tl;dr
The Colorado River is in immediate crisis: Lake Powell is at critically low storage, and projected inflows from weak snowpack and extreme heat are unlikely to stabilize the system this year.
Without major changes to water usage, climate trends, or operational policy the Colorado River is staring down the barrel of an existential crisis.
The focal point of this crisis is the Glen Canyon Dam which impounds Lake Powell on the border between Utah and Arizona and which, at capacity, is the second largest reservoir in the United States.
The Glen Canyon Dam was constructed in 1963 by the United States Bureau of Reclamation as part of a larger Colorado River Storage Project designed to tame the ferocious nature of the Colorado River and store water for agricultural, municipal, and industrial use. While the Glen Canyon Dam is only one of many dams within the larger context of the Colorado River, it is found almost exactly at the geographic and political center of the seven states that lay claim to allocations of the Colorado River watershed.
While Lake Powell behind the Glen Canyon Dam rapidly filled to capacity, including years in the mid-1980s where Lake Powell threatened to flow over the top of the dam, the water storage in the reservoir has collapsed in recent years due to historic and persistent drought that looks to be largely a result of long-term climactic change.
The Glen Canyon Dam has numerous features that present imminent challenges to the Colorado River, especially as allocated in the existing legal context. The most pressing of which is the inability of the dam to supply expected downstream allocations, even when considerable storage of water remains behind the dam. There are two intakes that provide channels for water to continue downstream beyond the dam, one is a set of 8 channels used for hydropower generation and is functional when the elevation of Lake Powell is above 3490 feet (although, realistically more like 3525 ft). The other intakes are a set of two channels that lead to 4 output tubes that can supply [some capacity] of water until the elecation of Lake Powell reaches 3370 feet.
That we are rapidly approaching the level where the dam can no longer accept water into it's hyrdopower intakes, meaning that any water released by the dam must run through bypass channels not designed for long-term use means that the Colorado River downstream of Lake Powell is facing mandatory and considerably reduced flows. While Lake Powell reached similarly low elevations in 2022, the winter of 2022-2023 provided a considerable boost to inflows from a record snowpack. This year, just 3 years later, the water equivalents in the Upper Colorado River Basin Watershed are at all-time lows while average year-to-date temperatures are at all-time highs, meaning that this year will likely produce the lowest inflows to Lake Powell ever observed.
There is some wiggle room in the operation of the Colorado River Storage System to buy some additional months of runway in the form of lowering release volumes and releasing limited volumes from upstream reservoir capacity, but the overarching situation, in hydrological terms, is nothing less than a pressing emergency.
Context
The Colorado River is a 1,450 mile long ribbon of life that flows through the Southwestern United States before finding the ocean at the northern tip of Mexico's Gulf of California.
The watershed of the Colorado River encompasses parts of seven states and two countries. Within the United States, the river has been divided into two legally defined entities: the States of the Upper Division consisting of Colorado, New Mexico, Utah, and Wyoming and the States of the Lower Division consisting of Arizona, California, and Nevada.
Climate
Lake Powell
A Trend
This is the Lake Powell elevation time-series line that inspired this whole exploration.