Arkansas River Basin Water Forum recap: “There is no such thing as an average year” — Nolan Doesken

Upper Colorado River Basin May 2015 precipitation as a percent of normal
Upper Colorado River Basin May 2015 precipitation as a percent of normal

From The Pueblo Chieftain (Chris Woodka):

Many of those who attended the Arkansas River Basin Water Forum showed up wearing short sleeves and enjoyed rafting or fishing adventures on the first day of the event.

Thursday, it was spitting snow.

Nothing better could illustrate the “trend” of climate in Southern Colorado.

State Climatologist Nolan Doesken illustrated this by flashing up a series of graphs that showed historical temperatures, precipitation and snowpack moving up and down seemingly at random. One graph showing multiple years with brightly colored lines looked more like an Op Art poster from the 1960s than weather data.

“It could be a hot summer. Rain? Who knows?” Doesken shrugged. “When in doubt, put out your rain gauge. There is no such thing as an average year.”

Still, scientists and engineers are determined to put numbers to this chaotic system.

Doesken described last year’s Miracle May, which boosted water supply, but got hoots from some water managers because of the flooding problems it caused. On a graph, it produced a fat bulge seldom equaled in many parts of the state.

And the effects of that month of moisture are still felt one year later.

Garrett Marcus, engineer for the Southeastern Colorado Water Conservancy District, outlined the current reservoir storage for the Fryingpan-Arkansas Project.

Release of water stored in Lake Pueblo this year seemed likely because of high storage levels coupled with a revision of capacity because of sedimentation. But cooperative efforts in March, coupled with a lack of precipitation, allowed levels to reach the mark deemed necessary for flood control by mid-April.

New snow now is improving the outlook for water supply.

“The last couple storms gave us the jump we needed,” Marcus said.

Bill Tyner, assistant division engineer for the state Division of Water Resources, talked about storage. The basin has 118 reservoirs, which can store up to 1.7 million acre-feet of decreed water rights.

The five largest reservoirs (John Martin, Pueblo, Twin Lakes, Turquoise and Nee Noshe) could hold 1 million acre-feet. Of those, John Martin and Nee Noshe are typically largely empty, but fuller than usual because of the 2015 rains.

The others are small, and in some cases restricted.

“To maintain the storage we think we have, we’ll have to spend a lot of money,” Tyner said.

Tammy Ivanenko, of the U.S. Geological Survey, outlined water use in Colorado and the Arkansas River basin based on the agency’s five-year reports from 1985-2015.

Surprisingly, state municipal water use has plateaued during that time, despite a growth in population to 5 million people from 3.5 million in 1985.

She speculated that conservation efforts, including water smart appliances, have caused the decreasing per capita use.

In the Arkansas River basin, about 68 percent of the water is used for irrigation, an amount lower than is often cited. Power generation uses about 15 percent; public supply, 8 percent; and industrial, 5 percent, according to the USGS data.

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