Epic Water levels, why Shasta Lake filled in 2010

Shasta Dam Water Levels Schedule

Shasta Dam Water Levels Schedule

Undoubtedly, if you’ve been houseboating on any lake, you notice that the water level changes on a regular basis.  On Shasta Lake, the water level is determined by the Bureau of Relclamation via the Central Valley Water Project, a waterway that stretches four hundred miles and includes twenty dams and reservoirs between Redding and Bakersfield.  Shasta Dam is one of eleven hydropower plants in the plan and with this past year’s increased rainfall, it reached 99 percent capacity, leaving only a few feet at the top for flood control.  With potential for late season rainstorms, the project cannot allow the water level to exceed dam’s 100 percent capacity, so it is safe to say, that this year, we “topped out.”

The challenge to the Bureau of Reclamation and the California Water project is and always will be conflicting water needs.  After my conversation with Larry Ball, director of Shasta Dam, I began to understand the complexities of keeping ‘the Dam’ full and why we so often see it below ‘full pool’.

Consistency in water inflow is difficult to predict as the rainfall we have in the north state is a poor indicator of the lake level.  As the ground changes in saturation, the water may drop in levels combined with the potential for flooding, a complicated issue at best.  Transportation and evaporation of water are also large factors in water retention.  Flood control is mandated by a formula that takes into account annual timing and specific dates allowed for water elevation.  For example, on December 23rd, the height allowed on Shasta Lake is 1018.5 feet, nearly 50 feet below our capacity to allow for future rainfall and upstream water releases from other reservoirs, like the McCloud and Pit.

Shasta Lake is the largest California lake based on shoreline mileage. At full pool, Shasta Lake has 365 miles of shoreline.

Even at its lowest, Shasta Lake still retained 124 miles of shoreline

(California’s second biggest reservoir, Oroville’s capacity is 167 miles of shoreline at full pool)

Shasta Dam from the air (Courtesy of the Dept. of the Interior)

Shasta Dam from the air (Courtesy of the Dept. of the Interior)

Lake level is allowed to rise to 1037 feet by March 20th, allowing only another 2o feet of water.  The potential for flooding downstream for other areas is the reason for conservative water releases (dumping water).  Consistency in precipitation is the key.  Too much water too early in the season and poor rainfall later can keep the lake level down.  Larry Ball explains, “If we have a wet December and a wet January, but a dry February, March and April, we are going to have a hard time filling the reservoir.” He continued, “We can have good years in terms of inflow, but if we have to dump a bunch of it, it can result in not as good of storage as some years.”

Forecasting for flood control is done through the National Weather Service, but projections don’t protect from flooding if sudden storms don’t keep allow water to be released.  Because reservoirs downstream also receive rainfall, releasing water upstream to an already full reservoir could be catastrophic.  “Releases are more governed by releases downstream, in other words, there are some restrictions on how fast and how high our releases can go.”  High releases in the winter are slowly reduced during their release due to environmental demands. Only ten percent every 24 hours can be cut back to allow salmon fry to return to the main stream.

Building Shasta Dam, Shasta Lake, California

Building Shasta Dam, Shasta Lake, California (Courtesy of the Library of Congress)

Water is one of our most precious global resources, particularly throughout California.  This year, we’ve been blessed with nearly sixty-nine inches of rain on Shasta Lake, allowing us to have a wonderful summer season.  With the Water Project and Shasta Dam Bureau’s oversight, we are sure that next year will be just as magnificent.

What does a full lake mean to you?  Well, consider the amount of shoreline that is exposed with high water.  Three hundred and sixty five feet of shoreline means that houseboats can shore in near the trees, creating easy access to hiking trails and historic sites situated throughout the Shasta-Trinity Forest.  The water storage remaining on the lake also means that crops downstream (Central and Southern California) will have the water they need if and when they need it.  Don’t tell them that, they always want more water.  We love you SoCal, but please conserve; our water has to be shared far and wide.

For houseboating, a full lake is a more enjoyable experience as Shasta Lake’s beauty comes from it’s majestic mountain views and craggy outcroppings, further enhanced when the water meets the treeline. “We love the masterpiece that was created by the dam but also fear the potential for low water.”  According to Larry, this past year’s carryover of water should help next summer’s water level and make for another superb houseboating year on Shasta Lake.

Elevation when article was written (1/26/2011) : 1027.33 feet

(Elevation above sea level – Full lake elevation and dam crest is 1067)

Distance from dam crest – 39.67 feet

Facts about Shasta Dam: 602 feet high

4.27 million acre feet of water (1 foot deep by 1 acre wide)

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Water flowing down spillway tunnels on Shasta Dam 3.19.2011

Here is a picture of Shasta Dam with water flowing through spillway tunnels on March 19th.  The Bureau of Reclamation allowed releases in an attempt to get the water level down for flood control.  The water level hasn’t been this high at this time of year since 1995.