6. the primary cause of wet winters in southern california is
Climate of Los Angeles The winter wet season normally runs from November through early May. Precipitation episodes in Los Angeles, with a few notable exceptions, are largely caused by extratropical disturbances approaching California from the west or northwest during the winter season. The normal seasonal rainfall measured at downtown Los Angeles is 14.77 inches, of which 92% falls between November 1st and April 30th. [1] While there is a great increase in rainfall in the winter months, the winter months in the Los Angeles are still frequently sunny and pleasant with mild temperatures. The average highs range from the upper 60's F to 70 F (17-21 C) with cooler overnight lows in the upper 40's and lower 50's F (8-12 C).
Water in California Water use in California is divided into approximately 51% for environmental uses, 39% agricultural use and 11% urban uses, though that varies considerably between regions and between wet and dry years.[21] Solely relying on these statewide volumes is controversial because they don't consider the fact that most of the volume of water used for environmental purposes includes flows down Wild and Scenic Rivers in the North Coast where there is no practical way to recover it for either agricultural or urban use because it lacks many connections to the statewide water supply system.[22] It also doesn't factor in the amount of water required to keep salty water from the Pacific Ocean from intruding into the Delta beyond a certain small concentration.[22] Otherwise, "reduced water quality resulting from large amounts of salt water drawn into the Delta could shut down the export pumps that supply fresh water to agriculture and cities."[23][24]