Application of an in-stream water quality model to assist the implementation of the Water Framework Directive to a catchment in Southwest Finland
Thouvenot, M.; Hämäläinen, H.; Kirkkala, T.; Boorman, D. B.; Hutchins, M.; Kämäri, J.
The problems of implementing the Water Framework Directive (WFD) to the naturally eutrophic River Eurajoki, located in Southwest Finland are presented. A review of the methods and data available to classify the ecological status of a river was undertaken and revealed that biological data from the river are sparse. A provisional regression model, which predicts the ecological status (Ecological Quality Ratio, EQR), based on benthic invertebrate fauna, from water quality, and which is built on data from more northern rivers, was found not to be applicable in the region. It was concluded that given the lack of regional reference data, biological elements could not be used for the definition of the ecological status of River Eurajoki. Therefore, chemical elements supporting biological elements (dissolved oxygen, ammonium and total phosphorus) were chosen instead to classify the water quality of the river. The use of a modelling approach to simulate present-day conditions of these chemical elements was explored, and an in-stream water quality model was assessed for its usability in the implementation of the WFD in Finland. The model generated simulations of water quality, which were similar to the observed data over the period 1980-2002, but required a large amount of data to obtain a good simulation. The modelling approach proved to be useful for analysing different scenarios and in particular to estimate the reduction in loading needed to achieve the goals set by the WFD. In conclusion, this model can be recommended for the use by water managers in the implementation of the WFD on river basins with sufficiently monitoring data available.