Estimation of Nitrogen Yields and Loads from Basins Draining to Long Island Sound, 1988–98

Water-Resources Investigations Report 2002-4044
By: , and 



Monitoring data on total nitrogen concentrations and streamflow were used to estimate annual nonpoint nitrogen loads for 1988?98 at 28 monitoring sites and 26 unmonitored basins that drain to Long Island Sound. The estimated total nitrogen yields at monitoring sites were used with basin characteristics and ancillary data to develop a multiple-linear regression equation to estimate nonpoint nitrogen yields from monitored and unmonitored basins. The estimated nonpoint nitrogen load to Long Island Sound from the basins studied ranged from 21 million pounds in water year 1995 to 50 million pounds in water year 1990. Statistically significant regression variables include time, population density, annual mean runoff (minus wastewater return flow), pointsource nitrogen yields, percentage of basin area classified as urban/recreational grasses, percentage of the basin classified as agricultural land, and the ratio of deciduous to total forest area. Nonpoint nitrogen loads from monitored and unmonitored basins were computed using the regression equation by setting the point-source nitrogen yields and wastewater return variables to zero, and incorporating streamflow information from index stations in or near unmonitored basins. Nonpoint nitrogen load information obtained through use of this equation was summarized by six Long Island Sound management zones. Estimates of nonpoint nitrogen loads from these basins can be improved by additional sampling, and by developing data on nitrogen loads from municipal wastewater-treatment facilities outside of Connecticut, compiling information on annual interbasin diversions of flow, studying instream losses of nitrogen, and analyzing the processing and storage of atmospheric nitrogen in different forest types.

Suggested Citation

Mullaney, J.R., Schwarz, G.E., Trench, E.C.T., 2002, Estimation of nitrogen yields and loads from basins draining to Long Island Sound, 1988–98: U.S. Geological Survey Water-Resources Investigations Report 2002-4044, 84 p.,

Study Area

Table of Contents

  • Abstract
  • Introduction
  • Data Collection and Analysis
  • Nitrogen Loads and Yields from Basins Draining to Long Island Sound, 1988-98
  • Information to Improve Nitrogen Load Estimates
  • Summary and Conclusions
  • References Cited
  • Appendix 1. Parameter estimates and coefficient of determination for explanatory variables used in ESTIMATOR total nitrogen load calculations at monitoring stations in basins draining to Long Island Sound
  • Appendix 2. Model calibration and prediction
  • Appendix 3. Regression model input data and nitrogen loads from monitored basins draining to Long Island Sound, 1988–98
  • Appendix 4. Nonpoint nitrogen yields and 90-percent confidence intervals for unmonitored and monitored basins draining to Long Island Sound, 1988–98
  • Appendix 5. Estimates of total nitrogen load from municipal wastewater-treatment facilities (1998) and estimates of return flow (1990) used in multiple regression analysis
Publication type Report
Publication Subtype USGS Numbered Series
Title Estimation of nitrogen yields and loads from basins draining to Long Island Sound, 1988–98
Series title Water-Resources Investigations Report
Series number 2002-4044
DOI 10.3133/wri024044
Year Published 2002
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Connecticut Water Science Center, New England Water Science Center, WMA - Integrated Modeling and Prediction Division
Description viii, 84 p.
Country United States
State New York
Other Geospatial Long Island Sound
Online Only (Y/N) Y
Additional Online Files (Y/N) N
Google Analytics Metrics Metrics page
Additional publication details