Headwater Stream Biology

What lives in streams that go dry for part of the year? This question started a six-year exploration to characterize the biology and ecology of headwater streams across the State in order to support protective policies for headwater streams in NC, such as requirements for mitigation for intermittent stream impacts.

The simple answer is that it depends on how long a piece of stream has water, and whether that water flows. In ephemeral reaches (features that only carry water during and just after a rain) most of what you find are terrestrial species. In intermittent streams, which are wet for several months a year but dry up during other months, mostly what is found are aquatic species with short life cycles (a few weeks to a few months). In perennial streams (streams with water in them all year round) you find almost everything in intermittent streams plus a wide array of animals with life spans of a year or more. These species are different in streams that always flow and streams where flow stops. One result of this work is a list of  common macroinvertebrate taxa in headwater streams and their requirements for water presence and flow.

This information has also proven useful for developing stream restoration success criteria, development of a rapid method to assess stream quality (NC Stream Assessment Method), and helping the Corps of Engineers understand their new jurisdiction in light of the 2006 Rapanos v United States Supreme Court decision (Biological Justification in Streams for Significant Nexus in North Carolina). The EPA has recently awarded the NC PDU a grant to perform a similar survey of the biology of headwater streams throughout the southeast and those efforts are underway.

Questions about the biology of headwater streams should be directed to Larry Eaton, larry.eaton@ncdenr.gov.

Webpage last updated December 10, 2009