Baltimore Ecosystem Study Institute of Ecosystem Studies

2011 BES Annual Meeting Presentation and Poster Abstracts

Reflections on a year of deployment of high-frequency sensors in BES streams
Miller, Julia
Co-Authors: Julia Miller, Jason VerHoef, Claire Welty, Michael McGuire, Roxanne Sanderson, Andrew Miller, Sujay Kaushal, Jon Duncan, Peter Groffman, Larry Band, Kenneth Belt, and Reed Maxwell

Abstract: Beginning in October 2010, we deployed SUNA nitrate sensors paired with YSI specific conductance/temperature sensors at 6 USGS nested stream gage stations in Dead Run. Data have been collected continuously at a 30-minute interval. All stations show pronounced diurnal signals in nitrate, temperature, and specific conductance at constant stream discharge (base flow). Isolated incidents such as sewer overflows and other illicit or accidental discharges are also apparent from the high frequency data. During storm flow, both nitrate and specific conductance signals are diluted and then recover to pre-storm concentrations as the storm recedes. A binary mixing model has been applied to specific conductance data to determine the contribution old/pre-event water to stream hydrographs during storm flow. Results show that the fraction of old water contribution to streamflow decreases with increasing watershed size, but that the fraction increases across all scales with decreasing storm size. Additional goals of this year-long trial included evaluation of data quality and labor cost compared to manual sampling. Data collected from the sensors show good greement with long-term BES weekly data at DR Franklintown where the two data sets are available. The main issues identified that require ongoing labor include (1) pump replacement (approximately every 60 days); (2) cleaning of pump tubing and other parts to reduce biofouling (approximately every 3 months); and (3) problems with solar controller functioning. An additional issue is turbidity interference with optical nitrate measurement during some storm flows, which renders the sensor unable to record a number.