Stream monitoring site location for spatial detection of pollutant introductions.

摘要

Increased concern about water quality has focused attention on the economic efficiency of watershed management and policy decisions. Monitoring systems are one component of watershed information systems that can be used to decrease uncertainty and improve these decisions. Stream water quality monitoring network design depends on many considerations, one being station location. This thesis examines monitoring station location and develops mathematical programming models to evaluate station siting decisions.;The relationship between station location and data value used in the models presented here is based on the assumption that we can, by appropriate siting, reduce the distance a pollutant can travel downstream without being detected by a monitoring station. As the distance within which detection can occur is decreased, the uncertainty of the location of pollutant introduction decreases. As the uncertainty of the location decreases, the watershed manager can more efficiently target limited inspection and enforcement resources to identify and eliminate the source of the pollutant. The more accurately the manager can identify the location, the greater the value of the data.;Firstly, a set of integer programming formulations are developed based on reach coverage. Increasing levels of complexity and realism are incorporated into modifications of a basic model which trades off the length of stream reaches monitored against the cost of a monitoring network. Then additional requirements are added that; (1) limit the separation between stations to a maximum distance, (2) monitor tributaries, (3) compare coverage of all stream reaches versus coverage of a few selected reaches, (4) compare different levels of monitoring effort, (5) trade off monitoring of differently grouped stream reaches, and (6) minimize the average (and maximum) distance between stations raised to a power. Secondly, dynamic programming, the shortest path method and heuristic formulations, specifically using vertex substitution, are developed to minimize the average (and maximum) distance between stations raised to a power.;The different formulations and methods are compared using test problems. Results indicate that these formulations can be used to select, in a cost efficient manner, those monitoring station locations that are effective in both covering reaches and in reducing the lengths between sites.