Weather Watch

How drought affects the health of Morro Bay Estuary

A Morro Bay National Estuary Program staff member uses a GPS unit to find transplanted eelgrass. Staff members monitor areas where eelgrass was re-planted to determine survival rates.
A Morro Bay National Estuary Program staff member uses a GPS unit to find transplanted eelgrass. Staff members monitor areas where eelgrass was re-planted to determine survival rates.

The last year the Central Coast received above-average rainfall was way back in 2010.

Since then, San Luis Obispo County, as well as other Central and Southern California counties, has been mired in a six-year drought.

The most recent rain so far this year in San Luis Obispo County was April 22, when a storm near the San Juan Islands drove a cold front through our area and produced one-tenth of an inch of precious precipitation at Diablo Canyon Power Plant’s rain gauge. As of Sunday, that’s 164 straight days without a drop, except for periods of night and morning mist and drizzle.

Of course, the drought’s effects upon the land are substantial — vast numbers of trees are either severely stressed or dead, wildfires spread explosively, water tables are dropping and Central Coast lakes and reservoirs are well below capacity. Lake San Antonio is at a mere 7 percent of capacity, Lake Nacimiento is at 26 percent, Whale Rock is at 32 percent, Santa Margarita (Salinas) is at 10 percent and Lopez Lake at 24 percent capacity. Unfortunately, a warming ocean and atmosphere will continue to exacerbate these conditions.

But what effect does the drought have on the coastal waters and, specifically, Morro Bay Estuary, where freshwater from local streams and creeks meets saltwater from the Pacific?

For me, it’s fascinating how quickly Morro Bay changes from a brimming body of water during high tide to silvery mud flats at low tide. The Central Coast usually experiences two flood and ebb tides per day as the seawater flows in and out of the estuary.

Rain can have a dramatic effect on the estuary. In mid-December 2006, for instance, more than 8 inches of rain fell in just four days. Despite 6-foot-plus high tides, the water flowed continuously out to sea through the bay’s mouth, according to a current meter installed inside the bay’s entrance. That meant much less salty ocean water flowed in, and the salinity level dropped significantly.

That condition hasn’t happened in years.

Conversely, drought also plays a major role in the health of the Morro Bay Estuary and watershed, said Lexie Bell, executive director of Morro Bay National Estuary Program. Her nonprofit organization works with Cal Poly, community volunteers, landowners and local, state and federal agencies to protect and restore the health of Morro Bay.

“Some effects are challenging; less water in the creeks for steelhead,” she said. “Also, the lesser amount of freshwater input to the bay may be one factor that affects eelgrass growth. However, some effects are positive; a reduced amount of runoff to the bay means lower bacteria levels for oyster farmers.”

The loss of eelgrass is problematic in the estuary.

“Eelgrass warrants strong protection because of the important biological, physical and economic values it provides. Eelgrass functions as important nursery grounds and foraging areas for many aquatic species,” Bell said.

According to Scott Kimura of Tenera Environmental, not only is eelgrass important for aquatic life, but Morro Bay is an important stop-over for migratory birds on the Pacific Flyway, such as the brant geese that rely on eelgrass for food.

On Thursday, Gov. Jerry Brown signed into law Senate Bill 1363, which advances the protection and restoration of eelgrass beds in California’s coastal environments. The bill was written by Central Coast state Sen. Bill Monning.

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PG&E donated $10,000 to the American Red Cross of the Pacific Coast to support Chimney Fire relief efforts.

“We are proud of our partnership with the American Red Cross and pleased to provide this contribution, which will help with relief efforts following the Chimney Fire. Many of our employees also serve as volunteers for the America Red Cross, including the Central California Region, and they are committed to giving back to the communities in which we live and serve,” said Ed Halpin, PG&E senior vice president, generation and chief nuclear officer.

John Lindsey is PG&E’s Diablo Canyon Power Plant marine meteorologist and a media relations representative. Email him at or follow him on Twitter @PGE_John.