They see the purchase as part of a water grab to send more water to Los Angeles through Gov. Jerry Brown’s $15.5 billion twin tunnels plan, at the expense of fish and wildlife. Either way, some 20,000 acres of island is moving toward a change of ownership that is stirring up waves in California’s water politics.

After months of negotiations, the Metropolitan Water District board authorized its general manager Tuesday to enter into a contract to buy the islands from the privately owned Delta Wetlands Properties. The deal, valued at some $200 million, is expected to wrap up soon.