Driving a car over the Golden Gate Bridge is a challenging endeavor. The lanes are narrow, cross-winds strong, and the surrounding scenery almost impossible to ignore. If you’re not mesmerized by the bridge’s soaring towers, you’ll certainly be awed by the dramatic coastline, weaving boats, and unobstructed view of San Francisco. Though I’ve probably driven on the Golden Gate at least a thousand times, I only recently began appreciating the view from an ecological perspective, rather than a purely aesthetic one.
When teaching middle school students on Save The Bay’s Restoration Education Programs, our field educators frequently compare the San Francisco Bay watershed to a bathtub, in which the channel under the Golden Gate represents the drain. The analogy is an apt one. This channel not only serves as the Bay’s sole input and output for ocean water, but is also the exit point for the entire San Francisco Bay Watershed. This watershed drains snowmelt and rain from 75,000 square miles of land, roughly 40% of the State.
Peering towards the water from the Golden Gate, ocean swells appear small, and currents almost imperceptible. Though we may not see under the surface of the Bay, the water beneath the Golden Gate is 350ft. deep—by far the deepest point in the Bay—and can move at up to 6 knots (6.9 mph). At this pace, water exits the Bay at 2.3 million cubic feet per second, about 3.8 times the outflow from the Mississippi River. Next time you find yourself cruising over the Golden Gate Bridge, take a second to recognize the tremendous energy and activity present under your car, as well as the critical role this mile-wide channel serves in defining our estuary.