Municipal Water Districts Principle Enabling Act
Water Code §71000 et seq.
Powers and Functions: Develop and sell water; promote water use efficiency; operate public recreational facilities; provide fire protection; collect and dispose trash, garbage, sewage, storm water and waste; and generate, sell and deliver hydroelectric power.
Formation: Any county or counties, or of any portions thereof, whether such portions include unincorporated territory only or incorporated territory of any city or cities; cities and unincorporated territory does not need to be contiguous.
5 Directors, elected by resident voters to 4 year terms.
Here is a link to the full details of the Water Code.