Cal. WAT § 2100

After the department has submitted to the board recommendations for the protection of the quality of ground water pursuant to Section 12617.1 or 12923.1 of this code, or in reliance upon investigation by any governmental agency, the board may file an action in the superior court to restrict pumping, or to impose physical solutions, or both, to the extent necessary to prevent destruction of or irreparable injury to the quality of such water. In such action, all of the claimants to the use of the affected water known to the board, except claimants to the use of minor quantities of water as defined in Section 2102, shall be named as defendants. In any watershed or ground water basin wherein (a) all or substantially all of the rights to water have been adjudicated and the court has retained continuing jurisdiction arising from the adjudication, or (b) wherein such action is pending, any such proceedings by the board shall be undertaken only by intervention by the board in such existing action.