Processes controlling the episodic streamwater transport of atrazine and other agrichemicals in an agricultural watershed

Saved in:
Authors:Hyer, Kenneth E.; Hornberger, George M.; Herman, Janet S.
Author Affiliations:Primary:
University Of Virginia, Department of Environmental Sciences, Charlottesville, VA, United States
Volume Title:Journal of Hydrology
Source:Journal of Hydrology, 254(1-4), p.47-66. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0022-1694
Publication Date:2001
Note:In English. 50 refs.; illus., incl. 4 tables, sketch map
Summary:Episodic streamwater transport of atrazine (a common agricultural herbicide) and nutrients has been observed throughout agricultural watersheds in the United States and poses a serious threat to the quality of its water resources. Catchment-scale atrazine and nutrient transport processes after agricultural application are still poorly understood, and predicting episodic streamwater composition remains an elusive goal. We instrumented a 1.2-km2 agricultural catchment near Harrisonburg, Virginia, and examined streamwater, overland flow, soil water, groundwater, and rainfall during the summer of 1998. Storm chemographs demonstrated different patterns for constituents derived primarily from weathering (silica and calcium), compared to constituents derived primarily from early spring land applications (nitrate, atrazine, DOC, potassium, chloride, and sulfate). During storms, the concentrations of silica and calcium decreased, the atrazine response was variable, and the concentrations of nitrate, DOC, potassium, chloride, and sulfate increased; the elevated nitrate signal lagged several hours behind the other elevated constituents. Graphical and statistical analyses indicated a relatively stable spring-fed baseflow was modified by a mixture of overland flow and soil water. A rapid, short-duration overland-flow pulse dominated the streamflow early in the event and contributed most of the potassium, DOC, chloride, suspended sediment, and atrazine. A longer-duration soil-water pulse dominated the streamflow later in the event and contributed the nitrate as well as additional potassium, DOC, sulfate, and atrazine. The contributions to the episodic streamflow were quantified using a flushing model in which overland-flow and soil-water concentrations decreased exponentially with time during an episode. Flushing time constants for the overland-flow and soil-water reservoirs were calculated on a storm-by-storm basis using separate tracers for each time-variable reservoir. Initial component concentrations were estimated through regression analyses. Mass-balance calculations were used for flow separations and to predict the observed streamwater composition. Model forecasts indicated that reduced fertilizer and pesticide application (rather than elimination of overland-flow or soil-water contributions) was necessary to improve the episodic streamwater composition. This study provides important additional understanding of the catchment-scale processes by which land-applied pesticides and nutrients can move through agricultural systems. Abstract Copyright (2001) Elsevier, B.V.
Subjects:Agriculture; Agrochemicals; Atrazine; Case studies; Controls; Geochemistry; Graphic methods; Herbicides; Hydrochemistry; Hydrology; Mass balance; Nitrate ion; Organic compounds; Periodicity; Pesticides; Pollution; Prediction; Regression analysis; Rivers and streams; Runoff; Soils; Solutes; Statistical analysis; Storms; Stream transport; Streamflow; Triazines; Water quality; Water regimes; Watersheds; Appalachians; North America; Rockingham County Virginia; United States; Valley and Ridge Province; Virginia; Muddy Creek
Coordinates:N383200 N383200 W0785730 W0785730
Record ID:2002003808
Copyright Information:GeoRef, Copyright 2018 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands
Tags: Add Tag
No Tags, Be the first to tag this record!