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Become a Salt Watcher in your Community

Science Scope—March/April 2023 (Volume 46, Issue 4)

By Jill Nugent

Each winter, we often see salt applied to roadways to help make roads safer for automobile travel. But what is the long-term environmental impact to local waterways when the road salt runs off into streams, rivers, and creeks? Salt Watch is a project that was started to address this question.

Salt Watch began when an Izaak Walton League of America (IWLA) Fellow for Clean Water noticed a sizable amount of road salt left behind by a salt truck near a storm drain. The IWLA Fellow knew that the storm drain led into a stream that feeds into the Potomac River. Seeing this, the Fellow contacted local officials to share this information. It became evident that municipalities were not aware of the potential runoff issues, and the environmental impacts of salt runoff were not being studied at scale. This led to the development of the IWLA Salt Watch citizen science project.

When snow melts, or rainfall starts, road salt flows into local waterways. The salt runoff travels into storm drains, creeks, rivers, and streams, and into sources of drinking water. As salt settles and sinks, it can also impact groundwater. Salt can also play a role in corroding water pipes. The Salt Watch Project engages participants in monitoring chloride levels in local waterways. Since its launch over five years ago, the program has received 9,000 submissions of chloride data from citizen scientists around the country. Your students can be a part of this innovative large-scale effort to learn more about local road salting practices and the environmental impacts of road salt runoff.

Project goal: Monitor chloride levels in local streams and creeks

Your task: Monitor pollution from road salt runoff

Science discipline: Earth and Environmental Science

When students think of salt, they typically think of table salt, which is sodium chloride. Road salt, also known as rock salt, is often sodium chloride or magnesium chloride. Some municipalities treat winter roads with both salt and sand, and others use salt and water, which is often referred to as salt brine. Each year, roughly 10 to 20 million tons of salt are used on roadways in the United States. The ripple effects in the environment are not fully understood, and impacts from salt runoff are felt year-round. Chloride can be harmful to aquatic life, such as mayfly larvae. In higher temperatures (such as warmer months of the year), elevated salt concentrations in the water can be toxic to invertebrate organisms, including mayflies.

Students are invited to take part in year-round monitoring to discover the local environmental impacts of road salt runoff. Students can take the Salt Watch pledge and receive a free kit to participate in this exciting real-world project (see Figure 1). The Salt Watch kits come with four chloride test strips, which allow for four separate samples to be taken. Freshwater at your local sampling site (such as a stream, river, or creek) can be collected using a vial or a small glass container. Once you have your freshwater sample in the container, you will put one test strip from the kit into the container of water. You will wait until the orange bar on the test strip turns purple (or black) across the top. You’ll then hold the test strip against the kit’s postcard. Next, take an image of this with a phone or mobile device. You will submit this image to the app that IWLA uses as the project data portal. Along with your image, you will include the geographic location of your sample site. Participants are encouraged to add notes or comments to their observation and to add the hashtag #saltwatch!

Figure 1
The Salt Watch project test kit provided to participants.

The Salt Watch project test kit provided to participants.

Materials you will need:

  • Salt Watch kit (see ‘Project home”)
  • Vial or glass container
  • Mobile device (to take a photo and upload data)

Participating in Salt Watch leads to meaningful student engagement in authentic science and connects learners to a multitude of Earth Science topics. Teachers may be interested in leading students on a tour of the school grounds to see if the class can observe evidence of salt in the school parking lot or on sidewalks. During the outdoor exploration, the class can also look for storm drains where runoff would flow.

Additionally, hands-on classroom explorations of the topic can be conducted. For example, pond water can be collected and students would observe microscopic organism activity under a microscope at low, medium, and high levels of saltwater exposure added to the slide. Table salt can be used for this indoor activity, and students can observe that the higher concentration of salt water applied to the pond water slide results in decreased mobility of the microorganisms observed in the sample. This leads to questions about impacts of salt on the environment and living things.

The Salt Watch Project provides an array of resources to support learners, including ways that students can help spread awareness of this issue in their local community (see “Take Action”). Help make a difference in your local community and become a Salt Watcher!

Salt Watch at a glance

When: Anytime

How: Visit the Salt Watch Project page (see “Project home”) for participation information and how to acquire the test kit.

Where: United States, local waterways such as a stream, creek, or river

Time needed: Varies

Special equipment needed: Salt watch kit (see “Project home”)

Cost: Free

Contact for more information:

Safety: As with any science lab, classroom, or field activity, always ensure that you are following recommended safety practices; for more information on safety in the science classroom visit


Project home—

Project link on SciStarter—

Salt Watch story map—

Take action—

Jill Nugent ( teaches science online, engages educators in citizen science experiences for the classroom, schoolyard, and beyond, and serves on the SciStarter Team. Follow SciStarter on Twitter: @SciStarter. This column is the result of a partnership between SciStarter and the National Science Teaching Association. For more information about SciStarter and other citizen science projects, please visit

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