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Published April 24, 2013
Arizona Reservoir Volumes(data through 3/31/13)
Data Source(s): National Water and Climate Center
Combined storage in lakes Mead and Powell stood at 49.8 percent of capacity as of March 31 (Figure 6), a decrease of 578,000 acre-feet from the previous month and almost 10 percent less than it was one year ago. Storage in the two reservoirs will continue to decrease until late spring snowmelt begins in earnest. The April–July inflow into Lake Powell is expected to be only about 34 percent of average, which would be the fourth lowest inflow since Lake Powell became operational in 1963 and slightly more than last year’s inflow. Storage in most other Arizona reservoirs reported in Figure 6 increased in March, which is typical for this time of year, while storage in San Carlos Reservoir decreased slightly. Storage in the combined Salt and Verde basin system is at 62.6 percent of capacity, down almost 4 percent from last year. However, this is only 6 percent below average, and well within the range for robust water deliveries to the Phoenix metropolitan region.
In water-related news, the U.S. Bureau of Reclamation (BOR) projects a 65 percent chance that the water-level elevation in Lake Powell will decrease enough in the next year to lower water releases to the Lower Colorado River Basin in 2014 (Arizona Daily Star, April 16). The decreased release, called the mid-elevation release tier, would not result in shortages to Arizona cities. However, BOR states there is a 35 percent chance that the Central Arizona Project will experience a shortage by 2016.
The map gives a representation of current storage 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 (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 (dotted line) and the 1971–2000 reservoir average (red line).
The table details more exactly the current capacity (listed as a percent of maximum storage). Current and maximum storage 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
- Gregg Garfin, Founding Editor, Institute of the Environment
- Zack Guido, Managing Editor, CLIMAS Associate Staff Scientist
- Nancy J. Selover, Arizona State Climatologist
- Jessica Dollin, CLIMAS Publications Assistant
- Dave Dubious, New Mexico State Climatologist
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