Stuff I Wrote Elsewhere

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We’re seeing some extraordinary snowmelt right now. Coming a month early, it’s setting this-date-in-history records up in the Rio Grande Gorge:

Never, in more than a century of record keeping, have we seen a March snowmelt like that flowing down the Rio Grande Gorge in northern New Mexico right now.


Record warmth across the mountains of northern New Mexico and Colorado is rapidly turning a middling snowpack into soup. The question is how much of that soup ends up in New Mexico’s rivers and reservoirs and how much evaporates before it gets to water users in New Mexico and points south.

So far, according to National Weather Service hydrologist Ed Polasko, it looks like the rivers are winning.

“Even though the snowpack is coming down like a rock, the rivers are coming up like crazy,” Polasko said Wednesday.

It’s worth revisiting Tom Pagano’s EOS paper on the 2004 March melt, which was a memorable epic early spring. Also Dan Cayan’s paper from 2001 using phenological data to look patterns of early spring onset. And Phil Mote’s work on declining mountain snowpack in the West.

I don’t want to misstate the importance of what’s going on here. In terms of water supply, there is some argument to be made that a big part of what’s happen is merely earlier melt – that it all ends up in the reservoirs anyway, just at a different time. With the enormous buffer of the big southwestern reservoirs, timing is irrelevant. (Different story in the Pacific Northwest, but I’m less familiar with the issues there.) But to the extent that part of what goes on in these early springs is increased evaporation/transpiration, this signals an interesting regime change for those of us living here in arid country.

Update: Down in the comments, Dano makes a good point worth pulling out:

A slower snowmelt generally means slower percolation thru the soil, making soil moisture last longer. Not always, but a good rule of thumb. Native grasses are adapted to that moisture being there in April-May. Just because it ends up in the reservoir anyway doesn’t do the biota adapted to a different regime any good. We’re conducting an experiment with no control.

He’s absolutely right, and I didn’t mean to give the ecosystem issue short shrift. I’m real focused on water supply issues right now, but we shouldn’t ignore the various other systems influenced by the changes underway.

10 Comments

  1. A slower snowmelt generally means slower percolation thru the soil, making soil moisture last longer. Not always, but a good rule of thumb. Native grasses are adapted to that moisture being there in April-May. Just because it ends up in the reservoir anyway doesn’t do the biota adapted to a different regime any good. We’re conducting an experiment with no control.

    Best,

    D

  2. But who cares about the biota? Humans after all are not part of the biota, so as long as we get ours… (:

    John, I wasn’t aware that the Southwestern reservoirs have the kind of capacity you describe. The PNW ones certinly don’t, being operated as flood control dams in the early part of the season and (other than sometimes during flood conditions) only being allowed to fill all the way after the flood risk has passed.

  3. Steve –

    Yeah, the major dams down here are all multi-year structures designed to buffer against multi-year variability – catch the extra in the wet years so you can use it in the dry years. Flood control was one of the early drivers for the development of Hoover Dam (the Imperial Valley farmers kept ending up under water) but multi-year buffering is really the dams’ dominant role. Very different from the wet climate dams on the Columbia.

  4. don’t know if you caught the hubbub in Mote’s universe:

    http://seattletimes.nwsource.com/html/localnews/2003618979_warming15m.html

    (Dano, aren’t you in Seattle?)

    but this is one piece in the picture of people at AGU bending my ear about climate change/overselling stuff. Questioning Mote’s results was the subject of one of my interactions there; two researchers that I respect highly had a poster (and paper under review right now) calling into question Mote’s methodologies and conclusions, but the lead author was worried that even approaching the subject would make people think he’s become a skeptic b/c Mote’s results have become so internalized in the policy discussion.

  5. I think Kevin’s concerns are an illustration of the difficulties posed by the argument Eli recently raised that academics are responsible not only for the substance of their work, but also for the way it might be misused by others in the tribal climate wars:

    http://rabett.blogspot.com/2007/03/dear-john.html

    It is an argument with which I disagree.

  6. I would be very interested to learn more about kevinv’s statement “two researchers that I respect highly had a poster (and paper under review right now) calling into question Mote’s methodologies and conclusions” What were they concerned about? Who were these researchers?

  7. Extending the ecological analysis… I expect an earlier snowmelt to increase stress more on woody plants than on herbaceous plants, quite possibly favouring grasses because of a shift in the competitive balance. Shrubs fare better than grasses when moisture infiltrates to depth because of the respective rooting strategies. As snow melts faster, moisture won’t get so far down. To illustrate, and hitting close to home, was the expansion of shrubs in the US SW during a period of wetter winters from ~1970s-2000s [Brown et al. 1997, PNAS].

  9. I caught that, Kevin, & the back and forth was interesting. I had a couple of those folks as guest lecturers and I have my opinions that somewhat echo yours, but I don’t wish to send the thread OT & I’d be interested to follow the thought Cliff is implying here. [BTW, the clouds chased me out of Seattle & am now between Mr Fleck & Mr Rabett.]

    And I thank Daniel for clarifying my comment – I had European grasses in mind (esp cheatgrass) leading to fuel buildup and fire potential, but shorthanded it due to lunchtime post haste.

    This changed moisture regime will certainly favor Euro grasses IMHO and its certainly possible that bunchgrasses could quickly adapt due to the change in degree days with earlier warmups like this year [I wonder what spring cold snaps like this weekend will do to degree days and green-ups…]. And I think we have an interesting confounding factor (that John has mentioned before) with the spread of juniper in the changing moisture/fire regime potential.

    Fun times ahead for the folks in the field, collecting data in their plots.

    Best,

    D

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