The University of Arizona

Arizona Reservoir Volumes | CLIMAS

 SW Climate Outlook

Arizona Reservoir Volumes

(data through June 30, 2013 )
Data Source(s): National Water and Climate Center

Combined storage in lakes Mead and Powell stood at 47.6 percent of capacity as of June 30 (Figure 6), a decrease of 168,000 acre-feet from the previous month and roughly 9 percent lower than it was one year ago. Lake Powell elevation peaked in mid-June, and will continue to decline until spring 2014. Water year 2013 inflow to Lake Powell is forecasted to be 41 percent of average, which will be the second consecutive year of below-average inflow. Projected total Colorado River Basin storage for the end of water year 2013 is  45 percent of capacity.  Elsewhere in Arizona, reservoir storage declined. Combined storage in the Salt and Verde river basins decreased by about 82,300 acre-feet. Reservoir storage in these basins is around 85 percent of average and 58 percent of capacity, down 1 percent from last year.

In water-related news, Arizona senators John McCain and Jeff Flake are urging elected officials in the Verde River watershed to develop a long-term management plan that protects groundwater supplies and riparian habitat (Verde Independent, July 2). The impetus for their advocacy is a recent USGS report that shows declining groundwater levels and future river flows in the watershed.


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).