Salt River Project watches water, weather to deliver life-supporting supply to Valley - East Valley Tribune: News

Salt River Project watches water, weather to deliver life-supporting supply to Valley

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Posted: Wednesday, February 5, 2003 10:11 am | Updated: 1:37 pm, Thu Oct 6, 2011.

Without water, a human dies in five hours or less in the Sonoran Desert summer.

Because of that, only about 100 people lived in the Valley before the Salt River Project. Now more than 3 million live here — every one of them guzzling, washing, flushing, hosing, and swimming — where nature says they’re not supposed to.

In between death in the desert and the thirsty 3 million stand hundreds of SRP scientists, engineers, and technicians. They watch water, weather and earth over a 13,000 square-mile watershed, guided by managers more conservative than Swiss bankers.

Martini ice and Jacuzzi water begin as rainfall and snow, far from the Valley. Raindrops roll down the flanks of antelope grazing the Aubrey Plains west of Flagstaff and splash above Apache trout undulating in White Mountain streams.

Here’s how water comes from those silent, wild places to slake the thirst of a dusty collection of desert cities.

Surface water — two-thirds of SRP’s traditional supply — travels from snowy mountains in Arizona’s far northern and eastern reaches. Company helicopters outfitted with snowshoes land on wilderness ridgelines while technicians leap out and tromp onto the snow to measure precipitation.

"We watch over our watershed like a hawk," said John Sullivan, water group associate general manager.

When spring arrives and the weather heats up, snowmelt begins running south about the time the snowbirds begin their diaspora north. While they’re driving up Interstate 17, melted snow is dripping, trickling and streaming down the walls of Oak Creek Canyon, over the lip of the Mogollon Rim, through the rock halls of Hellsgate Canyon.

The water wants to go down as far as it can go. It knows exactly how to get there: Gravity drives almost all of SRP’s system except for one spot on the Highline Canal near South Mountain, where water is boosted by a pump into Ahwatukee Foothills.

Up where the Black and White rivers meet, about 10 miles southwest of Fort Apache in the White Mountains, the Salt River begins about a 40-mile trip to Roosevelt Lake. What started as an inaudible trickle under black wet rocks turns into a torrent rushing so hard rafters call the Salt River the Little Grand Canyon because of the powerful and dangerous Class IV rapids.

SRP runs the water system somewhat like a bank account. The six reservoirs filling canyons northeast of the Valley are like a checking account. Underground storage facilities and groundwater wells are like savings accounts.

Sullivan said the reservoir system, with a capacity of 2.3 million acrefeet, "is the drought protection for the Valley." An acre-foot is enough water to supply a family of four for a year, or enough water to cover an acre of ground to a depth of 1 foot.

About a week ago, the reservoirs held a little more than 618,000 acrefeet — 27 percent of what they’re capable of holding.

Compared to SRP water managers, investment bankers behave like drunken sailors.

"We take a pretty conservative approach to planning how we will operate our reservoir system," Sullivan said. "We’re always planning as if we’re either at the beginning or somewhere in a seven-year drought, which is the drought of record."

All six reservoirs feed into the Granite Reef Diversion Dam north of Mesa. It has been around since 1908, although an older wooden version was in place in the late 1800s.

"It wasn’t reliable; it kept washing out," said Paul Cherrington, water engineering and transmission manager.

Granite Reef shunts water to two canals: The Arizona Canal on the north side of the river, and the South Canal, on the south side of the river.

"That’s the beginning of the delivery system in the Valley," Sullivan said.

All the states adjoining the Colorado River are entitled to an allotment of river water. Arizona takes its full entitlement — about 2.5 million acre-feet — which is siphoned off through the Central Arizona Project Canal running hundreds of miles across the desert.

The CAP Canal meets SRP’s system at the Granite Reef dam. "We take excess Colorado River water and recharge it so we’re taking advantage of the right we have to the water," Cherrington said. "Rather than let it get wasted down the river or go to California, we put it in storage underground."

There are hundreds of reclamation projects in the West. SRP is the largest in the West to convert to serving a city rather than farms and ranches. In the 1960s about 85 percent of SRP water went to cotton, cattle, and citrus. Now about the same amount is delivered to homes and businesses.

"Every year we have a feel for how much water we’re going to have to deliver," Cherrington said. "The demand is pretty constant based on the number of people."

Water in the system belongs to the land; SRP just delivers it. In other words, if a farm is converted to a subdivision, the subdivision still gets the water.

Allocations are based on the amount of water in the system, typically 3 acre-feet per acre. The current drought is so bad that allocations were cut to 2 acre-feet per acre a month ago, the first time SRP has rationed water since 1951. SRP also can fall back on 260 groundwater wells in the Valley.

"Since we’re very low now, we’re running every well we can find and we have the additional tool of being able to bring in CAP water now," Cherrington said.

The Valley’s 131-mile long canal system literally follows contours laid down by the Hohokam Indians.

"They were amazing engineers," Sullivan said. "Their ditches were very shallow; they were very good at figuring out the contours of the lands so their entire system was obviously all gravity-fed."

The Hohokam used brush dams to divert water. They jammed sticks in the riverbed, then piled brush, hides and other material to push water into adjacent ditches and toward fields all over the Valley.

Now, every day, city water officials, farmers and neighborhoods order water. Residential customers can walk down the street to neighborhood bulletin boards to sign up for irrigation. They also can do the same on the Internet.

The orders flow into a room at SRP with an electronic map of the Valley

covering one wall. The transmission room is the nerve center of water operations, where the canals and dams are controlled and water nitrate levels monitored. People sitting at two big desks buried in computer monitors run the show.

"All of those orders are accumulated down here by our watermasters," Cherrington said. "They then divert water out of the lower reservoirs on the dams for the next day, because it takes 24 hours to get here."

Ditches are owned by homeowners, who have responsibility to take delivery of the water by getting up at odd hours to pull the friction gate that backs up the water and floods the yard. It’s the Phoenix version of Moses smiting the rock with his rod.

"For urban users, we are given a prescribed time at a certain delivery rate so we can fill our yards with water and let that water seep in and make a pretty lush lawn or water fruit trees or water your garden or whatever," Sullivan said.

"Part of the charm of the Valley is that the old areas still have the oldstyle irrigation, although I must admit by the first of August I’m pretty tired of cutting that lawn."

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