What is a headwater stream?

 

The headwaters of a river system are the small streams and wetlands that are the sources of its water. There are three types of headwater streams: perennial (flowing throughout the year); intermittent (flowing seasonally, when the water table is higher); and ephemeral (flowing only in response to precipitation).

 

A river system has branches like a tree. And like a tree, the different parts of a river system perform specialized functions. Just as the leaves that feed a tree generally grow on the ends of its branches, and not on its trunk, headwater streams perform functions for which they are uniquely suited.

 

But though a river system may branch like a tree, it does not regenerate like one. Unlike a healthy tree that responds to pruning by putting its energy into remaining branches and growing new ones, a river system can’t grow new “branches” in the form of ephemeral and intermittent streams, in its upper reaches. And while restoration ecology has made significant advances in recent years, it is still hard to replicate the multi-faceted natural processes of headwater streams.

 

Healthy headwaters, healthy streams

By Robin Mann

“The very foundation of our nation’s great rivers is a vast network of unknown, unnamed, and underappreciated headwater streams.” 

This assessment of the role played by small streams and associated wetlands in maintaining healthy rivers appeared in the 2003 report, Where Rivers are Born:  the Scientific Imperative for Defending Small Streams and Wetlands. The report, written by a team of nationally known scientists, including two from Pennsylvania’s own Stroud Water Research Center, was issued in response to the Bush administration’s plans to reconsider the extent to which such waters warrant protection under the Clean Water Act.

In recent years, intensive study of the river ecosystem has revealed the critical role that headwaters play in maintaining healthy conditions further downstream. We now know even more about the vital role played by headwaters than we did when many of our water quality laws were adopted—and as a result, we now also know how much more needs to be done when it comes to headwater protection. 

The services of headwater streams are many. They maintain water quality, by processing nutrients and other pollutants; attenuate flooding, by slowing and storing flood flows; maintain water supplies, by recharging groundwater; trap and retain sediments; process organic matter such as leaf litter into food sources for aquatic life; maintain aquatic biodiversity, by offering habitat for a variety of species, many of them threatened or endangered; and provide nurseries for young fish and refuge from predators.

The consequences of past destruction have also helped us better understand the nature of these ecosystem services. An intact stream network will have most of its channel length composed of small headwater streams. Where those streams have been enclosed in pipes, or filled in completely, the stream system loses important metabolic functions and is less able to slow floodwaters. This results in degraded water quality downstream, along with greater erosion and sedimentation, and the increased likelihood of flooding.  

While our understanding of the critical importance of headwater streams has greatly advanced in recent years, public policy has been dragging behind, and in some cases, moving in reverse. One example of outdated policy is Waiver 2 under Pennsylvania’s dam safety and waterway management code, which exempts landowners from applying for permits to fill in streams that drain 100 acres or less of land. The original intent of the waiver was to allow farmers to put more land into cultivation without getting a permit. However, in recent years, developers have used Waiver 2 to relocate streams or to bury them in pipes so that they can develop more land for subdivisions. This one Waiver alone routinely results in the burial of thousands of feet of stream for a single subdivision development. 

Meanwhile, at the federal level, the administration’s policy of excluding so-called isolated waters from protection under the Clean Water Act has undermined headwaters in Pennsylvania. A comprehensive and effective Clean Water Act is vital to ensure that even in states like Pennsylvania, which have fairly comprehensive programs, the protections are reliably applied.

Thankfully, the resistance of the Pennsylvania Department of Environmental Protection (DEP) and other state agencies, along with a groundswell of opposition from the environmental community has, to date, discouraged the Bush administration from proceeding with plans to officially remove headwater streams and wetlands as protected “waters of the United States.” The DEP is to be applauded for joining the Attorneys General of 33 other states and the District of Columbia in submitting a brief in support of the government’s claim of jurisdiction over tributaries and adjacent wetlands in the Rapanos and Carabell cases currently before the U.S. Supreme Court.

If the DEP now moves ahead to eliminate the Waiver 2 loophole, it will force developers and mining companies to practice less destructive alternatives and save miles of Pennsylvania streams.

For more information, download a copy of Protecting Headwaters: The scientific basis for safeguarding streams and river ecosystems.

Robin Mann is a member of the Southeastern Group has served as our Chapter's water Chair. Mann currently serves on the Club's national board.

Published March 2006