In each watershed, a measuring tape was run along the stream channel
and measurement locations were flagged approximately 50m apart,
starting at the weir of the waterhsed and moving upslope. (In WS1,
reach 11a corresponds to an in-between sampling point that was later
added because it was determined that there was a seep entering at this
location which was extremely rich in NO3.) In the event of a fork in
the stream, the main stem of the stream was followed, as determined by
greater upslope accumulated area. For each survey, unfiltered grab
samples were taken at each sample point, starting at the weir and
continuing upstream until first flowing water. Samples were
immediately analyzed in the field using a SUNA optical nitrate sensor
(Seabird Scientific, Halifax, NS) which had parafilm wrapped around
the optical path to create a sample cell. Discharge at the weir for
each sampling time was calculated using the USFS 5 minute stage data
and a rating curve created from the historical stage and discharge
data. If no time wasrecorded for a survey, the average discharge over
the interval of 8 AM to 12 PM is reported here, as these surveys took
place in the morning according to field notes. Units: Liters per
second. Discharge at each sampling point was calculated by multiplying
the discharge at the weir by the proportion of the watershed drained
by the stream at each sampling point.
Additional details on methods and analysis can be found at:
Marinos, R. E., Campbell, J. L., Driscoll, C. T., Likens, G. E.,
McDowell, W. H., Rosi, E. J., Rustad, L. E., & Bernhardt, E. S.
(2018). Give and Take: A Watershed Acid Rain Mitigation Experiment
Increases Baseflow Nitrogen Retention but Increases Stormflow Nitrogen
Export. Environmental Science & Technology, 52(22), 13155–13165.
https://doi.org/10.1021/acs.est.8b03553