4. San Francisco Bay Watershed


Students get an introduction to the San Francisco Bay watershed by studying a map of California. The concept of a watershed is solidified using the San Francisco Bay watershed as an example. Major geographical landmarks are identified on the map. Students then turn their hands into a portable map of the watershed. They discover how the water cycle determines the flows of water in different seasons, and therefore determines the utility of dams and reservoirs to even out the flow. In the process, students learn about the reasons the Bay is so important to California’s people, economy, and wildlife. This lesson may be extended into a history of the San Francisco Bay lesson.

Can feel a sense of place and connectedness to other parts of the state.
Can identify the major landmarks in the San Francisco Bay watershed.
Can see similarities between very large watersheds (on a statewide level) and very small ones (on a neighborhood level).

Large San Francisco Bay

Sierra Nevada Mountains
Central Valley
Sacramento River
San Joaquin River
California Delta
San Francisco Bay
Suisun Bay
San Pablo Bay
Central San Francisco Bay
South San Francisco Bay
Pacific Ocean


Attachment Size
4sfbay_watershed.doc 64 KB

4. San Francisco Bay Watershed - Logistics

20-30 minutes




  1. Physical map of California, preferably 3 dimensional (see Sources for suppliers)
  2. Removable color coding labels (available at most drug stores and office supply stores) or small Post-It Notes
  3. Optional: satellite image of the San Francisco Bay (see Sources for suppliers)
  4. Optional: map of your local watershed (see Sources for suppliers)

California shaded relief map


4. San Francisco Bay Watershed - Background


Teacher Background
The San Francisco Bay watershed covers 40% of the state of California. It provides drinking water for 2 out of 3 Californians and is the mainstay of the $18 billion dollar agricultural industry in this state. But it’s not just people who benefit. California is one of the biodiversity hotspots of the world, right alongside the Amazon River basin, Hawaii, and southeast Asia. There are large numbers of specialized habitats (like redwood forests) and endangered species who depend on the San Francisco Bay watershed for their survival. All Californians should know something about this critical aspect of their state.

Historically, the San Francisco Bay is relatively young. A million years ago (very recently in geologic time), a lake filled the Central Valley and drained out Monterey Bay. It was only 560,000 years ago that movement along the San Andreas Fault sealed off the passage through Monterey Bay and opened a new passage through San Francisco. Since then, due to the melting and refreezing of glaciers and ice sheets during the Ice Ages, at least 5 different San Francisco Bays have been known to exist. During an Ice Age, Earth’s water is primarily trapped in the mountains and polar regions as glaciers. The sea level drops up to 300 feet or more and beachfront property is miles offshore near the Farallon Islands. During inter-glacial periods, the glaciers melt, refill the oceans, and a Bay forms approximately where we find the Bay today.

My students had a very difficult time with the concept of the Ice Ages. Most held the mistaken belief that during the Ice Age, world temperatures plummeted suddenly (in a single lifetime or less) and the entire Bay was frozen as a gigantic skating rink. They believed the average temperatures on a typical October day to be around negative 20 degrees Fahrenheit. They knew there were animals but believed there were no plants that could possibly live in such cold temperatures. It took a lot of coaxing and evidence to convince them that this was not the case. In fact, the average temperatures during the Ice Ages were only 10-12 degrees less than they are now. While this does not sound like a big change, this is approximately equivalent to moving Canadian weather down to San Francisco.

San Francisco Bay History The most recent cycle started 20,000 years ago during the middle of the last Ice Age. Ice Age animals such as bison, camels, ground sloth, mastodon, and saber tooth cats roamed the area surrounded by an assortment of Mediterranean plants. Around 10,000 years ago, the large animals began dying off, the Ice Age receded, and a small spike of ocean water entered what is now San Francisco Bay. 5,000 years ago, early Native Americans settled in the Bay Area. The Bay continued to grow by several inches per year. By 2,000 years ago, the Bay had filled to near its current size.

The Gold Rush has an enormous impact on the Bay. Hydraulic mining, a mining technique in which high pressure water hoses washed away entire hillsides to reveal the gold within, washed 12 billion tons of sediment down the rivers and into the Bay. Riverbeds became shallow and caused massive flooding in the Central Valley. The Bay itself became far more shallow and is now an average of only 14 feet deep. Transportation channels must be continually dredged to permit large boats to pass. Moreover, miners used the deadly toxin mercury to help extract gold. 12 million pounds of mercury washed downstream to mix with the sediments of the Bay.

California Delta

California’s Sacramento River Delta is unusual in that it is an inverted river delta where two rivers converge and are forced through a single pass rather than a traditional river delta where a single diverges into many rivulets on its final journey to the ocean.

The soil is exceedingly rich in nutrients, which has made the delta region a rich agricultural area. However, levees built around the many delta islands have contributed towards extensive subsidence. Today, much of the delta lies below the waterline and is in danger of flooding if any of the levees should break.

San Francisco Bay Satellite Image
The San Francisco Bay is not technically a bay. It is an estuary – a partially enclosed body of water where salt water and fresh water mix. While fresh water enters from the Delta, from rain, wastewater treatment plants, and groundwater, salt water rushes in with each tide through the Golden Gate.

The Bay itself has 4 lobes. The Delta feeds into Suisun Bay which then extends into San Pablo Bay. The Central Bay then opens out to the Pacific Ocean through the Golden Gate. The South Bay drains the areas surrounding San Jose and also exits via the Central Bay to the Pacific. In a satellite image, the Bay looks like a mermaid in profile. San Pablo Bay forms her head with Suisun Bay and the California Delta as her hair stretching towards the mountains. The Central Bay forms her body with her arms in prayer (“Please help save me!”) or others claim her arms reach out through the Golden Gate to the sea. The South Bay forms her tail.

This lesson is an excellent prelude to
field trip to the San Francisco Bay Model in Sausalito or before a trip with the Marine Science Institute on their fabulous research vessel, the SS Bownlee, where students can catch and observe the Bay’s creatures up close.

Student Prerequisites
Students should know what a watershed is (see
Watersheds and Wetlands activity) and be familiar with the water cycle (see Water Cycle Stories activity).

4. San Francisco Bay Watershed - Getting Ready

Getting Ready

  1. Post maps at the front of the room.
  2. Have a sheet of color labels ready.

4. San Francisco Bay Watershed - Lesson Plan

Lesson Plan

  1. Have students look at the shaded relief map of California. Have a volunteer locate:
    • Their school
    • The tallest mountains, the Sierra Nevadas (Mount Whitney is the tallest mountain in the lower 48 states at 14,491 feet tall)
    • The San Francisco Bay
    • The state capital (Sacramento)
    • Los Angeles
    • The Pacific Ocean
    • Any other important landmarks they know from history and geography
  2. Next lead the students through the watershed by following the journey of water through the seasons, similar to what they’ve already done in Water Cycle Stories. Focus on how water gets to the Bay and the differences in water flow through the seasons. The way I did this in my classes was a “Finish My Sentences” lecture. I walked students through the watershed, pausing and holding my hand out to invite students to fill in my silences at specific times. For instance I might begin, “Ok, we all know that water can’t run uphill, it only runs __(downhill)__. So water in California will start up high in the __(mountains)__ and make its way downhill towards the __(ocean)__. Look up here at the tops of the tall Sierra Nevada Mountains. Throughout the winter they become covered in __(snow)__. When spring comes, the snow __(melts)__, and the water runs through these __(valleys)__ as rivers.”
  3. Next, have students decide whether or not a drop of rain that falls in a certain place will eventually find its way to the Bay (if it doesn’t evaporate first). Label those drops that make it to the Bay in one color and those that don’t make it in another color. For instance, have students raise their hand if the think a drop that falls in the Delta will end up in the Bay. Place a blue dot in the Delta since it will make it to the Bay. Next, ask them about a drop that falls in Los Angeles. Place a red dot there since it won’t make it to the Bay. Continue asking about various places around California until a pattern develops – any drops in or around the Central Valley will make it while any drops outside this area won’t.
  4. Point out how students have just identified the San Francisco Bay Watershed. Review the definition of a watershed and highlight the borders of the watershed with your finger on the map. Stress the idea that the watershed is land, many of my students focused exclusively on the rivers and water features. If you choose to discuss the importance of the watershed to people, the economy, and wildlife, this is a good time to do so.
  5. Show students how their hands can be turned into a model of the watershed that they can take with them wherever they go. Have students cup their hands together. Their hands should form a bowl with the pinkie-side of the palms touching and their fingers cupped outward and upward. This bowl represents the watershed. The tallest points, the fingertips, are the Sierra Nevada Mountains. The white ends of your fingernails are the snow-capped peaks. The left thumb represents the Siskiyou Mountains in the north. The right thumb represents the Tehachapi Mountains in the south. The heels your palms below your thumbs are the Coast Range Mountains. As the snow melts off your fingertips, the water runs along the valleys between your fingers as rivers. As they reach your palms, the Central Valley, they collect into 2 large rivers. The crease in your left hand is the Sacramento River while the crease in your left hand is the San Joaquin. The 2 rivers meet at the Delta and run out of the Central Valley down the place where your hands meet into the San Francisco Bay.
  6. Ask the students whether this model can be used for other watersheds besides the San Francisco Bay watershed? Do all watersheds have high places? Do all watershed collect water into rivers? Explore the possibilities of using this model to represent your local watershed with its landmarks and special features.

4. San Francisco Bay Watershed - Assessments


  1. Have students label and color line drawing maps of California. Have them label the major landmarks (see vocabulary list) and shade in all the land that is part of the San Francisco Bay Watershed.
  2. If your parents won’t go crazy with students writing on their hands, have pairs of students work together to label each other hand watershed models with a ball point pen.

Going Further

  1. Do a webquest on Save the Bay’s Bay Classroom website.
  2. Save the Bay has written an excellent map reading lesson, “Mapping your Watershed” that provides an excellent extension of the ideas covered here. Their mapping activity also leads into the From Maps to Models activity on MyScienceBox. You may download the lesson below. Teach students about the history of the Bay and make timelines to represent the major events and how they impacted the Bay.
  3. Teach students about the history of the Bay and make timelines to represent the major events and how they impacted the Bay.
  4. Visit the San Francisco Bay Model. The Army Corps of Engineers built a functioning hydraulic model of the San Francisco Bay that simulates the tides and currents. They have a marvelous visitor center and will give students a guided tour of the model.
  5. Study the California Delta in more depth. There have been many hotly debated proposals on how to fix the delta in recent months, particularly since Hurricane Katrina. The California Department of Water Resources website provides detailed information about the Delta. The Sacramento River Watershed Program provides a listing of recent news articles concerning the state of the California Delta and the Sacramento River.

Attachment Size
Mapping_Your_Watershed.pdf 78.14 KB

4. San Francisco Bay Watershed - Sources and Standards

The idea for this activity came from the “Watershed in your Hands” Lesson from Save the Bay’s watershed curriculum (downloadable below). I have also seen Mike Moran, a naturalist at Black Diamond Mines, present this lesson at a teacher workshop in much the same way as I have described here – although his presentation is far better in my estimation.

Hubbard Scientific makes exceptional relief maps for most states. The California relief map is aroun $30 and is absolutely worth the cost. Students love the tactile quality of running their fingers across the mountains and much more readily grasp the idea of topographic maps in later lessons.

The USGS Store has the best deal on maps. For around $7-10 you get gorgeous relief maps and satellite images. The California State relief map is product #43555. The San Francisco Bay satellite image is #47251. You can find a map for virtually any US geographical area.

Blank line drawing California maps for students to color and label may be printed from Net State.

There are excellent free digital satellite images that may be downloaded and printed on the USGS website.

History of the San Francisco Bay
Zpub.com has published an exceptional history of the San Francisco Bay.

Save the Bay’s Bay Classroom has a wonderful, kid-friendly Bay history section.

A gorgeous book was recently put together by the Bay Institute and the Audubon Society called San Francisco Bay: Portrait of an Estuary.

The Bay Institute also has produced an excellent report about the history of the San Francisco Bay called From the Sierra to the Sea: The Ecological History of the San Francisco Bay-Delta Watershed. The full report can be downloaded for free from the internet.

The San Francisco Estuary Project has a number of excellent fact sheets that may be downloaded and printed out.

And if these aren’t enough, go to the California Academy of Science San Francisco Bay resources list. They provide a huge list of books, videos, scientific papers, curriculum guides, and more all related to the San Francisco Bay.

Teacher Training Opportunities
I attended Save the Bay’s “Gold Rush to the Golden Gate” summer teacher training which was an extraordinary experience. We camped and canoed all along the watershed, experiencing the watershed first hand and drawing connections between the various parts of the watershed through speakers, activities, and discussions. GO! It’s amazing!

The Watershed Project offers wonderful training opportunities for teachers about the San Francisco Bay and its watershed.

Grade 6
Plate Tectonics and Earth’s Structure
Plate tectonics accounts for important features of Earth’s surface and major geologic events. As a basis for understanding this concept:
f. Students know how to explain major features of California geology (including mountains, faults, volcanoes) in terms of plate tectonics.

Shaping Earth’s Surface
Topography is reshaped by the weathering of rock and soil and by the transportation and deposition of sediment. As a basis for understanding this concept:
a. Students know water running downhill is the dominant process in shaping the landscape, including California’s landscape.
b. Students know rivers and streams are dynamic systems that erode, transport sediment, change course, and flood their banks in natural and recurring patterns.
d. Students know earthquakes, volcanic eruptions, landslides, and floods change human and wildlife habitats.

Attachment Size
Watershed_in_Your_Hands.pdf 82.38 KB