Last December, the Bureau of Reclamation released the final draft of a very detailed Colorado River Basin supply and demand study. This column, like most media coverage of the study, focused on the big picture it paints:
We're already using more water than rain and snow bring into the basin each year (reservoirs will let you do that, for a while), and the situation is likely to get worse as demands continue to grow and supplies are quite likely to shrink.
A wide range of options for how to fix the imbalance was also studied —the option of piping water from the Missouri River across Kansas to Denver got a lot of press, even as officials downplayed it as a plausible project.
In late February, at the Colorado Water Congress annual convention in Denver, water providers and stakeholders from around the state had the opportunity to hear presentations and commentary on some of the study's finer points and limitations. Here are a few of the key messages that came through in that discussion.
The lower basin is already in a pickle
Lower basin water users, those that pull water from the Colorado River downstream from Lake Powell, are already using more water each year than they have a right to expect under the terms of the 1922 compact that divided the river between upstream and downstream users.
That's because the upper basin states, including Colorado, have grown more slowly than California and Arizona, and have consequently allowed more water to flow downstream than is legally required. That's why there's still a debate in Colorado about how much more water can be taken out of the Colorado up here, despite the fact that basin-wide, uses are already exceeding supplies.
Environmental and recreational flows are very vulnerable
The study included modeling different supply and demand scenarios and management actions to see how they would affect the likelihood of hitting key indicators of shortages, both for human water users (levels in Lake Mead, for example) and the environment (low flows at key points). Projecting out toward 2060, the models indicate increasing numbers of years when fish are likely to be in trouble. Some of the management tools appear to have promise for reducing this vulnerability, but no actions would eliminate it. The study also showed that flows too low for enjoyable (and profitable) whitewater recreation were also likely to become more frequent.
The median of a bunch of model runs does not equal
Several panelists made the point that climate change models, downscaled to fit the Colorado Basin, produce many different projections of water supply. The median of all the outputs shows water inflows to the basin reduced by 9 percent by 2060, but that doesn't mean that this is what will actually happen.
Depending on what happens in the atmosphere and which of the models turns out to be most accurate, it could be either a lot wetter than that or a lot drier. Even if we do get a 9 percent reduction in water inflows into the basin, how we experience that could be very different depending on a mix of wet and dry years along the way. In the middle of a seven-year extreme drought, the prospect of future floods wouldn't help much.
This study is very large and complex, with lots of different variables and options to consider. You can review it yourself at http://www.usbr.gov/lc/region/programs/crbstudy.html and draw your own conclusions.
This is part of 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 www.coloradomesa.edu/WaterCenter.blog comments powered by Disqus