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Published June 27, 2012
Arizona Reservoir Levels(data through 5/31/12)
Data Source(s): National Water and Climate Center
Combined storage in Lakes Mead and Powell decreased by 320,000 acre-feet in May but is still about 8 percent greater than it was one year ago due to copious winter snow in 2010–2011. Currently, total reservoir storage in the Colorado River Basin is 61.4 percent of capacity. For Lake Powell, the water level elevation on May 31 was 3,637 feet; storage stood at 64 percent of capacity (Figure 6). The April–July forecast issued in June for Lake Powell calls for inflow into the lake to be about 2 million acre-feet (MAF), or 28 percent of average. This is the third driest June forecast for Lake Powell since these forecasts first were issued in 1963. The most probable (i.e., 50 percent likely to be exceeded) unregulated inflow into Lake Powell for the 2012 water year (October–September) is projected to be 5 MAF, or 46 percent of average. If this projection holds true, 2012 would rank as the third driest year since the closure of Glen Canyon Dam in 1963. The driest unregulated inflow volume into Lake Powell was in 2002, when only 2.64 MAF, or 24 percent of average, flowed into the reservoir.
Elsewhere in Arizona, storage in Lyman Reservoir is almost 20 percent lower than it was last year. Storage in the San Carlos Reservoir is at about 1 percent of capacity, reflecting low precipitation in southeastern Arizona during two consecutive La Niña winters.
The map gives a representation of current storage levels for reservoirs in Arizona. Reservoir locations are numbered within the blue circles on the map, corresponding to the reservoirs listed in the table. The cup next to each reservoir shows the current storage level (blue fill) as a percent of total capacity. Note that while the size of each cup varies with the size of the reservoir, these are representational and not to scale. Each cup also represents last year’s storage level (dotted line) and the 1971–2000 reservoir average (red line).
The table details more exactly the current capacity level (listed as a percent of maximum storage). Current and maximum storage levels are given in thousands of acre-feet for each reservoir. One acre-foot is the volume of water sufficient to cover an acre of land to a depth of 1 foot (approximately 325,851 gallons). On average, 1 acre-foot of water is enough to meet the demands of 4 people for a year. The last column of the table list an increase or decrease in storage since last month. A line indicates no change.
These data are based on reservoir reports updated monthly by the National Water and Climate Center of the U.S. Department of Agriculture’s Natural Resources Conservation Service (NRCS).
Portions of the information provided in this figure can be accessed at the NRCS website:
Southwest Climate Outlook Staff
- Michael Crimmins, UA Extension Specialist
- Stephanie Doster, Institute of the Environment Editor
- Dan Ferguson, CLIMAS Program Director
- Gregg Garfin, Founding Editor, Institute of the Environment
- Zack Guido, CLIMAS Associate Staff Scientist
- Gigi Owen, CLIMAS Assistant Staff Scientist
- Nancy J. Selover, Arizona State Climatologist
- Jessica Swetish, CLIMAS Publications Assistant
Please direct your Southwest Climate Outlook comments and suggestions to Zack Guido.
The CLIMAS Web site contains official and non-official forecasts, as well as other information. While we make every effort to verify this information, please understand that we do not warrant the accuracy of any of these materials.... Read full disclaimer