Development of Streamflow Duration Assessment Methods

The availability of long-term hydrologic data to assess streamflow duration is often limited, especially for streams that do not flow year-round, yet these data are needed to support implementation of federal, state, and local programs. For example, they are crucial to determining whether a stream may be subject to jurisdiction under the Clean Water Act. For decades, land managers, regulators, and water resource managers have been working to develop and refine rapid, reach-scale stream duration assessment methods to serve as standardized and defensible survey methods for determining annual flow duration.

For several years, PG Environmental (a division of ERG) has been supporting the U.S. Environmental Protection Agency’s development of streamflow duration assessment methods. These rapid field-based assessment tools utilize physical, hydrological, geomorphological, and biological indicators, including field identification of macroinvertebrates, to determine stream flow duration (i.e., perennial, intermittent, or ephemeral). Since 2019, PG Environmental crews have conducted SDAM rapid assessments during hundreds of site visits within the eastern, central, and intermountain-west regions of the United States. At each site, they implement the standardized SDAM protocol and deploy Stream Temperature, Intermittency, and Conductivity (STIC) data loggers to validate field-based data collection.