Biomonitoring in low-gradient rivers with shifting-sand substrates has not been fully addressed. This research project, supplementary to the U.S. Geological Survey's National Water Quality Assessment (NAWQA) program, examines macroinvertebrate communities from substrates representing three major habitats in low-gradient rivers: (1) shifting-sand; (2) submerged woody debris; and (3) rock. Objectives include determining the variability of macroinvertebrate communities on these substrates and whether a particular substrate or combination is more appropriate for distinguishing between stations of differing water quality. The research area is exposed to the cumulative effects of urban and agricultural point and non-point source pollutants and flow regulation. Grain size, velocity, and other geomorphic variables were analyzed to determine the similarity of hydraulic controls among stations. Several metrics for invertebrate data were evaluated. Water quality data and EPA's habitat assessments were examined to determine whether changes in benthic communities between stations were due to changes in water quality alone or in combination with habitat limitations. Results should assist in determining the number of samples, selection of substrates, and choice of metrics for future biomonitoring.
1 Department of Earth Resources, Colorado State University, Fort Collins, CO 80523