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Published January 23, 2013
Arizona Reservoir Volumes(data through 12/31/12)
Data Source(s): National Water and Climate Center
Combined storage in Lakes Mead and Powell stood at 52.2 percent of capacity as of December 31, a slight decrease of about 250,000 acre-feet from the previous month (Figure 6) and 9 percent lower than it was one year ago. Decreases in reservoir storage during 2012 primarily were due to a La Niña event, which helped push storms north of the Upper Colorado River Basin. Storage in the San Carlos Reservoir increased by 2,000 acre-feet in December, but the reservoir continues to store only about 1 percent of capacity, or 43 percent of average. While the Verde River systems gained about 11,000 acre-feet, storage in the Salt River system dropped by about 12,000 acre-feet. Higher elevation winter snowpacks, which substantially contribute to Arizona’s water supply, are off to a good start. Precipitation in December was more than 125 percent of average in many of the higher elevation locations, and water contained in snowpacks measured at snow telemetry sites (SNOTEL) recorded above-average conditions in the Verde watershed, Mogollon Rim, Salt River Basin, and the Lower Colorado River headwaters as of January 1. The first spring streamflow forecast calls for near-average runoff in the Verde River Basin and below-average to well-below-average runoff in the Little Colorado River, Salt River, and San Francisco-Upper Gila river basins.
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
- 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.
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