From The Pueblo Chieftain (Chris Woodka):
A state report predicts climate change would stress Colorado’s water supplies by mid-century.
“It shows why the state water plan effort is timely,” said Alan Hamel, who represents the Arkansas River basin on the Colorado Water Conservation Board. “There’s a lot of good information that can help the state in the report.”
Warmer temperatures are projected to reduce spring snowpack, cause earlier snowmelt and increase the water use by all types of vegetation as the growing season expands, a report for the CWCB states.
“While future increases in annual natural streamflow are possible, the body of published research indicates a greater risk of decreasing streamflow, particularly in the southern half of the state,” it concludes.
The report was written by a team of climate scientists from the University of Colorado and Colorado State University, looking at historic records and future projections. It was funded by the CWCB, Western Water Assessment and the National Oceanic and Atmospheric Administration.
Annual temperature averages have heated up by 2.5 degrees Fahrenheit over the past 50 years, and the trend is expected to continue. However, there has been no longterm trend in precipitation, according to the report.
Although snowpack has been below average in all basins since 2000, no long-term trend has been detected. But runoff is occurring one to four weeks earlier because of higher spring temperatures and dust on snow.
Tree-ring research indicates that there were multiple droughts more severe than anything experienced since 1900 in Colorado.
The rise in temperature is expected by nearly all climate models to continue at the same rate or greater in Colorado through 2050, and climb even faster in the second half of the century.
There is little agreement about precipitation in climate models, except that more of it is expected to occur in the winter months and that it will melt off earlier.
The models project an increase in heat waves, droughts and wildfires.
The report suggests water planners incorporate climate change into scenarios, rather than focusing on a single trajectory of the future.
That’s already been initiated by the CWCB, which has used scenarios for variable climate and growth conditions in the state.
“Planning for longrange water supplies, it is critical to consider changes in climate,” Hamel said. “You have to have scenarios going forward. Just look at 2013 with record droughts, record fires and record floods, all in the same year. You have to plan for variability, as many of the state’s utilities are doing.”
From TheDenverChannel.com (Phil Tenser, Mike Nelson):
“Climate Change in Colorado,” the report issued Tuesday and led by a University of Colorado researcher, is based on compiled climate science. It focuses on current observed trends and forecasts for the mid-21st century.
Over the past 30 years, average temperatures in Colorado have increased by 2 degrees Fahrenheit, the report finds. That is the same amount by which North America has warmed over the same period.
“These global changes have been attributed mainly to anthropogenic (human-caused) influences, primarily the increase in greenhouse gases in the atmosphere to the highest levels in at least 800,000 years,” the report’s executive summary says.
While it says that warming in Colorado is “plausibly linked to anthropogenic influences,” it says recent variability in annual precipitation here “has not exhibited trends that might be attributed” to humans. The next paragraph, however, states human influences may have increased the severity of the drought in the western United States.
“Drought is not just a matter of precipitation, the amount of evaporation is just as important. Even if the total annual precipitation were to remain the same, a warmer Colorado will experience more drought due to the increase in evaporation,” 7NEWS Chief Meteorologist Nelson said…
The report says, “The uncertainty in projections of precipitation and streamflow for Colorado should not be construed as a ‘no change’ scenario, but instead as a broadening of the range of possible futures, some of which would present serious challenges to the state’s water systems.”
According to the report, these observations and predictions could influence reservoir operations including flood control and water storage. Changes in the timing and volume of runoff may also “complicate” future water rights issues and interstate water compacts. Lower streamflows could also lead to higher concentrations of pollutants.
Earlier peak flows could have impacts on aquatic ecosystems and rafting or fishing industries, while reduced snowpack may also impact Colorado mountain tourism.
Every climate model assessed in the report indicates future warming will increase average annual temperatures by 2.5 to 5 degrees Fahrenheit by 2050 if greenhouse gas emissions are in the lower range of estimates. If emissions are in a higher range, the increase could be 3.5 to 6.5 degrees.
“We will still have cold winters and cool summers, but as the global climate warms, these cooler trends will become less frequent in the coming decades,” Nelson said.
“Climate model projections show less agreement regarding future precipitation change for Colorado,” the report states. Most predict additional precipitation by 2050 during the winters, but there is weaker consensus in the projections for the other seasons.
Hydropower facilities or power plants that need water for cooling could also be impacted, it says.
“Water truly is liquid gold in Colorado, the long term trend toward a warmer and drier climate is something we will need to plan for in the future,” Nelson said.
More CWCB coverage here.