USGS

Diazinon and Chlorpyrifos Loads in the San Joaquin River Basin, California, January and February 2000

By Charles R. Kratzer, Celia Zamora , and Donna L. Knifong

 

U.S. GEOLOGICAL SURVEY

Water Resources Investigation Report 02-4103

Sacramento, California 2002


Prepared in cooperation with the

California Department of Pesticide Regulation

 


Report with cover (1.3 MB PDF) Download Acrobat reader)

 

Abstract

The application of diazinon and chlorpyrifos on dormant orchards in 2000 in the San Joaquin River Basin was less than 21 percent of application in 1993 and 1994. A total of 13 sites were sampled weekly during nonstorm periods and more frequently during two storm periods. The sites included five major river and eight minor tributary sites. The highest concentrations of diazinon and chlorpyrifos occurred during the storm periods. Four samples from major river sites (Tuolumne River and two San Joaquin River sites) had diazinon concentrations greater than 0.08 microgram per liter, the concentration being considered by the state of California as its criterion maximum concentration for the protection of aquatic habitat. One sample from a major river site (San Joaquin River) exceeded the equivalent State guideline of 0.02 microgram per liter for chlorpyrifos. At the eight minor tributary sites, 24 samples exceeded the diazinon guideline and four samples exceeded the chlorpyrifos guideline. The total diazinon load in the San Joaquin River near Vernalis during January and February 2000 was 19.6 pounds active ingredient; of this, 8.17 pounds active ingredient was transported during two storms. In 1994, 27.4 pounds active ingredient was transported during two storms. The total chlorpyrifos load in the San Joaquin River near Vernalis during January and February 2000 was 5.68 pounds active ingredient; of this, 2.17 pounds active ingredient was transported during the two storms. During the frequently sampled February 2000 storm, the main sources of diazinon in the San Joaquin River Basin were the San Joaquin River near Stevinson Basin (25 percent), Tuolumne River Basin (14 percent), and the Stanislaus River Basin (10 percent). The main sources of chlorpyrifos in the San Joaquin River Basin were the San Joaquin River near Stevinson Basin (17 percent), Tuolumne River Basin (13 percent), and the Merced River Basin (11 percent). The total January and February diazinon load in the San Joaquin River near Vernalis was 0.17 percent of dormant application; total January and February chlorpyrifos load was 0.16 percent of dormant application.

CONTENTS

Abstract

Introduction

Study Area

Application of Diazinon and Chlorpyrifos

Sampling Design and Methodology

Sampling Design

Sample Processing and Laboratory Methods

Quality-Control Samples

Hydrology During the Study

Concentrations of Diazinon and Chlorpyrifos

Diazinon

Chlorpyrifos

Loads of Diazinon and Chlorpyrifos

Diazinon

Chlorpyrifos

Summary and Conclusions

References Cited



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Water Resources of California


U.S. Department of the Interior, U.S. Geological Survey
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