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Officials with the National Weather Service are predicting rain toward the end of the week in the Bay Area. Rain could move into the area Thursday night and spread south from the North Bay on Friday. This is the rainy season’s first atmospheric river, which is region in the atmosphere responsible for bringing water vapor from the tropics. Weather officials said that it’s important to prepare for the rain by changing windshield wipers, checking tires, fixing leaks at home and finishing outdoor projects.

“We thought we were doing the right thing to save water,” Staci Terrace Goldfarb, a Southern California homeowner, said late last winter. “I hate looking at it.” It had been a little more than a year since Goldfarb had the small, semicircular lawn in front of her 1960 Cape Cod in the San Fernando Valley replaced with drought-tolerant landscaping. Yet her front yard was a flat patch of gravel, the kind you can buy in bulk at Home Depot. It was the work, she said, of a company called Turf Terminators.

Evidence of what scientists are calling the planet’s Sixth Mass Extinction is appearing in San Francisco Bay and its estuary, the largest on the Pacific Coast of North and South America, according to a major new study. So little water is flowing from the rivers that feed the estuary, which includes the Sacramento-San Joaquin River Delta, Suisun Marsh and the bay, that its ecosystem is collapsing, scientists who conducted the study say.

The contentious struggle to restore threatened fisheries in the San Francisco Bay-Delta and the Central Valley has focused mostly on reducing the amount of water exported from the Sacramento-San Joaquin Delta to farms and Southern California cities. That’s now changed. The State Water Resources Control Board has asked San Francisco and other communities that withdraw water from rivers that feed into the delta from the south to be part of the solution. Declaring that “the Bay-Delta is in ecological crisis,” the state water board has proposed leaving 40 percent of the natural flow of these rivers untouched.

California’s drought has helped the public see what many researchers have known for a long time: Water and energy are deeply intertwined. Kelly Twomey Sanders has been exploring this energy-water nexus in depth. She joined the Sonny Astani Department of Civil and Environmental Engineering at the University of Southern California in 2014 after having completed her PhD at the University of Texas. Sanders is working to identify the technical, market and regulatory interventions that can help reduce water-related disruptions to energy services in the context of a changing climate.