SIERRA VISTA — The continued loss of water from lack of rain and snowfall throughout the state became a national storyline as water rights claims for the declining water levels in Lake Mead and Colorado River become more difficult to manage.
Lake Mead and the Colorado River system are coming up short to meet demands for the Central Arizona Project (CAP).
According to CAP, the 336-mile canal system shuttles water for residential, business and agricultural use to central and southern Arizona is the “single, largest renewable water supply” serving some “80 percent of the state’s population.”
The state looked to underground water to fulfill obligations, but the realization is now there might not be an adequate or assured water supply in some of the state’s largest cities and agricultural areas, as has been reported in numerous local, state and national news outlets.
The Kyl Center for Water Policy at the Arizona State University (ASU) Morrison Institute released a report, “The Elusive Concept of an Assured water Supply, the Role of CAGRD and Replenishment,” compiled by Kathleen Ferris, ASU Senior Research Fellow and Sarah Porter, ASU Executive Director, in which they analyzed a decision made in 1993 to change the method of determining 100-year assured water supplies from “renewable,” CAP surface water to the non-renewable groundwater supply.
“The promise was the groundwater would be replenished with surface water acquired after the fact by the Central Arizona Groundwater Replenishment District (CAGRD),” stated the researchers.
CAGRD was authorized “to enter into agreements with member service areas seeking designations of assured water supply when sufficient groundwater was not physically available by requiring the replenishment of groundwater to be in the location where it is pumped,” according to the CAP website.
However, with water levels in the lake and river in decline, researchers noted “serious challenges for prudent water management,” due to “the unexpected popularity” of the enrollment of members in the CAGRD, the report states.
Estimates indicate nearly 400,000 “member land homes” will be enrolled in the program in just five more years. In 100 years, CAGRD’s replenishment obligations will reach “113,000 acre-feet, an amount equal to the water use combined of the yearly allocations for the cities of Mesa, Glendale and Scottsdale.” And, that does not include urban expansion anticipated for the west valleys of Maricopa County or Pinal County, they determined.
Predictions of having excess CAP water to replenish underground aquifer sources to last through 2046 have evaporated.
“Pumping groundwater at greater depths pose grave consequences,” stated Ferris and Porter. “Arizona’s assured water supply rules allow groundwater for a new subdivision to be pumped from depths of 1,000 feet below land surface in Phoenix and Tucson and from 1,100 feet below the land surface in Pinal County.”
They also determined there is a “disconnect” between location of pumping and location of replenishment if the water is not returned in the area from which it was pumped.
“The replenished water will not reduce the local geological impacts of pumping, and will do nothing the recharge the aquifers,” the continued.
There is more bad news. The assessment rate for the greater Phoenix area has increased from $154 per acre-foot to $727 per acre-foot and CAGRD’s consultants have warned of a potential “financial catastrophe” as rates continue to rise.
Suggested actionsFerris and Porter offered some possible actions the Arizona Department of Water Resources (ADWR) and state can take to address the current and coming water supply issues.
First, CAGRD and ADWR should take a “rigorous examination of how much water for replenishment is realistically available.”
Second, ADWR should decrease the depth of wells “to prevent the damage caused by draining aquifers, protect the quality and availability of groundwater for the future, and ensure against the very real possibility that in some areas groundwater may run out.”
Third, CAGRD must replenish any underground water pumping to the area where it was taken from the ground to benefit the aquifer.
Fourth, CAGRD should “deny membership” if it “runs into trouble acquiring replenishment water” or locating areas for replenishment facilities.
Fifth, the researchers recommend CAGRD conduct a “comprehensive review of its financing mechanisms to avoid financial catastrophe and protect homeowners on CAGRD member lands from skyrocketing costs.”
This is the second in a series of stories on the water problems faced across Arizona and in Cochise County.