Answer:
There are two main sources of fresh water in California.
1) Groundwater: This water source is present inside the earth at a specific depth. In california this water is extracted from pumping it through machine.
2) Surface water: This water consist of lakes, rivers etc that flows from mountainous part to the lower region. In california this water is collected in dams and big reservoirs when snow is melted in the mountainous regions of the state and used when it is needed.