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Researchers from Stanford and the University of Calgary have transformed pulses of electrical current sent 1,000 feet underground into a picture of where seawater has infiltrated freshwater aquifers along the Monterey Bay coastline. The findings, which will be published in an upcoming issue of the Journal of Hydrology but are available online now, help explain factors controlling this phenomenon, called saltwater intrusion, and could help improve the groundwater models that local water managers use to make decisions about pumping groundwater to meet drinking or farming needs.

Long before a fractured spillway plunged Oroville Dam into the gravest crisis in its 48-year history, officials at a handful of downstream government agencies devised a plan they believed would make the dam safer: Store less water there. Sutter County, Yuba City and a regional levee-maintenance agency brought their recommendation to the Federal Energy Regulatory Commission in 2006, when FERC was considering the state’s application to relicense Oroville Dam.

Last summer it was a jarring symbol of California’s historic five-year drought. San Luis Reservoir — the vast lake along Highway 152 between Gilroy and Los Banos, the state’s fifth-largest reservoir and a key link in the water supply for millions of people and thousands of acres of Central Valley farmland — was just 10 percent full. A parched expanse of cracked mud, littered with old beer bottles and millions of tiny clam shells, San Luis was at its lowest level in 27 years.

Thousands of salmon have begun their lives not in sparkling mountain streams but in plastic trays stacked 16 high in a building. The Merced River Hatchery, near Snelling, has assisted Mother Nature since 1970. It removes eggs from adults that have returned after a few years in the Pacific Ocean, then rears the young until they are ready for their own journey to the sea. Upgrading the hatchery is part of a plan the Merced Irrigation District devised in response to a state proposal to sharply increase releases from Lake McClure.

America’s infrastructure is close to failing. That’s the assessment of the American Society of Civil Engineers, which released its 2017 “infrastructure report card” Thursday, giving the nation’s overall infrastructure a grade of D+. The report came a day after President Donald Trump held a high-profile meeting with a group of executives to discuss his campaign pledge to invest a trillion dollars to upgrade the nation’s critical infrastructure, such as highways, bridges, airports and dams.