Earlier this week, KPCC learned Southern California’s largest water importer, the Metropolitan Water District, was considering more than doubling its investment in a plan to reconfigure how supplies are diverted from one of the region’s most important sources of water: the Sacramento-San Joaquin River Delta just east of San Francisco. Three MWD board members have floated the idea of spending an additional $6 billion to revive a plan to build two giant tunnels under the delta.