LOCATION DESCRIPTION
Samples are collected from a road culvert outfall approximately 25m upstream from the lake, 10m upstream of the USGS
stream-gauging flume. This sub-catchment (24 ha area) of the Mirror Lake watershed contains 4 seasonal homes,
one year-round residence, one unpaved (un-salted in winter) public road, and one paved private driveway (salted in winter).
Numerous studies have been conducted on Mirror Lake since the mid-1960s, including extensive chemical, biological, and
paleoecological research which are described in detail in the book: An Ecosystem Approach to Aquatic Ecology (Likens, 1985).
SAMPLING DESIGN
Samples are collected in acid-washed, deionized water-rinsed, polyethylene bottles. The normal sampling interval is weekly, with more
frequent samples taken at times of increased discharge.
DATA DESCRIPTION
Concentrations (mg/L) in weekly streamwater samples. Base cation and pH data are available since 1967. Ammonium,
anions, and dissolved silica have been measured routinely since 1970, and phosphate was determined routinely first
in 1972, although some data are available prior to these dates for each solute.
NOTE REGARDING NITRATE DATA: After careful and exhaustive inter- and intra-laboratory tests we determined that nitrate concentrations in stream water were no longer remaining stable after collection, as they had in the past (see Buso, Likens and Eaton 2000). It is possible that the biological community in some streams of the HBEF has changed in recent years, affecting the nitrate concentration in complicated ways. While there was no systematic bias to the data, the situation occurred primarily during summer, when nitrate concentrations and streamflows are very low. Thus, we urge some caution in using the streamwater nitrate data collected since 2006, when nitrate stability was last confirmed. In 2013, new protocols were instituted to prevent decay of nitrate concentrations after collection and the problem has been resolved. There is no evidence that nitrate concentrations in the long-term precipitation record have been affected.
Buso, Donald C.; Likens, Gene E.; Eaton, John S. 2000. Chemistry of precipitation, streamwater, and lakewater from the Hubbard Brook Ecosystem Study: a record of sampl
ing protocols and analytical procedures. Gen. Tech. Rep. NE-275. Newtown Square, PA: U.S. Department of Agriculture, Forest Service, Northeastern Research Station. 52
p.
Likens, G.E. (1985). An Ecosystem approach to aquatic ecology: Mirror Lake and its environment. Springer-Verlag New York, Inc.
