University of California Water Resources Center

This project analyzes the legal and institutional opportunities and constraints on conjunctive management of groundwater and surface water in California. Conjunctive water use involves the coordination of groundwater and surface water management, usually by recharging the groundwater basin with surface water during times of hydrologic surplus and withdrawing the stored water during times of drought. The goals of conjunctive management include: (1) augmentation of total usable water supplies; (2) recharge of overdrafted aquifers; (3) increase in total available water supplies at less economic, political, and environmental cost than through construction of additional surface storage; (4) improvement of water quality; and (5) enhanced reliability of water supplies during times of drought.

There are a number of examples of conjunctive water management in California, particularly in adjudicated groundwater basins in Southern California. These management arrangements generally work well because the rights to groundwater are quantified and the management agencies have legal authority to enforce the pumping limitations, pricing rules, and other policies that govern groundwater and surface water use. In unadjudicated basins, however, the feasibility of conjunctive management is less certain. This is particularly true in basins in which a portion of the surface water is imported, stored as groundwater, and then later withdrawn for uses outside the groundwater basin. In these situations there exist an array of legal and institutional uncertainties that render conjunctive management more difficult than in adjudicated basins. These uncertainties include questions about the ownership of the imported water, liability for displacement of in-basin recharge capacity, regulation of groundwater users who are not parties to the conjunctive management agreement, the authority of local water agencies over the importation and exportation of surface water, and liability for changes in water quality.

To facilitate the creation of conjunctive water management programs in unadjudicated groundwater basins, the California Legislature should modify the current laws governing groundwater and conjunctive use to help accomplish more efficient conjunctive management of interconnected waterresources. By clarifying the authority of local agencies to design, maintain, and enforce conjunctive use agreements, the Legislature could remove barriers that presently create disincentives for participation in such programs.

This report recommends a variety of such legislative reforms, including express authorization for local entities with groundwater management authority to engage in conjunctive use programs, clarification of the respective powers of the local agency and the importing agency to control the water stored and used in such programs, and clarification of the authority of local agencies to enact and to enforce anti-export ordinances.