Paper No. 97110 of the Journal of the American Water Resources Association. Discussions are open until December 1,1999.
TRANSPORT OF DIAZINON IN THE SAN JOAQUIN RIVER BASIN, CALIFORNIA†
Article first published online: 8 JUN 2007
JAWRA Journal of the American Water Resources Association
Volume 35, Issue 2, pages 379–395, April 1999
How to Cite
Kratzer, C. R. (1999), TRANSPORT OF DIAZINON IN THE SAN JOAQUIN RIVER BASIN, CALIFORNIA. JAWRA Journal of the American Water Resources Association, 35: 379–395. doi: 10.1111/j.1752-1688.1999.tb03597.x
- Issue published online: 8 JUN 2007
- Article first published online: 8 JUN 2007
- surface water;
- water quality;
- San Joaquin River Basin;
- storm runoff;
- storm hydrology
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 federalstate collaborative study found that diazinon accounted for most of the observed toxicity of San Joaquin River water in February 1993. Previous studies focused 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 travel times, ephemeral west-side creeks probably were the main diazinon source early in the storms, whereas the Tuolumne and Merced rivers and east-side drainages directly to the San Joaquin River were the main sources later. Although 74 percent of diazinon transport in the San Joaquin River during 1991–1993 occurred in January and February, transport during each of the two 1994 storms was only 0.05 percent of the amount applied during preceding dry periods. Nevertheless, some of the diazinon concentrations in the San Joaquin River during the January storm exceeded 0.35 μ/L, a concentration shown to be acutely toxic to water fleas. On the basis of this study and previous studies, diazinon concentrations and streamflow are highly variable during January and February storms, and frequent sampling is required to evaluate transport in the San Joaquin River Basin.