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Published January 24, 2012

Arizona Reservoir Levels

 (data through 12/31/11)
Data Source(s): National Water and Climate Center

Combined storage in Lakes Mead and Powell increased slightly, by 240,000 acre-feet, in December. As of December 31, combined storage in both lakes was about 61 percent of capacity (Figure 6), which is about 12 percent more than a year ago. While Lake Powell declined by 724,000 acre-feet, Lake Mead increased by 964,000 acre-feet. The discrepancy is because joint management of the two lakes under current conditions sends water from Lake Powell to Lake Mead. Storage in other reservoirs within Arizona’s borders reported in Figure 6 rose by about 80,000 acre-feet in December, driven primarily by increased volume in Lake Mohave and the Salt River Basin, which rose by about 80,000 and 23,000 acre-feet respectively; Lake Havasu fell by about 30,000 acre-feet. San Carlos Reservoir remains very low, at 2 percent of capacity.

In water-related news, the Arizona Department of Water Quality (ADEQ) released a draft assessment report that describes the status of surface water in Arizona in relation to state water quality standards. The report is open to public comment and can be accessed at www.azdeq.gov/environ/water/assessment/assess.html.

Arizona Reservoir levels as a percent of capacity
Notes:

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).

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