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Michael Mahoney

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Kern Valley Sun 6-5-2013


Posted: Wednesday, June 5, 2013 12:00 am

June is here, and it already feels like summer in the central valley. Rafting, fishing and swimming at the lake are just some of the ways to survive the heat. However, all those activities also require water. There’s not a lot of water right now in Isabella Lake and the Kern River. So I’d like to take a moment to clear up any confusion about how the Corps’ on-going dam safety project and associated actions are (and are not) impacting the reservoir, and how they are benefiting the safety of the hundreds of thousands of people who live and work downstream.

When deficiencies at the Isabella dams were first identified in 2006, the Corps implemented a pool restriction, reducing the amount of water that could be stored during the spring and summer months by more than one-third – from 570,000 acre feet of water down to 360,000 acre feet. The Corps implemented this restriction for one reason: safety. More than 350,000 people live and work downstream of the reservoir. If the dam were to fail when full, it’d be like a fire hydrant pouring into a bathtub, and the town of Lake Isabella, the city of Bakersfield, major rail lines, and two major highways would be overwhelmed by a massive flood wave that would leave the areas under water for a long time. If there’s a decision between safety and anything else, we’re choosing safety every time.

With that said, Isabella Lake has only reached the Corps’ pool restriction twice since 2006. The last time was 2011, but no additional releases were ordered by the Corps because normal water deliveries got the lake below the restriction within a few days. In fact, our role in maintaining Isabella Lake’s pool has been and continues to be very minimal. The Corps is only responsible for directing releases from the lake from Nov. 1 to Feb. 1 to maintain storage space for the rainy season and anticipated snowmelt. The rest of the year, downstream water users control the outflow based on irrigation demand. The Corps plays no role in those decisions.

During the winter, the Corps regulates releases from the lake following the guidance of the original water control manual, which explains how the dam will be operated. The manual states that by Nov. 1, the reservoir must be below 170,000 acre feet so that large floods can be stored - preventing flooding downstream. That’s the level regardless of the pool restriction and how much water was in the reservoir the day before. That number has not changed. It is not related to the planned construction, but to the water control manual.

While the Corps has allowed the number to be exceeded in the past, requests have not been granted since 2006. From 2007 through 2013, Isabella Lake has not had more than 170,000 acre feet of water on Nov. 1.

One time, in Dec. 2010, significant rainfall caused the reservoir to exceed the limit. The Corps did not bring the lake below the 170,000 acre feet mark at that time because it would not have been safe to immediately do so without putting further stress on already overwhelmed downstream levees. Our forecasts also showed that the reservoir could store the additional water while the high flows downstream remained.

Looking back, could the Corps have allowed additional water to stay in the lake in the fall of 2011? As the saying goes, “hindsight is 20/20.” But we don’t have the luxury of foreseeing the future. We couldn’t have known what Mother Nature would have in store for the region, and it just isn’t worth it to risk lives downstream.

Our goal, as we continue with design and construction on our Isabella Dam modification project, is to create a project that can be used without restriction. We want the businesses around the lake to thrive on the recreation the lake brings. We want the water users to be able to request and receive the water they need. Most importantly, we want Isabella dam to continue to provide flood risk reduction, irrigation and recreation benefits, as it has for more than 60 years, to the people who live and work in the region.

Today, we’re significantly closer to achieving our goals than we were this time last year, but we’re not going to sacrifice safety to get there.

Michael Mahoney
Construction Operations Division Chief
U.S. Army Corps of Engineers


Post edited by: KRVR.org Website Admin., at: 2013/06/07 12:14
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