Originally Published: January 11, 2015 6 a.m.
PRESCOTT - Three of the City of Prescott's projected sources of water have not lived up to the projections of six years ago.
According to a report to the Prescott City Council this week, neither the amount of surface water withdrawn from Willow and Watson Lakes, nor the amount of treated wastewater, has reached the level that city officials anticipated.
In addition, the Big Chino Water Ranch pipeline - at one time projected to be importing water from the Paulden-area Big Chino sub-basin by 2009 - is nowhere near the construction stage.
While water for Prescott's current customers comes from well fields in Chino Valley, the city projected in 2009 that its alternative sources also would generate thousands of acre-feet in water credits, which, in turn, could be allocated to future development.
Indeed, both alternative sources have resulted in significant recharge into the aquifer.
This week's water portfolio report indicated that the city withdrew and recharged an average of 1,049 acre-feet of water from Willow and Watson lakes between 2000 and 2013. (An acre foot equals 325,851 gallons of water).
That total compares, however, with a projection of 1,359 acre-feet of annual recharge from the lakes.
Leslie Graser, the city's water resource manager, noted that the amount of recharge fluctuates, depending on the area's precipitation, and the levels of the lakes. "The issue with the surface water supply is that it is seasonal in nature," she told the council.
The amount of recharged surface water over the past five years ranged from 450 acre feet in the dry year of 2012 to 2,834 in 2010.
Likewise, the recharge from treated wastewater (effluent) has failed to live up to projections. In 2009, the city expected to recharge 3,650 acre-feet of effluent per year, but actually recharged between 2,346 and 3,321 over the previous five years.
"The city's projections from much earlier years is not happening," Graser said of the effluent recharge.
Central to that, she said, is the fact that the community did not grow to the level that was anticipated in the 2000s, and therefore did not produce the expected amount of wastewater.
"I think what's important here is that the treated effluent for recharge and recovery - that was a function of the projected population," Graser said. "The world looked much different in 2003, 2004, even 2007" (before the economic downturn).
Despite the shortfall in alternative water, though, officials say the city still will be able to grow at a reasonable rate for the next two decades or more.
"The city's water portfolio contains other supplies and reservations that can be relied upon to support significant new development, despite the aforementioned shortfalls regarding physical availability," stated Graser's presentation.
Among the sources: the groundwater that was reserved in the late 1990s for subdivisions and undeveloped lots in the city (enough to serve about 7,000 homes); the alternative water reserved in 2009 for residentially zoned vacant lots (1,920 homes); and the first two increments of alternative water reserved for the Deep Well Ranch northeast of Prescott (950 acre-feet, which could serve roughly 2,850 homes).
The city also has about 314 acre-feet of alternative water available to new development, which it is recommending be split between the years of 2015, 2016, and 2017.
While acknowledging that the 100-acre-foot proposed allocation is half of the 200 acre-feet that the city had been making available in previous years, City Manager Craig McConnell maintains that the water on hand still is sufficient to provide for 20 to 25 years of growth at a level similar to that in the boom years in the early 2000s.
"There is depth in the city's water portfolio," McConnell said. "We have conservatively, responsibly managed it."
Even so, the shortfall in surface-water recharge prompted Councilman Steve Blair to question Graser and McConnell about the city's current management policies for Willow and Watson lakes.
"We bought the lakes for water storage," Blair said of the city's 1998 purchase. "They're not truly lakes; they're water storage facilities, the way I look at it."
He asked whether the city's policy of retaining enough water in the lakes to maintain a "conservation pool" (level that must be retained for recreation purposes) could be changed. "Is there a drive or a need to sidestep that conservation pool, and drain (the lakes) lower to reach a higher level in recharge?" Blair asked.
Graser responded that any changes in the conservation pool would be a policy decision of the City Council.
McConnell said a resolution regarding a water budget would go back to the City Council on Jan. 13.
Follow Cindy Barks on Twitter @Cindy_Barks
More like this story
- Prescott cuts alternative water availability by half for 2015
- 'Diminishing' alternative water causes City Council to consider halving '15 budget
- 'Turning off the flow': Prescott eyes temporarily stopping alternative water agreements
- Dwindling alternative water could force amended Prescott water policy
- Prescott suspends alternative-water requests for 90 days