By Dr. Ken Fritz

Half of the world’s river networks are at least partially intermittent, meaning they have channels that are periodically dry.  Due to human activities, perennial rivers (i.e., rivers with year-round continuous flow) are increasingly becoming intermittent. In the past, the scientific field of river ecology has largely focused on perennial systems. However, after years of little attention, the ecological study of intermittent rivers is trending upward.

Intermittent waterways are interesting systems because they are fundamentally transformative in nature. While nearly all waterways expand and contract with pulses of water availability, these changes are particularly noticeable for intermittent waterways. They transition from flowing (even flooding,) to fragmented pools, to completely dry channels. This makes it more of a challenge in predicting patterns and processes compared to rivers which flow year-round. Recognition of the increasing prevalence of intermittent waterways across the globe has spurred greater interest in these systems, particularly in how they function and influence downstream waterbodies.

This intermittent stream is in a flowing state in April (left) and a dry state in September (right). North Fork of Bakers Fork, Wayne National Forest, Ohio, looking upstream.

That’s why the August 2016 special issue of the scientific journal Freshwater Biology focuses on intermittent waterways research. This special issue is titled Intermittent River Ecology as a maturing, multidisciplinary science: Challenges, developments and perspective in intermittent river ecology, and it brings together 13 manuscripts that guide the research and management of this dynamic field of freshwater science. It addresses the most recent intermittent river ecology developments and is freely accessible until August 31^st.

As one of the Guest Editors for this issue, I had the privilege of working with Co-Guest Editors Drs. Thibault Datry (Institue National de Recherche en Sciences et Technologies pour l’Environment et l’Agriculture) and Catherine Leigh (Australian Rivers Institute) who were both funded through the project, Intermittent River Biodiversity Analysis and Synthesis (IRBAS). This special issue is one of the many products on intermittent rivers coming from this group of researchers.

As the special issue testifies, the study of intermittent waterways is not a dry topic but a multifaceted and exciting one. I encourage you to read these articles if you are interested in the ecology and management of systems where stationarity is a myth.

Check out these resources to learn more about EPA research related to intermittent streams:
Headwater Streams Studies
Field manual for determining permanence in headwater streams
Ephemeral streams report
Connectivity report.

About the Author: Dr. Ken Fritz has been a Research Ecologist in EPA’s Office of Research and Development since 2002. He is among the Agency’s leading researchers of intermittent and ephemeral streams.