A federal judge this week criticized the federal government for failing to consider the risk of a Colorado River Compact call in its environmental review of the planning for Denver Water’s expansion of Gross Reservoir in Boulder County.

Wrangling over the risk of a compact call – which the judge said could force water use reductions in the Upper Basin if the Upper Basin states fail to deliver enough water past Lee Ferry to the Lower Basin – has been a key point in current negotiations between the two basins over future Colorado River operations.

The ruling, in a lawsuit against Gross Reservoir expansion by Save the Colorado River and others, allows construction to proceed, but criticizes the project’s planners for not considering the fact that the risk of a compact call means there might not be enough water to fill it. (Here’s Michael Booth’s Colorado Sun story on the decision.)

In the decision, federal judge Christine Arguello noted that the Army Corps of Engineers environmental review of the project “rests on the assumption that there will be no compact call…. However, considering the American West’s last few decades of severe aridity, such an assumption warrants considerable scrutiny.”

Here’s the full language from Arguello’s ruling. I’ve bolded the key bits:

The American West’s viability rests in large part on the Colorado River, which is an undeniably overutilized water source. The Colorado River’s over-allocation is due to a fatal flaw baked into the 1922 Colorado River Compact—the bedrock-level agreement that forms the basis of the various overlapping management systems dictating the River’s death by a thousand cuts. The Colorado River Compact rests on a politically unpalatable truth—the Compact promised the basin states water that simply does not exist. According to water experts, the Compact’s apportionment scheme draws from deliberately misleading hydrological modeling of the Colorado River’s flow rates. See generally Eric Kuhn & John Fleck, Science Be Dammed: How Ignoring Inconvenient Science Drained the Colorado River 1 (Univ. Ariz. Press 2019). That fatal error now sits enshrined within the Compact, and all of the basin states’ various agreements with each other (and with the Department of the Interior) are forced to overcorrect for the Compact’s flawed hydrology because revisiting the agreement would require a virtually unthinkable amount of time, energy, money, and political will. However, should Colorado River diversions exceed the river’s available water supply—which appears inevitable, at this rate—the 1922 Compact provides a “compact call” mechanism whereby the upper basin states are bound to curtail their water users’ diversions to ensure enough water reaches the lower basin states and Mexico to satisfy the artificially inflated water delivery obligations set forth in the Compact. This Court emphasizes this context for good reason: the cracked foundation of the Colorado River’s management system all but demands skepticism over any proposal that will affect the hydrology of the Colorado River basin. In the instant case, the Corps noted in its FEIS that its reasoning rests on the assumption that there will be no compact call. AR 159092; but see AR 0014667. However, considering the American West’s last few decades of severe aridity, such an assumption warrants considerable scrutiny. See, e.g., Anne Castle & John Fleck, The Risk of Curtailment under the Colorado River Compact 5, 34–35, 40 (2019) (emphasis added) (“Even if the risk of curtailment of Colorado River rights were assumed to be low, the consequences are not. Cities, and farmers and ranchers on the West Slope, would lose economic activity, jobs, income, and community benefits.”); Cherokee Water Dist. v. City of Colo. Springs, 519 P.2d 339, 340–41 (1974) (“Water is essential to the existence of a community.” (emphasis added)). In light of this context, it is perplexing to this Court that the Corps dismissed the possibility of a compact call in its analysis of a proposed water management project.

Further reading of the judge’s sources:

• Science Be Dammed
• The Risk of Curtailment under the Colorado River Compact