California Code, Water Code - WAT § 26604

The acceptance of the county's terms by the district as evidenced by the board's resolution shall constitute a contract between the county and the district which shall become effective on the last Friday of December next following its adoption and which shall continue for a term of four years from its effective date.  The contract shall be automatically renewed for successive four-year terms unless terminated by either the district or the county by the adoption of a resolution and its service on either the clerk of the board of supervisors by the district, or on the secretary of the district by the county, at least 90 days prior to the expiration of the then current term of the contract.