COLUMBUS, OH - The St. John's dam in Seneca County impounded several miles of the Sandusky State Scenic River for nearly 100 years. But in November 2003, the dam was removed with hopes of allowing the river to return to its natural state. A groundbreaking study, started nearly two years ago, continues to evaluate the impact of the dam's removal on the river's water quality, riverbed and wildlife.
The study marks the first time such extensive research has been done in Ohio to examine how a formerly impounded river naturally recovers over time. Study of the area above and below the St. John’s Dam began shortly before its removal and continues today for a total of five years.
“Dam removal is an effective method to restore the health of river habitat and return streams to their natural condition,” said Bob Gable, scenic rivers manager for the ODNR Division of Natural Areas & Preserves. “We continue to look at obsolete dams across the state and the positive impact that removing such dams could have on the state’s scenic river system.”
The study includes surveying fish communities and other river life, analyzing water chemistry and the transporting of river sediments, mapping of the river, and monitoring water levels in nearby wells two months after the removal.
The concrete arch dam was built in the early 1900s to create a reservoir for public water supply for the City of Tiffin, but the dam was never used for that purpose. By 1999, state dam inspectors determined the deteriorated dam was in need of repair or removal.
A 2001 report by the Ohio Environmental Protection Agency found the environment created by the St. John’s dam - lack of flow and depositing of silt - was not favorable to habitat creation and river life.
The Division of Natural Areas & Preserves, through its Ohio Scenic Rivers Program, initiated the study, enlisting the assistance of the ODNR divisions of Wildlife, Water and Geological Survey in the pre- and post-dam removal monitoring.
Researchers with the Division of Wildlife are studying the fish community along the Sandusky River and how it responds to the dam removal. Each year a fish sampling gauges how the environment might be changing. For example, as the river system regains its momentum, researchers anticipate the aquatic habitat above the former dam to change from one that supports still-water species to those that thrive in moving water.
“In order for this river system to recover successfully, it needs to be able to flow and move within the channel to naturally create different kinds of habitat,” said Mike Wilkerson, a Division of Wildlife biologist. “When this happens, we expect the waterway to go from a system dominated by carp to one dominated by smallmouth bass.”
ODNR’s Division of Geological Survey mapped the river before the dam removal and will continue to survey its structure post-dam removal. Specifically, geologists are surveying the physical changes of the riverbed sediment and river morphology to observe changes in spawning habitat that fish may occupy. Aerial photographs as well as Global Positioning System and Geographic Information System technology are being used to help identify any changes in the river channel.
“This mapping plays a critical role by providing us a physical framework from which we can better understand the biological and chemical changes that may occur as a result of the St. John's dam removal,” said Connie Livchak, geology program manager with the ODNR Lake Erie Geology Group.
The St. John’s Dam research project is partially funded by the Ohio Scenic Rivers Protection Fund - a fund supported by the sales of Scenic Rivers license plates. The fund helps protect and restore scenic river forest corridors, improve water quality and river habitat for endangered species, facilitate river clean-ups and Ohio’s Stream Quality Monitoring Project, and promote river conservation and education.
Other partners in the St. John’s Dam removal research project include: The Ohio State University, Heidelberg College, the Ohio EPA and the Ohio Department of Transportation.