Predicting environmental flow metrics in the Tennessee and Cumberland River valleys

The need to understand how water-management decisions affect stream ecosystems has spurred development of a new class of streamflow metrics expressly related to the flow requirements of aquatic organisms.  These environmental flow metrics represent aspects of the streamflow hydrograph not generally reflected in traditional statistics such as low-flow or flood-frequency probabilities. Environmental flow metrics represent not only streamflow frequency and duration, but also timing, rates of change, and magnitude of certain aspects of the annual hydrograph.  The broad and varied nature of environmental flow metrics makes their prediction a challenging task, beginning with the basic questions of which metrics to predict and which explanatory variable to use in their prediction. We propose that four general groups of descriptive explanatory variables can be used to adequately predict environmental flow variables as well as describe the hydrologic processes that govern the delivery of water from land-surface to streams in the Tennessee and Cumberland River valleys: climate, regional, physical, and land-use characteristics.  This presentation represents the second phase of a three-phrase study by the U.S. Geological Survey to identify environmental flow metrics critical to fish in the Tennessee River valley.