Development of a Rivpacs Model for Wadeable Streams of Wyoming
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DEVELOPMENT OF A RIVPACS MODEL FOR WADEABLE STREAMS OF WYOMING By Eric G. Hargett 1, Jeremy R. ZumBerge 2, and Charles P. Hawkins 3 WYOMING DEPARTMENT OF ENVIRONMENTAL QUALITY WATER QUALITY DIVISION 1Wyoming Department of Environmental Quality - Water Quality Division, Herschler Bldg. 4W, 122 W. 25 th St., Cheyenne, WY 82002 USA 2Wyoming Department of Environmental Quality - Water Quality Division, 1866 S. Sheridan Ave., Sheridan, WY 82801 USA 3Department of Aquatic, Watershed and Earth Resources, Utah State University, 5210 Old Main Hill, Logan, UT 84322 USA October, 2005 CONTENTS EXECUTIVE SUMMARY ..............................................................................................................................iii ABSTRACT……………...……………………………………………………………………………………………1 INTRODUCTION...........................................................................................................................................2 METHODS AND MATERIALS ......................................................................................................................3 Study Area ..................................................................................................................................................3 Macroinvertebrates .....................................................................................................................................4 Water Chemistry .........................................................................................................................................5 Physical Habitat and Landscape Characterization .....................................................................................5 Reference and Test Samples……………………………………………………………………………………..6 Predictive Model Construction ....................................................................................................................7 Data Analysis ............................................................................................................................................7 Classification of Reference Samples ........................................................................................................7 Prediction of Class Membership ...............................................................................................................7 Estimating Probabilities of Capture, E, O/E, and Taxon Sensitivity to Stress ..........................................8 Model Validation and Responsiveness.......................................................................................................9 Application of the Model to Reference and Test Sites................................................................................9 RESULTS....................................................................................................................................................10 Operational Taxonomic Units....................................................................................................................10 Reference and Test Sample Characteristics…………………………………………………………………..10 The Predictive Model ................................................................................................................................11 Reference Site Classification ……………………………………………………………………………….....11 Predictor Variables..................................................................................................................................11 Predictive Model Validation.....................................................................................................................12 O/E Scores of Reference-Test Sites.......................................................................................................12 O/E Scores of Test Sites.........................................................................................................................12 Summary of Individual Taxa Responses ................................................................................................13 DISCUSSION..............................................................................................................................................13 Model Performance.................................................................................................................................14 Model Validation......................................................................................................................................15 Temporal Variability ................................................................................................................................15 Test Site Assessments............................................................................................................................16 Individual Taxa Responses.....................................................................................................................17 Model Limitations ....................................................................................................................................17 Comparability to other Models ................................................................................................................20 Assessment of Biological Condition using Narrative Criteria..................................................................21 Conclusions.............................................................................................................................................22 ACKNOWLEDGMENTS..............................................................................................................................23 REFERENCES............................................................................................................................................24 i TABLES Table 1 - Mean and range of values for selected environmental variables for reference and test samples ....................................................................................................................................................................28 Table 2 - Reference and test samples by ecoregion and sub-region. ........................................................29 Table 3 - Predictor variables (with corresponding F values) used in the discriminant model.....................30 Table 4 – Means, standard deviations (SD), percentiles, and minimum and maximum O/E scores for reference and test samples.........................................................................................................................31 Table 5 - Mean and standard deviation (SD) of reference calibration O/E scores by reference group......32 Table 6 – Means, p-values and F-values for comparisons between ecoregion/sub-region and landscape types for both refrence calibration and test samples. .................................................................................33 Table 7 – Mean, standard deviation (SD) and coefficient of variation (CV) of O/E scores for reference-test samples.......................................................................................................................................................34 Table 8 - Taxa response summary. ............................................................................................................35 FIGURES Figure 1 - Reference (solid circles) and test (open circles) sites in relation to ecoregions and sub-regions of Wyoming………………………………………………………………………………………………………….40 Figure 2 - UPGMA cluster analysis dendrogram that shows the fifteen biologically similar groups derived from the reference calibration dataset……………………………………………………………………………41 Figure 3 - Distribution of O/E scores for reference calibration samples. ....................................................42 Figure 4 - Distribution of O/E scores for reference validation samples. .....................................................43 Figure 5 - Linear regression of observed and expected scores for reference calibration samples............44 Figure 6 - Linear regression of observed and expected scores for reference validation samples. ............45 Figure 7 - Box and whisker plot distribution of reference O/E scores by sample type. ..............................46 Figure 8 - Box and whisker plot distribution of O/E scores by sample type................................................47 Figure 9 – Samples that were within (soild circles) and outside (open circles) model experience.............48 Figure 10 - Distribution of O/E scores by narrative biological criteria across Wyoming. ............................49 APPENDICES Appendix A - Operational taxonomic units (OTUs) derived from the reference calibration dataset...........50 Appendix B - O/E scores and narrative ratings for samples by ecoregions/sub-region. ............................54 ii EXECUTIVE SUMMARY RIVPACS (River InVertebrate Prediction And Classification System) models allow an assessment of biological condition by comparing the taxa observed at sites of unknown biological condition with taxa expected to occur in the absence of human stress. The deviation of the observed from the expected biota, known as the O/E index, is a measure of the compositional similarity expressed in units of taxa richness and thus a community-level measure of biological integrity. RIVPACS models have seen conventional use by environmental regulatory agencies in Great Britain and Australia for more than a decade. Use of these models in the United States for bioassessment purposes is still a relatively new concept,