Management of groundwater and surface water via decomposition

This paper develops a methodology for solving the problems of conjunctive use of a large‐scale complex groundwater system, a network of streams, and reservoirs all interacting with one another. Decomposing the model of a large‐scale aquifer system as well as that of a stream network into interacting submodels provided an improved mathematical model of the entire physical system. A theorem is proved that establishes the necessary conditions for the existence of a solution to the optimal control problem associated with the management of the groundwater system. A sample problem was formulated in which the options of groundwater operations and surface water supply are conjunctively utilized to meet the water needs of several water users in a basin. The management problem was solved via decomposition and multilevel approach.