This report provides the City Council with an update on the hydrologic conditions of the Salt and Verde Rivers, which make up the Salt River Project’s (“SRP”) watershed and the Colorado River, which is the Central Arizona Project’s (“CAP”) watershed. This report also provides information on the impacts of these conditions on water supplies available to the City and an update of current water use trends in Phoenix.

THE ISSUE

Much of the Southwestern United States has been in an extended drought for about a dozen years. There have been years within this drought period where runoff has been at normal levels, or above, on the Salt, Verde, and Colorado Rivers. However, in total, the runoff over the last decade on all three of these river systems has been below normal. Fluctuations in runoff from year to year are the norm in the Southwest. Drought has eased in the Salt and Verde River watersheds but continues in the Colorado River watershed.

A disconnect often exists between drought conditions in a watershed and water supply conditions for end users, especially when storage reservoirs exist. Likewise, visual drought signs, like a “bathtub ring” in Lake Mead, often appear to be a cause for alarm, regardless of water supply data, which points to a more positive situation.

Water supply projections can also be impacted by growth and development within a watershed when the genesis of the water supplies in question is reservoirs that collect water from large watersheds. Potential growth in the watersheds of the Colorado, Salt, and Verde Rivers may have an impact on the ultimate water supply availability for the City.

Despite the uncertainties attendant to growth in source watersheds that provide the City’s water supplies, debate over the status of drought in those watersheds, and annual fluctuations in runoff, there is considerable stored water in the reservoirs on the Salt, Verde, and Colorado Rivers so full water supplies continue to be available to the City.

OTHER INFORMATION

The Salt River originates in the White Mountains and runs primarily through the White Mountain Apache Reservation, the San Carlos Apache Reservation, north of Globe, and into the east portion of Roosevelt Lake. Tonto Creek is a major tributary to the Salt River that originates in an area about 20 miles east of Payson and north of Highway 260, and then runs south through Gisela and Punkin Center into the west portion of Roosevelt Lake. The Verde River originates south of Flagstaff and Williams and runs through Cottonwood, Clarkdale, and the Verde Valley on its way to Horseshoe Lake.

The Salt River Project manages four reservoirs on the Salt River and two reservoirs on the Verde River. Roosevelt Lake, on the Salt River, is the major water storage reservoir and has a maximum capacity of 1.65 million acre-feet. The three other Salt River reservoirs, Apache Lake, Canyon Lake and Saguaro Lake have a combined capacity of 373,000 acre-feet. Total water storage capacity on the Verde River at Horseshoe Lake and Bartlett Lake is 287,000 acre-feet. The total combined reservoir capacity of SRP is 2.3 million acre-feet. On average, the Salt River produces about 40 percent and the Verde River about 60 percent of the total surface water supply of SRP.

In the fall of 2008, climate model projections predicted equal chances of having a dry or wet winter in Arizona. As the winter season progressed, wet weather did hit the State. However, a shift to dry conditions, coincident with a “La Niña” forecast for the equatorial Pacific Ocean, occurred in February and March. La Niña is a relative cooling of the sea temperatures and is strongly correlated with dry conditions in the Southwest.

Dry conditions have dominated for over a decade. In the last nine years, the Salt and Verde Rivers have produced two of the lowest runoff years in history, a significant indicator of the severity of the drought. Those two years include 2006 when the Salt and Verde Rivers produced only 121,000 acre-feet of water, and 2002 when only 102,000 acre-feet was produced, the lowest runoff ever recorded. The historical normal runoff volume is 950,000 acre-feet per year. On the positive side, the winter of 2008-2009 produced significant runoff. As a result, the SRP reservoir system is 96 percent full and has over 2.2 million acre-feet of water in storage. For the first time since Roosevelt Dam was raised, water levels rose into the dedicated flood control space. SRP, following the dictates of the Army Corps of Engineers flood control criteria, spilled over 50,000 acre-feet of water from the Salt River Reservoirs. While there was significant precipitation on the Verde River, runoff was not sufficient to fill SRP’s reservoirs there. Currently, the combined storage volume of Horseshoe and Bartlett Reservoirs on the Verde River is 78 percent full.

On the Colorado River, runoff conditions have been below normal for over a decade as well. Currently, the Colorado River reservoirs are in reasonably good shape and are 54 percent full with 31.9 million acre-feet in storage. By comparison, at this time last year the reservoirs were 52 percent full with 30.8 million acre-feet in storage. The Colorado River reservoir system is large in relation to the average flow of the river so it takes several above-average runoff years to improve reservoir storage. The current runoff projection for the time period October 1, 2008 through September 30, 2009 is 89 percent of normal, or approximately 10.7 million acre-feet.

Snow pack is 91 percent of normal for this time of the year. Projections for runoff between April and July 2008, when the snow normally melts, are for 7.5 million acre-feet, or 95 percent of normal. Similar to Arizona, early winter storms were strong on the Colorado River watershed, followed by dry conditions in February and early March. However, several late season storms in March and early April will help the runoff situation.

Variability in precipitation from year to year, and month to month is typical for the western United States. Reservoir storage is essential to even out the variability in precipitation over time. Overall, shortages on the Colorado River that could potentially impact the City are not projected to occur for several years and shortage criteria that further minimize risk to the City were adopted by the Secretary of the Interior in December 2007.

Currently, the City’s supplies are comprised of about 57 percent SRP, 33 percent Colorado River (CAP), 7 percent reclaimed water, and 3 percent groundwater. City of Phoenix customers have continued to demonstrate increasing efficiency in their use of water. Despite the growth Phoenix has encountered, the City’s overall water use has stayed relatively stable. As a result, the per capita use rate dropped from 235 gallons per capita per day (gpcd) in 1999 to 177 gpcd in 2008. Fluctuations in gpcd rates can occur because of wet or dry years in Phoenix. The running average gpcd rate from 2004 through 2008 is 196. Both of these gpcd rates are well below the Arizona Department of Water Resources’ target conservation rate for the City established in the Third Management Plan.

RECOMMENDATION

This report is for information only. No Council action is required.

CITY COUNCIL REPORT
COMMITTEE OF THE WHOLE AGENDA
TO:	David Cavazos Deputy City Manager	AGENDA DATE:		May 12, 2009
FROM:	Tom Buschatzke Water Advisor	ITEM:	2
SUBJECT:	STATUS OF PHOENIX WATER SUPPLIES

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Phoenix - All America City - 2009