A TWO-YEAR COMPARISON OF NUTRIENT FLUXES IN DUTCH HOLLOW BROOK, OWASCO WATERSHED, CENTRAL NEW YORK

Dutch Hollow Brook (DHB) is the 2^nd largest tributary entering Owasco Lake, a Finger Lake in central New York. The lake is a critical a source of drinking water for ~44,000 residents, and supports an agricultural and tourism based economy. Dutch Hollow Brook drains 15% of the Owasco watershed, but is rich in crop and animal farmland (65% of the DHB watershed).

A Teledyne ISCO 6712 Portable Water Sampler (R2D2) was installed near the terminus of Dutch Hollow Brook to quantify nutrient fluxes to the lake. The sampler was programmed to autonomously collect 1-L of water every 8 hours through the March to October field season, anticipating sufficient data to compare seasonal variability, precipitation and other events to base-flow conditions.

The water sampler was serviced weekly and the collected water was analyzed for total phosphate (TP), dissolved phosphate (SRP), nitrates, silica, pH, conductivity, alkalinity, and total suspended solids (TSS) following standard limnological procedures. Further, the stream was sampled and measured on-site for stream discharge, pH, dissolved oxygen, conductivity and alkalinity on a monthly basis, and water samples were brought to the lab for nutrient and TSS analyses.

Graphical interpretation of the aforementioned analyzed parameters suggests rainfall events dictate variability in stream discharge and nutrient concentrations flowing down DHB. Rain events producing over 0.6 inches of precipitation profoundly increased the concentration of nutrients. Between years, the average concentration and flux of TP, SRP, TSS, nitrates and silica were larger in 2011, primarily because 2011 was a wetter summer in comparison to 2012. Rainfall events had a smaller impact on nutrient concentrations later in the summer, than the spring and fall seasons, and most likely correlated to drier soil conditions, more uptake by plants, and larger storage capacity allowing less direct runoff for similar precipitation totals.

Continued monitoring of Dutch Hollow Brook in the future will hopefully provide a two year comprehensive dataset recording rain events and their continued affect on nutrient loading within Dutch Hollow Brook during the spring, summer and fall months, and ultimately Owasco Lake. We anticipate that the results may pinpoint and dictate future mitigation and remediation efforts.