Streams Take Me By Surprise

Several links below exit EPA Exit EPA Disclaimer

By Travis Loop

As a teenager I spent a lot of time exploring the Catoctin Mountains in central Maryland. I especially loved a section of the mountains that was accessible by a few rough gravel roads and criss-crossed by a network of unmarked trails. I will always remember the time I was hiking and stopped in my tracks when I discovered water where it hadn’t been before. I realized that it had rained heavily the day prior and I had never been on that trail after rainfall.

Almost 20 years later, I’ve learned that these type of streams – that only flow after precipitation or in certain seasons – actually form the foundation of our nation’s water resources. It’s staggering that almost 60 percent of stream miles in the continental U.S., or more than 207,000 miles, only flow seasonally or after storms. These unknown, unnamed and underappreciated streams – like the one I discovered in the Maryland mountains – have a tremendous impact on everything downstream, including rivers, lakes and coastal waters, as well as people.

In fact, the stream I discovered was in the Frederick City Watershed, an area of 7,000 acres used as the source for about 20 percent of the drinking water for residents. So the water in that stream eventually came out of a tap and into someone’s glass. This isn’t unique to Frederick, MD. Approximately 117 million people– over one-third of the U.S. population – get part of their drinking water from these streams.

But these streams are important for many reasons. They are vital for recharging the groundwater supply because water enters through stream beds. Also, because these streams can store a lot of water, they help protect downstream communities from floods.  Seasonal and rain-dependent streams filter pollution and sediment, preventing them from traveling downstream and harming other waterways. One study estimated that small streams can remove 20 to 40 percent of the nitrogen that otherwise would pollute downstream waters. Additionally, protecting these streams is important for the economy, particularly for their key role in supporting fishing, hunting, agriculture and recreation.

Unfortunately, because they are often small, unnamed, not on maps and not always wet, these streams are very vulnerable. And they probably are important in your community. Now I live in Anne Arundel County, Maryland, and I just discovered that 75 percent of the streams only flow seasonally or after rain. These streams just keep taking me by surprise.

About the author:  Travis Loop is the director of communications for EPA’s Office of Water.

Editor's Note: The views expressed here are intended to explain EPA policy. They do not change anyone's rights or obligations. You may share this post. However, please do not change the title or the content, or remove EPA’s identity as the author. If you do make substantive changes, please do not attribute the edited title or content to EPA or the author.

EPA's official web site is Some links on this page may redirect users from the EPA website to specific content on a non-EPA, third-party site. In doing so, EPA is directing you only to the specific content referenced at the time of publication, not to any other content that may appear on the same webpage or elsewhere on the third-party site, or be added at a later date.

EPA is providing this link for informational purposes only. EPA cannot attest to the accuracy of non-EPA information provided by any third-party sites or any other linked site. EPA does not endorse any non-government websites, companies, internet applications or any policies or information expressed therein.