Estimation of Total Nitrogen and Phosphorus in New England Streams Using Spatially Referenced Regression Models

By Richard Bridge Moore, Craig M. Johnston, Keith W. Robinson, and Jeffrey R. Deacon

Scientific Investigations Report 2004-5012

The full report is available in PDF format.

Errata Sheet


The U.S. Geological Survey (USGS), in cooperation with the U.S. Environmental Protection Agency (USEPA) and the New England Interstate Water Pollution Control Commission (NEIWPCC), has developed a water-quality model, called SPARROW (Spatially Referenced Regressions on Watershed Attributes), to assist in regional total maximum daily load (TMDL) and nutrient-criteria activities in New England. SPARROW is a spatially detailed, statistical model that uses regression equations to relate total nitrogen and phosphorus (nutrient) stream loads to nutrient sources and watershed characteristics. The statistical relations in these equations are then used to predict nutrient loads in unmonitored streams.

The New England SPARROW models are built using a hydrologic network of 42,000 stream reaches and associated watersheds. Watershed boundaries are defined for each stream reach in the network through the use of a digital elevation model and existing digitized watershed divides. Nutrient source data is from permitted wastewater discharge data from USEPA's Permit Compliance System (PCS), various land-use sources, and atmospheric deposition. Physical watershed characteristics include drainage area, land use, streamflow, time-of-travel, stream density, percent wetlands, slope of the land surface, and soil permeability.

The New England SPARROW models for total nitrogen and total phosphorus have R-squared values of 0.95 and 0.94, with mean square errors of 0.16 and 0.23, respectively. Variables that were statistically significant in the total nitrogen model include permitted municipal-wastewater discharges, atmospheric deposition, agricultural area, and developed land area. Total nitrogen stream-loss rates were significant only in streams with average annual flows less than or equal to 2.83 cubic meters per second. In streams larger than this, there is nondetectable in-stream loss of annual total nitrogen in New England. Variables that were statistically significant in the total phosphorus model include discharges for municipal wastewater-treatment facilities and pulp and paper facilities, developed land area, agricultural area, and forested area. For total phosphorus, loss rates were significant for reservoirs with surface areas of 10 square kilometers or less, and in streams with flows less than or equal to 2.83 cubic meters per second.

Applications of SPARROW for evaluating nutrient loading in New England waters include estimates of the spatial distributions of total nitrogen and phosphorus yields, sources of the nutrients, and the potential for delivery of those yields to receiving waters. This information can be used to (1) predict ranges in nutrient levels in surface waters, (2) identify the environmental variables that are statistically significant predictors of nutrient levels in streams, (3) evaluate monitoring efforts for better determination of nutrient loads, and (4) evaluate management options for reducing nutrient loads to achieve water-quality goals.


     Purpose and Scope
     Description of the SPARROW Modeling Technique
Description of Data Used in the New England Sparrow Models
     Hydrologic Network
     Channel-Transport Characteristics Data
     Stream Nutrient-Load Data
     Nutrient-Source Data
     Physical Watershed Characteristics Data
          Climatic Factors
          Land-Surface Characteristics
Spatially Referenced Regression Models for Nutrients in New England Streams
     Model Assumptions and Limitations
Model Estimates of Nutrient Loads
Use of SPARROW Model Results in Water-Resources Management
     Determining Sources and Transport of Nutrient Loads
     Determining Nutrient Concentrations
     Determining Nutrient Loads Delivered to Coastal Waters
Selected References

Complete text of report (5,306 KB PDF)

Errata Sheet

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For technical questions regarding this report, contact:

Richard Moore,
phone: 603-226-7825
U.S. Geological Survey
361 Commerce Way
Pembroke, NH 03275

To order a paper copy of this report, contact:

USGS Information Services
Box 25286
Denver Federal Center
Denver, CO 80225-0046
Tel: 888-ASK-USGS; Fax 303-202-4693

For more information about USGS activities in New Hampshire,
visit the USGS New Hampshire-Vermont District home page.

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