Arizona's two largest water providers spilled billions of gallons of water onto dry riverbeds and flat, undeveloped desert over the past decade, enough since 1994 to fill Tempe Town Lake 600 times, the Arizona Republic reported.
Salt River Project and the Central Arizona Project spilled the water and continue to do because of water recharge, also called water banking. The process helps store long-term water supplies, allowing Arizona to collect its full share of the Colorado River, even when it doesn't use it, and shields the water from the pressures of growth or a long dry spell, according to the report.
A water-recharge project could be used as an underground storage reservoir at a time when the above-ground kind, like Roosevelt Lake or Lake Powell, are too expensive and too environmentally unpopular to build.
So far SRP has recharged about 770,000 acre-feet of mostly Colorado River water in the Granite Reef Underground Storage Project northeast of Mesa. The CAP has stored more than 400,000 acre-feet of water in five projects between Peoria and Tucson. In all, including several smaller projects, the state's water banking program has put away more then 1.8 million acre-feet. An acre-foot is 325,851 gallons, enough to serve a five-person household for one year, according to the Arizona republic.
Although Interior Secretary Gale Norton held up the recharge program as an example of good water management and urged other Western states to consider it, some of Arizona's drought-stricken neighbors grumble about the practice, suggesting it is little more than water hoarding.
"We're just storing water here instead of Lake Mead, where Nevada or California could have access to it," said Bruce Hallin, manager of water business development for SRP, which opened the first water bank 10 years ago this month. "It lets Arizona use its allocation, and by storing it underground, we don't have all the evaporation."
Currently Chandler, which puts some of its SRP and CAP allocations into the Granite Reef project, is given a "credit" for the deposit. It can then pump water from one of its municipal wells without running afoul of the state's strict groundwater regulations.
"It's an economical way of utilizing all of our resources," said Doug Toy, senior engineer for Chandler's water-resources department. "It also allows us to meet our peak demands in the summertime."
Glendale has also signed on with SRP to use part of a new recharge project set to open in 2005 near the confluence of the Agua Fria and New rivers. However, the city plans to recharge effluent from its treatment plant not far from the new recharge project.
"Storing water is like putting money in the bank, and we're fortunate to be able to put water in this bank," said Doug Kukino, Glendale's environmental resources director. "This is a way to take another source and not use groundwater."
Water officials of some Western states doubt that recharging is entirely beneficial use of water, especially during a drought. Colorado officials indicated that if the Colorado River can't meet demands in future years, they might challenge the water bank and try to force Arizona to leave the water in the river. Arizona officials doubt such a challenge would stand. Other states are studying Arizona's blueprint, and both SRP and the CAP see a need for water banking to help the state manage its growth and to handle future water surpluses, according to the report.