A projected increase of water temperatures in the Southwest could cause a rise in the frequency and intensity of floods and droughts that would leave Southern California with water shortages in the coming decades, Loyola Marymount University researchers said Tuesday. Scientists predict that by 2050, rising temperatures will increase the amount of precipitation falling as rain rather than snow in the Sierra Nevada and Rocky Mountain ranges where the Southland imports 60 percent to 70 percent of its water supply.