1. to evaluate the sufficiency of number of sites representing the high/good and good/moderate quality class boundaries in different types;
2. to evaluate if the type characteristics of the selected sites followed the agreed criteria for the type they are submitted for (including evaluation of possible outliers);
3. to summarise the availability of data for specified biological, physicochemical and other quality parameters regarding also the length of the time-series and sampling frequency;
4. to analyse differences of pressures along the indicated quality class gradient;
5. to analyse the availability of reference conditions and the methods used to establish them.
The intercalibration exercise should be carried out for all agreed common intercalibration types for which it was agreed to have a minimum number of five sites per type and per quality class boundary1. Each type should be shared at least between two countries (i.e. at least two or more countries should submit sites for each common type). Most of the river (94%) and lake (88%) types and quality class boundaries had a sufficient number of sites. However, for coastal, and especially in transitional waters, several types and quality boundary groups had only one site. The sharing criterion (types should be shared by at least two countries, which all should have submitted sites for this type) was fulfilled in most cases, if sufficient number of sites was selected for the type in question. According to the Guidance on the Intercalibration Process2, the Intercalibration network will be directly used only in the process option 3 and, perhaps, also in some hybrid options in which national methods will be directly compared at intercalibration sites. Hence, the Geographical Intercalibration Groups (GIGs) planning to use option 3, should look for possibilities to use test sites beyond the current Intercalibration Register.