Colorado River crisis averted? — Jonathan P. Thompson (@Land_Desk) #ColoradoRiver #COriver #aridification

Lake Mead’s stark bathtub ring. Jonathan P. Thompson photo.

Click the link to read the article on The Land Desk website (Jonathan P. Thompson):

Maybe by now you’ve heard that the collective users of the Colorado River have come together in harmony and agreed to cut water consumption significantly to avoid further depletion of Lakes Powell and Mead. Well it’s true! And the feds even seem ready to sign onto the plan. Maybe you’ve also heard this means the crisis is over and we can all relax and go home now. 

I don’t think so. 

A refresher: The 1922 Colorado River Compact divvied up the river between the Upper and Lower Basin states (Mexico was added later). They assumed at least 16.5 million acre-feet ran down the river each year, when in fact it was more like 14 million acre-feet. This discrepancy became clear over the last two decades as the water users’ giant savings accounts — Lakes Mead and Powell — were depleted to critically low levels.

The “Natural Flow” is an estimate of how much water would flow past Lees Ferry if there were no diversions or dams upstream. Basically it’s the amount of water available for all of the river’s consumers. Source: USBR

That prompted federal water officials to call on the states to cut consumption by 2 million to 4 million acre-feet per year, or else they would implement the cuts themselves. After a lot of wrangling, the Lower Basin states (Arizona, California, and Nevada) finally relented and proposed 3 million acre-feet of cuts. Perfect, right?

Wrong. Their cuts would be spread out over three years, meaning their reductions only amounted to 1 million acre-feet per year, which is far less than needed. The deal seemed to many of us like a non-starter — or at least like very faulty math

But it so happens that the proposal came on the heels of an extraordinarily wet winter in the Colorado River Basin, giving a bit of a boost not only to the reservoirs, but also to forecasters’ optimism regarding river flows over the next few years. Also, water users have responded to mandated cuts and done some voluntary cuts of their own, and the wet year meant they had to irrigate less, bringing Lower Basin water consumption to its lowest point in decades.

“New plot using the nClimGrid data, which is a better source than PRISM for long-term trends. Of course, the combined reservoir contents increase from last year, but the increase is less than 2011 and looks puny compared to the ‘hole’ in the reservoirs. The blue Loess lines subtly change. Last year those lines ended pointing downwards. This year they end flat-ish. 2023 temps were still above the 20th century average, although close. Another interesting aspect is that the 20C Mean and 21C Mean lines on the individual plots really don’t change much. Finally, the 2023 Natural Flows are almost exactly equal to 2019. (17.678 maf vs 17.672 maf). For all the hoopla about how this was record-setting year, the fact is that this year was significantly less than 2011 (20.159 maf) and no different than 2019” — Brad Udall

All of that was enough to prompt the feds to include the proposed Lower Basin cuts in an updated environmental impact statement and to make it the preferred alternative. They seem to think it will be enough to fend off the crisis, for now. And maybe it will be. But here are some numbers to consider:

  • Lake Powell currently holds about 8.7 million acre-feet of water, which is higher than the last two years, but 2.2 million AF less than on this date in 2020.
  • Lake Mead currently holds about 8.8 million acre-feet, which is less even than in 2021.
  • Lake Powell, alone, lost 136,550 acre-feet — or about 44.5 billion gallons — to evaporation between July 1 and Nov. 1 of this year.
  • The combined storage of Lake Meads and Powell is currently at about 17.5 million acre feet, which is less than a third of the total capacity. In other words, the reservoirs are still two-thirds empty — even after the big winter.

Crisis averted? Probably, at least for now. And with an El Niño pattern likely in coming months, we might get another big winter. Still, it seems somewhat imprudent to relax efforts to cut consumption — and to discount more drastic plans for dealing with the diminishing Colorado River.

Click here to read “Breaking down the’breakthrough’ Colorado River deal” from Jonathan written last May.

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