Nevada filed a federal lawsuit on Monday challenging the Trump administration’s new plan for the imperiled Colorado River, launching what could become the first of many court battles over the waterway that supplies 40 million people, dozens of tribes and 5.5m acres of farm land across the American west.

The federal plan, issued Friday, cut roughly 20% from the water supplied to lower basin states – Nevada, Arizona and California – over the next two years, with a potential for harsher cutbacks in the future, based on conditions.

Filed in the US district court of Nevada, the state of Nevada, the Colorado River commission of Nevada and the Southern Nevada Water Authority filed the suit against the Department of Interior and the US Bureau of Reclamation.

Southern Nevada stood to lose more than 70% of its share under the framework, according to Joe Lombardo, the Nevada governor, who said in a statement issued with an announcement of the lawsuit that the so-called upper basin states – Colorado, Utah, New Mexico and Wyoming – were “not required to contribute a drop”.

The governor echoed a complaint at the heart of the conflict between seven states that depend on the Colorado River, which have struggled to reach a consensus over how to inflict the enormous cuts needed to pull the system back from the brink. Long-term overuse and the rising toll from the climate crisis have served as a one-two punch that has left the river in crisis.

The upper-basin states have resisted any mandatory cuts to their share, insisting they source their supply from the headwaters and that lower-basin states are responsible for the declining water levels at Lake Mead and Lake Powell – the federally-managed reservoirs that also supply hydroelectric energy to millions.

The lower basin has balked at the idea. They have already agreed to take substantial cuts and are demanding their neighbors to the north share the burden. While disagreements range across a series of issues, this has been a major sticking point.

While the federal government has limited authority over the states’ water policy and cannott force cuts across the board, the Bureau of Reclamation operates Lake Powell and Lake Mead, which gives it more jurisdiction over the lower basin’s water supply.

Now the complex conflict could be decided in the courts. It’s an outcome that could sink urgent management decisions into years of drawn-out courtroom battles and leave critical decisions in the hands of judges rather than experts.

“[Litigation] kind of freezes everything – and environmental values are one of the first things to go,” said Dr John Berggren, regional policy manager at Western Resource Advocates, earlier this year when the states missed a key deadline for a deal. “They’ll protect the reservoirs as best they can, but they’re probably not going to be able to consider environmental flows and things that actually benefit the river itself.”

While Nevada was the first to file a legal challenge, more lawsuits are likely. Arizona has also voiced strong objections to the federal plan and outlined how the state believes it violates the original Colorado River compact, agreed to in 1922, in a letter issued last week.

The states could also challenge one another directly. Legal disputes would center on whether the upper basin can be held responsible for losses in supply due to the climate crisis.

“By this September or October, there’s going to be a pretty compelling argument from the lower basin that the upper basin hasn’t met its delivery obligation,” said Rhett Larson, a professor of water law at Arizona State University, before the federal plan was finalized.

But with little hope of a reprieve from warm and dry conditions that have widened the gap between water demand and supply in a region where water has long been the source of survival and conflict, the continuing challenges have left the basin and those who rely on its essential water resources, into uncertain territory.

“This isn’t about political posturing,” Lombardo said. “This is a matter of survival for a community that represents about two-thirds of our state’s citizens and the lion’s share of its economy.”

The water cuts for Nevada would be felt in fast-growing population centers, including in the city of Las Vegas, according to officials.

John Entsminger, Southern Nevada Water Authority general manager, said the area has effectively reduced consumption by roughly 40% even while more than 800,000 residents moved into the area. “However, conservation has its limits,” he said in a statement provided to the Las Vegas Sun. “There is just no way to meet even the basic needs of this community with the volume of water interior [department] has proposed.”