A heavy train is moving at 5 miles per hour toward... a cliff? A collision? And how far away might this unknown calamity be?These were the images and questions I was left with at the Upper Colorado River Basin Water Conference hosted by the Water Center at Colorado Mesa University Nov. 8-9. I deeply appreciate the fact that our presenters used such colorful language!The heavy train is our collective use of Colorado River water, and the calamity we are facing is our potential inability to balance supply and demand in an orderly way. According to a nearly complete study on Colorado River Basin water supply and demand coordinated by the US Bureau of Reclamation, we've passed the point where use of the basin's water resources exceeds the quantity provided by Mother Nature. The fact that the train wreck isn't here yet is because of big reservoirs that store water from year to year. Climate change shows no sign of helping: The mean of all the models used in the bureau study indicates higher variability from year to year and a decline in average natural flows at Lee Ferry of 9% by 2060.The story and its potential resolutions are complicated by the fact that how fast the train is moving and how far it is from calamity depend in part on where you are sitting, and in part on what the climate dishes out over the coming decades. This is where the train metaphor, and its suggestion that we are all in this together, begins to break down. Residents of the Lower Basin - the part downstream from Lee Ferry, below Lake Powell, including Arizona, Nevada and California and small parts of New Mexico and Utah - are already using more Colorado River than they are guaranteed under a 1922 compact between the Upper Basin and Lower Basin states.We residents of the Upper Basin, on the other hand, still appear to have more of our share left to develop, even as climate change and natural variability raise the specter of longer and more severe droughts in the future. As we develop more of our share, and there is less to go around, the situation downstream will get even tighter. Top water officials from Colorado, Utah and New Mexico who spoke at the conference said that while we need to help the Lower Basin states solve their water problems, the solutions most definitely do not include eating into the Upper Basin's share of the river. On that score, the Upper Basin officials were united. The Lower Basin train can wreck without us. However, under the terms of the 1922 compact, if hydrology and increased use in the Upper Basin conspire to drop flows past Lee Ferry below 7.5 million acre feet in any 10-year period, we could be required to curtail uses until those flows are restored. This, a "compact call," is the Upper Basin's own train wreck scenario. It appears to be farther off than the Lower Basin's train wreck, but it's likely enough and close enough to be taken seriously.Within Colorado, despite the fact that most senior water rights (anything pre-1922 would be immune to curtailment) are Western Slope agricultural rights, there is concern that water would "flow uphill to money," causing great disruption to Western Slope communities. While Upper Basin state officials showed a unified front in defending each others' rights to full development under the 1922 compact, signs of potential future conflict between them arose as they discussed what numbers to use to determine how much water is left to develop, and how much it is acceptable to increase the risk of a compact call in order to enjoy the benefits of additional water use. So, back to that train... The cars across the basin may not all be coupled together or going the same speed, but it does appear that we are all moving toward a point where supply and demand will collide in an unpleasant way. What can we do to avert calamity? Fortunately, the bureau's study, recent history and presentations by other conference participants do show encouraging signs that the principal players can work together to identify options. The bureau study itself is an example of cooperation among numerous stakeholders. It is subjecting numerous options for adding to supply and curtailing demand to rigorous analysis on their reliability, financial cost and environmental cost. The options include desalination, re-use, and importation of water from elsewhere. The seven basin states have also cooperated recently to coordinate reservoir operations between Lake Powell and Lake Mead, and a new proposed agreement with Mexico would allow for releases to recharge wetlands in Mexico. Work is also underway to figure out how to temporarily transfer water from farms to cities in times of drought, rather than permanently dry up farmland.As the parties continue to work together, with input from the public, we may be able to curve the tracks so our various train cars skirt the edge of the cliff, instead of going over it. Or something like that. To find out more about the study, go to http://www.usbr.gov/lc/region/programs/crbstudy.html.To find out more about the presentations given at the Upper Colorado River Basin Water Conference, go to www.coloradomesa.edu/watercenter.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 & let the roundtables know what you think, go to www.coloradomesa.edu/WaterCenter. Hannah Holm is coordinator of the Water Center at Colorado Mesa University.