The clear-cutting of forests in the 19th century adversely affected the ecology of the Larrys Creek watershed and its water quality.
Polluting industries on the creek and its tributaries during that period included coal and iron mines and tanneries.
As of 2006, water quality in Larrys Creek is quite good, although two small unnamed tributaries of Roaring Run do receive acid mine drainage from an abandoned coal mine.
Agricultural runoff is another source of pollution.
Effluent limits for Larrys Creek in Mifflin Township for the 5-day test for carbonaceous biochemical oxygen demand (CBOD₅) are 25 mg/L, while fecal coliform bacteria count limits are 200 per 100 mL in May through September, and 2000 per 100 mL in October through April.

The mean annual precipitation for Larrys Creek is 40 to 42 inches (1,000 to 1,100 mm).
According to the Pennsylvania Fish and Boat Commission: "Pennsylvania receives the most acid deposition of any state in the nation because, in addition to being the third highest producer of the gases that cause acid deposition, we are also located downwind from the highest concentration of air pollution emitters."
The region's geology gives it a relatively low capacity to neutralize added acid.
This makes the creek especially vulnerable to increased acidification from rain, which poses a threat to the long term health of the plants and animals in the creek.

The Jersey Shore Area Joint Water Authority's water filtration plant is on Larrys Creek, near the border between Mifflin and Anthony Townships.
The plant has been there since at least 1914 and provides water from the creek to 2,500 industrial and residential customers in the boroughs of Jersey Shore and Salladasburg, as well as Anthony, Mifflin, Nippenose, Piatt, and Porter Townships in southwestern Lycoming County, and Pine Creek Township in the southeastern part of neighboring  Clinton County, Pennsylvania.
The clear-cutting of forests in the 19th century adversely affected the ecology of the Larrys Creek watershed and its water quality. Polluting industries on the creek and its tributaries during that period included coal and iron mines and tanneries. As of 2006, water quality in Larrys Creek is quite good, although two small unnamed tributaries of Roaring Run do receive acid mine drainage from an abandoned coal mine. Agricultural runoff is another source of pollution. Effluent limits for Larrys Creek in Mifflin Township for the 5-day test for carbonaceous biochemical oxygen demand (CBOD₅) are 25 mg/L, while fecal coliform bacteria count limits are 200 per 100 mL in May through September, and 2000 per 100 mL in October through April.
The mean annual precipitation for Larrys Creek is 40 to 42 inches (1,000 to 1,100 mm). According to the Pennsylvania Fish and Boat Commission: "Pennsylvania receives the most acid deposition of any state in the nation because, in addition to being the third highest producer of the gases that cause acid deposition, we are also located downwind from the highest concentration of air pollution emitters." The region's geology gives it a relatively low capacity to neutralize added acid. This makes the creek especially vulnerable to increased acidification from rain, which poses a threat to the long term health of the plants and animals in the creek.
The Jersey Shore Area Joint Water Authority's water filtration plant is on Larrys Creek, near the border between Mifflin and Anthony Townships. The plant has been there since at least 1914 and provides water from the creek to 2,500 industrial and residential customers in the boroughs of Jersey Shore and Salladasburg, as well as Anthony, Mifflin, Nippenose, Piatt, and Porter Townships in southwestern Lycoming County, and Pine Creek Township in the southeastern part of neighboring  Clinton County, Pennsylvania.
Larrys Creek