Southern California’s powerful water supplier has completed the $175-million purchase of five islands in the heart of the Sacramento-San Joaquin River Delta, the ecologically sensitive region that’s a key source of water for the Southland.

The top attorney for the Metropolitan Water District said in a memo Monday that the agency had finalized the purchase of the islands from Delta Wetlands Properties. The purchase comes less than a week after the state Supreme Court lifted an order that had barred the water agency from buying the islands.