The Importance of Small Streams

02 June 2015 Written by   Ellen Wohl
Along Bumble Bee Creek Along Bumble Bee Creek

As we come out of an unusually wet late spring in northern Colorado, I am enjoying the sight of small streams appearing in normally dry gulches. My weekly hike on the shortgrass prairie near my home is enlivened by the calls of meadowlarks, as it is every year at this time, but also by the unaccustomed sound of swiftly flowing water. Little streams flow bank-full with turbid brown water along channels I have never seen flow before. Further east, near the Colorado-Nebraska border, I know the Arikaree River will be flowing steadily, too. Only in a place as dry as the Great Plains would the Arikaree be designated a river. Most years it flows continuously only during spring, drying back to disconnected pools later in the summer. But these pools host endangered fish such as the brassy minnow, which is barely hanging on in Colorado.


Arikaree River

The Arikaree River


Small, mostly dry streams are easy to ignore. They don’t support many fish or other obvious forms of river life; they are not a dependable source of drinking water; and you certainly can’t navigate them. Consequently, most small streams in the United States receive little, if any, legal protection under legislation such as the Clean Water Act. As a river scientist, I consider this a travesty. Ecological studies clearly indicate that small streams, even if they don’t flow year-round, provide vital services. They include different habitat than larger rivers, and this habitat can support different species of plants and animals, as well as juvenile forms of some fish that move throughout a river network. Small streams and their riverside vegetation help to filter excess nutrients, such as nitrogen and phosphorus, from water passing downstream into the greater river network, thereby improving water quality.

In most river networks, relatively small streams make up 70 to 80 percent of total river length. This makes it particularly important to protect small stream ecosystems, which cumulatively exert a substantial influence on the health of larger rivers. It also makes it difficult to protect small streams, because they seem to be everywhere. The United States Environmental Protection Agency just issued a ruling extending federal protection to many small streams, but Congressional Republicans are threatening to overturn the ruling. Farmers, developers, utilities, and other groups claim that they will need to go through abundant red tape for every little channel that lies in their path. Certainly, the ability to construct infrastructure and use soil and water for consumptive purposes will be affected. A similar outcry greeted the original Clean Water Act in the 1970s, but our economy and society have been able to accommodate the need to protect such fundamental qualities as surface water clean enough to support fish. I predict that the new ruling will similarly improve our environment and quality of life.

You appreciate the value of water when the well runs dry. We are just beginning to appreciate the value of small streams as water quality in so many rivers like the Mississippi steadily declines as their headwater filters are lost. 

Ellen Wohl teaches geology at Colorado State University. She is a Fellow of the American Geophysical Union and the Geological Society of America and a Fulbright Fellow. She has received the G. K. Gilbert Award from the Association of American Geographers and the Kirk Bryan Award from the Geological Society of America and has written nine books. Read more of her work in Island of Grass, Wide Rivers Crossed, or Transient Landscapes.

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