1 GREAT-ER PROJECT: MONITORING PROGRAM AND VALIDATION OF THE RUPEL BASIN (BELGIUM) Report PROCTER & GAMBLE ETC P&RS Frederik Verdonck & Diederik Schowanek January 7, 2000 Abstract In the GREAT-ER project (Geography-referenced Regional Exposure Assessment Tool for European Rivers), an accurate aquatic exposure prediction tool for chemicals was developed and validated for use within environmental risk assessment schemes. The model GREAT-ER has already been validated on several catchments, namely in the UK, Italy and Germany. In this report, a monitoring strategy for the Rupel basin in Belgium is proposed in order to i) validate the way in which the Rupel basin is implemented in the GREAT-ER system and ii) assess how accurate the simulations are of a large catchment with a simplified river network. Several monitoring strategies with statistical background were considered, but none of them could be applied on the Rupel basin. Therefore, the network was determined based on expert judgement. The proposed Rupel monitoring network consists of 21 stations, which will have to be extensively monitored for boron and LAS (or any other selected chemicals), and 6 existing stations, which will have to be monitored only once on MBAS and LAS. This network can be used in the future for other chemicals as well. Seven stations are scattered out over the entire Rupel basin. The twenty other stations are more concentrated to cover specific subbasins. There is room for some additional monitoring points, which can be of use during the monitoring strategy. 1. Introduction In the GREAT-ER project (Geography-referenced Regional Exposure Assessment Tool for European Rivers), an accurate aquatic exposure prediction tool for chemicals was developed and validated for use within environmental risk assessment schemes. In GREAT-ER, a new database, model and software system were worked out to calculate the distribution of PEC’s of 'down-the-drain' chemicals in European surface waters, on a river and catchment area scale. The system uses a Geographic Information System (GIS) for data storage and visualisation, combined with simple mathematical models for the prediction of chemical fate. At present, the system contains information for four catchments in Yorkshire (UK), one in Italy, and two in Germany. GREAT-ER 1.0 has been validated by comparing simulations with the results of an extensive monitoring campaign for the detergent ingredients Linear Alkylbenzene Sulphonate (LAS) and Boron (Feijtel et al., 1997; Schowanek et al., in press). The output of GREAT-ER 1.0 is three-fold (Schowanek et al., submitted): (1) a colour-coded GIS map with the distribution of a chemical’s PEC in the river basin, (2) a profile of the chemical concentration as a function of the distance for a selected branch of the river, and (3) aggregated PEC’s (i.e. PEC initial and PEC catchment ) to integrate the results for an entire catchment (Boeije et al., in press). In this report, on the initiative of ECETOC, a monitoring strategy for the Rupel basin in Belgium (Figure 1) is presented in order to validate the implementation and simulations of the Rupel basin.