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U.S. Geological Survey

Data Series 152

National Water-Quality Assessment Program


Water-Quality, Streamflow, and Ancillary Data for Nutrients in Streams and Rivers Across the Nation, 1992–2001

By David K. Mueller and Norman E. Spahr


Sample Collection and Laboratory Analysis

Compilation of Environmental Sample Data
Review and Revision of Environmental Sample Data
Modification to Data Censoring
Estimation of Nutrient Loads
Summary Statistics
Ancillary Data
References Cited
Data Files

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 ( 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