Connectivity and effects of streams and wetlands on downstream waters: A review and synthesis of the scientific evidence

Authors: ALEXANDER, L.C. - Us Environmental Protection Agency (EPA); AUTREY, B. - Us Environmental Protection Agency (EPA); DEMEESTER, J. - Us Environmental Protection Agency (EPA); FRITZ, K. - Us Environmental Protection Agency (EPA); Goodrich, David - Dave; KEPNER, W.G. - Us Environmental Protection Agency (EPA); LANE, C.R. - Us Environmental Protection Agency (EPA); LEDUC, S.D. - Us Environmental Protection Agency (EPA); LEIBOWITZ, S.G. - Us Environmental Protection Agency (EPA); MCMANUS, M. - Us Environmental Protection Agency (EPA); POLLARD, A. - Us Environmental Protection Agency (EPA); RIDLEY, C.E. - Us Environmental Protection Agency (EPA); SCHOFIELD, K. - Us Environmental Protection Agency (EPA); WIGINGTON, P.J. - Us Environmental Protection Agency (EPA)

Submitted to: Environmental Protection Agency
Publication Type: Other
Publication Acceptance Date: 10/1/2014
Publication Date: 6/1/2015
Publication URL: http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=296414]
Citation: Alexander, L., Autrey, B., Demeester, J., Fritz, K., Goodrich, D.C., Kepner, W., Lane, C., Leduc, S., Leibowitz, S., Mcmanus, M., Pollard, A., Ridley, C., Schofield, K., Wigington, P. 2015. Connectivity and effects of streams and wetlands on downstream waters: A review and synthesis of the scientific evidence. Environmental Protection Agency. EPA/600-R-14/475F, 408.

Interpretive Summary: Maintaining clean water supplies and the human, economic, and ecological systems they support are of paramount importance to the health, economy, and environment of our society. To maintain our systems of clean water it is critical to know how water moves through and is connected across our landscapes and watersheds. The purpose of this document is to review and synthesize more than 850 publications from the peer-reviewed literature pertaining to three questions: 1) What are the connections (physical, chemical, and biological) to and effects of ephemeral, intermittent, and perennial streams on downstream waters? 2) What are the connections to and effects of riparian or floodplain wetlands and open-waters (e.g., oxbow lakes) on downstream waters? 3) What are the connections to and effects of non-riparian wetlands and open-waters (e.g., potholes) on downstream waters? This review supports three major conclusions: (1) Tributary streams, including perennial, intermittent, and ephemeral streams, are physically connected to rivers via channels and associated alluvial deposits where water and other materials are concentrated, mixed, transformed, and transported downstream. (2) Riparian and floodplain wetlands and open-waters (e.g., oxbow lakes and ponds) have complex connections with rivers via the export of channel-forming sediment and woody debris, transport of organic matter, provision of nursery habitat for breeding fish, and colonization opportunities for stream invertebrates. (3) Non-riparian wetlands and open-waters (e.g., kettles, potholes) provide numerous services of potential benefit to rivers and other protected waters, including storage of floodwater; retention of nutrients, metals, and pesticides; and re-charge of groundwater sources. These functions will affect downstream waters if the wetland is connected to the river network through a channel. In non-riparian wetlands that are not connected to the river network through a stream channel, connectivity varies within a watershed and over time. The literature we reviewed does not provide sufficient information at this time to evaluate the degree of connectivity (absolute or relative) of these particular non-riparian wetlands.

Technical Abstract: The purpose of this document is to review and synthesize more than 850 publications from the peer-reviewed literature pertaining to three questions: 1) What are the physical, chemical, and biological connections to and effects of ephemeral, intermittent, and perennial streams on downstream waters? 2) What are the physical, chemical, and biological connections to and effects of riparian or floodplain wetlands and open-waters (e.g., oxbow lakes) on downstream waters? 3) What are the physical, chemical, and biological connections to and effects of non-riparian wetlands and open-waters (e.g., potholes) on downstream waters? This review supports three major conclusions: (1) Tributary streams, including perennial, intermittent, and ephemeral streams, are physically connected to rivers via channels and associated alluvial deposits where water and other materials are concentrated, mixed, transformed, and transported downstream as well as by dispersal and migration of species that use both habitats during one or more stages of their life cycles. (2) Riparian and floodplain wetlands and open-waters (e.g., oxbow lakes and ponds) have complex physical, chemical, and biological connections with rivers via the export of channel-forming sediment Woiand woody debris, transport of stored (short or long term) organic matter, provision of nursery habitat for breeding fish, and colonization opportunities for stream invertebrates. (3) Non-riparian wetlands and open-waters (e.g., kettles, potholes) provide numerous services of potential benefit to rivers and other protected waters, including storage of floodwater; retention of nutrients, metals, and pesticides; and re-charge of groundwater sources of river baseflow. These functions will affect downstream waters if the wetland is connected to the river network through a channel. In non-riparian wetlands that are not connected to the river network through a stream channel, connectivity varies within a watershed and over time. The literature we reviewed does not provide sufficient information at this time to evaluate the degree of connectivity (absolute or relative) of these particular non-riparian wetlands.