Baykeeper Update

Drought’s Impact on San Francisco Bay

California is experiencing one of the driest years on record, and the state is gripped by drought. A lack of rain has major impacts on how we consume freshwater. What does it mean for water quality in the Bay?

Drought doesn’t necessarily increase or reduce pollution in the Bay, but it can change the timing and vary the intensity. Take runoff pollution, for instance. When rain falls on exposed industrial areas and city streets, it washes pollutants into gutters that lead to storm drains that empty directly into the Bay. Contaminants can 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 the pollutants build up between storms, so when rain does fall, the water that rushes into the Bay carries a higher pollution load. This big pollution surge endangers birds, seals, and other wildlife who are exposed to high levels of toxins.

People are vulnerable to surges in pollution, too. It’s always a good idea for swimmers, surfers, kiters, 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, when the pollution load is largest.

Baykeeper’s work is also being impacted by the drought, because it hampers our efforts to stop runoff pollution in the Bay. Normally in the rainy season, we spend lots of time collecting runoff from industrial facilities that we suspect are polluting the Bay. When it rains, we go to the perimeters of the facilities, collect samples of runoff, 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. This year, fewer storms have resulted in fewer chances to collect evidence.

The drought can also challenge the health of the broader Bay ecosystem. 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, that means less food for migrating hawks and other wildlife that eat smaller shoreline creatures.

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. However, some wetland plants along rivers and creeks may suffer or die back if they don’t get enough freshwater, decreasing the pollution filtering they provide.

The Bay creatures hit hardest by drought are the fish that need freshwater spawning habitat in the Bay’s tributaries. 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, during spawning season the Bay and rivers that fed the Bay teemed with salmon, despite periodic droughts.

But for years, the state’s water management system has choked off the habitat these fish need. Even during wet years, so much water is being taken from the Bay’s tributary rivers in the Sacramento-San Joaquin Delta that fish have great difficulty reproducing. Drought makes the problem even more severe, first, because less freshwater flows into those rivers. Second, to meet the needs of cities and farms in this dry year, water managers will pull out even more water from the Delta than during wet years.

Salmon and steelhead spawn not only in the large rivers that converge in the Delta, but also in creeks that flow into the Bay. Baykeeper has recently secured cleanups of industrial facilities that have been allowing toxic runoff to contaminate creeks in the South Bay, which will make the water healthier for fish that swim there to spawn. But with less rain flowing into these creeks, fish may not succeed at spawning.

For some types of fish, drought causes fewer problems. This year, despite dry weather, the herring that swam in from the ocean to spawn in the salty Bay near the Golden Gate were plentiful.

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 diverted more runoff into rain barrels and rain gardens, the volume of pollutant-laden rain water washing into the Bay would be greatly reduced. Plus, we could use this stored rain water, instead of freshwater, for needs like landscaping during dry months. With greater investment in efficient rain water use, we can both protect our freshwater supplies and help protect San Francisco Bay from pollution.