The optimization of operating policies of multiple unit and multiple purpose water resources systems by traditional dynamic programing with the use of high speed digital computers encounters two major difficulties: memory requirements and computer time requirements. This paper presents an iterative method that can ease the above difficulties considerably. The method starts with a trial trajectory satisfying a specific set of initial and final conditions and applies Bellman's recursive equation in the neighborhood of this trajectory. At the end of each iteration step a locally improved trajectory is obtained and used as the trial trajectory in the next step. The method has proved particularly effective in the case of so‐called ‘invertible’ systems. The merits of the proposed approach are demonstrated through its application to a four‐unit, two‐purpose water resources system. To save computer time the example is restricted to deterministic inflows.

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A ground water management model based on the linear systems theory and the use of linear programming is formulated and solved. The model maximizes the total amount of pound water that can be pumped from the system subject to the physical capability of the system and institutional constraints. The results are compared With analytical and numerical solutions. Then, this model is applied to the Pawnee Valley area of south‐central Kansas. The results of this application support the previous studies about the future ground water resources of the Valley. These results provide a guide for the ground water resources management of the area over the next ten years.