Regional in-situ optical water quality sensor network quantifies influence of land use and seasonality on storm event nitrate and dissolved organic carbon loading
Monday, 14 December 2015
Poster Hall (Moscone South)
High frequency optical water quality sensors were used to determine the influence of land use and seasonality on storm nutrient loads at nine stream sites in the North East Water Resources Network (NEWRnet). S::can spectrolysersTM were used to measure UV-Visible absorbance spectra at sub-hourly intervals in streams with primarily forested, urban, and agricultural watersheds. Calibrations for nitrate (NO3) and dissolved organic carbon (DOC) concentrations were developed for in-situ spectrophotometer measurements using multivariate statistical techniques applied to absorbance spectra and laboratory measurements. Calibrations were evaluated for predictive power and compared to assess applicability across multiple land uses and geographical areas. Calibrations were applied to sub-hourly absorbance spectra to determine NO3 and DOC loads for all storms in 2014 and 2015 for which data were available. Hydrographs were partitioned into direct runoff and baseflow components using a digital filter technique. In addition, the amount of biodegradable DOC (BDOC) was determined for a subset of samples and related to spectrophotometer measurements to determine influences of land use on BDOC content during storms. Comparing NO3 and DOC export per watershed area to storm runoff shows that storm severity, storm frequency, and land use have strong influences on regional NO3 and DOC storm export. This study highlights the value of high frequency continuous stream monitoring for land use and watershed management, particularly in the context of storm event loading.