Lower Basin U.S. use

Preparing for A Thing I’m doing next week, I updated the Crazy Fleck Spreadsheet this morning of data from Reclamation’s annual Lower Basin decree accounting reports.

Amid all the angst and rhetoric, it is easy to miss the salient fact made clear by this graph: Lower Basin water users have reduced their take on the Colorado River substantially since the early 2000s.

• Nevada’s use was the lowest since 1992.
• Arizona’s use was the lowest since 1991.
• Records that far back in time are tricky*, but California’s take on the river in 2023 was appears to have been the lowest since the late 1940s.

To be clear, the use in the late 1990s and early 2000s was unsustainably large. Praise is due for shrinking Lower Basin use, but the praise should be tempered by the fact that that they didn’t do it until the reservoirs had dropped to scary low levels.

But – crucially – everyone’s economy is doing fine. We’ve absorbed dramatic water use reductions without harming the basic structure and function of the Lower Colorado River Basin communities that depend on the river.

Upper Basin Data

Upper Basin water use

Working with Upper Basin data is trickier*. There’s a new dataset from Reclamation that uses remote sensing to estimate consumptive use from 1971 to 2023. There’s been a good deal of back-and-forth among Colorado River data nerds because of some confusing aspects of the data, which we hope to sort out soon to enable a more useful analysis. But the top line numbers tell a different but also ultimately an optimistic story.

The curve appears (see data nerd confusion caveat above) to show an upward trend since the 1970s with a huge amount of interannual variability. So we haven’t hit the conservation brakes yet, at least at the basin scale. But it also is clear that the Upper Basin is using far less than the 7.5 million acre feet tagged for us in the 1922 Colorado River Compact.

We Can Do This

It is easy to get tangled these days in the anger and finger pointing about who should cut, and by how much, about who has already cut and how and why, about questions that are both technical but more importantly deeply emotional about equity and fairness. We need to remember and learn from our successes.

* A Note on Data

The Lower Basin data from 1964 to the present is contained in the decree accounting reports, prepared by the Bureau of Reclamation since the Supreme Court ruling in the Arizona v. California case back in the 1960s. Prior to that, I have stitched in a dataset created by the numbers wizards at the Metropolitan Water District of Southern California.

The Upper Basin data comes from the new Upper Basin Consumptive Uses and Losses reports published by the Bureau of Reclamation. The were originally published in May, then a revised set was published in June, I’m cautious in my analysis and citation because there are still some things I don’t understand about them.