No one knows for sure what will happen to Colorado’s water supply as climate changes.
By Lori Ozzello
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Daily headlines declare the latest discoveries and observations about global warming’s effects, from melting glaciers to changes in upland bird hunting to proposals of how to manage forests, fires and energy production in new ways. Since the 2002 drought, water managers are acutely aware that the past is no certain indicator of the future. Amid climate models, data and theories, many scientists say climate is changing and the effects may dramatically alter Colorado’s water outlook. The models present “a thousand realizations,” says Joel Smith, vice president of Stratus Consulting and
a modeling grid. Why not make the grids smaller? “If we have a grid and cut it in half, the computation goes up by a factor of eight,” Yates explained. For example, say calculations that take a day. Grids half the size would tie up a computer for eight days. To get the grids down to a better representative size, scientists would need 20 times the computing power now possible. “The models are getting better, but we still don’t know the (answers) around precipitation,” said John Roach, a Trout Unlimited aquatics specialist. “We’re pretty confident about air temperature.”
former deputy director for the EPA’s Climate Change Division. Stratus analyzes potential climate change issues. David Yates, project scientist at the National Center for Atmospheric Research in Boulder, echoes Smith’s sentiment. “No one really knows for sure,” said Yates. He consults with Colorado Springs Utilities, Denver and Aurora about their contingencies for managing their water supplies. “We don’t know. Honestly. “I’ve heard people say Lake Mead will be dry by 2025. It’s absurd.” While some data can be plugged into models, some others elude analysts. “Water vapor is very difficult to represent in the model,” says Yates. Add that to Colorado’s Rocky Mountains, wind and the limitations of computers and models, and the results are less than definitive. For instance, computer modeling study areas are divided into 150 square kilometer parcels. That’s slightly more than 37,000 acres or nearly 58 square miles. By comparison, Denver International Airport sits on 53 square miles, making it slightly smaller than one square on
The models indicate a temperature increase in the state, along with changes in precipitation. “I recognize there is something changing,” said Marc Catlin, Uncompahgre Valley Water Users’ general manager. “There’s more wind and it’s longer and harder. We’re getting a dusty wind from the desert. When it’s on the mountain, snowmelt starts two weeks early.” In the winter of ’08, Catlin said the area received more snow than it had in 15 years. As spring approached, many in the Uncompahgre Valley, including Catlin, expected flooding. Instead, the weather was hot for a week, then cooled off. The pattern repeated itself “bringing the runoff off in steps.” By June, water users were getting their full allotments, but with humidity below 10 percent and a 10 mph wind, “the wind was sucking the moisture out.” Low humidity plus heat stressed feed corn crops. More people pay attention to weather forecasts since climate change hit the mainstream media, Catlin said. More irrigators are “putting their
Colorado Foundation for Water Education