Earth Protect Blog

By Bruce Finley

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Mountain snow-melting intensified this week with an unusually abrupt “flick of the switch” from cold to hot, leading to flooding that on Thursday cut off northwestern Colorado’s main transportation route and forced the shutdown of schools.

The statewide heat that brought Denver temperatures to 85 degrees, breaking two records, combined with mountain snowpack more than a third above the norm, also has boosted the potential for early replenishment of water supply reservoirs, including those along the Colorado River.

This may help California, Arizona and Nevada, the lower-basin states that rely heavily on the river for city and agricultural water.

The Lake Powell reservoir has fallen to 22% of its capacity, the lowest since it was filled after the 1963 completion of the dam across the top of the Grand Canyon, and federal authorities are considering cuts to manage the depletion there and in an equally depleted Lake Mead.

“We will be sending a substantial amount of water down to those lower reservoirs, including Lake Powell, in addition to filling up reservoirs inside Colorado, like Blue Mesa, Lake Granby and McPhee. It is just beginning,” said Peter Goble, water availability specialist for the state climatology office, based at Colorado State University.

“But we’re not expecting Lake Powell, or Lake Mead, to fill up. Those reservoirs are enormous, and the deficits are enormous,” Goble said. “It would take another couple years of snowpack well above average to really reset those reservoirs.”

The federal government’s projected infusion from Colorado and the other upper basin states (Wyoming, New Mexico, Utah) along the Colorado River into Lake Powell this year — 11.5 million acre-feet — would exceed by 4 million acre-feet the legally required 7.5 million acre-feet share of river water due to the lower basin states.

Climate scientists widely agree that extreme weather — droughts, floods, exceptionally heavy snow, heat waves — will become more common as the planet warms. The record-high global average concentrations of carbon dioxide and other heat-trapping “greenhouse” gases in the atmosphere — from humans burning fossil fuels — are expected to bring steadily increasing global average temperatures for at least two more decades.

“While we’ve seen these ‘flicks of the switch’ where we have record warmth not long after a cold spell historically, a more carbon-intensive atmosphere tends to make rapid oscillations between extremes more probable,” Goble said.

Sharper spring swings from cold to heat may alter mountain water runoff patterns, said Jennifer Gimbel, senior scholar at CSU’s Colorado Water Center, a former federal government water policy official and director of the Colorado Water Conservation Board.

The big snow this year will help to replenish those two over-tapped Lake Powell and Lake Mead reservoirs, in addition to replenishing Colorado reservoirs and ensuring healthy stream flows for fish, Gimbel said.

“It will take off some of the pressure” on water users in the Southwest, “which may provide breathing room to further discussions among the states and the U.S. Department of the Interior to find an agreed approach for the next three years,” Gimbel said. “We’re in the throes of aridification, which means extreme events are increased but overall temperatures are hotter and the air is drier.”

In the future, Colorado should install “more strategic storage” to capture surplus water, Gimbel contends, “to take advantage of those extreme events” such as sudden rapid melting of heavy mountain snow.

Flooding in Colorado typically happens after heavy rainstorms during summer.

But rapid melting here and around the Southwest this week has brought higher-than-expected flows in rivers, such as the Mancos River in southwestern Colorado, along U.S. 160, and in the Yampa River in northwestern Colorado, along U.S. 40.

Water in the Yampa and tributaries on Thursday gushed over banks and submerged a bridge near Hayden, forcing state transportation officials to close U.S. 40, the main transportation route in northwestern Colorado, between Steamboat Springs and Craig.

The flooding also forced a shutdown of schools. Hayden Valley Schools Superintendent Christy Sinner cited safety concerns.

As the Mancos River swelled near Cortez, Montezuma County officials who had anticipated possible flooding in May or June suddenly faced those perils a month early.

Volunteers rallied this week, distributing sandbags to residents of Dolores, Mancos and other communities where, after painful dry times last year, the sudden big water threatens to inundate homes.