A local water district is proposing an ambitious plan to turn ocean water into drinking water, and while the idea of a “Blue Water Farm” sounds promising, some environmental groups say that ocean desalination should be a last resort and that more can be done to conserve water in affluent communities.   Over the last two years, customers of the Las Virgenes Municipal Water District (LVMWD) have seen restrictions and fines over how much water they use. [District communications manager Mike] McNutt added that the water district is exploring new ways to keep lawns lush and green in big-money neighborhoods like Calabasas, Westlake Village and Hidden Hills. … Officials are hoping that they can bring in precisely 10 million gallons of fresh water a day to the district.