Wetland Wednesday
March 4, 2020
There are a few subtle and not so subtle implementation aspects of the final Navigable Waters Protection Rule (NWPR). Chief among these is the definition of a tributary. On the surface (pun intended) only streams, wetland and other waterways that have a surface connection to a Traditional Navigable Waterway (TNW) are federally jurisdictional. At issue is what is meant by surface connections?
Tributaries have been segmented for years into three broad classifications. These classifications were used for Section 401 Clean Water Act (CWA) water quality standards implemented by the states. There are differences in the way each state interprets the classifications but overall, they follow these general definitions,
These definitions come from the North Carolina Methodology for Identification of Intermittent and Perennial Streams and Their Origins (2010) and are specifically referenced in the final rule preamble.
Perennial stream means a well-defined channel that contains water year-round during a year of normal rainfall with the aquatic bed located below the water table for most of the year. Groundwater is the primary source of water for a perennial stream, but it also carries stormwater runoff. A perennial stream exhibits the typical biological, hydrological, and physical characteristics commonly associated with the continuous conveyance of water.
Intermittent stream means a well-defined channel that contains water for only part of the year, typically during winter and spring when the aquatic bed is below the water table. The flow may be heavily supplemented by stormwater runoff. An intermittent stream often lacks the biological and hydrological characteristics commonly associated with the conveyance of water.
Ephemeral (stormwater) stream means a feature that carries only stormwater in direct response to precipitation with water flowing only during and shortly after large precipitation events. An ephemeral stream may or may not have a well-defined channel, the aquatic bed is always above the water table, and stormwater runoff is the primary source of water. An ephemeral stream typically lacks the biological, hydrological, and physical characteristics commonly associated with the continuous or intermittent conveyance of water.
In order to be federally jurisdictional both the perennial and intermittent stream types must meet the new definition of a tributary. These streams contribute surface flow to traditional navigable waters in a typical year. They must flow more often than just after a single precipitation event.
In order to accomplish perennial or intermittent flow groundwater is needed to provide a base flow. For the purposes of the NWPR groundwater is not federally regulated and they say as much in the regulation. But as a good friend had always told me this is regulatory and not reality. So be sure your stream has a perennial base flow and don’t worry about where it is coming from.
Have a great week!
Marc