| Many people will often say agricultural uses 80% of the water. This is not the whole picture. "Nature provides about 200 million acre-feet of precipitation to California in average years. Of this total, 65% is lost through evaporation and transpiration by trees and other plants. The remaining 35% stays in the state’s system as runoff. More than 30% of this runoff flows out to the Pacific Ocean or other salt sinks. The rest is used by agricultural, urban, and environmental purposes. About 75% of the annual precipitation falls north of Sacramento, while more than 75% of the demand for water is south of the capital city. Most of the rain and snowfall occurs between October and April, while demand is highest during the hot and dry summer months" [1] While evaporation is part of the natural process, I question how much is self-inflicted by transporting / storing large volumes of water where evaporation will occur at high rates. Further, while residential may only use around 10% of the roughly 49 million square feet allocated for human use, we really should consider the evaporation costs incurred from transporting part of the base 200 million square feet down south. I have been unable to find a reliable source that measures the evaporation from the 16 aqueducts [2], let alone the 100s of reservoirs [3]. Please share if you have one. [1] - http://www.acwa.com/content/california-water-series/californ... [2] - http://en.wikipedia.org/wiki/List_of_aqueducts [3] - http://en.wikipedia.org/wiki/List_of_dams_and_reservoirs_in_... |