Willamette Contaminants

Oregon District Completed Projects

OR165 Willamette River Basin Contaminants

Study Area

PROJECT CHIEF: Chauncey W. Anderson

LOCATION: Willamette River Basin

PROJECT EXTENT: Multicounty

TOTAL AREA IN SQUARE MILES: 11,500

BACKGROUND

The Willamette Pesticides Project (Phase III) is a cooperative effort with the Oregon Department of Environmental Quality (ODEQ). This project builds on information obtained during previous cooperative ventures with ODEQ in the Willamette Valley (Phases I and II) that focussed on large tributaries to the Willamette River and the main stem. As a result of Phases I and II, it was established that a large variety of organic pesticides are present in the largest streams in the basin, and that some of those pesticides are present at concentrations that approach criteria for the protection of human or ecological health. Phase III was designed to focus on the very small streams, with drainage basins on the order of 10 sq mi, that feed into the larger tributaries.

OBJECTIVES

The objectives of this study are: 1) to characterize the distribution of hydrophilic pesticide concentrations in a representative set of small streams throughout the basin and document exceedances of water-quality guidelines, 2) to identify the relative importance of several categories of crop or land-use types in defining a site's pesticide concentrations, 3) to define the relative importance of seasonal variations in defining a site's pesticide concentrations, and 4) to determine if relations exists between pesticide applications and instantaneous stream loads. ODEQ considers these objectives crucial to its mission of defining water-quality problems associated with pesticides in the Willamette River basin.

APPROACH

The first step in this process was to identify 110 sites within the basin that each drained approximately 10 sq mi of primarily agricultural land. From this large pool of potential sites, a representative set of 16 small streams was obtained by a random drawing. Each drainage basin was inventoried in detail during the summer to obtain the acreages of crop types being grown. The pesticide application rates were calculated from these crop acreages and literature values for application of compounds to each particular crop. Four sites draining primarily urban land also were chosen in order to provide a comparison between agricultural and urban land uses.

Water-quality sampling was done five times between April and November, 1996--twice in the spring to coincide with spring storms, once during summer low flow, and twice in the fall during fall storms. All 20 sites were visited during each round of sampling; usually the entire set of samples was collected within 3 days. Water samples were collected for organic compound analyses (one for each of the 2010 and 2051 schedules at the National Water Quality Laboratory). Ancillary measurements of discharge, pH, dissolved oxygen and temperature were taken concurrently, and samples also were collected for analysis of fecal-indicator bacteria, BOD and nutrients.

This project incorporated the use of relatively inexpensive immunoassay tests for metolachlor and atrazine. During the spring, many immunoassay samples were collected simultaneously with the laboratory samples in order to generate a comparison between the two methods. In the fall, the immunoassays were used largely to augment the data set by getting concentrations at selected streams at several points over the hydrograph. A complete set of immunoassays also was collected in December, 1996 after the collection of samples for laboratory analysis had been completed, in order to get a winter "baseline" concentration distribution.

REPORTS FROM THIS STUDY TO DATE

OFR 95-373. Analytical data from Phases I and II of the Willamette River Basin Water Quality Study, Oregon, 1992-94, by H.E. Harrison, C.W. Anderson, F.A. Rinella, T.M. Gasser, and T.R. Pogue, Jr. Abstract | Data | Online version of report

WRIR 95-4196. Sediment oxygen demand in the lower Willamette River, Oregon, 1994, by James M. Caldwell and Micelis C. Doyle. 1995. Abstract | Online version of report

WRIR 95-4205. Process controlling dissolved oxygen and pH in the upper Willamette River Basin, Oregon, 1994, by Ted R. Pogue, Jr., and Chauncey W. Anderson. Abstract

WRIR 95-4284. Precipitation-Runoff and Streamflow-Routing Models for the Willamette River Basin, Oregon, by Antonius Laenen and John C. Risley. Abstract | Online version of report

WRIR 96-4234. Occurrence of selected trace elements and organic compounds and their relation to land use in the Willamette River Basin, Oregon, 1992, by Chauncey W. Anderson, Frank A. Rinella, and Stewart A. Rounds. Abstract | Online version of report

WRIR 97-4268. Distribution of Dissolved Pesticides and Other Water Quality Constituents in Small Streams, and their Relation to Land Use, in the Willamette River Basin, Oregon, 1996, by Chauncey W. Anderson, Tamara M. Wood, and Jennifer L. Morace. Abstract | Data | Online version of report

Journal article. Qian, Song S., and Anderson, Chauncey W., 1999, Exploring factors controlling the variability of pesticide concentrations in the Willamette River using tree-based models: Enviromental Science and Technology, v. 33, no. 19, p. 3332-3340. Abstract

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Last modified: 4/28/00