After respondent Pajaro Valley Water Management Agency (Agency) enacted three ordinances (Ordinance Nos. 2002-02, 2003-01, 2004-02) that increased groundwater augmentation charges for the operators of wells in the Agency‟s jurisdiction, several lawsuits challenging the constitutionality of the ordinances were filed. In 2008, these lawsuits were resolved by a stipulated agreement for entry of judgment. In 2010, appellant John G. Eiskamp filed a complaint against the Agency seeking a declaration that the Ordinance No. 2002-02 (Ordinance) was invalid, a refund of augmentation charges, and an order directing the Agency to cease collection of the augmentation charges. The trial court sustained the Agency‟s demurrer to the complaint without leave to amend and entered judgment in favor of the Agency. We hold that the doctrine of res judicata bars relitigation of the causes of action in Eiskamp‟s complaint and affirm the judgment.