ASSESSMENT OF AQUATIC BIOLOGICAL CONDITION USING WY RIVPACS WITH COMPARISONS TO THE WYOMING STREAM INTEGRITY INDEX (WSII) Eric G. Hargett Wyoming Department of Environmental Quality Water Quality Division 122 W. 25th St. Herschler Building 4-W Cheyenne, Wyoming 82002 Document #12-0151 March 2012 Assessment of Aquatic Biological Condition Using WY RIVPACS with Comparisons to the Wyoming Stream Integrity Index (WSII) TABLE OF CONTENTS EXECUTIVE SUMMARY .............................................................................................. IV INTRODUCTION .......................................................................................................... 1 METHODS AND MATERIALS ........................................................................................ 2 STUDY AREA ................................................................................................................................................................. 2 REFERENCE AND TEST SAMPLES ........................................................................................................................................ 3 MACROINVERTEBRATES ................................................................................................................................................... 3 WATER QUALITY, CLIMATE AND LANDSCAPE CHARACTERIZATION ............................................................................................ 6 MODEL CONSTRUCTION .................................................................................................................................................. 6 A. Data Analysis .............................................................................................................................................. 6 B. Classification of Reference Samples ........................................................................................................... 6 C. Prediction of Class Membership ................................................................................................................. 7 D. Estimating Probabilities of Capture, E and O/E .......................................................................................... 7 E. Model Validation and Responsiveness ....................................................................................................... 7 F. Application to Reference, Degraded and Test Samples .............................................................................. 8 G. Aquatic Life Use Attainment Category Thresholds ..................................................................................... 8 H. Comparisons, Bias, Sensitivity and Precision between WY RIVPACS and WSII ........................................... 9 RESULTS....................................................................................................................10 SITE CLASSIFICATION .................................................................................................................................................... 10 ALL POSSIBLE MODELS AND FINAL PREDICTOR VARIABLES ................................................................................................... 10 PREDICTIVE MODEL VALIDATION .................................................................................................................................... 11 TEMPORAL VARIABILITY IN O/E VALUES ........................................................................................................................... 15 O/E VALUES OF TEST AND DEGRADED SAMPLES ................................................................................................................ 15 SAMPLES OUTSIDE THE EXPERIENCE OF THE MODEL ........................................................................................................... 15 ATTAINMENT CATEGORY THRESHOLDS ............................................................................................................................. 24 COMPARISONS OF WY RIVPACS AND WSII ..................................................................................................................... 24 A. Precision.................................................................................................................................................... 24 A. Bias ........................................................................................................................................................... 24 B. Sensitivity .................................................................................................................................................. 25 DISCUSSION .............................................................................................................33 CLASSIFICATION AND PREDICTOR VARIABLES ..................................................................................................................... 33 MODEL PERFORMANCE AND VALIDATION ......................................................................................................................... 34 TEMPORAL VARIABILITY IN REFERENCE CONDITION ............................................................................................................. 34 DETECTION OF ANTHROPOGENIC DISTURBANCE ................................................................................................................. 34 WY RIVPACS LIMITATIONS .......................................................................................................................................... 35 COMPARABILITY BETWEEN WY RIVPACS AND WSII .......................................................................................................... 36 AQUATIC LIFE USE ATTAINMENT ..................................................................................................................................... 38 CONCLUSIONS ............................................................................................................................................................. 38 ACKNOWLEDGMENTS ................................................................................................................................................... 39 REFERENCES .............................................................................................................39 LIST OF TABLES Table 1 – Predictor variables (with corresponding F-values) used in the predictive model. ....................................... 11 Table 2 – Means, standard deviations, percentiles and minimum and maximum O/E values for reference, test and degraded samples. ....................................................................................................................................................... 15 i Assessment of Aquatic Biological Condition Using WY RIVPACS with Comparisons to the Wyoming Stream Integrity Index (WSII) Table 3 – Mean O/E values, P-values and F-values for comparisons between bioregions for both reference calibration and test samples (significant values are italicized). Numbers of samples for each bioregion are noted in parentheses. Capital letters denote homogenous groups as determined from the Tukey multiple comparison tests. ..................................................................................................................................................................................... 21 Table 4 – 2012 and 2005 WY RIVPACS O/E value numeric thresholds and associated aquatic life use attainment categories for each bioregion. ..................................................................................................................................... 23 Table 5 - Mean and standard deviations of O/E and rescaled 2011 WSII scores for reference calibration samples among all bioregions. .................................................................................................................................................. 25 Table 6 - Mean O/E and rescaled 2011 WSII scores with corresponding Paired t-test and p-values, regression statistics, NSE and drel for test samples among all bioregions. Italicized values are significant at P<0.05. ................ 25 Table 7 - Concurrence between WY RIVPACS and WSII aquatic life use assessments among test samples in all bioregions. Values represent percentages within concurrence categories. Numbers of samples are in parentheses. Italicized values are significant at P<0.05. ................................................................................................................... 26 LIST OF FIGURES Figure 1- Location of reference (black circles) and non-reference (white circles) sites sampled from 1993 to 2009, in relation to major perennial streams and counties in Wyoming. ................................................................................... 4 Figure 2 – Wyoming bioregions, large river segments and selected municipalities (Hargett 2011). Reference data are not available or limited for cross-hatched areas though are assumed to have similarities to the bioregion of the same color. .................................................................................................................................................................... 5 Figure 3 – Illustration of aquatic life use attainment categories derived from interval and equivalence tests (Kilgour et al. 1998). The normal distribution of reference site O/E values is represented by the bell-shaped curve. The equivalence and interval lines represent the ‘full-support’ and ‘partial/non-support’