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Published June 26, 2013
Arizona Reservoir Volumes(through 5/31/13)
Data Source(s): National Water and Climate Center
Combined storage in Lakes Mead and Powell stood at 47.9 percent of capacity as of May 31 (Figure 6), a decrease of 142,000 acre-feet from the previous month and about 10 percent lower than it was one year ago. Storage in the two reservoirs likely will remain at current levels for a couple of months, as inflow from runoff often matches reservoir releases until the late summer. Levels are then expected to decline. The most recent April–July streamflow forecast for runoff into Lake Powell is expected to be only about 42 percent of average. Elsewhere in Arizona, reservoir storage decreased in most basins. Combined storage in the Salt and Verde river basins decreased by about 37,100 acre-feet. Reservoir storage in these basins is around 90 percent of average and 61 percent of capacity, down 1 percent from last year.
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.
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