Data provided from the Virginia Department of Environmental Quality (DEQ) including simulated values of 72 hydrologic metrics, or indicators of hydrologic alteration (IHA), 37 fish metrics, and 64 benthic invertebrate metrics were reviewed to assess significant flow-ecology relations that may be developed. Hydrologic alteration was represented by simulation of streamflow record for a pre-water-withdrawal condition (baseline) without dams or developed land, compared to the simulated recent-flow condition (2008) including withdrawals, dams and altered landscape to calculate a percent-alteration of flow. Biological samples used represent a median condition of the biological community from 1972 to 2010.
This study reviewed more than 7,272 linear regression models that relate altered flow conditions to biological sample metrics in Virginia. Decreasing flow conditions were the focus of this evaluation because of their relevance to the water-supply permitting process. The data tables highlight relations which may be significant and useful in future study and were further explored in the companion report; and relations that do not meet basic assumptions for valid linear regressions which were noted and omitted from the companion report. The three regions in Virginia defined by major drainage and physiographic boundaries as the Ohio River Drainages, Atlantic non-Coastal Plain, and Atlantic Coastal Plain were evaluated as well as a statewide grouping for fish and benthic data.
This extensive dataset provided the opportunity for hypothesis testing and prioritization of flow-ecology relations that have the potential to explain the effect(s) hydrologic alteration has on biological metrics in Virginia.