Click the link to read the article on the Aspen Daily News website (Austin Corona). Here’s an excerpt:
July 28, 2024
Two prominent water researchers and the state of Colorado disagree on the significance of new water use data published by the federal government in June. The state claims the data confirms its argument that headwaters states use less Colorado River water during dry years. Meanwhile, former Colorado River Water Conservation District general manager Eric Kuhn and Utah State University professor Jack Schmidt say the data paints a more complex picture.
“Reclamation has worked extremely hard to bring the best cutting-edge science they can to a better and more accurate estimate of agricultural water use,” Schmidt said. “It’s just that the relationships that arise from better data are just as murky.”
The June data details the “consumptive” water use by “Upper Basin” states (Colorado, New Mexico, Utah and Wyoming) since 1971. It is meant to quantify all the water those four states have consumed in that period (see footnote * at story’s end). The Bureau of Reclamation, the federal agency that manages most of the large dams on the Colorado River, has updated the data in five-year reports since 1971, but June’s report is different. This time, the bureau collected the data using a new methodology. The results are notable — past data seemed to indicate that Colorado and other Upper Basin states used more Colorado River water during dry years, directly contradicting Colorado’s arguments about its use. According to the state, the new data corrects that inconsistency. This conclusion could be vitally important for Upper Basin states. The relationship between the Upper Basin’s water use and the natural water supply is a central component of its position in interstate negotiations over the river…
Located at the river’s headwaters, Colorado and other Upper Basin states argue that they already take “natural” water cuts in dry years. Without a large upstream reservoir to fall back on, these states say they rely heavily on yearly precipitation for their water supply, meaning drought years are already tough…The argument foundered on the fact that the reclamation bureau’s consumptive use data didn’t support it. In 2022, three notable water researchers — Kuhn, Schmidt and University of New Mexico professor John Fleck — published a blog post laying out the disconnect between the federal government’s numbers and Colorado’s claims. In their piece, the three researchers wrote that while certain parts of the Upper Basin certainly cut their use in dry years, the basin’s overall use did not reflect that anecdotal reality…
*** One way for the Upper Basin states to make their case stronger is to change the way the Bureau of Reclamation accounts for consumptive use in transmountain diversions, or TMDs — the tunnels that carry water from inside the Colorado River Basin to cities and farms outside the basin (there are two that take water out of the Roaring Fork watershed and send it to the Front Range). There is a gray area in which the actual “consumption” takes place for TMDs that have storage reservoirs at their intakes. Colorado and Upper Basin states would like to say consumption occurs when they take water from the river system and put it in the reservoirs while the reclamation bureau currently sees consumption occurring when the water leaves the reservoir and enters the tunnel. Using the Upper Basin states’ preferred method, the basin’s consumptive use changes to 4.5 million acre-feet in wet years, 4.1 in average years and 3.9 in dry years, making a much stronger case for the argument that the basin uses less in dry years.