Dispersion Modelling for a Complex Estuary – The Case of the Tagus

Abstract

Estuarine dispersion models have been commonly used to define the pollutant loads permissible to achieve pre-defined water quality levels and improve our knowledge of estuarine phenomena. Those models for large estuaries with complex hydrodynamic and ecological processes usually have extremely high running times. This paper presents an approach based on the use of increasingly complex models, which attempts to circumvent the problem of initial lack of data, as well as to give some initial insight into the processes of the Tagus Estuary, within acceptable levels of precision. As a first stage, simple models were developed and applied to the estuary, one of the largest in Europe, with more than 300 sources of pollution and intensive use for recreation, fishing, and navigation. The computational exercises undertaken with these models were also used to accumulate information on the response of the Tagus Estuary to a number of forcing conditions. This information, synthesized in ‘if … then' rules, was integrated to form a data base on the estuary, which is currently being developed. The data base will organize existing information and, providing that learning mechanisms are included, it will also create new knowledge, as well as supplying the complex models under development with reasonable initial values.