Southwest monsoon!

Sorry, that was a clickbait headline. Let me walk it back: Odds shifted slightly toward a wetter Southwest monsoon this summer!

Summer seasonal outlook

Summer seasonal outlook

 
The usual forecast explainer: this shifts the odds from the climatological one-in-three-years-is-wet statistical binning to a 33-40 percent chance of wet in the light green area, upwards of 40 percent in the dark green area.

That translates to a seasonal forecast of continued drought, but some improvement, across the Colorado River Basin:

Seasonal drought outlook

Seasonal drought outlook

What do we mean by drought?

Darren Ficklin at Indiana University has a new paper exploring trends in drought in the United States which notes that the trends are not universal:

[F]our regions of increasing (upper Midwest, Louisiana, southeastern United States (US), and western US) and decreasing (New England, Pacific Northwest, upper Great Plains, and Ohio River Valley) drought trends….

By one measure, increasing drought in the west. From A climatic deconstruction of recent drought trends in the United States,Darren L Ficklin et al 2015 Environ. Res. Lett. 10 044009 doi:10.1088/1748-9326/10/4/044009

By one measure, increasing drought in the west. From A climatic deconstruction of recent drought trends in the United States,Darren L Ficklin et al 2015 Environ. Res. Lett. 10 044009
doi:10.1088/1748-9326/10/4/044009

But we need a more fine-grained analysis, Ficklin and colleagues acknowledge, in order to be careful in what we mean by “drought”:

While the general definition of drought—a deficit of precipitation—is well known, quantifying drought is more difficult. The challenges result from the diversity of questions one can ask about drought leading to differences in the classification of drought over varying timespans, and the influence of drought on a variety of socioeconomic factors.

Jim Dalrymple has a terrific piece in BuzzFeed today that takes this insight and runs with it:

You may have heard that the current drought is California’s worst in 1,200 years. That oft-cited figure comes from a paper by Daniel Griffin, of the University of Minnesota, and Kevin Anchukaitis, of the Woods Hole Oceanic Institution.

In conversations with BuzzFeed News, both researchers explained that they came to that conclusion after studying tree ring samples, as well as using what’s known as the Palmer Drought Severity Index, or PDSI. Basically the PDSI measures soil moisture as it compares to what is “normal” for a particular place.

What Anchukaitis and Griffin ultimately found is that the soil moisture in central and southern California has fallen to it’s lowest level for any three year period on record. Other droughts may have been longer or drier, but they were punctuated by rainy years.

But that isn’t the end of the story. Griffin and Anchukaitis were looking only at one type of data, and both said there are other ways to evaluate the drought.

“There’s no one definition of drought,” Anchukaitis explained.

Both Ficklin and Darlymple are worth your clicks.

And an additional recommendation: if you’re on the Twitter, I suggest you follow Kevin Anchukaitis, the Woods Hole climate scientist who is quoted in Dalrymple’s story, and whose tweets brought both of these to my attention.

Medjool dates

Date orchard, Bard, Calif., by John Fleck

Date orchard, Bard, Calif., by John Fleck

I know, I know, beware the romanticism of desert agriculture, but these trees are such a nostalgic throwback to my childhood.

I grew up on the fringe of the Los Angeles suburbs. Trips to the desert were part of my childhood. And date palms along the highway were an iconic image of those jaunts.

The story I heard on my trip last week was that these six trees in the foreground are the original Medjool date trees that came to this area (Bard, in California’s far southeast corner) in the 1940s, and that the trees around them are all direct descendants therefrom. Dates are one of those high-labor, high-value crops that take advantage of desert sun and abundant Colorado River irrigation water.

I’ve been able to trace Imperial County date acreage back to the late 1970s (still haven’t found any older data than that) and see a steady increase in land devoted to these beautiful trees. According to USDA, the California farmers gross about $5,000 per acre growing dates, which puts ’em in the higher end of value per acre and unit water used. But they’re also incredibly labor intensive. This is one of those crops that early farmers in the region thought would make them rich, but it remains a very small portion of the irrigated land down there.

Mostly this was just an excuse to post some pictures that I love. Here’s another:

Canal carrying water to date orchards in Bard, California. By John Fleck

Canal carrying water to date orchards in Bard, California. By John Fleck

Lake Powell takes a big hit in latest Bureau forecast

More than a million acre feet of water disappeared from Lake Powell in the latest U.S. Bureau of Reclamation operational forecast for the 2015 water year, translating to a 13 foot drop in the big Colorado River reservoir’s projected end-of-September elevation in this month’s forecast compared to just a month ago.

Colorado River storage, graph by John Fleck, data courtesy USBR

Colorado River storage, graph by John Fleck, data courtesy USBR

The change in this month’s USBR “24-Month Study” (pdf) is the latest fallout from a dismal March, with hot temperatures and little snow across the Colorado River Basin.

For now, the forecast will have little impact downstream at Lake Mead, the reservoir that supplies Arizona, Nevada, and California. Mead is at historically low levels (where by “historically” I mean “lowest since it was filled”) and is teetering on the brink of a shortage declaration, so the numbers here matter, but the latest forecast suggests the odds remain against a 2016 formal shortage declaration (gory details of what “shortage” means here). But the forecast contains a caveat that, if the crappy weather continues, released from upstream Powell to downstream Mead could be throttled back later this year, which would Mead closer to the shortage line by the end of the year.

Karl Flessa on the Colorado River pulse flow, one year on

The University of Arizona's Karl Flessa getting a first hand look at the pulse flow as it arrives at San Luis. March 2014, by John Fleck

The University of Arizona’s Karl Flessa getting a first hand look at the pulse flow as it arrives at San Luis. March 2014, by John Fleck

Vanessa Barchfield:

University of Arizona geoscientist Karl Flessa said Tuesday that the eight-week flooding helped to germinate and establish cottonwoods and willows that will live for up to 50 years, demonstrating that even a small amount of water can have long-lasting effects on an ecosystem.

But, Flessa said, the impact of the water varied.

“In some places the pulse flow did enormous amount of good work in establishing vegetation and sustaining that vegetation. In other parts of the river it didn’t really make that much of a difference,” he said.

 

California hay acreage down

Almonds get all the attention, but hay, that most pedestrian of crops, still covers more acres of California farmland. But less than it used to. In the drought of 2015, California farmers are planning to plant and maintain past plantings of 1.23 million acres of hay, according to new USDA data published last week. That’s the lowest since at least 1950 (which is as far back as I could figure out how to easily get data). This is what we should expect – land, water moved out of lower-value crops in drought:

 

California hay acreage

For comparison, 860,000 acres in California were planted in almonds last year.

Potholes: A cemetery in the desert

This cemetery, on the “banks” of the All-American Canal overlooking Bard on the California-Arizona desert, has no grass:

Potholes Cemetery, near Bard, California, April 2015

Potholes Cemetery, near Bard, California, April 2015

Immediately behind me as I stood to take this picture last week was the All-American Canal, an artificial river built in the 1930s to carry Colorado River water to the Imperial Valley. A lot of water. The original cemetery, dating to the 1800s, was located a few hundred feet to the north. When they built the canal, they dug up and re-interred the remains of 151 early settlers.

I was thinking of Potholes when I read this story this morning about cemeteries in the California drought:

Cemeteries across Inland Southern California are bracing for the effect of Gov. Jerry Brown’s sweeping order to curb water use 25 percent from 2013 levels, in the wake of a drought of unprecedented severity.

At Potholes, there’s 3 million acre feet of water flowing by annually, but they decided long ago not to water a cemetery in the desert. Just one more data point about our attitudes toward water an arid land.

Tree rings, telling another story

From the Newbury Daily News:

In May, 2002, the Coffin House on High Road in Newbury was run through a battery of tests to determine its age. Dendrochronology, the science of dating timbers based on patterns of tree growth, was used to determine that the oldest portion of the house was built by trees cut down in 1677 and 1678. It was common to build houses with green timbers, and most were used within a year of being cut, so a conclusive date of 1678 was assigned to the house. Timbers from the front range of the house, known to be an addition, were dated at 1713.

Though pleased to have an accurate date for the construction of the house, the Historic New England staff who gave tours of the house were also surprised. The house had been dated to 1654 for centuries by the Coffin family.

I love these. I wrote a book for kids about how tree rings tell tales.

 

1,075: What a Lake Mead “shortage” would mean in practice

tl;dr There is a clear possibility of a shortage declaration on Lake Mead in August, which would force a reduction in Lower Colorado River water deliveries, primarily to Arizona, in 2016. Nevada and Mexico would also see small shortages. Neither California, nor the states of the Upper Basin (New Mexico, Utah, Colorado and Wyoming) will see any curtailments.

This is a big deal, but it is almost entirely an Arizona big deal. Arizona currently has the slack in its system to absorb the reductions, including possibly deeper cuts if Mead continues to drop, without major disruptions. The Phoenix and Tucson metro areas are not going to dry up and blow away.

Longer details below:

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