The South Platte-Colorado Basin linkage

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Add the South Platte in the state of Colorado to my list of watersheds outside of the Colorado River Basin that I need to pay attention to in order to understand what’s happening inside the Colorado River Basin.

I’ve written here before about the linkage between the Sacramento-San Joaquin River system and the Colorado, because both are key watersheds for Southern California. The Rio Grande, where I live, is another river outside the Colorado Basin that’s integrally connected by human plumbing to what happens inside the Basin. Now a legislative discussion in the state of Colorado suggests a need for similar attention.

Courtesy Wikimedia

Courtesy Wikimedia

The South Platte flows out of the Rockies through the state of Colorado’s urbanizing Front Range communities and across the agricultural plains, providing a key water supply for both. There is a discussion underway now about adding storage on the South Platte, as Marianne Goodland explains in the Colorado Independent:

Millions of gallons of water flow into Nebraska, far exceeding the amount required under the Colorado-Nebraska compact that governs South Platte water use. And Colorado wants and needs to keep that water.

The question lawmakers have to answer now is how to store the water and more importantly, where.

Remember that this is on the other side of the Continental Divide from the Colorado River Basin. But the question of “transmountain diversions” is a hot one in the state of Colorado – should/could more water be taken from west of the divide and shipped across to the east? We already do a lot of this, but there’s pressure to do more.

Goodland’s piece raises this intriguing question – could additional storage on the South Platte increase pressure to move more water out of the Colorado River Basin, because now farms and cities on the eastern side of the divide have more places to put it?

The only opposition to Brown’s bill came from Trout Unlimited’s David Nickum, who said he sympathized with Western Slope residents who fear the water shortfall will require more diversions of mountain water into the Front Range….

The fear of another transmountain diversion prompted concerns from Rep. Diane Mitsch-Bush, a Steamboat Springs Democrat. She proposed an amendment to ensure the study wouldn’t look at mountain water as a way to fill a South Platte reservoir.

We’ve built at artificially vast watershed. I guess I need to start paying attention to water management on the South Platte, too.

 

One of the driest February-March’s in Albuquerque history

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Correction (update?): As of Friday, March 25, 2016, it’s now not likely to rain in March after all.

Correction (update?): It might rain after all!

 

In 1934, the official Albuquerque weather station received 0.04 inches of rain in February and 0.01 in March.

GFS forecast model run through the end of March

GFS forecast model run through the end of March

This year, we received 0.05 in February. So far, we’ve gotten just a trace of precipitation in March. The latest forecast model runs suggest we are likely to get no more.

Weather records before the 1930s for Albuquerque get a bit sketchy. The official tally recorded just a trace of precipitation in February and March of 1902, and there are a few years for which we don’t have complete records. But it’s fair to say that we are on track to have one of the most depressingly dry February-March’s since people began measuring and writing stuff down.

update: I missed 2011 when I wrote this, which was also down in this same cellar, with 0.04 in February and just a trace in March.

Hitting “send” on my book’s manuscript, again

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yuma

E. Conklin, Bridge across the Colorado River, at Yuma, Ariz., 1877, courtesy Library of Congress

There’s no way to pin down the moment I started working on my book, because it happened in fits and starts that extend back in one form or another for more than a decade. But the first time I really went all in was in the spring of 2010, when I made a trip down to Yuma and then up the Colorado River over several days to Las Vegas. It was the first time I went beyond just saying I was working on a book and actually spent money on fast food and cheap motels.

There was still sunlight left when I dumped my stuff at the motel, so I did what I always do, wherever I go. I went down to the river. Below and to the right of where this old railroad bridge used to cross the Colorado, the good folks of Yuma have built a fine city park, and on that April Sunday it was hopping. I got the last space in the parking lot, most every picnic table was in use, the barbecue grills were fired up, there were tubers in the river.

I asked the first person I ran into whether there was a community festival or something going on. Why all the people? No festival, she told me. Just a nice Sunday at the river.

Easter parties on the Colorado River at Yuma, 2015

Easter parties on the Colorado River at Yuma, 2015

At that moment I bonded with Yuma, a community that in many ways for me captures the 21st century Colorado River. It’s a desert farm town, with all the dry and hot and poor that goes along with that. But more than any town as you head up the Colorado River until perhaps Moab in Utah, Yuma has embraced its river. Most of the West we built around the Colorado River has required moving water out of the Colorado River and using it elsewhere. And in fact Yuma does that too. Most of the Yuma County ag water is diverted 20 miles upriver at Imperial Dam. But Yuma emphatically remembers that it’s a river town. The network of canals that brings the water down is a marvel all its own.

But Yuma remembers the river at its heart, too. Last year I was there again on Easter, pulled in at dusk to the Hilton Garden Inn overlooking the park, and it was the same scene. The light was fading (it was darker than this picture looks, thank you Adobe photo modification products), but the people were still out at their river.

This is part of what motivates the project that my book turned into. I started the effort with a dismissive bias against desert agriculture. Does it make sense to grow alfalfa in the desert? By many measures, the water is more valuable in other uses. The economic benefits of urban water use dwarf those of desert agriculture, while at the same time environmental values press in from the other direction. But I’m unwilling to tell these folks, “Sorry, not enough water, we need it elsewhere.” I believe there is an alternative.

In the book I document three basic trends:

  • farm communities like Yuma, growing their agricultural economies while using less water
  • cities like Los Angeles and Las Vegas, growing their economies while using less water
  • the growth of institutions needed to capitalize on those trends and develop the next level of water allocation and sharing rules to thread the needle left us by drought and climate change

There’s a fourth trend that’s not so clear, but about which I choose to be optimistic – a shift toward returning some water for the environment. In the book, I lay out an argument for how the institutions of that third bullet can leverage the first two. I am optimistic. I think we can do this.

I sent off the final copy-edited version of the book to the fine folks at Island Press this afternoon. There’s still one more wave of editing to come, proofing galleys in a couple of months. On the shelves, I hope, by September. Dying to share it with y’all. Soon.

5 million years ago, when the Colorado River made its first dash to the sea

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In a neat new paper looking at sediment layers near Blythe, California, Jordan Bright of the University of California and colleagues (paper here, $ gated) argue that they’ve found evidence of the moment (in geological time, the “moment” is really hundreds of years) when the Colorado River made its first dash to the sea.

The Blythe Basin, they argue, was a vast inland lake/sea thing, until the water finally busted through the “Chocolate Mountain paleodam” in what must have been an impressive geologic woosh:

We suggest that Blythe basin was filled with a hydrologically complex Colorado River-fed lake that was abruptly breached in an over-spilling event at Chocolate Mountain paleodam near its southern margin….

The work involved looking at isotopic changes in the composition of rock layers in Hart Mine Wash, which is on the Arizona side of the Colorado River about 15 miles south of Blythe. Their map of the hypothesized lake is really cool:

Regional map showing the relationship between the course of the modern lower Colorado River, Blythe basin (intermediate blue), basins to the north that contain the Bouse Formation (light blue), proposed paleodams (black bars with names), and the study location (solid black star). Numbers in parentheses denote highest elevation (masl) of Bouse Formation in the respective basins. Figure modified from image provided by R. Dorsey.

Regional map showing the relationship between the course of the modern lower Colorado River, Blythe basin (intermediate blue), basins to the north that contain the Bouse Formation (light blue), proposed paleodams (black bars with names), and the study location (solid black star). Numbers in parentheses denote highest elevation (masl) of Bouse Formation in the respective basins. Figure modified from image provided by R. Dorsey.

The warm, dry spring pushing Colorado River reservoir forecast levels down

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This month’s US Bureau of Reclamation reservoir forecast model runs show the implications of the warm, dry spring, with a drop of 620,000 acre feet and six feet in elevation in the estimated end-of-year storage in Lake Powell, the major reservoir in the Upper Colorado River Basin. Here’s my long term forecast graph, updated with the latest estimates through the end of water year 2017:

Colorado River storage

Colorado River storage

Tony Davis had a good story earlier this week discussing this year’s big snowpack fail:

The low expected runoff does not mean a shortage in deliveries of Central Arizona Project water for 2017 — at least not yet. The U.S. Bureau of Reclamation has predicted a very low chance of a 2017 shortage but forecast a greater than 50 percent chance of a 2018 shortage.

Haven’t seen the latest model runs yet, but I assume that 2017 shortage number is going up.

Poverty, income inequality, and US water infrastructure

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Brett Walton wrote a smart piece about the relationship between poverty, income inequality, and decaying US water infrastructure:

Affordable water requires an all-in effort that cuts across the political spectrum, a mix of redirected spending priorities, tax policy, social programs, and engineering assessments at the local, state, and federal levels. The urgency, experts assert, will grow, as water systems enter the Replacement Era — to use American Water Works Association’s phrase — while a high-tech economy widens the distance between the well-compensated haves and the struggling have-nots.

 

Technology is easy, but it’s water policy that matters

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Brett Walton had a piece last week that suggested an appropriate damper for the US water community’s enthusiasm for the Obama administration’s recent Big Water Push:

The budget request drew praise from water experts, who, even with the small sum, were happy to see more recognition from the country’s leadership. But those same voices note that the most fruitful prospects for refashioning the country’s relationship with water are not technological. They are political: changing the laws, policies, and incentives that guide water use at the local, state, and federal levels. In other words, tinkering with the rules of the game, not just adding new pieces to the board.

“It makes sense to invest in research and technology,” Doug Kenney, director of the Western Water Policy Program at the University of Colorado, told Circle of Blue. “The key is that it needs to be balanced with policy changes. There’s nothing wrong with technology and research. But it’s the easy piece, I’m afraid.”

New evidence that a warming climate is already reducing Colorado River flows

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Connie Woodhouse at the University of Arizona and colleagues have a new paper presenting the most direct link yet between a greenhouse-warmed climate and reduced flows in the Colorado River.

Woodhouse et al

Comparison of hydroclimatic variables (Colorado River at Lees Ferry water year streamflow, October–April total precipitation, March–July average temperature, and prior November soil moisture) averaged for the years in each of six droughts in the upper Colorado River basin, percentile values with standard errors. Woodhouse et al

Modeling has for many years projected such an effect in the future, but the new Woodhouse et al. paper (Increasing influence of air temperature on upper Colorado River streamflow, GRL, I believe it is ungated) is the first direct published measurement I’m aware of suggesting that it is already underway:

An important finding revealed by this work is the clustering over the last two decades of anomalous years in which already low flows are lower than might be anticipated given cool season precipitation totals. Drought conditions have persisted over the past 15?years in the upper Colorado River basin, negating any substantive positive effect of a handful of wet years (2005, 2008, and 2011) within this interval of time. In most recent drought years, low flows have been further exacerbated by warm temperatures. (emphasis added)

Woodhouse and her colleagues looked at a range of influences in annual flow on the river, including how much precipitation fallows, soil moisture in the preceding season, and spring-summer temperatures. They found that the drought of the 21st century was actually the wettest of the droughts in the historic record, as measured by the amount of precipitation falling across the Upper Colorado River Basin. But the extraordinary temperatures (it has been by far the warmest drought) pushed down the river’s flow.

This is scientifically unsurprising. When it’s warmer, plants transpire more water, and evaporation is greater. But there’s some subtle statistical analysis in the new Woodhouse et al. paper that goes beyond this obvious point to tease out the relationship between precipitation, temperature, and antecedent soil moisture. (One of the surprises to me was the relatively small impact of soil moisture going into the winter. I’d have expected the effect to be larger.)

Worth noting: the forecast this year is for a warm spring.

A forecast for another dry year on the Rio Grande

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The March 1 forecast for the Rio Grande in New Mexico suggests we are heading into another dry year on the Rio Grande in New Mexico, with a median forecast of 80 percent of the 1981-2010 average flowing into Elephant Butte Reservoir. (source pdf)

Flow at Otowi, on the Rio Grande in New Mexico

Flow at Otowi, on the Rio Grande in New Mexico

That is close enough to average that there is a lot of room on the wet side of the probability distribution to yet have a wet year. But when I wrote that last sentence I chose “average” rather than “normal” with some care, because “normal” for the years since 2000 has been dry. The graph to the right is what is called the “Otowi Index Flow”, a measure of native Rio Grande water flowing past Otowi, the key measurement point in northern New Mexico for Rio Grande Compact compliance calculation. The horizontal line is the long term mean, going back to 1940. You can see that just two years since 2000 have been above that mean. If the March forecast holds, 2016 will be the eighth consecutive year below that mean. One expects high variability on this system, with a big gap between wet years and dry years.*

But eight consecutive dry years would be extraordinary. The previous longest runs were four consecutive dry years. Since 2000 inclusive, flows on the Rio Grande at Otowi have average 30 percent less than the 1940-1999 average.

* In statspeak, the “coefficient of variation”, the size of the standard deviation relative to the mean, is 54 percent, which is big. By comparison the Colorado River at Lee’s Ferry has a coefficient of variation of 29 percent. The Mississippi at St. Louis is 34 percent.