Aquatic insect abundance data from eight Dutch water authorities

In the Netherlands, regional Water Authorities (also called Water Boards, and in Dutch: Waterschappen or Hoogheemraadschappen) have collected data on the abundance and distribution of macrofauna (i.e. small invertebrates still detectable without magnifier or microscope) in Dutch surface water bodies (brooks, ditches, ponds, lakes, canals, rivers, etc.). Here we focus only on the insects found in those macrofauna samples and archive a subset of the insect counts used in analyses like that of Hallmann and Jongejans (2021, STOWA report). This dataset contains samples from 1990 till 2018. Data from eight water authorities were included as long as the length of the sampled transect was recorded. Samples also had to be complete (i.e., no common and expected groups of insects missing) and sample processing protocols needed to have been followed. The eight water authorities selected based on the quality and availability of their data were: HHD: Hoogheemraadschap van Delfland WHD: Waterschap Hollandse Delta (also known as WSHD) WAM: Waterschap Aa en Maas Waterschap De Dommel WPM: Waterschap Peel en Maasvallei (now part of Waterschap Limburg) WRD: Waterschap Regge en Dinkel (now part of Waterschap Vechtstromen) WRIJ: Waterschap Rijn en IJssel WRO: Waterschap Roer en Overmaas (now part of Waterschap Limburg) The archived data files ‘sampleData.csv’ and ‘taxonData.csv’ can be linked based on their spatial coordinates (RD x and y) and dates (year and dayNumber: day of the year). Ten insect groups were made based on taxonomy: IDCHI = Chironomidae IDSIM = Simuliidae IDREM = other Diptera INCOL = Coleoptera INEPH = Ephemeroptera INHET = Heteroptera INLEP = Lepidoptera INODO = Odonata INTRI = Trichoptera INREM = other insects CollectorID of the person or organization collecting the macrofauna sample in the field has been anonymized. Sampling length is in meters. Taxon-specific counts in taxonData.csv are in some cases counts of subsamples, in accordance with the processing protocol (Beers et al. 2014).