Australian citrus, table grapes and almonds has opened a floodgate of local and international investment in irrigation properties in the lower Murray — all of whom are vying for a share of that water.

To grow those new trees and keep them alive, water has to be traded from upstream, placing increasing pressure on the Barmah Choke and Goulburn River.

A record 420 gigalitres was traded from the Goulburn system to water new developments in Sunraysia, according to the MDBA.

Development is occurring at such a pace that farming bodies like the Almond Board, the Victorian Farmers' Federation, and the National Irrigators' Council are united in calls for a moratorium on new developments.

During the January heatwave, competition for water got so intense that some irrigators were paying $600 a megalitre for water, after budgeting for around $200.

"It's all about sustainability, there's not much point in handing someone approval to go and develop if, five years down the track, they're not going to be able to get water," Mr Bennett said.

The dark blue bars are projections of water demand downstream of the Barmah Choke, and the yellow and red lines show water availability under average and drought conditions respectively. ( Supplied: Victorian Department of Environment, Water, Land and Planning )

The groups want state governments to stop issuing permits to develop new land and conduct an audit of what's already been approved to ensure that, in the future, enough water will make it through the Barmah Choke and Goulburn River.

To make it work, all three states would have to back the plan, but only Victoria is actively investigating how it might work in practice.

It will be a key point of discussion when state and federal water ministers meet in August.

In a recent report, real estate firm Colliers said investors were becoming increasingly worried that it won't.

"The market appears to be cognisant of looming delivery constraints in the southern Murray-Darling Basin, although authorities appear to be turning a blind eye and continue to approve developments in some instances in excess of 5 kilometres from the source," the report reads.

Concern growing over river's ability to deliver water

Emma Bradbury, CEO of the Murray-Darling Association, which represents all the local governments in the Murray-Darling Basin, said she watched huge volumes of water bound for downstream flow past her home on the Murray in Echuca this summer.

"Irrigation demand has been changing over the last couple of years based on a proliferation of permanent planting in the Sunraysia region," she said.

"There's been constant demand from established businesses and industries right down the system, and of course there's the usual demand for water supply for safe town water supplies for communities right along the river and off to the sides.

"Our members right across the Basin are expressing uncertainty in relation to how the river will continue to supply the needs for existing users and also to support what is emerging as an increasing footprint of irrigation down in the Sunraysia region."

As banks along the Barmah Choke and the Goulburn River collapse under the pressure of supplying water downstream, Victoria's Water Minister Lisa Neville has joined the ranks of concerned parties.

"I am concerned about high flows in the Murray and Goulburn Rivers caused by water delivery and the impact this has on the environment, as well as the deliverability of water to irrigators and other entitlement holders," Ms Neville told Landline.