California’s biggest water supplier is hurting for cash this year as the recent record-breaking rainy winter means its customers need to buy less water.  The Metropolitan Water District of Southern California is facing a more than $300 million budget shortfall – about a quarter of its normal revenue from selling water. The agency, which provides drinking water for 19 million people including San Diego, is drawing money out of its cash reserves and taking out a $100 million loan to make up the shortfall. But long term, its leaders are talking about changing the way they charge for water, realizing that decades of conservation policies in California and diversification of water supplies with desalination and wastewater recycling means water sales will continue to drop.