Though Ventura, like most of California, is deep into a severe drought, imported water will buffer many residents against water shortages this summer and fall, local water managers said. The Calleguas Municipal Water District, which supplies roughly 75% of the county’s population — from Simi Valley to the Oxnard plain — expects no mandatory cuts this year in the amount of imported water it buys from the Metropolitan Water District of Southern California, said Dan Drugan, resources manager for the Thousand Oaks-based wholesaler.