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A new method for groundwater plume detection under uncertainty

Luís Miguel Nunes¹, maria da conceição Cunha², luís Ribeiro³ & João Azevedo³

1 Faculty of Marine and Environmental Sciences, University of Algarve, Campus de Gambelas, 8000 Faro, Portugal

lnunes@ualg.pt

2 Civil Engineering Department, University of Coimbra, Pinhal de Marrocos, 3030 Coimbra, Portugal

3 Instituto Superior Técnico, Lisbon Technical University, Av. Rovisco Pais, 1096 Lisboa Codex, Portugal

Abstract Groundwater contamination plume characterization is a very hard task to perform and usually requires a large number of sampling sites. In this article a method for optimizing a monitoring network for plume detection and delimitation is proposed. It is assumed that an extensive sampling campaign has already been conducted and that only a few sampling sites should be included in the optimal monitoring network. The objective function incorporates the prior knowledge about concentration variability in the form of its density function, and also a measure of spatial coverage (space-filling method) in order to best distribute the stations over the field. The method was applied to a synthetic case study with 160 sampling locations, and a final optimal monitoring network with 40 stations was obtained. A simulated annealing optimization algorithm was used to solve this very difficult combinatorial problem, which has more than 8.6 ´ 10³⁷ possible solutions.

Key words groundwater; monitoring; optimization; plume

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