California regulators on Tuesday approved a plan to spend nearly $400 million over 10 years to slow the shrinking of the state’s largest lake, a vital migratory stop for birds and a buffer against swirling dust in farming towns. Funding for the Salton Sea is unclear but the plan enjoyed support of major water agencies and environmental advocacy groups and preserves a fragile peace among urban and rural areas in California on distributing the state’s share of Colorado River water.