PHOSPHORUS AND SEDIMENT VARIABILITY ALONG DUTCH HOLLOW BROOK IN THE OWASCO LAKE WATERSHED, CENTRAL NEW YORK

Past research has shown that Dutch Hollow Brook is susceptible to event-induced delivery of phosphorus and sediment to Owasco Lake. Owasco Lake is a mesotrophic, mid-sized, Finger Lake of central New York State. Its water quality has become stressed in recent years due to nutrient loading from the agriculturally-rich, rural landscape, and has experienced harmful algal blooms. Dutch Hollow Brook, located at the northeast end of the watershed, drains the second largest portion of the watershed. The nutrient and sediment sources include agricultural practices and stream bank erosion. In this presentation, we focus on the change in phosphorus and sediment concentrations along the lower reaches of the stream to investigate the impact along the lower, meandering portion of the watershed.

The water quality of this stream was monitored at three successively upstream locations: Rt. 38A, Martin Rd, and North St that effectively bracket the lower meandering portion of the stream. Each site was continuously monitored during the 2015 field season (4/06/15 through 10/25/15) using Teledyne ISCO 6712 portable water samplers programmed to collect water samples every eight hours. The sampler was serviced weekly. Water samples were filtered through pre-weighed glass fiber filters and dried at 80C for at least 24 hours for total suspended solids (TSS) concentrations and analyzed for total phosphorus (TP) after a 1 hour digestion in 100C per-sulfate and colorometrically analyzed by spectrophotometer following standard techniques.

The TP and TSS concentrations during precipitation events were compared from one site to the next to investigate potential sources of nutrients and sediments along this stream reach. Total phosphate concentrations typically increased between the North St site and the Martin Rd site and subsequently declined farther downstream for 20 of the 41 events. TP event variability did not correlate with the sediment trends. The majority of the largest sediment concentrations were detected at the 38A site, especially during the spring when stream discharge was high. During the reduced summer discharge, the largest TSS event concentrations were instead detected at the two upstream sites. It indicates that stream bank erosion is partially responsible to the phosphorus and sediment loading to Owasco Lake.