What criteria were used in the trend analysis for streams?
Streams were selected for analysis on the basis of the following general criteria: (1) record of nutrient concentrations beginning in 1993 or earlier and ending in 2003 or later; (2) approximately quarterly sampling each year; (3) continuous streamflow record between 1993 and 2003 at that site or a nearby representative site; (4) data gaps no longer than 2 years and only during the middle 6 years of record; (5) representative coverage of samples over the hydrograph to avoid bias toward low or high streamflows; and (6) representative coverage over all seasons to avoid bias towards certain times of year (See Sprague and others, 2009 for details http://pubs.usgs.gov/sir/2008/5202/).
