Nevada sued the U.S. Department of the Interior on Monday, asking a federal judge to throw out the government’s new Colorado River operating plan before it can take effect. The state’s core argument is stark: under the plan’s driest-year scenario, Nevada could lose more than 70 percent of its already small share of the river.
That 71 percent figure, repeated by Gov. Joe Lombardo and nearly every outlet covering the case, describes a cut to Nevada’s paper entitlement, the amount the state is legally allowed to draw, not the amount it actually uses. Southern Nevada has spent 25 years using less water every year even as its population grew.
Run the same worst-case cut against actual 2025 water use instead of the legal allocation, and the reduction comes to about 56 percent. Still severe, but a different number than the one driving headlines, and one nobody else appears to have run.
What Nevada Is Asking a Judge to Do
The complaint, filed as State of Nevada, et al. v. Doug Burgum, et al., case number 2:26-cv-02665 in the U.S. District Court for the District of Nevada, names Interior Secretary Doug Burgum, the Interior Department, the Bureau of Reclamation and the bureau’s principal deputy commissioner as defendants.
The plaintiffs are the State of Nevada, the Colorado River Commission of Nevada and the Southern Nevada Water Authority.
The suit challenges three federal documents at once: the Record of Decision issued August 21, the final environmental impact statement issued July 31, and the operating guidelines set for 2027 and 2028. Nevada’s six claims argue the federal government violated the Administrative Procedure Act and the National Environmental Policy Act by failing to properly weigh alternatives, analyze the plan’s effects on Nevada’s economy and environment, respond to public comments, or name the states as cooperating agencies in drafting it.
The state wants the court to vacate all three documents and block them from taking effect until Interior starts over.
“This isn’t something we did lightly. We are not naturally litigious people,” SNWA general manager John Entsminger said. “We weren’t looking for a fight, but when the federal government says they can cut your water supply by 71%, that’s time to stop talking and start fighting.”
Two Numbers, Two Denominators
Nevada’s total Colorado River allocation has stood at 300,000 acre-feet a year since the river was first divided among the states, a single acre-foot being the water needed to cover an acre of ground one foot deep.
Under the driest-year tier of the new operating plan, the complaint states, that allocation could be cut by 213,556 acre-feet, leaving Nevada with less than 86,500 acre-feet a year. Divide 213,556 by 300,000 and the cut is 71.2 percent of the state’s legal entitlement, the number Lombardo and Entsminger have both cited publicly.
But Southern Nevada did not use its full 300,000-acre-foot entitlement last year. The same complaint states the region’s actual consumptive use in 2025 was 198,570 acre-feet, roughly two-thirds of what it is legally owed.
Measured against that real number instead of the paper allocation, dropping to 86,444 acre-feet a year is a reduction of about 56 percent from what Southern Nevada is currently drawing from the river, not 71 percent.
Nevada’s paper entitlement would fall 71 percent under the driest-year scenario. Its actual 2025 water draw would need to fall about 56 percent to hit the same floor. Neither number is small for a desert region of more than two million people.
Both figures describe the same 86,444-acre-foot floor. The 71 percent version is the one built into the lawsuit and the one Washington will read in Nevada’s legal filings. The 56 percent version is the one that would actually show up in monthly water bills and supply planning if the cut is ever imposed.
How Nevada’s Cut Compares to Arizona’s and California’s
Nevada is not the only state facing mandatory reductions, and its guaranteed floor for 2027 and 2028, separate from the driest-year scenario in the lawsuit, is proportionally smaller than what Arizona has already agreed to absorb.
| State | Total Colorado River allocation | Mandatory 2027-2028 cut | Share of that state’s allocation |
|---|---|---|---|
| Arizona | 2.8 million acre-feet | 760,000 acre-feet a year | about 27% |
| California | 4.4 million acre-feet | 440,000 acre-feet a year | 10% |
| Nevada | 300,000 acre-feet | 50,000 acre-feet a year | about 17% |
Those figures, confirmed across the Record of Decision coverage and state allocation totals, sum to the combined 1.25 million acre-feet a year the three states must collectively give up. On that guaranteed floor alone, Nevada’s percentage hit sits between California’s and Arizona’s.
What makes Nevada’s lawsuit different is the driest-year tier layered on top, the one that could push its cut all the way to 213,556 acre-feet if Lake Mead keeps falling. Neither Arizona’s nor California’s worst-case ceiling under that same tier was specified in the sources reviewed for this article.
Twenty-Three Years of Conservation, Overtaken by Hydrology
Nevada’s court filing leans heavily on its conservation record because it is, by the state’s own numbers, real. Southern Nevada’s Colorado River consumption fell from 325,000 acre-feet in 2002 to 198,570 acre-feet in 2025, a drop of nearly 39 percent, while the region added more than 875,000 new residents over the same period. Entsminger has put the reduction at “about 40 percent” in public remarks, consistent with the complaint’s own figures.
The complaint also states Southern Nevada has banked 2.2 million acre-feet of water in storage, more than eleven times its entire 2025 consumptive use, water saved during wetter years that the region cannot draw down without federal sign-off under the new rules.
The Las Vegas Valley draws about 90 percent of its water supply from the Colorado River, and the water authority has set a target of cutting per-person use to 86 gallons a day by 2035, down from higher historical rates, as part of the same conservation push.
The States Facing Zero Cuts Use More of Their Share
Nevada’s lawsuit repeatedly notes that Colorado, Utah, New Mexico and Wyoming, the Upper Basin states, face no mandatory reductions under the new plan.
Comparing actual use to entitlement across the basin sharpens that complaint. The four Upper Basin states have used a combined 4.3 million acre-feet a year on average from 2021 to 2025, against a 7.5 million acre-foot compact allocation, meaning they draw about 57 percent of what they are legally owed while facing no required cuts at all.
Nevada, by contrast, already draws about 66 percent of its own entitlement (198,570 of 300,000 acre-feet) and could be pushed down to just 29 percent of it if the driest-year cut takes effect.
A river-sharing system that leaves the states using more of their unused entitlement exempt from cuts, while pushing the state already living closest to its limit toward using less than a third of its legal share, is the imbalance at the center of Nevada’s case. “There are four states upstream of us that are facing zero mandatory reductions,” Entsminger said.
What Happens Next
Nevada is the first state to sue over the plan, but it may not be the only one. Arizona has set aside $9 million for potential Colorado River litigation and has discussed its own legal options, though it has not filed. Arizona Department of Water Resources Director Tom Buschatzke said he learned of Nevada’s suit from his Nevada counterpart around 5:45 a.m. the day it was filed.
“We’re still evaluating, and we’ll provide more information at a later date on how we’re going to deal with this complaint,” he said. California has not announced a similar filing.
The backdrop to all of it is a shrinking reservoir. Lake Mead stood at 1,039.3 feet in elevation on August 24, the day Nevada filed suit, a level NASA has described as the lowest recorded since the reservoir was filled in 1937. Nevada Rep. Dina Titus called the driest-year scenario “a death sentence for Southern Nevada.”
No statement from the Interior Department or the Bureau of Reclamation responding to the lawsuit turned up in the coverage reviewed for this article.
Nevada’s complaint asks the court to block the plan from taking effect while the case is heard, but sets no specific deadline of its own, so the driest-year cut and the litigation over it are likely to run alongside each other well past the 2027 date the operating guidelines are meant to start.
