HYDROLOGIC CONTROLS ON FISH AND MACROINVERTEBRATE COMMUNITIES IN OHIO'S WESTERN ALLEGHENY PLATEAU

The US EPA has been working toward creating a measure of stream biological condition along gradients of impairment. These refined biocriteria are a practical tool that can be used by the States in order to achieve the long-term aquatic biological integrity sought by the Clean Water Act. Researchers at the Ohio University's Voinovich Center for Leadership and Public Affairs are working on a watershed classification system to predict habitat variables in Ohio's Western Allegheny Plateau. The purpose of this project is to integrate biological, geomorphological, hydrological, and geochemical data to refine biocriteria of stream and watershed health.

The work reported here provides the hydrologic component of this project. The objectives are to: (1) correlate hydrologic predictor variables with biologic response variables, via bivariate correlations, for relatively undisturbed watersheds in Ohio's Western Allegheny Plateau and (2) determine the best set of independent hydrologic variables. The biologic response variables to be used in this project are the Index of Biotic Integrity (IBI) and the Invertebrate Community Index (ICI). Historic biologic data will be included in the analysis thus hydrologic variables will be estimated when necessary.

The hydrologic predictor variables were grouped into three categories: flow-volume, flow-variation, and network position. The flow-volume variables are maximum depth and velocity, mean annual discharge, and drainage area; they were determined via field measurements, linear regression with USGS annual mean flow gage data, and Geographic Information Systems (GIS), respectively. The flow-variation variables are: probable duration of flow, coefficient of variation of flow, and metrics representing low-flows, high-flows, and flushing flows; they will be determined via streamflow estimation methods using basin characteristics and USGS gage data. The network position variables are Strahler stream order, stream link magnitude (Shreve stream order), downstream link magnitude, and distance from headwaters; they were determined with GIS.