what are the main uses of water in california
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.[20] 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.[21] 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.[21] 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."[22][23]
Water security The most common threat to water security is water scarcity. There can be several causes to water scarcity including low rainfall, climate change,[14] high population density, and overallocation of a water source. An example of periodic water scarcity in the United States is droughts in California. Another category of threats to water security is environmental threats.[15] These include contaminates such as biohazards (biological substances that can harm humans), climate change and natural disasters. Contaminants can enter a water source naturally through flooding. Contaminants can also be a problem if a population switches their water supply from surface water to groundwater. Natural disasters such as hurricanes, earthquakes, and wildfires can damage man-made structures such as dams and fill waterways with debris. Other threats to water security include terrorism and radiation due to a nuclear accident.[16]