Animation of "Age of Water" in Shasta Lake for 1995

This animation sequence summarizes a 365-day simulation of Shasta Lake's hydrodynamics for calendar year 1995. Each image represents a single simulation day's output, with contours depicting the relative age of the water in a vertical slice of the reservoir along its longest dimension. River inflows are the youngest water (age zero) with all else being older.

The hydrodynamics depicted in this "movie" are largely dominated by the inflows from the Pit River, the largest tributary to Shasta. They can be seen entering the reservoir at the upper right side of the image and flowing a distance of some 40 km to the dam shown on the left side of the image. The red triangles on the dam mark the approximate locations of various outlets in the dam. For 1995, most of the water exited from the two middle outlets. The stair-step like bottom of the reservoir denotes the physical geometry seen by the hydrodynamic model (CE-QUAL- W2). However, the "fuzzy" nature of that bottom is complicated by anomalies introduced by the software that calculates the contour intervals and colors the gradient. The legend indicates the relative age of the water through time, with blue being new and orange or red being old. The date, starting January 1, will be indicated in the upper left portion of the screen image as the movie plays.

As the movie begins (ignoring the first day or two's initial conditions), inflows to the reservoir are colder than the reservoir and can be seen moving along its bottom. However, during early 1995, two large storm events caused huge inflows into Shasta resulting in extreme mixing and raising the water surface elevation substantially. About mid-March, there is a normal period of mixing as the reservoir begins to warm. Then in mid- to late April, the reservoir begins to stratify and becomes quite stable in early June. As summer proceeds, inflow volume declines and the reservoir heats further, remaining stratified through early October. During this stratified period, the inflows may be seen traversing the reservoir just below the thermocline in the metalimnion. This so-called interflow phenomenon is a well-documented occurrence caused by the inflows "seeking" their own thermal density within the reservoir. In November, as the thermal stratification dissipates, the inflows may be seen to slowly settle such that, by the end of the year, they once again travel near the reservoir's floor.

If you are interested and have the time, we recommend you run this animation three times. The first time, notice the changing water surface elevation. As previously mentioned, this will clearly show the two peak inflow events during January 9-17 and March 9-14. During this first viewing, you should also acquaint yourself with the axes, legend, etc.. On the second viewing, keep your eye on the youngest water. This will give you an idea of how long it takes inflows to reach the dam and indicate the relative temperature (and therefore density) of the inflows compared to the main body of the reservoir. On your third viewing, if you make it that far, keep your eye on the oldest water. Early in the year you will be able to see the red back eddies that indicate the plunge zone where the inflows dive to the bottom. Later in the year, you can get an idea of where the reservoir is relatively stagnant and susceptible to lower dissolved oxygen during the July through November period.

We have found this type of animation useful. Not only is it eye-catching, but it has also helped us share our modeling results with others across disciplines, taught us a few things about complex reservoir hydrodynamics, helped us identify errors in the model's input, and been an aid in model calibration.

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1 U.S. Geological Survey, Fort Collins Science Center, 2150 Centre Avenue, Bldg C, Fort Collins, CO 8052