Optimal Expansion of Water Quality Monitoring Network by Fuzzy Optimization Approach

Abstract

Abstract. River reaches are frequently classified with respect to various mode of water utilization depending on the quantity and quality of water resources available at different location. Monitoring of water quality in a river system must collect both temporal and spatial information for comparison with respect to the preferred situation of a water body based on different scenarios. Designing a technically sound monitoring network, however, needs to identify a suite of significant planning objectives and consider a series of inherent limitations simultaneously. It would rely on applying an advanced systems analysis technique via an integrated simulation-optimization approach to meet the ultimate goal. This article presents an optimal expansion strategy of water quality monitoring stations for fulfilling a long-term monitoring mission under an uncertain environment. The planning objectives considered in this analysis are to increase the protection degree in the proximity of the river system with higher population density, to enhance the detection capability for lower compliance areas, to promote the detection sensitivity by better deployment and installation of monitoring stations, to reflect the levels of utilization potential of water body at different locations, and to monitor the essential water quality in the upper stream areas of all water intakes. The constraint set contains the limitations of budget, equity implication, and the detection sensitivity in the water environment. A fuzzy multi-objective evaluation framework that reflects the uncertainty embedded in decision making is designed for postulating and analyzing the underlying principles of optimal expansion strategy of monitoring network. The case study being organized in South Taiwan demonstrates a set of more robust and flexible expansion alternatives in terms of spatial priority. Such an approach uniquely indicates the preference order of each candidate site to be expanded step-wise whenever the budget limitation is sensitive in the government agencies.Keywords: environmental systems analysis, fuzzy multi-objective programming, monitoring network, river basin planning, water quality management NotationThe following symbols are used in this article: SHU-KUANG NING AND NI-BIN CHANGE ij = the distance between the j th monitoring station located at the ith tributary and the nearest potable water intake in the upper stream area (km); L c = allowable overlapped half-life distance in this systems analysis (km); L i = the lower bound of tolerance interval in the ith fuzzy membership function; L ij k = the distance required for a decay of half concentration of the kth pollutant where the j th monitoring station in the ith tributary is located (km); M = the upper bound of the number of monitoring stations (no unit); p = the number of tributary in Kao-Ping River basin; P ij = the population covered within the 10 km in radius where the j th monitoring station in the ith tributary is located (capita); q i = the total number of candidate station in the ith ...

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