Lake Mead
NPS photo
Projections incorporate updated 30-year climate normals utilized in inflow forecasts
October 25, 2021 - COLORADO RIVER BASIN - The Bureau of Reclamation has released its October 24-Month Study and 2-year projections of major reservoir levels within the Colorado River system. These projections detail hydrologic conditions and projected operations for Colorado River system reservoirs and are used by Reclamation and water users in the basin for future water management planning.
The October projections are the first to include inflow forecasts developed by the National Oceanic and Atmospheric Administration’s (NOAA) Colorado Basin River Forecast Center (CBRFC) that incorporate updated climate conditions and data sets known as the “U.S. Climate Normals.” Compared to the previous period used by the CBRFC to develop the inflow forecasts (1981-2010), the more recent 30-year period (1991-2020) eliminates the wetter hydrology experienced in the 1980s and includes most of the 22-year drought that started in 2000 (and continues to the present). NOAA updates the “Climate Normals” to a new 30-year period every 10 years, consistent with weather and forecasting offices in the U.S.
As a result of this update, the median water year 2022 inflow forecast into Lake Powell decreased by 800,000 acre-feet and Reclamation’s October projections show lower Lake Powell elevations compared to the September projections.
Lake Powell Projections
With the decrease in the inflow forecast in water year 2022, Reclamation’s October projections indicate Lake Powell’s elevation at the end of water year 2022 (Sept. 30, 2022) will be about eight feet lower than the September projections. The projections also indicate the increased potential of falling below minimum power pool, elevation 3,490 feet, in 2022. Should extremely dry hydrology continue into next year, Lake Powell could reach elevation 3,490 feet as early as July 2022.
“Incorporating the updated climate normals into the CBRFC forecasts, and, in turn, into our modeling projections, provides us with a better understanding of what is happening now and will give us a more informed assessment of potential future conditions,” said Reclamation’s Upper Colorado Basin Regional Director Wayne Pullan.
Lake Mead Projections
At Lake Mead, the October projections indicate Lake Mead will be at elevation 1,050.63 feet at the end of calendar year 2022, less than one foot above the Tier 2 shortage elevation threshold of 1,050 feet. Recent analysis indicates approximately a 16% chance of a Tier 2 shortage condition in 2023.
“We have had to make difficult choices this year, and we will all have to make more difficult decisions if it continues to remain dry next year to protect Lake Mead and Lake Powell," said Reclamation’s Lower Colorado Basin Regional Director Jacklynn Gould.
Most of the flow of the Colorado River originates in the Rocky Mountains. The Upper Basin experienced an exceptionally dry spring in 2021, with April to July runoff into Lake Powell totaling just 26% of average, despite snowpack reaching 89% of median, due to dry soil conditions and above-average temperatures.
Reclamation remains committed to reducing the collective risk of both Lake Powell and Lake Mead falling to critical elevations and will continue to work with all partners across the Colorado River Basin to ensure that both facilities continue to function as authorized to meet the natural, municipal and agricultural needs of the basin.
To view the most recent Colorado River system projections, visit Colorado River System Projections Overview (usbr.gov).
Source: USBR
