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Compilation of Environmental Sample Data
The digital data sets available in this report are listed below. The
environmental data set contains more than 28,000 nutrient samples collected
during the National Water-Quality Assessment (NAWQA) Program Cycle I
time period (water years 1992–2001) at 500 NAWQA stream and river
sites. Analytic results were retrieved from the U.S. Geological Survey
(USGS) National Water Information System (NWIS) database (http://waterdata.usgs.gov/nwis) during
March–July 2002. Data for NAWQA sites were included even if they
were collected separately from the NAWQA Program. In addition to nutrients,
data are provided for streamflow (instantaneous at the time of sampling
and mean daily for the sampling date), physical measurements (in-situ
temperature and dissolved oxygen, plus specific conductance and pH of
the sample), and concentrations of suspended sediment and organic carbon
(dissolved and particulate). Mean daily streamflow data were retrieved
along with water-quality data or were added to the data set by selecting
flow values for sampling dates from the NWIS daily values database. For
sites that were not located at USGS streamflow-gaging stations, NAWQA
study-unit staff provided daily streamflow values from a non-USGS gage
or by computation using more than one USGS gage.
| Data set |
Brief description |
| Environmental samples |
Nutrient samples, including selected other data, collected during
water years 1992–2001 at NAWQA stream and river sampling sites |
| Load-model coefficients |
Regression coefficients and selected diagnostics for models of
nutrient loads at NAWQA sampling sites |
| Daily streamflow |
Daily values of streamflow used to estimate nutrient loads for
selected water years at NAWQA sampling sites |
| Summary data |
Mean annual loads, yields, and concentrations of five nutrient
constituents, plus selected ancillary data, at NAWQA sampling sites |
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