Water Quality Monitoring

Tracking Harmful Bacteria in Streams

Bacteria monitoring helps identify the presence of E. coli in Rock Creek. Elevated bacteria levels can result from stormwater runoff carrying pet waste, broken or leaking sewer pipes, and failing or poorly sited septic systems. Monitoring provides critical insight into water quality, seasonal trends, and public health risks.

Volunteers collect weekly water samples from May through September at sites throughout the DC and Montgomery County portions of the Rock Creek watershed. During each sampling event, volunteers measure E. coli bacteria, turbidity, pH, water temperature, and air temperature. This data collection helps identify pollution patterns and determine whether bacteria levels meet EPA recreational water quality standards.

Rock Creek Conservancy collaborates with regional partners, including Alliance for the Chesapeake Bay, Anacostia Riverkeeper, and Potomac Riverkeeper Network, to support bacteria monitoring efforts and provide weekly, up-to-date water quality data for streams with high recreational use.

Measuring Road Salt Impacts on Streams

Salt Watch tracks sodium chloride (NaCl) levels in streams to understand the impacts of winter road salt on water quality. Each year, roughly 20 million tons of salt are applied to roads, sidewalks, and parking lots across the U.S. That salt is washed into streams, where it can persist for months or years, harming aquatic life, degrading drinking water sources, and corroding infrastructure.

Volunteers monitor streams throughout the Rock Creek watershed monthly, as well as before and after winter storm events. Using test kits, participants measure chloride levels to identify pollution hot spots, track changes from winter weather and salt application, and document conditions that may affect stream health.

Since 2024, Rock Creek Conservancy has partnered with the Izaak Walton League of America to monitor road salt pollution through Salt Watch, a national community science program. This collaboration helps expand monitoring coverage, raise awareness, and encourage more efficient and environmentally responsible salt use in local communities.

Assessing Stream Health Through Aquatic Life

Benthic macroinvertebrates are small aquatic animals that live on the bottom of streams. Since different species have varied tolerances to pollution, they serve as excellent indicators of long-term stream health.  Streams dominated by pollution-tolerant species (such as worms and midges) and lacking sensitive species (such as mayflies and crayfish) typically indicate poorer water quality.

At Normanstone Run, the Conservancy leads monitoring efforts, visiting the stream three to four times per year. Volunteers collect, identify, and count macroinvertebrates while also evaluating habitat conditions, providing a comprehensive picture of stream health at this site. This is the only location where all three water quality monitoring programs occur.
The data collected is used to calculate a Benthic Index of Biotic Integrity (B-IBI) score, with higher scores indicating a healthier and more diverse aquatic community. Rock Creek Conservancy partners with Nature Forward on its Community Science Water Quality Monitoring Program.  Findings are shared with agencies, watershed groups, and the public to guide restoration and protection efforts.