This dataset contains information about 128 river catchments placed in Wales, compiled over 30 years through different research projects. The majority of these catchments were surveyed at three time points over this period (one spring sample per year at 1984, 1995, 2012/13). A small subset of 14 streams (Brianne streams) have been surveyed continously from 1981-82 to 2014 (one spring sample per year). This dataset contains biological information about aquatic macroinvertebrates (genus and species level), water birds (European dipper) and fish (species level, commercial and non-commercial). As environmental descriptors, GIS catchment information (elevation, geomorphology, lithology), water chemistry (pH, nutrients, suspended solids, etc.) and climatic information are available. More information on this dataset can be found in the Freshwater Metadatabase - MARS_19 (http://www.freshwatermetadata.eu/metadb/bf_mdb_view.php?entryID=MARS_19).