Management Alternatives for River-Alluvial Groundwater Supply Systems

Abstract

An integrated approach for evaluating water supply and treatment options for a river-alluvial groundwater supply system is presented. Such systems are important because they are commonly used for drinking water supplies due to their proximity to large populations. However, there is limited understanding of the natural mechanisms that impact water quality and of the options for managing these impacts. The combinatorial problem of selecting water supply sources and treatment options is complicated by this lack of information, the interrelationships between these options, the urgent need for a sound public health decision, and other institutional and historical constraints. A framework is developed for evaluating tradeoffs among alternative combinations of source and treatment in the short-term and for addressing the management of such systems over time. The alternatives will be evaluated with respect to the following objectives: the cost of the various treatment alternatives, as well as pumping and monitoring costs; the risk of contamination due to pathogens and the resulting risks to human health; and the available water yield. The framework decomposes the classical groundwater supply system into three subsystems: the source water, water treatment and water distribution network subsystems, and uses reliability-based optimization models to determine operations in each subsystem considering output from adjacent subsystems as constraints. The uncertainties related to information and mechanisms that drive each subsystem are accounted for in the reliability analyses. This approach is developed considering the water supply conditions for the City of Fredericton, New Brunswick; however, it may be generalized for the many similar hydrologic settings that exist in North America.