Godfrey Sykes, Map of the Colorado River Delta, 1905

When Daniel Trembley MacDougal of the New York Botanical Garden rode a flood pulse through the Colorado River Delta in 1905, he found a puzzling landscape – one of the most arid regions of North America sliced through by “swampy jungles”. At a time when beaver was being trapped into oblivion elsewhere, it was a landscape that seemed to MacDougal to offer hope:

The area actually irrigated by the river in normal low water and flood … is surrounded on all sides by desert and salt water, and is in reality a biological island….

The quantity of food furnished by the swampy jungles is sufficient to support a vast amount of native animal life, and furnishes inviting feeding grounds for migrating birds. The countless millions of young willow and poplar shoots supply food for the beaver, which bids well to hold out long in the impassable bayous and swamps against the trapper foe.

Of course it wasn’t trapper foes who reduced the delta’s beaver population but dams upstream that choked off the “swampy jungles” and “impassable bayous”. But a survey done in the 1990s by Eric Mellink and Jaime Luevano found remnant beaver populations did hold out, sometimes even when the only water available was standing, stagnant pools. As long as there were willows and cottonwoods (MacDougal called them “poplars”) Mellink and Luevano found beavers.

When I toured the Laguna CILA (pdf) habitat restoration site in the delta last month, before the Minute 319 environmental pulse flow arrived, we saw a little beaver dam:

beaver dam at Laguna CILA site, March 27, 2014, by John Fleck

We’re beginning to see details of a pilot program to conserve water in the Colorado River Basin to prop up declining water levels in the basin’s major reservoirs by paying water users to not use water.

The Southern Nevada Water Authority’s board last week approved that agency’s $2 million contribution to what would be a $13 million effort funded by the four largest Colorado Basin municipal water users – SNWA, the Central Arizona Project, Denver Water and the Metropolitan Water District of Southern California, each kicking in $2 million – and the U.S. Bureau of Reclamation, which would kick in $3 million.

A staff report last week from SNWA General Manager John Entsminger to his board (pdf) describes the program thus:

The purpose of the program is to determine if voluntary demand management actions (including agricultural land fallowing, curtailment of industrial uses, municipal conservation, etc.,) would be feasible to create Colorado River system water to mitigate the impacts of ongoing drought.

Las Vegas feels an acute need because dropping reservoir levels threaten its intakes, while everyone feels the drought pinch, Entsminger told his board.

Here’s how Kathryn Sorensen, water services director for the city of Phoenix, described it in a report to her city council this week (pdf):

Under the program, entities entitled to use Colorado River water would be compensated for voluntary reductions in water use, which would create conserved water that would benefit the system through increased reservoir levels. These increased reservoir levels then would forestall or mitigate future shortage declarations.

(h/t Betty Reid at the Arizona Republic for the mention of Phoenix’s interest in this.)

If this goes forward, it’s a potentially significant development in Colorado River Basin water management for a couple of reasons.

First, the mechanism on the surface looks a bit like the “Intentionally Created Surplus” and “Intentionally Created Mexican Allotment” (ICS and ICMA, and yes, they we really pronounce it “ick-ma”) mechanisms. Under those mechanisms, Lower Basin and Mexican water users can get credit for water conservation measures, creating storage banks in Lake Mead. But this new Colorado River Conservation Program would be different in a key way. The water saved wouldn’t be tagged as belonging to any particular water user. It would simply increase the overall amount of water available in the system for all users. (The pseudo-economist in me is curious about free rider problems. A subset of the basin’s water users are paying, everyone benefits. But that’s a subject for later, I guess.) The significance here is a general effort, with money behind it, to increase conservation in the basin as a whole, for the benefit of all.

Second, the effort crosses the Upper Basin-Lower Basin boundary. Denver Water is part of the deal. ICS and ICMA are entirely a Lower Basin/Lake Mead thing. Adding Denver and taking steps to prop up Lake Powell are a big deal.

Entsminger told his board the pilot program would begin this year and run through 2016.

One of the epic Colorado River stories involves the Great El Niño of 1983, the year they almost lost Glen Canyon Dam. With a massive snowpack melting off in a hurry in June of that year, Lake Powell filled to the spillways, which couldn’t handle the load, and it is said we came close to catastrophe. (See John Weisheit, pdf)

As we head into what may be another big El Niño year, can we expect another big snowpack and a Powell-filling runoff? No.

Paul Miller at the Colorado Basin River Forecast Center ran the numbers and sent along this graph of El Niño vs. La Niña and its impact on Colorado River flow:

Colorado River runoff and ENSO, courtesy Paul Miller, CBRFC

“GLDA3” is CBRFC-speak for the natural inflow into Lake Powell – what you’d get if there were no dams. You can see 1983 hanging out there in the upper right – big El Niño, big runoff. But of the nine El Niño years in his data set, three were wet, three were middling, and three were dry. 2002, an epic dry year, was also an El Niño year. Here’s how Paul explains it:

There’s not a huge correlation between ENSO and the Upper Colorado River Basin, where we get most of our water supply….

But there is a bit of correlation in the Lower Colorado River Basin, which, hopefully, will provide a little extra water to the system. Maybe some of that water can be used to meet Mexico water deliveries or southern California agricultural demands, which could potentially reduce releases from Hoover Dam and Lake Mead.