For all sites, the following chemical variables are measured on filtered water (0.45 micron) unless noted: Ca, Mg, Na, K, nitrate, total alkalinity (unfiltered water), chloride, sulfate, ammonium, soluble reactive phosphorus (PO4-P), total dissolved phosphorus (TDP), dissolved organic carbon (DOC), dissolved Si, and specific conductance (Cond; uS/cm corrected to 25 degrees C).

Since August 2006 dissolved Ca, Mg, Na and K are measured by ion chromatography (IC) instead of flame atomic absorption spectrophotometry (AA) and are distinguished as, e.g., Ca-IC and Ca-AA, respectively, in the datatables. Overlapping analyses showed comparable results from the two methods.

The pH, water temperature, and dissolved oxygen as percent saturation and mg/l are measured in the field. Specific conductance is sometimes measured in the field (Cond-Field) as well as later in the lab (Cond-Lab); the lab measurements better correspond with the lab analyses since they are made in the same water sample. For pumped groundwater sampled from wells, field measurements are taken in an overflowing container after stabilization.

Additional lab measurements may also include total suspended solids (TSS) and total phosphorus (TP). Stream discharge is measured at a nearby site on Augusta Creek by the USGS.

See the following references for methods:

Hamilton, S.K., J.L. Tank, D.F. Raikow, W.M. Wollheim, B.J. Peterson, and J.R. Webster. 2001. Nitrogen uptake and transformation in a midwestern US stream: A stable isotope enrichment study. Biogeochemistry 54(3): 297-340.

Hamilton, S.K., A.L. Kurzman, C. Arango, L. Jin, and G.P. Robertson. 2007. Evidence for carbon sequestration by agricultural liming. Global Biogeochemical Cycles 21, GB2021, doi:10.1029/2006GB002738.

Hamilton, S.K., D.A. Bruesewitz, G.P. Horst, and O. Sarnelle. 2009. Biogenic calcite-phosphorus precipitation as a negative feedback to lake eutrophication. Canadian Journal of Fisheries and Aquatic Sciences 66(2): 343-50.