Chandler opts into $10M Bartlett Dam study - SanTan Sun News SanTan Sun News

Chandler opts into $10M Bartlett Dam study

December 20th, 2021 development
Chandler opts into $10M Bartlett Dam study
Community
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By Ken Sain, Staff Writer

Chandler has joined nearly two dozen communities that are beginning to look at climate change’s impact on future water availability in their backyards.

“We are on the cusp of the first-ever Colorado River shortage,” said Ron Klawitter, the principal of water system projects for Salt River Project. “We need to look at alternative supplies.”

City Council voted to join a $10 million, four-year study looking at increasing the water capacity at Bartlett Lake, which is on the Verde River north of Phoenix. Half of the cost of the study would be paid for with federal funds while the balance will be split between 21 entities if everyone agrees to participate.

Chandler’s cost for a seat at the table is $100,000 a year.

“There’s an old saying, if you’re not at the dinner table, you’re usually dinner,” Councilmember Matt Orlando said. “So let’s make sure we’re not dinner.”

The Salt River Project, founded in 1903, operates six dams on the Salt and Verde rivers, making up the Salt and Verde Reservoir System with a combined storage capacity of about approximately 2.3 million acre-feet of water. An acre food equals about 326,000 gallons of water.

One of those dams is the Horseshoe Dam on the Verde River northeast of Phoenix, an earthen structure about 58 miles northeast of Phoenix that is 202 feet high and has a reservoir capacity of 131,500 acre-feet.

Klawitter said there are two issues at play in considering this study.

The first is that sediment has built up behind Horseshoe Dam, robbing it of about a third of its capacity. The second is the rising threat of climate change.

“Climate change is a critical component to what we’re planning on,” he said. “Droughts and flood periods are going to increase and we have to prepare for that.”

In previous studies, SRP and the federal Bureau of Reclamation decided the best solution was to raise the height of Bartlett Dam – about 10 miles south of Horseshoe Dam – thereby increasing the capacity of that reservoir. SRP could then continue using Horseshoe Dam to manage the sediment.

Other solutions Klawitter said were looked at but dismissed included: forest restoration to keep sediment from getting into the river; building a new dam; and removing sediment from behind Horseshoe Dam.

“Horseshoe Dam was built as part of the war-time effort,” Klawitter said. “It was built safely, but quickly. The goal was to keep mining copper for the war. It’s very effective capturing water, but, unfortunately, also sediment.”

Klawitter said dredging behind Horseshoe Dam would cost $1 billion and would only be a temporary fix, calling it a band-aid.

There are two proposals for raising Bartlett Dam’s height – one by 62 feet, which would expand the capacity by 100,000 acre-feet; or raising it by 97 feet and expanding capacity by 300,000 acre-feet.

Raising it 62 feet would basically replace the lost capacity behind Horseshoe Dam. Going to 97 feet would increase total supply to deal with future water needs. Also, raising it that much would fill the canyons between Horseshoe and Bartlett dams completely, creating one giant reservoir.

The study would look at the environmental and financial implications of both options.

Asked why it will cost millions, Klawitter said the study is very detailed technically and includes engineering, detailed design, and cost estimates of each alternative, as well as an analysis of both options’ environmental effects.

He said the cost also reflects the level of detail and effort that will go into the study, including public engagement and input, so SRP can fully vet the options before making a recommendation to the federal government.

He said SRP and Phoenix have agreed to pay a larger share than their partners because of an existing stake in the Verde reservoir system.

Klawitter said to sediment from continuing to build, SRP could try to flush it out during floods when it needs release a lot of water. That would also increase capacity.

He said the Valley tends to go through 25-year cycles and is nearing the end of a dry cycle. He said older Valley residents will recall 100-year and 500-year floods happening often in their youth and that that cycle is coming soon.

By increasing capacity, SRP would be able to hold on to more of that water than simply releasing it it.

“We will be hotter and dryer in general,” Klawitter said. “We suspect to see under climate change … the Salt and Verde watershed will look similar. What we want to do is to capture those big flood events.”

Chandler officials said they want to have a role in deciding how to divide any additional water supply that may come from the project, and that’s why they agreed to be part of the study.

“This should help us manage future water shortages,” Klawitter said. “They won’t go away. We’re trying to figure out the best use of our central Arizona supply.”

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