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Surface-water quality changes after 5 years of nutrient management in the Little Conestoga Creek headwaters, Pennsylvania, 1989-91

Water-Resources Investigations Report 97-4048
By: , , and 
https://doi.org/10.3133/wri974048

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Abstract

A 5.82-square-mile drainage basin in the headwaters of the Little Conestoga Creek in Lancaster County, Pa., was investigated from October 1989 through September 1991 as part of a longer-term effort to determine the effects of nutrient management on surface-water quality. A previous investigation found no statistical evidence that implementation of nutrient management from 1986 to 1989 affected water quality. Basin land use is 68 percent agriculture and includes all or part of 51 farms. Agricultural land under nutrient management ranged from 55 percent in 1989 to 80 percent in 1991. Nitrate nitrogen, the dominant nonpoint-source contaminant, averaged about 7.5 milligrams per liter in base flow.

Implementation of nutrient management on 90 percent of applicable land in a 1.42-square-mile subbasin resulted in a 7 percent decrease in nitrogen applications from before nutrient management. Recognizing that some uncertainty exists in the nutrient-application data, the decrease consisted of a 44-percent decrease in commercial fertilizer nitrogen combined with a 3-percent increase in manure nitrogen applications. Manure accounted for 83 percent of the applied nitrogen. Amounts of nitrate nitrogen in the top 4 feet of soil ranged from 43 to 315 pounds per acre in the subbasin and were not substantially reduced from before nutrient management.

Statistical analysis of nutrient and suspended-sediment concentrations detected few significant step trends in water quality in a comparison with water quality before nutrient management. A decrease in base-flow concentrations of dissolved ammonium and suspended sediment was detected at a site draining a 1.43-square-mile subbasin with 40-percent implementation of nutrient-management plans. An increase in base-flow concentrations of suspended sediment was detected at a site draining the 1.42-square-mile subbasin with 90-percent implementation. A comparison of the dissolved nitrate plus nitrite in base-flow relations between paired subbasins detected no change from 1984-86 (before nutrient management) to 1989-91. Mean concentrations in stormflow were not reduced significantly from 1984-86 to
1989-91. Data collected during the entire 1986-91 nutrient-management period suggest a reduction in nitrogen input as large as the
30-percent reduction recorded from 1986-89 is needed to effect a 0.5-milligram-per-liter decrease in dissolved nitrate plus nitrite.

Suggested Citation

Koerkle, E.H., Gustafson-Minnich, L.C., and Bilger, M.D., 1997, Surface-water quality changes after 5 years of nutrient management in the Little Conestoga Creek headwaters, Pennsylvania, 1989-91: U.S. Geological Survey Water-Resources Investigations Report 1997–4048, 43 p., https://pubs.er.usgs.gov/publication/wri974048.

Study Area

Table of Contents

  • Abstract
  • Introduction 
  • Site description
  • Methods of data collection and analysis
  • Hydrologic setting and conditions
  • Nutrient management, sources, and sinks 
  • Changes in surface-water quality after nutrient management
  • Summary and conclusions
  • References cited
Publication type Report
Publication Subtype USGS Numbered Series
Title Surface-water quality changes after 5 years of nutrient management in the Little Conestoga Creek headwaters, Pennsylvania, 1989-91
Series title Water-Resources Investigations Report
Series number 97-4048
DOI 10.3133/wri974048
Year Published 1997
Language English
Publisher U.S. Geological Survey
Publisher location Reston, VA
Contributing office(s) Pennsylvania Water Science Center
Description vi, 43 p.
Country United States
State Pennsylvania
Other Geospatial Little Conestoga Creek headwaters
Online Only (Y/N) Y
Google Analytic Metrics Metrics page
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