Data Analysis

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Data Analysis
The Data Analysis section is intended to encourage students to practice describing and interpreting patterns in spatial data.

This activity contains 6 questions.

These questions require that you review the information on Water Budgets in Ch. 9 of your text. If you haven't already done this, do so.

Water budgeting is basically a bookeeping method to keep track of 1) how much water we are getting from nature (precipitation or PRECIP), 2) how much water nature is trying to take away (potential evapotranspiration or POTET), and 3) how much water is soaking into or evaporating from the soil (+/-STRGE).

Look at the sample water budget for Sacramento, CA (don't let all the numbers distract you) and answer the following questions.

For reference sake, these numbers are in millimeters and represent the average totals at the end of the particular month. Describe Sacramento's annual pattern of PRECIP and POTET. In other words, when does the rain come (there is no snow), and when are the evaporative (or drying) conditions the strongest? Look at NETWTR (this author's term only -- not widely used). This basically represents PRECIP-POTET. When is there water available (shown by a + sign) and when is water needed (shown by a - sign)?

To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.

As you scan across the months starting in September, how does STRGE (amount of water in the soil) change when NETWTR goes from being needed (-) to being available (+)? When does water tend to soak into the soil (called soil moisture recharge) and when does it tend to dry out of the soil (called soil moisture utilization)? Explain the changes in STRGE as straighforwardly as you can.

To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.

When STRGE hits 0 (i.e., when the soil drys out), what happens to DEFIC (deficit)? When STRGE hits 100 (i.e., when it is at capacity and can't hold more), what happens to SURPL (surplus or runoff)? Based on SURPL, what time of year do the local streams tend to run their highest? Explain.

To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.

By November and December, POTET decreases significantly, and PRECIP increases significantly. Yet, the creeks generally don't start flowing and there is rarely flooding. Where is the water going? Explain.

To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.

Much of California's important agricultural land in the Great Central Valley has a water budget somewhat like Sacramento's. Look at the following water budget for Donner Summit at about 7000 feet on the western slope of the Sierra Nevada Mountains and you will begin to understand when and where some of the water is coming from.

As you can begin to decipher, the major difference is that snow falls (SNWFL), accumulates, (SNWPK), and then melts (SNWMLT) at this location over the course of winter and spring. (Please note that these numbers are based on some assumptions and averages and may not always reflect reality.) Once the temperature begins climbing above freezing in April, what happens to the snowpack? How does this affect SURPL? How do you think this affects the rivers which flow from this area westward to Sacramento?

To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.

From a water resources perspective, the timing of deficits in Sacramento and the timing of surpluses in the Sierra Nevada is nearly perfect. Explain. Occasionally, warm storms from the vicinity of Hawaii have been known to move over the Sierra Nevada between January and March. This has taught dam operators in the Sierra to leave their dams fairly empty during these months. Explain.

To create paragraphs in your essay response, type <p> at the beginning of the paragraph, and </p> at the end.

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