Classifying flow regimes in seven states in the southeast: Implications for regional environmental flow standards and management

River regulation has resulted in substantial losses in natural flow variability, habitat integrity, and consequently, species diversity.  River managers are faced with a growing need to protect the key aspects of the natural flow regime, which is easier said than done.  A practical approach to providing environmental flow standards is to classify unregulated streams into groups of similar hydrologic properties, which represent natural flow regime targets.  The purpose of this study was to classify streams within a seven-state region into groups in order to provide environmental flow standards for managers with regard to relicensing agreements and withdrawl permitting.  Using USGS daily stream gauge information, we calculated 155 hydrologic statistics of 310 unregulated streams using the USGS program HIT (Hydrologic Index Tool) and classified streams using a k-means clustering method.  Ten flow classes were isolated that ranged from extremely stable to highly-variable  to intermittent.  We provide summary statistics for each flow class, which can be used as a basis for setting environmental flow standards.  To provide an example of the utility of this data set in providing environmental flow standards, we use the flow classifications in a case study for the Cheoah River, a regulated river in western NC.