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Publications—Data Series

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


This report is the companion data report for: Nutrients in Streams and Rivers Across the Nation — 1992–2001 (Mueller and Spahr, 2006).

The data contained in this report were collected as part of the National Water-Quality Assessment (NAWQA) Program. Investigations were conducted in 51 large river basins and aquifer systems, which are referred to as "study units." Implementation of study-unit investigations were phased so that high-intensity sampling occurred in about one-third of the study units at a time. Investigations in the first 20 study units began in 1991, and stream sampling began in 1992; however, most samples were collected during water years 1993–95. (Water year is defined as the period from October through September and is identified by the year in which it ends.) A second group of 16 study-unit investigations began in 1994, with most of the sampling completed during water years 1996–98. A third group, consisting of 15 study units, began in 1997 with most of the data collected during water years 1999–2001. At some sites, additional sampling continued after the high-intensity time period. Gilliom and others (1995) provide additional information about study-unit sampling design. Additional information about the NAWQA program is available at



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