The Bureau of Reclamation has tuned up its estimates of the chances of release of extra water to help Lake Mead, now putting them at one in four this year, according to an update published today (Wed. 2/10). The jargon here is “equalization,” which happens when there is enough extra water upstream in Lake Powell to release additional water beyond the nominal 8.23 million acre feet to, in effect, “equalize” the water levels in the two giant reservoirs. From today’s Lake Powell status report:
Given the current conditions of Lake Powell and Lake Mead, it is possible, if hydrologic conditions become wetter than what is currently projected, that an April adjustment to Equalization could occur. If this adjustment were to occur in April, the projected water year release from Glen Canyon Dam could be greater than 10.5 maf. As of early February, given the hydrologic conditions within the Colorado River Basin and the range of possible inflow scenarios that could occur in 2010, Reclamation estimates that there is about a 25% probability that an April adjustment to Equalization will occur.
Last Friday’s Colorado Basin River Forecast Center update on upper basin flows showed a 400,000 acre foot drop in the median runoff forecast, but the range of possible outcomes is still large. The situation is particularly grim in the Upper Green, with flows at Green River, Utah, with a median forecast of just 65 percent of normal. That’s based on Feb. 1 snowpack measurements. Since then, snowpack in the Upper Green has continued to lag, dropping farther behind.