Continuous water quality to capture all events: how good are the new sensors?

Abstract:

A revolution in the way we measure, understand, and predict the fate and transport of C, N, and P in streams and rivers is made possible with the availability of new continuous water quality sensors. For the first time in history of hydrological sciences, there is the possibility to capture the changes in parameter concentrations for all events, in particular the large and extreme ones which weigh so heavily in the total exports. While these sensors provide unprecedented insight on the dynamics of water quality dynamics (e.g., diel concentration fluctuations, concentration increase/decrease during events), it is important to know the uncertainty associated with these instruments. In particular, mass balance and stoichiometry are crucial to understand and quantify the fate of C, N, and P. We report here the uncertainty that may be expected on annual loads of Nitrate, Organic Nitrogen, Dissolved Organic Carbon, Total Phosphorus, and Total Suspended Solids, due to sensor uncertainty in coastal plain watersheds of North Carolina. For this, we tested the impact of the stratification and number of discrete samples to calibrate UV-Vis spectrophotometers from S::CAN for three watersheds. We compare the uncertainty calculated on the annual loads to those induced by infrequent sampling