National monitoring networks cannot be used to assess the status of all water bodies, as they were usually not explicitely designed for that purpose. Consequently, another approach than direct monitoring is needed to assess the status of water bodies which are not surveyed. A solution has previously been attempted that consisted in using expert judgment or in grouping water bodies. However, this option may lead to a heterogeneous assessment across member states within Europe. For this reason a solution might be to associate both extrapolation models based on pressure/impacts knowledge and expert judgment is probably a promising way to achieve that goal. While the use of a model is an objective approach, it may have bias and be inappropriate to specific local conditions not taken into account in learning dataset used to build the model. Taking into account expert expert judgment could correct for this bias, but can not be considered alone.