THE EFFECT OF BEAVER DAMS ON PHOSPHORUS CYCLING

Beaver dams change the hydrology of rivers by altering the distribution of sediments and nutrient cycling. The ponds created behind dams decrease water velocity causing sediment deposition. This possibly causes the build up of phosphorus in sediment behind the dam as it gets trapped behind it. This study focuses on a stream that has a beaver dam built downstream of a water treatment plant that discharges water rich in nitrogen and phosphorus into the stream. The hypothesis being tested is whether or not more sediment and phosphorus is stored behind the beaver dam, downstream of the effluent than in a natural pool upstream of the discharge point. This study requires collecting and testing sediment from downstream of the treatment plant and behind the beaver dam and comparing it to sediment from upstream of the water treatment plant. The data collected included sediment samples from downstream of the effluent and samples from the pond upstream of the dam and effluent. These samples are analyzed using a four-step phosphorus extraction procedure with results showing the amount of phosphorus stored in the sediment. This study also requires surveying and creating cross-sections of the sample area by the dam and the pool upstream. The data indicate that there is much more phosphorus in the sediment downstream of the treatment plant by the dam than in the sediment upstream of the treatment plant discharge. Cross sections of the beaver pond and natural pool are being periodically surveyed to estimate the change in stored sediment at each location.