Water supply projected below average for Gunnison Basin

Blue Mesa and Taylor reservoirs won’t be full

At first glance, the level of precipitation this winter and spring looks pretty solid. According to the manager’s report for the April 26 Upper Gunnison River Water Conservancy District meeting, “the Gunnison Basin received 95 percent of its normal precipitation in March and 94 percent of normal thus far for the 2010 water year beginning October 1.”

But that doesn’t translate to the same level of runoff, and according to UGRWCD general manager Frank Kugel, when we are “slightly below normal on snowpack we often end up significantly below on runoff.” Why that happens is largely unknown, as it’s not a linear relationship between the two, though Kugel said soil moisture plays a role.
In line with that precipitation-runoff equation, Kugel’s report stated the unregulated inflow into Blue Mesa Reservoir was 82 percent of average for March and the projected April-through-July info is only 74 percent. That despite precipitation levels being 94 percent of normal.
“Dust and high temperatures brought the snowpack down in a hurry,” said Kugel. The dropoff is clearly evident in the graph pictured above—the inside line represents 2010, and you can see the dramatic fall starting in early April.
The information presented in the graph is the result of averaging data from five Snotel sites in the basin, including sites on Mt. Crested Butte, Schofield Pass, Porphyry Creek, Park Cone, and Slumgullion Pass near Lake City.
 “The latest projections are that we won’t fill Taylor Reservoir and Blue Mesa,” Kugel concluded. For Taylor, Kugel projected that the maximum content will be 96,080 acre-feet or 90 percent of capacity, and the inflow forecast is 75 percent of normal. The same projections for Blue Mesa were unavailable at press time.
What are the implications of a low-water year? According to Kugel, there are concerns with the potential for downstream calls increasing if there is not sufficient water in the Aspinall Unit for the Gunnison Tunnel or for Redlands Power Canal. Both of those are senior water rights and they have priority.
According to Kugel’s report, Blue Mesa and Taylor Park Reservoirs are currently at 69 percent and 62 percent of capacity, respectively (compared to 65 percent and 60 percent last month).
For comparison, storage levels in two other prominent western reservoirs, Lake Powell and Lake Mead, dropped over the past month. They are currently at 56 percent and 44 percent of capacity, respectively.