Colorado water planners are ahead of other states in anticipating shortfalls on the Colorado River, but realize cooperation is needed all along the river as its resources are stretched.

��� An interim report by the Bureau of Reclamation this week outlines a 50-year scenario that could mean less water supply even as demand increases because of population growth and a longer growing season.

��� The report provides scenarios compiled from various climate models. While the models differ on precipitation, all indicate there will be, on average, hotter temperatures, earlier runoff and a greater percentage of moisture from rain than snow in the next 50 years.

��� The result could mean a 10 percent reduction in supply.

��� �The report is important because you�re trying to balance higher demand against the available supply,� said Alan Hamel, executive director of the Pueblo Board of Water Works and a member of the Colorado Water Conservation Board. �Colorado is ahead of the other states that receive some of their supply from the Colorado River, but we can still garner important information out of the study.�

��� The Arkansas Basin Roundtable on Wednesday heard an update on the CWCB�s study of availability of water from the Colorado River. It is important to most of the state, because about 500,000 acre-feet of supplemental water is imported each year to the Front Range communities in the Arkansas and South Platte basins.

��� There is still frustration because so much information is available, while the changes in climate are uncertain.

��� �The more uncertainty we have, the wider the range of results,� said Matt Brown, a consultant with AECOM engineering.

���� The Colorado River basin touches seven states and drains 242,000 square miles, it is geographically diverse � just look at the mix of drought-induced wildfires and record snowpack this year. It also contains distinct climate zones over a range of 14,000 feet in elevation.

�� That may seem like a lot of territory, but long-term climate models cannot accurately reflect changes that might occur in the region. There are more than 125 climate models to choose from, and the CWCB could afford to analyze the projected impacts in only five of those, Brown explained.

��� The 1922 Colorado River Compact was negotiated among the seven states � Arizona, California, Colorado, Nevada, New Mexico, Utah and Wyoming � at a time when more water was available in the basin. At the time, it was estimated 16.4 million acre-feet annually were available from the river, but the actual number is between 13.2 million-14.3 million acre-feet annually.

��� In 2007, the states agreed on a 20-year plan to share shortages and balance storage between Lake Mead and Lake Powell.

��� Colorado officials, however, remain wary that a call on the Colorado River by downstream states could curtail water rights claimed after 1922 � including the vast majority of diversions to the Front Range.

��� Hamel and other water leaders have been involved in a water banking plan involving Blue Mesa Reservoir on the Gunnison River as a way to protect the junior rights in Colorado. Negotiations with Reclamation are still a few years away, he said.

��� In the meantime, more storage is needed on both sides of the mountains within Colorado, Hamel said.

��� �Storage becomes even more important when you talk about climate change,� Hamel said. �We will need more reservoirs to collect rain as well as snow melt, and to balance the cycles between wet and dry years.�

��� Along with other members of the roundtable, Hamel would like to see the state studies home in on how the specific needs of the Arkansas River basin would be affected by climate change. Longer growing seasons are likely in the eastern part of the state as well � although there is scant evidence of that actually happening � and water needs for agricultural use could increase.

��� �We have to balance municipal and industrial needs with agriculture while protecting the environment and recreation,� Hamel said.

�� Other municipal water suppliers also hailed Reclamation�s study of the entire basin as a step forward in meeting future needs. The Colorado River supports 30 million people, most of them living in metropolitan areas that divert water from remote locations.

�� Denver Water recently announced the Colorado River Cooperative Agreement with 35 partners on the Western Slope.

��� �That agreement achieves greater certainty for our present and future supplies,� said Jim Lochhead, CEO and manager of Denver Water. �Given the potential impacts of climate change and drought throughout the Colorado River basin, we need to work actively toward a similar collaboration for the entire Colorado River Basin.�

��� Denver and Aurora have joined Colorado River Municipal Utilities, which includes the largest water utilities in Arizona, California and Nevada.

� Collectively, they use 15 percent of the river�s water, but have issued a statement that says joint use of the river is required to fill environmental, recreational and agricultural needs.

��� �The Colorado River�s impact, not only on the state, but the entire southwest United States, is so extreme that all parties must work together to find solutions to future water shortages,� said Mark Pifher, director of Aurora Water.