River flow near record low

Listen to this post

RBC | “Every organization needs a Cassandra and an Eeyore, and I’m it,” is how Dr. Bob Dorsett pre-empted his presentation to the White River Alliance last week. He discussed conditions on the White River, covering subjects like snowpack, streamflow projections, long term precipitation trends and algae blooms.

Dr. Dorsett painted a picture he described as “grim” and “dismal” for the summer of 2021 and continuing “for the foreseeable future,” based on a few key points:

  • runoff is very low
  • algae is already beginning to bloom in the White River
  • there are early signs of stress to fish due to low flows and high temperatures
  • the projected long term trends are “not hopeful”

STREAM FLOWS/RUNOFF

The White River is running well below the 25th percentile for this time of year, and has been for virtually all of 2021. Dorsett pointed out that even prior to the noted recent flow trends, flows were still “barely above” the 25th percentile, lining up with a much longer trend of increasing temperatures and decreased precipitation/snowpack/runoff.

The above map shows the snowpack water equivalent today versus 1981–2010 median.

“We have two years [of] water flow now since the big 2019 runoff, where the flow in the White River has been towards record lows,” said Dorsett. As of Tuesday, June 22, the river discharge measured at 425 cubic feet per second (CFS) near Elk Creek. From 2014 through 2020, measurements at the same location averaged around 1,636 CFS on the same date. The river peaked this year on June 5 at 1,290 CFS, compared to the average peak of around 1,884 CFS from 2014-2020, years in which for the most part also saw below-avera☻ge flows, apart from 2019 when the river peaked at 4,660 CFS.

Near term streamflow projections are not looking so good either. NRCS snotel sites report remaining snowpack in the White/Yampa River drainage at around 1% of the historical median for this time of year. Snowpack in nearby basins isn’t much better, with the South Platte at 8%, Colorado headwaters at 17%, and Rio Grande headwaters at 6% of the historical median. The Upper Arkansas basin is faring the best amid the drought, at 54% of the historical median.

STREAM TEMPERATURES

The White River near Meeker on June 13 measured around 63 degrees Fahrenheit, which Dr. Dorsett said was “within a couple degrees of stopping growth in brook trout,” noting that other species including brown/rainbow trouts and white fish are more temperature tolerant. “But we’re approaching temperatures in the river already this summer that will stress fish,” said Dorsett.

Looking at data through 2020, mean daily temps in August and January at Trappers Lake are pushing 9 degrees Fahrenheit warmer compared to mean daily temperatures 35 years ago in August 1986. Burrow Mountain and Ripple Creek SNOTEL sites show the same temperature trends.

Increasing temperatures correlate with “significant downward trends” of cumulative precipitation on the flattops. “We’ve lost about 50,000 acre feet [of] total yearly runoff from 100 years ago,” said Dr. Dorsett.

ALGAE

Algal growth has also been observed in the White River, including “about 10 percent coverage” near County Road 14 according to one White River Alliance member, who also described it as “more visible than any other time since 2018,” another year with very low stream flows. Dorsett noted that high oxygen saturation levels, which were also measured June 13, also indicate significant activity from algae in the river. The normal range for oxygen saturation is around 84%. He said algae was “going to town” pumping oxygen into the river, which is good during the daytime but has a negative effect at night time as the algae reverses its metabolism and sucks oxygen out of the water. Dorsett added that he had not taken night-time measurements yet, but said oxygen saturation levels in the past have dropped low enough to stress fish populations.

CLIMATE WHIPLASH

On a broader and more long term scale, the country’s southwest is predicted to see an “enormous shift” in vegetative zones by the end of the century. Temperatures are expected to increase by 10 degrees centigrade minimum.

Dorsett took time to comment specifically on a common point he hears when discussing both historic and projected climate trends, for example that “we’ve seen this before,” or that this is “just an unusual year,” part of a broader narrative that recent/current conditions are part of a natural cycle, and thus nothing to be concerned about.

“I would come back to these trends that we’re seeing in temperature, snowpack, precipitation and runoff,” he said. “We are on a long downward trend historically, even though there is considerable year-to-year variability.”

Dorsett spoke further about noted “variability” specifically in precipitation trends most recently observed during the 2018-2019 winter season. “The hope is that the variability will dump a whole lot of moisture occasionally from time to time,” he said, describing the phenomenon as a “bifurcation.” He said the term means as temperatures increase and overall precipitation levels continue to trend downward, occasional “enormous storms” like hurricane Harvey and other recent weather events could result in sudden, massive precipitation increases in specific years.

“On the other hand, in off years, we will see really, really bad drought,” he said, adding that worsening drought would continue in the long term despite potential increase in intermittent major weather events.


By LUCAS TURNER | lucas@ht1885.com

Be the first to comment

Leave a Reply

Your email address will not be published.


*