California has always had an unequal distribution of water. To help remedy the problem of unequal water distribution, an extensive water system has been created to keep Southern California from drought and Northern California from flooding, provided the system works correctly. The concept of a water system lies in equaling out the water differences in the state. In Northern California the greater rainfall than in Southern California, collects in a series of reservoirs and dams. The water from these facilities then travels through a system of rivers and canals, with levees on the sides to protect against flooding.
Levees are earthen barriers that prevent lower lying land from flooding.
The water also travels through aqueducts, and pipelines. As the water travels through the system, it may be stored in reservoirs until needed for the general water supply. In theory, the water system thereby furnishes the entire state with the necessary amount of water. In Northern California, the system controls flooding that occurs from the largest percentage of the rainfall in California. The water is stored in reservoirs which are large areas to store the water.