Covering 129 square miles, Seneca Creek is the largest watershed in this report and the largest watershed in Montgomery County, MD. The watershed includes Great Seneca, Little Seneca, and Dry Seneca Creek along with their tributaries. The creek begins with two tributaries, Great Seneca Creek in Damascus and Little Seneca Creek in Clarksburg, and all three tributaries join the mainstem to eventually empty into the Potomac River.

Report Highlights and Opportunities for Improvement:

Seneca Creek had fair scores on Biodiversity & Habitat, scoring a 70 overall. Seneca Creek’s “Fair” scores for Fish Passage are reflected in its “Good” fish index or FIBI scores. Seneca Creek has migrating fish species, such as trout and smallmouth bass that can thrive with fewer barriers to its migration. 

While Seneca Creek has a good fish index score, it scored “poor” in its Benthic Macroinvertebrate or (BIBI) score. This is likely due to its moderately poor scores for Invasive Plants and Tree Canopy. Invasive plants directly affect tree canopy by taking resources necessary for tree growth and survival. When streams have less tree canopy, they are more vulnerable to pollution, thereby not being able to support benthic macroinvertebrates.