Twenty years after Tucson Water began serving Colorado River water to its customers, the Central Arizona Project is finally making headway in the city’s suburbs.
One pipeline project is in operation, a second is under construction and a third is in final design stages — all for the purposes of bringing CAP water from the river to suburban areas north and south of Tucson.
Decades in the planning, these projects are aimed at bringing what has been seen as renewable supplies to areas long suffering from overpumping of ancient groundwater aquifers. When all are complete, they’ll reduce — although hardly eliminate — these areas’ demands on a stressed aquifer.
Water levels have dropped significantly outside the city, by as much as 80 feet in northwest-side suburban areas, for instance, even as they’ve risen by that much or more underneath Tucson since CAP went permanently online in the city in 2001.
There’s no comprehensive accounting of the well declines south of Tucson, but eight “index” wells in the region measured most years by the state show declines ranging from 13 to 92 feet over periods ranging from 15 to 22 years.
Two private water companies in the area, Community Water Company of Green Valley and Green Valley Domestic Water Improvement District, say their drinking wells’ water levels fall about 2 feet annually.
The decline has been caused by extensive groundwater pumping for the fast-growing suburbs of Oro Valley, Marana, Green Valley and Sahuarita, and by continued pumping by the pecan groves and copper mines south of Tucson.
Consequences of unbridled pumping
Authorities have warned for many years that these areas need to take CAP supplies, to avoid consequences of unbridled pumping such as subsidence — sinking and possible cracking of ground — and declining water quality due to a higher concentration of salts the further the aquifer drops.
But the cost of building pipelines and other infrastructure to deliver water to these areas, running in the tens of millions of dollars, along with a severe economic slump in the late 2000s and early 2010s, kept the projects on hold for a prolonged period.
Now, ironically, these projects are online or getting near that stage just as CAP appears very likely to see its first shortages in deliveries through its $4 billion system of canals and pipelines. Drought and climate change are dropping the water levels in the Colorado River and its reservoirs.
The first round of cuts, slated for 2022, won’t affect CAP deliveries to cities and suburbs; they’ll be felt mostly by Pinal County farmers. It could be three to five years or longer before Tucson-area, municipal and industrial water users will swallow cuts.
But the prospect of such cuts raises questions about how long suburban water users will have access to renewable supplies, to avoid returning to heavy pumping.
Details of the new pipelines:
The Sahuarita-Green Valley area’s pecan groves, long one of the most prolific groundwater pumpers in the Tucson metro area, started taking CAP last September following construction of a $17.1 million pipeline from the project’s terminus at Pima Mine Road and Interstate 19. Freeport McMoRan, which runs the neighboring Sierrita Mine, paid $11.2 million toward construction. Farmers Investment Co., which owns and operates the groves, paid the rest.
A pipeline costing more than $30 million to bring CAP water to Green Valley customers and for use by the proposed Rosemont Mine has been under construction off and on since the middle 2000s. Arturo Gabaldon, president of Community Water Company of Green Valley, predicts the pipeline will be finished and delivering water by 2023. Hudbay Minerals Inc., which would build the mine if it’s approved, is paying for the pipeline.
A $43 million pipeline bringing CAP water to Oro Valley, Marana and Metropolitan Water will start construction next year and start delivering substantial amounts of water by 2023 as well, utility officials say.
In addition, Oro Valley has since 2012 already taken one-fourth of its CAP supplies into the town through Tucson Water’s pipelines and reservoirs — a process known as “wheeling.” The private Vail Water Co. and the Pascua Yaqui Tribe also get their CAP water through Tucson Water’s infrastructure, and for Vail, that has virtually halted its groundwater use.
CAP waters 43% of pecan groves
The pecan groves’ underground pipeline, 36 inches in diameter, starts at the end of the CAP in a patch of scrub desert just west of Interstate 19.
Then it follows Pima Mine Road across the Santa Cruz River before entering the groves near that road and Old Nogales Highway. From there, the main pipeline splits into three, smaller pipelines to take water across the groves’ northern half, ending at Sahuarita Road. In all, the pipeline project covers 11.3 miles — but only 5.5 miles as the crow flies, north-south from Pima Mine Road to Sahuarita Road.
The pipeline gets about 10,000 acre-feet a year, about one-tenth as much water as all of Tucson Water’s customers use in a year, although it has capacity to serve three times that much. Freeport, whose Sierrita Mine lies just west of Green Valley, supplies about two-thirds of the pipeline’s CAP water. Tucson Water provides the rest.
CAP water replaces about 43% of the groves’ total water use, and covers more than one-third of the company’s 4,500 acres of pecan fields. The groves stretch south along the Santa Cruz River to Canoa Ranch, south of Green Valley.
FICO intends to ultimately extend the pipeline another 3 miles south, to the southern end of its Sahuarita Farm, but has no timeline for that work. But the company has no plans to extend the pipeline south of that onto its second farm, Continental Farm, which ends at Canoa Ranch.
FICO’s pipeline idea surfaced publicly back in the mid-2000s as a way to take pressure off the aquifer. The company had long been criticized for its heavy groundwater pumping.
During the 2010s, it pumped about 25,000 acre feet of groundwater a year, says a report prepared by the Upper Santa Cruz Providers and Users Group, which represents all major water users in southern Pima County. That much water would serve about 100,000 typical households living in Tucson Water’s service area.
The pipeline was delayed for some years in part due to the Great Recession of 2007 through 2009, “when most things came to a standstill in this area until 2011 to 2012,” said Tim Campbell, FICO’s land resource director. Getting permits to build the line took more time, he said.
“We probably have 11 or 12 government agencies we had to have approval from,” he said. “We had to secure easements, cross Tohono O’odham land, cross (Arizona Department of Transportation) right of way. We had to deal with the Federal Highway Administration, the CAP, the Bureau of Reclamation and EPA.”
Construction began in 2016, but most of the construction work occurred between 2018 and 2020, Campbell said.
“It’s just a slow process. I would describe it as just plodding. You just need to stay at it and not let the time frame discourage you. It’s just perseverance,” Campbell said.
Over time, having the pipeline will save the company money, because less pumping means lower electricity costs, said Campbell and Rich Walden, FICO’s Sahuarita-area farm manager.
Wells under the groves range from 800 to almost 2,000 feet deep. In theory, at least, the pipeline also will extend the farm’s life, Campbell added.
“That this water is not pumped out of this aquifer means the aquifer is not being depleted,” he said. “If you need to rely on it in the future, it is helpful.”
Recharging offsets pumping elsewhere
Community Water Co. of Green Valley’s pipeline will be the same size as FICO’s: 36 inches in diameter.
But it will move much less water, at least in its early years of operation. It will deliver all of Community Water’s 2,857 acre- feet a year CAP allocation and 5,000 to 6,000 acre-feet for Hudbay Minerals. Those two uses will fill almost one-fourth of the pipeline’s capacity of 28,000 acre-feet per year.
Also unlike the FICO pipeline, the Community Water Co. pipeline won’t send CAP water directly to its customers.
The pipeline will travel first east along Pima Mine Road from the CAP terminus, then head 6 miles south along Nogales Highway and then Old Nogales Highway to the Sahuarita area.
There, Community Water, and Hudbay Minerals if Rosemont ever starts operating, will deposit CAP water into a recharge basin lying about a mile east of Community Water’s service area, whose eastern boundary is the Santa Cruz River.
The water company has had a 99-year lease on 72 acres of state land for recharge since 2018. Community Water and Hudbay will recharge CAP water to compensate for the impacts of pumping groundwater elsewhere.
Gabaldon has pushed to bring renewable water into southern Pima County since 1977. In a 2015 news release promoting the pipeline, Community Water said well levels had dropped by as much as 150 feet in the last 50 years due to the increased demand that residents and businesses are placing on the aquifer.
But the pipeline has been built in fits and starts, with small segments being added to coincide with other construction projects. In 2012, for instance, the water company laid the pipeline into the base of a new Sahuarita Road crossing over the Santa Cruz River.
Other segments were added in 2015 and 2016 on Pima Mine Road, over and under the Santa Cruz River and Interstate 19, respectively. More segments were finished in 2018, 2019 and 2020. But construction on the bulk of the pipeline south of Pima Mine Road was delayed, for COVID-related and economic reasons, but Gabaldon said he expects it to resume later this year.
The delays for the Rosemont Mine caused by its prolonged environmental reviews and a 2019 federal court ruling haven’t affected pipeline construction, said Gabaldon. Whenever Hudbay has been asked for construction money, it’s always come through with it, he said.
Once the pipeline is built, the water company’s customers’ use of CAP water should end the 2-foot-per-year water level decline Gabaldon says the company’s four wells are experiencing. Their water levels range from 200 to 300 feet deep. The utility serves 13,000 homes and businesses.
Groundwater deficit won’t end
But Gabaldon is the first to admit that his company’s and FICO’s pipelines won’t end the chronic groundwater deficit in southern Pima County anytime soon.
The CAP water brought in by FICO and Community Water by next year will eliminate barely one-third of the overall area’s estimated overdraft of 36,000 acre-feet a year. The figure was most recently cited in a 2013 paper done by the Upper Santa Cruz Providers and Users Group.
If FICO extends its pipeline to all of Sahuarita Farm, the two pipelines together will bring in enough CAP water to reduce the overdraft by more than half the total. When and if the Rosemont Mine starts recharging water there, that will compensate for the mine’s new pumping elsewhere but won’t reduce the overdraft.
“I think you need to talk to some of the big users. Talk to Freeport and FICO. They use the majority of the water,” Gabaldon said when asked about the overdraft. “We are pipsqueak water users.”
In the past, Gabaldon talked often of trying to get more water users in that area to sign up for CAP water from the pipeline. So far, he’s had no takers.
Another CAP rights-holder in the area, the neighboring Green Valley Domestic Water Improvement District, once considered putting CAP water for which it has legal rights into the pipeline, but long ago put the idea on a back burner.
“We have no physical means to get the water to us. It would be more than 2 miles from our boundaries. It doesn’t do us all that much good,” said Dara Duffy, manager of the Green Valley water district and president of the water users group. “I wouldn’t say we’ll never take it. It’s just at the point right now where construction of the pipeline is cost prohibitive, and we’re not forced to take our CAP water.
“If that changes, if we decide we really need to use our CAP, if we start having issues with our wells, we’ll just have to do it,” Duffy said.
Northwest pipeline plan
Recharge of CAP water is nothing new on the Tucson area’s northwest side, but once the new pipeline there goes online in 2023, the entire system of getting water to the area’s customers will change.
Then, the northwest side’s CAP system will closely resemble how Tucson Water has used Colorado River water for two decades: Recharging it into the aquifer, pumping it out and shipping it via pipeline to customers.
For at least two decades, Metro Water, Marana and Oro Valley have deposited some or much of their CAP water supplies into large recharge basins, where it seeps into the aquifer. The new Northwest Recharge, Recovery and Delivery System will bring the water to homes and businesses for the first time.
Today, Metro Water also gives a large portion of its CAP supply, close to three-fourths annually, to neighboring farms to be spread on cropland as a substitute for nonrenewable groundwater.
It’s also leaving behind in Lake Mead about one-fourth of its CAP supply until 2026, to give the project more water to ease impacts of future shortages on other users.
Oro Valley also stores some of its CAP water on farmland, as does Marana.
For the new system, authorities have already drilled three wells within a mile of the recharge basins, from which the two towns and Metro Water will pump CAP from the aquifer. The pipeline will run 13 miles to a reservoir near Shannon and Overton roads in Metro Water’s service area. Along the way, separate pipelines will divert water to Marana and Oro Valley.
Metro Water will deliver 4,000 acre-feet, or about 30% of its annual CAP supplies, to homes and businesses. The rest of its CAP supply will continue to be deposited into recharge basins or placed on farmland.
Oro Valley will start with another 1,000 acre-feet of CAP on top of what it’s already getting through Tucson Water’s system. It plans to eventually take up to 4,000 more acre-feet total, but how soon depends on how fast the town grows, said Peter Abraham, Oro Valley’s water utility director.
For both utilities, the new influx of CAP water will halt their current overpumping of the aquifer, said Abraham and Metro Water General Manager Joe Olsen. In Oro Valley, water levels are falling from 1 to 5 feet a year. In Metro Water they’re falling about 1.5 feet annually.
In Marana, the town’s water utility will also use CAP from the recharge basins. But CAP’s impact will not be as great because water level declines aren’t as large there, averaging .7 foot across the system from 2019 to 2020. Since then, well levels have been “fairly stable” on average, said Stephen Dean, the town’s deputy director.
Pumping levels unsustainable
A CAP delivery system was proposed in a U.S. Bureau of Reclamation study 21 years ago — a study that warned the region’s pumping levels were unsustainable.
By 2005, Oro Valley, Marana and Metro Water officials were saying they hoped to have it online as early as 2012. Water levels in Metro’s and Oro Valley’s wells were plunging up to 12 to 13 feet a year back then.
But the real estate bust and subsequent recession from 2007 through 2010 put plans for CAP delivery on hold for years.
Also, ”we were pretty well maxed out on our debt,” recalled former Metro Water General Manager Mark Stratton. “We had borrowed a lot of money to reconstruct our system. Had we gone out for additional bond financing it would have drastically raised the rates.”
Since the 2000s, significant water conservation in both Metro Water and Oro Valley has slashed customer demand and the rate of water level declines.
Still, Eric Holler, a retired Bureau of Reclamation official who oversaw production of the 2000 CAP northwest-side study, said recently of the suburbs, “If 20 years ago you’d been taking the water when it was available and stored it underground, put the water under your feet, you’d be in much better shape than you are now,” because that would have stanched the decline in well levels long ago.
But Holler, a Metro Water customer himself, also sees the progress on all the pipelines positively, calling it “better late than never.”