Transport of diazinon in the San Joaquin River basin, California
Open-File Report
97-411
By: Charles R. Kratzer
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Abstract
Most of the application of the organophosphate insecticide diazinon in the San Joaquin River Basin occurs in winter to control wood boring insects in dormant almond orchards. A federal-state collaborative study found that diazinon accounted for most of the observed toxicity of San Joaquin River water to water fleas in February 1993. Previous studies focussed mainly on west-side inputs to the San Joaquin River. In this 1994 study, the three major east-side tributaries to the San Joaquin River, the Merced, Tuolumne, and Stanislaus Rivers, and a downstream site on the San Joaquin River were sampled throughout the hydrographs of a late January and an early February storm. In both storms, the Tuolumne River had the highest concentrations of diazinon and transported the largest load of the three tributaries. The Stanislaus River was a small source in both storms. On the basis of previous storm sampling and estimated traveltimes, ephemeral west-side creeks were probably the main diazinon source early in the storms, while the Tuolumne and Merced Rivers and east-side drainage directly to the San Joaquin River were the main sources later. Although 74 percent of diazinon transport in the San Joaquin River during 199193 occurred in January and February, transport during each of the two 1994 storms was only 0.05 percent of the amount applied during preceeding dry periods. Nevertheless, some of the diazinon concentrations in the San Joaquin River during the January storm exceeded 0.35 micrograms per liter, a concentration shown to be acutely toxic to water fleas. Diazinon concentrations were highly variable during the storms and frequent sampling was required to adequately describe the concentration curves and to estimate loads.
| Publication type | Report |
|---|---|
| Publication Subtype | USGS Numbered Series |
| Title | Transport of diazinon in the San Joaquin River basin, California |
| Series title | Open-File Report |
| Series number | 97-411 |
| DOI | 10.3133/ofr97411 |
| Edition | - |
| Year Published | 1997 |
| Language | ENGLISH |
| Publisher | U.S. Geological Survey ; Information Services [distributor], |
| Description | vi, 22 p. :ill., maps ;28 cm. |
| Google Analytic Metrics | Metrics page |