WATER LINES: The silver lining — flood ends drought in northern Colorado
September 23, 2013
The destruction from heavy rains on the Front Range last week is truly mind-boggling: Houses swept away by raging rivers, bridges gone, numerous rock slides, whole towns isolated, and countless farm fields under water. Thousands of people have had to leave their homes and hundreds remain unaccounted for.
Looking at the rainfall totals, it's not hard to see why — some areas received nearly as much precipitation in one week as they normally receive in an entire year. And September is normally a dry month!
The silver lining in this disaster is that it has ended the drought over a good chunk of northeastern Colorado. State Climatologist Nolan Doesken told the Denver Post that "drought as we know it will be ended at a number of locations." Areas recommended for removal from drought classification include Larimer, Boulder, Gilpin, Jefferson, Lake, western Weld, Northern Park, western Arapahoe, western Adams, Douglas, western Elbert, northern El Paso, central Teller and central Fremont counties.
The flood affected the balance between water supply and demand in two ways: Not only did it bring more supply, but it also decreased demand. Farmers don't need to, or can't anyway, irrigate flooded fields. Front Range water managers are banking the extra water in reservoirs, which are filling up at a time when they are normally being drawn down.
Since the Western Slope shares Colorado River water with the Front Range, reduced demands there mean less water diverted across the Continental Divide. As the storms got underway Sept. 12, the Bureau of Reclamation stopped diversions of Western Slope water through the Colorado-Big Thompson Project, which takes water through the Adams Tunnel from Grand Lake to the Eastern Slope.
Although we've been spared the floods, the Western Slope has also been pretty wet lately — wet enough that the experts have recommended that the US Drought Monitor put most of the region in the "moderate drought" category. The southwest corner of the state had previously been in the "extreme drought" category, while much of the rest of the Western Slope had been in the "severe drought" category. Between Aug. 18 and Sept. 16, most of western Colorado has received at least 150% of average levels of precipitation for this period.
Going into the fall with nice, moist soils means that more of next year's snowmelt is likely to run off and help refill reservoirs, instead of being absorbed into the ground. Those reservoirs still need filling. As of Sept. 16, Lake Powell was only 45% full, and Blue Mesa Reservoir, Colorado's largest, was just 41% full.
For more information:
• The Colorado Climate Center is compiling data on the big storm: http://ccc.atmos.colostate.edu/.
• This Denver Post article gives a good review of the impact of the storm on Front Range drought conditions: http://www.denverpost.com/environment/ci_24108534/colorados-flooding-rains-wash-away-drought-worries-some.
• The National Integrated Drought Information System posts weekly updates on drought conditions in the Upper Colorado River Basin and the rest of the state of Colorado at http://climate.colostate.edu/~drought/.
• The "Climate Dashboard" maintained by Western Water Assessment maintains a host of climate data, much of it updated daily, at http://wwa.colorado.edu/climate/dashboard.html.
Water Lines is a series of articles coordinated by the Water Center at Colorado Mesa University in cooperation with the Colorado and Gunnison Basin Roundtables to raise awareness about water needs, uses and policies in our region. To learn more about the basin roundtables and statewide water planning, and to let the roundtables know what you think, go to http://www.coloradomesa.edu/WaterCenter.
Hannah Holm is coordinator of the Water Center at Colorado Mesa University.