What is a Stream & How Can We Protect Them?

Photo © The Nature Conservancy (Erika Nortemann)

So what exactly is a streamopen_in_new? Technically speaking, streams are formed by the convergence of surface water and groundwater into the lowest topographic area of a valley which sustains a current and is confined within narrow beds and steep banks. Here, we explore the importance of streams and the threats they face along with different indicators of wellness and how to conserve and protect these important natural resources.

Aerial view of tidal creeks and tributaries of the Winyah Bay Basin area, primarily in Town Creek, South Carolina.

Photo © The Nature Conservancy (Mac Stone)

Streams are the capillaries of a continent. In the United States, there are over 3.5 million miles of rivers and streams carrying nutrients and water from one place to anotheropen_in_new. Every individual stream is part of a larger system (watershed) of waterbodies which are all connected, much like the circulatory system in the human body.

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Photo © Taylor Howard

Streams supply drinking water and irrigation for growing food. Your local stream or creek is a part of a larger watershed, draining into larger rivers, lakes, and reservoirs. These larger waterbodies are the main source of municipal drinking water, a food source, and provide critical recreation opportunities to fisherman, boaters and beach-goers. These resources, or ecosystem services, make the health of even the smallest backyard stream extremely important.

Ecosystem services are the benefits and resources we receive from the environment or, in this case, streams. They are often categorized in four waysopen_in_new:

  • Supporting services: necessary for the production of other ecosystem services
  • Provisioning services: products obtained from an ecosystem
  • Regulating services: processes that maintain an ecosystem, like climate regulation and water purification
  • Cultural or recreational services: are non-tangible benefits we regard with personal value
ecosystem services diagram

Photo © The Nature Conservancy

The above graphic depicts the ecosystem services of freshwater stream ecosystems. Streams not only provide many ecosystem services for citizens, they also serve as habitat for a diverse array of organisms and, in some cases, species only found in a specific ecosystem. Protecting these specialized organisms often comes down to preventing pollution from entering waterways from homes and businesses.

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Photo © Albert Bridge

People commonly mistake water clarity as a sign of a healthy stream; but, clear water is only one indicator of good health. Other signs include biological indicators like the presence of certain macroinvertebrate species or chemical signals like pH and dissolved oxygen levels. Aquatic macroinvertebrates serve as the most prominent biological stream health indicator (bioindicator) because they often require very specific conditions for living. Aquatic macroinvertebrates are tiny animals that do not have a backbone, can be seen with the naked eye, and spend at least part of their lives in water. You may be familiar with some of these animals, like clams, snails, and crayfish but they also include a wide variety of insects and worms.

Employees from Strond Water Research Center check a stream for emphemeroptera, plecoptera, and trichoptera bugs. These types of bugs all indicate healthy freshwater. On May 20 and 21, 2016, The Nature Conservancy and The National Parks Service partnered w

Photo © The Nature Conservancy (Devan King)

These macroinvertebrates are often used to determine the quality of waters based on species richness and where they are found. It’s not just the numbers of insects that matter, but also the types. Some species, like black flies or midges, can tolerate unhealthy stream conditions better than dragonflies or mayflies, which are dependant on specific environments and are more sensitive to changes in water quality. It is possible to sample animals like these to provide snapshots of stream health overtime.

Bioindicators example

Summer staff Julia Monk is counting insects that come from the Greater Sage-grouse habitat. At one point during their time at Centennial Sandhills Preserve the LEAF interns helped to gather the bugs that Julia is counting. The study is to see what the sag

Photo © The Nature Conservancy (Joanna Pinneo)

Stoneflies (Plecoptera), caddisflies (Trichoptera) and mayflies (Ephemroptera) are examples of taxa highly sensitive to pollutionopen_in_new. These taxa do not survive long in environments with excessive algae or inorganic sediments and their presence is an indicator of a healthy body of water. On the contrary, aquatic worms and leeches are more tolerant bioindicators and can indicate organic pollution when they dominate the majority of a river. Visit the Carnegie Museum of Natural History’s website to learn more about pollution tolerant and pollution sensitive organisms like stoneflies, mayflies, and caddisfliesopen_in_new.

The US Forest Service adds woody debris into Twelve Mile Creek to restore important salmon habitat on Prince of Wales Island in Southeast Alaska.

Photo © The Nature Conservancy (Erika Nortemann)

The health of streams are affected by a variety of disturbances. Some of these are natural and can support diversity, as with severe storms or droughts, at other times they’re anthropogenic, or human influenced, potentially reducing diversity. Anthropogenic disturbances can include, but are not limited to: pollution (stormwater runoff, CSO (combined sewer overflow systems)), the creation of dams, over harvesting of freshwater, invasive species such as Japanese knotweed (Polygonum cuspidatumopen_in_new), etc. When a stream’s riparian zone, which protects its waters from surrounding development, is disturbed or developed, the stream’s ability to function and provide ecosystem services can be reduced.

Cahaba River in Birmingham, Alabama. The longest free-flowing river in Alabama.

Photo © The Nature Conservancy (Devan King)

Riparian zones are referred to as buffers for a reason. Typically composed of trees, shrubs and herbaceous vegetation–roots and foliage filter and slow pollutants in runoff, which reduce erosion and trap sediments before they enter the stream. The shade they provide helps control temperature which, in turn, helps maintain dissolved oxygen in the water, vital for its inhabitants. Warmer water decreases the amount of oxygen that is soluble in the water while increasing rates of decay and other processes that take oxygen out of the water. Put simply, a damaged, or missing, riparian zone is major threat to the health and stability of a stream.

Oil pollution from the 2010 Deepwater Horizon accident coats beach and shoreline along Alabama's Gulf of Mexico coastline. The Nature Conservancy in Alabama is spending a great deal of staff time and resources responding to the Gulf oil spill.

Photo © The Nature Conservancy (Ami Vitale)

Anthropogenic disturbances are some of the most pressing threats to our streams (picture above is from an oil spill). Below we cover some of the ecological disturbances resulting from human impact.

Turbidity: the cloudiness of the water, typically caused by disturbance in the water creating movement in sediment. High turbidity raises water temperature and lowers dissolved oxygen. *Most aquatic organisms need dissolved oxygen for respiration and other biological functions.

Pollution: can result from close proximity to developments like roads, parking lots, schools, businesses, industries, etc. Carbon emissions, or particulates from cars, chemicals from lawns, fertilizers and pesticides from farm fields, and oils from roads can get directed into our streams when it rains, reducing oxygen and changing the pH or potentially adding toxic chemicals to the water.

Temperature variability: Insufficient canopy coverage can cause variations in temperatures along the stream. Open areas are warmer and often have reduced oxygen concentrations than cooler shaded regions.


Photo © The Nature Conservancy (Mark Godfrey)

Influencing stream health in your community may seem like an overwhelming responsibility but small actions from you and your neighbors can add up to a meaningful impact. One way to get involved is to join a local stream monitoring group. Almost every state has their own stream monitoring program. A second way to protect your local streams and watershed is to manage the water on your property.

Below we list a couple of actions you can take to manage water on your property (even if you don’t have a stream) using the Habitat Network Planning Tool.

If you have a small stream running through your backyard or neighborhood, make sure you map it so we can continue to collect information on how individuals are taking conservation into their own hands and protecting their part of the network of streams and creeks on which we all depend.

Adding a Stream to your Map

If you are lucky enough to have a stream on your property, consider mapping it and share how you are protecting it.

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Photo ©

First outline the portion of the stream that lies on your property, as demonstrated above, using the Water habitat.

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Photo ©

Then set the characteristics. Open the info-window by double clicking on the stream habitat polygon. Give it a name, like backyard stream and then tell us about it.