California Environmental Protection Agency

Department of Pesticide Regulation

1020 N Street, Room 161

Sacramento, CA 95814


December 9, 1996


The Sacramento River is the largest river in California both in flow and in drainage area (Figure 1). From Mount Shasta in the north to the Sacramento-San Joaquin Delta in the south the river flows for 327 miles. The river drains approximately 24,000 square miles including agricultural, urban and undeveloped (Friebel et al., 1995). The Sacramento River provides 35% of the State's water supply, both drinking and agricultural, and is also an important resource for recreation and wildlife (Reynolds, et al., 1993). The primary source of water entering the system is surface runoff from the Sierra Nevada Mountains to the east. Runoff from rain events occurring in the Sacramento Valley provides significant short term increases in river flow. Seasonal rains occur from October to March with little significant rain from June to September. River flow during the summer is composed of dam releases of snow melt water for agricultural, recreational and wildlife purposes.

In the Sacramento Valley, the organophosphorus insecticides diazinon or methidathion are applied with a dormant oil on nut and stone fruit trees to control peach twig borer, San Jose scale, European red mite and brown mite pests. The best time to achieve control of these pests is December through February, when the trees are dormant and better pesticide coverage is possible (Zalom et al., 1995). This dormant orchard spray application period, however, coincides with seasonal rainfall providing the potential for these pesticides to wash off target areas and migrate with runoff waters to the Sacramento River.

A one year Department of Pesticide Regulation (DPR) study and a three year U.S. Geological Survey (USGS) study of the Sacramento River have shown that most diazinon and methidathion concentrations were observed during the dormant spray season (MacCoy et. al. 1995; Nordmark, 1995). Analysis of rainfall data indicate that these higher concentrations occur almost exclusively in conjunction with rain events. The DPR study, using weekly three day composite samples, detected diazinon during January and February 1994 (Nordmark, 1995). No other organophosphate (OP) or carbamate (CB) insecticides were detected. The USGS study, using grab samples collected three times per week, detected diazinon each year from mid-January until late February or early March. Analysis of the pesticide use reports (DPR 1991-1994) indicate the majority of dormant spray insecticides are applied along the Sacramento River in northern Glenn and Butte Counties and along the Feather River north of the Bear River. The OP insecticides diazinon and methidathion are applied in nearly identical areas (Figures 2 and 3). Runoff from dormant orchards west of the Sacramento River may flow into the Colusa Basin Drain which enters the Sacramento River at Knights Landing. Runoff from dormant spray areas east of the Sacramento River principally drain into Butte Creek whose flow has been engineered to enter the Sacramento River at Karnak via the Sutter Bypass. Over half of the dormant spray applications of diazinon and methidathion occur along the Feather River (Figure 2 and 3). Runoff from areas east of the Feather River flows into the river prior to Nicolaus. However, runoff from the west side of the Feather River largely drains into the East Canal and enters the Sacramento River via the Sacramento Slough. In effect the entire dormant spray area between the Sacramento and Feather Rivers drains into the Sacramento River through Karnak. In past studies, diazinon levels have reached as high as 5 ppb in the Sacramento Slough (personal communication, Chris Foe, Central Valley Regional Water Quality Control Board, 1996). Toxicity has been found at Gilsizer Slough, which drains some of the area west of the Feather River and flows into the East Canal system. Ceriodaphnia dubia mortality was 100% in five of the seven consecutive weekly samples and appeared related to levels of pesticides detected in four cases (Foe and Sheipline, 1993).

In this study we will look at acute toxicity to C. dubia in a small watershed where the discharging waters do not contain major inputs from municipal or industrial sources. We will also investigate the potential for chronic toxicity in a section of the Sacramento River downstream of major dormant spray insecticide inputs in the watershed. Long term monitoring of acute and chronic toxicity will help scientists at the Department of Pesticide Regulation evaluate the effectiveness of programs designed to decrease the runoff of dormant spray insecticides.


The objective of this study is to monitor the levels of chlorpyriphos, diazinon, methidathion and the occurrence of acute and chronic toxicity in the Sacramento River watershed during the dormant spray season. A companion study will be established to monitor pesticide levels and toxicity in the San Joaquin River.


This project will be conducted by the Environmental Hazards Assessment Program (EHAP) under the general direction of Don Weaver, Senior Environmental Research Scientist (Supervisor). Key personnel are listed below:

Project Leader: Craig Nordmark

Field Coordinator: Dave Kim

Senior Scientist: Lisa Ross

Study Design/Data Analysis: Terrell Barry

Contractor (Toxicity Tests): Charlie Huang, California Department of Fish and Game

Chemist: Jean Hsu, Hsiao Feng, California Department of Food and Agriculture

Agency and Public Contact: Pat Dunn

Questions concerning this project should be directed to Pat Dunn at phone (916) 324-4100,

Fax (916) 324-4088


Sampling for acute toxicity will be conducted from a bridge across the East Canal at the Karnak pumping station, as this site receives water that is predominantly agricultural (Figure 4). Sampling for chronic toxicity will be conducted on the Sacramento River from the Bryte water intake platform as this site receives discharge from all the major agricultural tributaries (Figure 4) but is above the discharge of the largely non-agricultural American River and the urban runoff of the City of Sacramento. Discharge records are available for both the Karnak and Bryte sites from nearby gauging stations. This information will be used to correlate any changes in chemical concentrations to fluctuations in flow and may be useful for modeling efforts should they be undertaken.

Monitoring will commence prior to the onset of the dormant spray season (late November/early December 1996) and continue through the second week of March 1997. Background samples will be collected for one week, beginning prior to dormant spray applications, then monitoring will resume once applications have begun and continue until no later than March 28, 1997. Additional data collection will include in-situ measurements of water pH and temperature, dissolved oxygen, and specific conductance.


Acute toxicity sampling will be conducted twice per week at Karnak on Monday and Wednesday. Sampling for chronic toxicity will be conducted weekly on the Sacramento River at Bryte. One chronic sample constitutes the collection of samples on days zero, two and four of each week (e.g. Monday, Wednesday and Friday). Water collected on those days will be delivered the following day to the laboratory for testing and sample renewal. Chemical analysis will be performed on each sample collected for both acute and chronic tests. Selected OP and CB pesticides will be analyzed in three analyses (Table 1).

At each sampling site, water will be collected from as close to center channel as possible using a depth-integrated sampler (D-77) with a 3-liter Teflon® bottle and nozzle. Sampling at the Karnak site may utilize a grab pole from the river bank when bridge access is deemed unsafe. The grab pole will consist of a Teflon® or a glass bottle at the end of a three meter pole. Surface water sub-samples will be composited temporarily in a stainless steel container until the appropriate volume of water has been collected. The composited sample will be stored on wet ice until delivered to the processing facility at West Sacramento. Immediately upon arrival at the processing facility, the composite sample will be split into 1-liter amber glass bottles, using a Geotech® 10-port splitter, then sealed with Teflon® lined caps. The organophosphate and carbamate chemical analysis samples will be preserved by acidification with 3N hydrochloric acid to a pH between 3.0 to 3.5. Most OP and CB pesticides are sufficiently preserved at this pH with the exception of diazinon. Therefore, diazinon will be analyzed from a separate, unacidified, split sample. Samples submitted for toxicity tests will not be acidified. Sufficient water will be collected at each sampling event to provide approximately three liters for chemical analysis, two liters for each toxicity test, and any additional water required for quality control (QC) samples.

Split samples for chemical analysis will be transported on wet ice to the California Department of Food and Agriculture (CDFA) Center for Analytical Chemistry within three days. Split samples for toxicity testing will be delivered on wet ice to the California Department of Fish and Game (CDFG) Aquatic Toxicity Laboratory within 24 hours. CDFG will measure and record other parameters of the split samples including totals of ammonia, alkalinity, hardness, and specific conductivity as part of their toxicity testing.


Toxicity testing conducted by CDFG Aquatic Toxicity Laboratory will follow current USEPA procedures using the cladoceran Ceriodaphnia dubia (U.S. EPA, 1993). Acute toxicity will be determined using a 96-hour, static renewal bioassay in undiluted sample water. Chronic toxicity will be determined using a 7-day bioassay of undiluted sample water with C. dubia and will follow current USEPA guidelines (U.S. EPA, 1994). For example, test organisms used in chronic testing will be subjected to sample water from day zero on the following day (day 1). Sample water collected on days two and four will then replace test water on days three and five, respectively. All bioassays must commence within 36 hours of sample collection. Data will be reported to the project leader as percent survival on each day for the duration of the tests.

Chemical analysis will be performed by CDFA Center for Analytical Chemistry. The reporting limit will be the lowest concentrations of analyte that the method can detect reliably in a matrix blank. The reporting limits for this study are listed in Table 1. Chemical analytical methods will be provided in the final report. The total number of samples is presented below.

Number of Toxicity Tests

2 acute tests per week, 12 weeks of study 24

1 chronic per week, 12 weeks of study 12

Total 36

Additional Toxicity Testing Quality Control- see Barry (Protocol 156, 1996)

Number of Chemical Analysis

3 (OP, CB, and diazinon) per acute test

3 analyses X 2 acute samples/week X 12 weeks 72

3 (OP, CB, and diazinon) per chronic sampling event

3 analyses X 3 chronic sampling events/week X 12 weeks 108

Subtotal 180

Quality Control

intra-laboratory comparison 18

Total number of chemical analysis samples 198



To determine the variances within the primary laboratory, a quality assurance plan has been developed for this study (Barry, 1996). Briefly, additional samples from the acute toxicity monitoring site will be submitted as splits along with the field samples for intra-laboratory comparison. Also, two split samples from the acute toxicity monitoring site will be submitted to a second laboratory by the Central Valley Regional Water Quality Control Board (CVRWQCB). These splits will be tested at a laboratory of their choice, which may not be accredited by the California Department of Health Services. Comparability of the CVRWQCB results to those from CDFG will be based on analysis of the toxicity methods used.

Chemical Analysis

Quality control will be conducted in accordance with Standard Operating Procedure QAQC001.00. Ten percent of the total number of primary analyses will be submitted with field samples as rinse blanks, matrix blanks, and blind matrix spikes. An additional two split samples from the Karnak site will be given to the CRWQCB, Central Valley Region, for chemical analysis. These two samples will be collected on the same days as the CRWQCB toxicity samples.


Toxicity data will be used to establish baseline information on the occurrence of acute or chronic events at these sites. A correlation matrix will be established to identify potential relationships between measured environmental parameters, discharge, toxic events, and chemical concentrations. Measured concentrations will be compared to various established water quality parameters including Quantitative Response Limits (QRL) and both acute and chronic LC50s for C. dubia, to aid in interpretation of toxicity test results. Analysis will also be made comparing the timing of samples collected to storm events to examine the possibility that peak concentrations may have been higher than the maximums observed. Further analysis may include logistic regression, depending on preliminary analysis results.


Site Survey and Selection September 1996
Field Sampling Late November/ early December 1996 and application onset through March 28, 1997
Summary Memo May 1997
Draft Report August 1997


Barry, T.A. 1996. Protocol for obtaining a preliminary characterization of intra laboratory precision of acute toxicity tests performed on ambient water samples. California EPA/Department of Pesticide Regulation, Environmental Hazards Assessment Program. November, 1996.

California State Lands Commission (CSLC), 1993. California's rivers - A public trust report. Second Edition. California State Lands Commission, Sacramento, CA.

Foe, C. and R. Sheipline, 1993. Pesticides in Surface Water From Applications on Orchards and Alfalfa During the Winter and Spring of 1991-92. California Regional Water Quality Control Board, Central Valley Region, Sacramento, California. February 1993.

Friebel M.F., K.L. Markham, S.W. Anderson and G.L. Rockwell, 1995. Water Resources Data, California, Water Year 1994. Volume 4. U.S. Geological Survey Water-Data Report CA-94-4. Sacramento, California

Gorder, N. K.N. and J.M. Lee, 1995. Information on Rice Pesticides Submitted to the California Regional Water Quality Control Board Central Valley Region. Environmental Hazards Assessment Program, Department of Pesticide Regulation, Sacramento, California. December 28, 1995

MacCoy, D., K.L. Crepeau, and K.M. Kuivila. 1995. Dissolved pesticide data for the San Joaquin River at Vernalis and the Sacramento River at Sacramento, California, 1991-94. U.S. Geological Survey Rep. 95-110. U.S. Gov. Print. Office, Washington DC.

Nordmark, C., 1995. Preliminary Results of the Four River Monitoring Study, Sacramento River, November 1993-November 1994. Memorandum to Roger Sava, Environmental Hazards Assessment Program. Department of Pesticide Regulation, Sacramento, California. June 22, 1995.

Reynolds, F.L., T.J. Mills, R. Benthin, and A. Low. 1993. Restoring Central Valley streams: A plan for action. California Department of Fish and Game, Sacramento, CA.

U.S. Environmental Protection Agency. 1993. Methods for measuring the acute toxicity of effluents and receiving waters to freshwater and marine organisms. 4th ed. EPA/600/4-90/027F. August 1993.

U.S. Environmental Protection Agency. 1994. Short-term methods for estimating the chronic toxicity of effluents and receiving waters to freshwater organisms. 3rd ed. EPA-600-4-91-002. July 1994.

Zalom, F.G., R.A. Van Steenwyk, W.J. Bently, R. Coviello, R.E. Rice, W.W. Barnett, C. Pickel, M.M. Barnes, B.L. Teviotdale, W.D. Gubler, and M.V. McKenry. 1995. Almond pest management guidelines. University of California, Division of Agriculture and Natural Resources, UCPMG Publication 1.

Table 1. California Department of Food and Agriculture, Laboratory Services Branch: organophosphate and carbamate pesticide screens for the Sacramento River toxicity monitoring study.

Organophosphate Pesticides in Surface Water by GC

Method: GC/FPD

N-Methyl Carbamate in Surface Water by HPLC

Method: HPLC/Post Column-fluorescence

Reporting Limit


Reporting Limit


Chlorpyrifos 0.04 Carbaryl 0.05
Diazinon1 0.04 Carbofuran 0.05
Dimethoate (Cygon) 0.05
Fonofos 0.05
Malathion 0.05
Methidathion 0.05
Methyl parathion 0.05
Phosmet 0.05

1) Diazinon will be analyzed from a separate, unpreserved, split sample. Other chemical samples will be preserved with 3N HCl to a pH of 3-3.5 to retard analyte degradation. See text.