Bay Crossings Article

Drought’s Mixed Impact on San Francisco Bay

By 
Deb Self
From the March 2014 edition of Bay Crossings

Drought’s impact on San Francisco Bay is varied, but fish get hit the hardest.

Salmon and steelhead swim into the Bay from the ocean, then swim up rivers or creeks to spawn, depositing the eggs that become the next fish generation. Historically, despite periodic droughts, during spawning season the Bay and rivers that fed the Bay teemed with salmon.

But for years, a human-created drought has choked off the habitat these fish need. Even during wet years, so much water is being taken from the Bay’s tributary rivers that fish have great difficulty reproducing. Drought makes the problem even more severe because less water flows into those rivers. And it is even worse than that because this year, to meet the needs of cities and farms, water managers will pull out even more water from the Delta—where the rivers meet the Bay—than they would during wet years.

Drought makes the Bay saltier, and when less fresh water flows into the Delta from rivers and creeks, salt water washes farther up the Delta. Some fish, such as the Delta smelt, are adapted to the Delta’s mix of fresh and salt water, and can’t survive if the water becomes too salty. For other types of fish, however, drought causes fewer problems. This year, despite dry weather, the herring that swim in from the ocean to spawn in the salty Bay near the Golden Gate were plentiful.

On the Bay shoreline, drought could spell trouble for plants and animals. Young shoreline plants may not be able to establish themselves without rain. Shoreline plants may also produce fewer flowers, seeds and leaves. The result could be less food for insects, small birds and mice. Higher up the food chain, there may be less food for migrating hawks and other wildlife that eat smaller shoreline creatures.

Drought has a mixed effect on pollution in the Bay. There’s less runoff pollution on some days, but more on others. Runoff pollution happens when rain falls on exposed industrial areas and city streets, then washes into gutters that lead to storm drains that empty directly into the Bay. The water carries contaminants that include heavy metals, toxic chemicals, oil, pesticides and trash.

As long as rain isn’t falling, the Bay gets little or no runoff pollution. But in drought conditions, when rain does fall, more pollutants have built up, so the water that rushes into the Bay carries a higher pollution load. After a dry January, the major storm of early February washed lots of trash and other runoff pollution into the Bay, all at once. This big pollution surge endangers birds, seals and other wildlife, especially if they mistake plastic trash for food.

People are vulnerable to surges in pollution, too. It’s always a good idea for swimmers, surfers and others who come in contact with Bay water to stay out of the Bay for three days after a rain storm. But it’s even more important after a storm that follows weeks or months of dry weather.

Drought hampers Baykeeper’s work to stop runoff pollution in the Bay. When it rains, we go to the perimeters of industrial facilities to collect our own samples of runoff from the sites, and have the water tested for pollutants at a certified lab. We use the test results as evidence in our lawsuits to compel polluters to keep contaminants out of the Bay. Fewer storms mean fewer chances to collect evidence.

Some of the Bay’s natural pollution control is drought-proof. Wetlands naturally filter pollution, and the native plants in the Bay’s wetlands are well adapted to drought. They get all the water they need when the tides wash in from the Pacific. However, some wetlands plants along rivers and creeks may suffer or die back if they don’t get enough fresh water, decreasing the pollution filtering they provide.

The Bay Area could do a lot more to protect the Bay during drought. Southern California is way ahead of us in capturing rain water, storing it and reusing it to water landscaping. If Bay Area communities made better use of the rain that falls here, less drinking water would be needed for landscaping. Our drinking water supply would be more drought-proof, and less runoff pollution would wash into the Bay during storms.