Mathematical modeling of urban water management strategies

Abstract

The rapid expansion of many western urban centers has nearly outstripped available stream, flow and groundwater re-sources requiring municipal water departments to initiate exhaustive searches for new water supplies. Among the most feasible alternatives being investigated to date are acquisition and transfer of agricultural rights, interbasin water diversions, and wastewater recycling. A management level urban water system model has been formulated in which a system analysis format is employed to answer some of the basic questions concerning the optimal combination of these alternative supplies. The model in-corporates a non-linear differential optimization algorithm to coordinate urban water supply, distribution, and waste- water management. A test of the model's utility is made in an application to the water management problems of the Denver, Colorado metropolitan area. Denver has utilized both agricultural transfers and transmountain diversions to supplement the natural stream resources of the South Platte River. Although plans are being made to increase the capacity of these sources, increasingly stringent standards on the area's effluents are enhancing the feasibility of reclaiming and recycling a portion of the wastewater. The urban model used in this study indicates the decision points at which respective strategies are introduced. How-ever, by formulating the model from a planner's viewpoint, the most important results gained from the analysis are the costs of various institutional constraints which may re-strict the decision makers' ability to implement optimal policies. Some of the institutional constraints which have been quantified include the legal interpretation of water right laws, public sentiment towards reuse, consolidation of water supply and wastewater treatment responsibilities, and water quality control philosophies.