Neale Bennett, an almond grower in Mildura, ripped out his sultana grapes and dried fruit crop and began planting almonds in the 1990s. He’s ridden the wave of increased global demand for almond milk, almond meal and, well, just almonds.

Rising prices for the sweet brown nuts, mechanised equipment to harvest them and the ability to trade water up and down the Murray to water the thirsty trees have created a kind of agricultural gold rush along the waterway.

Over the last decade, big almond producers like Olam have bought up land around the booming town near the border of New South Wales and South Australia. Since 2016, 15,000 hectares of new trees have been planted, adding another 50% to the 32,000 hectares already there.

But with increasingly severe drought conditions, questions are being asked about whether the irrigators are facing a potential catastrophe of their own making.

Almond growers in the Murray-Darling basin have taken the unprecedented step of calling for a moratorium on the development of new plantations and a stocktake amid fears that there may not be enough water when summer arrives.

As well as almonds, there’s also been a boom in citrus plantings and new vineyards – all the way from Swan Hill in Victoria to South Australia. Like other permanent plantings, they require regular watering to survive.

“A lot of the development has gone on due to unbundling,” says Bennett.

The security of supply for irrigation and the environment is becoming more and more precarious Almond Board of Australia's Ross Skinner

What he’s referring to is the 2014 decision that allows water entitlements to be traded separate to the land. This has led to a water trading market, where water entitlements can be bought and sold, leased, or sold on a temporary basis year by year.

Water can be traded hundreds of kilometres down the river, with state water authorities charged with delivering the water that users order from their water accounts. The water is released upstream and then taken by the purchaser at the point of use.

“Water is a limited resource and the capacity to move it through the river system to where it’s needed by irrigators and the environment is restricted,” says the Almond Board of Australia chief executive, Ross Skinner.

“The security of supply for irrigation and the environment is becoming more and more precarious due to unlimited developments further downstream from where water was historically used for agricultural production,” he said.

The 15,000 hectares of almond trees planted since 2016 will require huge amounts of additional water.

While some development is underpinned by high-security entitlements, there is a lack of information about how much development has proceeded based on buying less secure water on the open market. The allocations for lower-security water entitlements could be dramatically reduced during the drought.

Then there is the question of actually getting the water from dams hundreds of kilometres away.

Each hectare requires 12-13 megalitres of water a year, the equivalent of five Olympic swimming pools. That means an additional 65,000 swimming pools of water will be needed just to water the new almond trees planted since that time. And if it doesn’t rain, farmers will be screaming for water to be sent down the river.

Most people along the Murray know about the aptly named Barmah Choke, a stretch where the river narrows and flow is restricted.

According to the Murray-Darling Basin Authority, the flow through the Barmah Choke is restricted to about 8,500 megalitres per day.

“During summer and autumn, river operation aims to keep flows at or below channel capacity to minimise unseasonal flooding of the Barmah-Millewa Forest,” the authority says. “This constraint provides challenges in meeting downstream peak water use demands and transferring water to Lake Victoria and South Australia, even in relatively dry years.”

Skinner says: “We recognise that development has put a strain on the system. That’s why we are calling for a moratorium and a full investigation.”

Part of the issue is that the states control the allocation of water licences and there are three states involved in the Murray.

Growers worry that there has not been sufficient consultation between the states, with the result that the water being licensed may result in an overallocation.

The almond board wants a moratorium on all new water use licences for greenfield irrigation developments in the southern Murray-Darling basin, pending a review of the system’s capacity to support more development without adverse third-party or environmental effects.

Other produce boards are also concerned about the situation, Skinner says.