THE ECOLOGICAL EFFECT OF DAM RECONSTRUCTION ON NEARBY STREAM SYSTEMS

The Conestoga River Basin lies within central Pennsylvania and drains into the Chesapeake Bay. Hammer Creek runs through the Conestoga River in Lancaster County and flows through a watershed influenced by agricultural use. In 1966, Speedwell Forge Dam was constructed on Hammer Creek to create a recreational lake. In 2011, storms in the area damaged the dam, forcing the lake to be drained. A local movement funded the re-construction of the dam to reestablish the lake. Reconstruction of the dam occurred from January to October, 2015, and the lake began to refill during the 2015-2016 winter. This research project’s goal is to assess the dam’s effect on the water quality of Hammer Creek.

Weekly water samples were collected both upstream and downstream of the dam in early summer 2015 (during dam construction) and in 2016 (after the lake had refilled). We measured temperature, DO, total nitrogen, ammonia, total phosphorus, reactive phosphorus, turbidity, COD, and metal composition for five weeks for each site. The data collected during and after the dam reconstruction event will be used with ecological data from 1949 (before dam) and 1997 (established original dam) to effectively display the health of Hammer Creek.

The water quality of Hammer Creek seems to have stabilized since the dam’s reconstruction. The presence of nitrogen and phosphorus compounds are the only contaminants present. Upstream of the dam was found to have nearly twice the amount of phosphorus, 4 times the amount of COD, and was also more basic than the site downstream of the dam. We suspect that the dam is limiting the biomass at the downstream location, thus decreasing the biochemical potential of Hammer Creek. Like many tributaries of the Conestoga River, the water quality of Hammer Creek is affected by a consistent influx of agricultural runoff from nearby farmlands.