Comparisons of Hester–Dendy and Hess sampling methods and environmental variation across study sites from 2010 to 2014 using non-metric multidimensional scaling (NMDS), multivariate dispersion, and principal component analysis (PCA) for the Niobrara River. (a) NMDS comparison of invertebrate assemblages, (b) multivariate dispersion of invertebrate assemblages, (c) distance-to-center of boxplots for the multivariate dispersion polygons shown in (b), (d) NMDS comparison of invertebrate assemblages across sites for both methods, (e) PCA comparison of environmental variation among sites, and (f) PCA comparisons of six bioassessment metrics for methods and years, Hash marks represent: (a) individual taxa and (b) sampling events for all years and methods. For (e) and (f), polygon corners represent sampling sites (e) or years (f) and only variables with non-negligible influence are shown though the full suite of relevant metrics were included for each PCA. Abbreviations: ORP = oxidative reduction potential, SPC = specific conductivity.