Section 319
NONPOINT SOORGE PROGRAM SOGGESS STORY
Stakeholders Cooperate to Reduce Diazinon in the San Joaquin River
Waterbodies Improved
Widespread use of the pesticide diazinon resulted in elevated
concentrations in the San Joaquin River (SJR) that were toxic
to aquatic invertebrates and exceeded water quality standards. Consequently, the SJR was placed
on California's Clean Water Act (CWA) section 303(d) list of impaired waters for diazinon in 1992.
Watershed stakeholders implemented agricultural best management practices (BMPs) in orchards
to lessen the use of organophosphate pesticides, including diazinon. Regulatory developments also
reduced diazinon use. SJR diazinon concentrations decreased, prompting California to remove two
reaches of the SJR from the state's list of impaired waters for diazinon in 2010.
Problem
The SJR watershed in California's Central Valley
is bounded by the Sierra Nevada Mountains
on the east, the Coast Range on the west, the
Sacramento-San Joaquin Delta to the north, and the
Tulare Lake Basin to the south. The 350-mile-long
SJR flows through an irrigated agricultural region.
In the early 1990s, monitoring by the U.S. Geological
Survey, the Central Valley Regional Water Quality
Control Board (CV-RWQCB) and the California
Department of Pesticide Regulation (DPR) detected
diazinon in the SJR at levels that were toxic to
aquatic life and exceeded water quality standards.
As a result, California added numerous SJR seg-
ments, including the 3-mile Stanislaus River to Delta
reach and the 14-mile Bear Creek to Mud Slough
reach (Figure 1), to the 1992 CWA section 303(d)
list of impaired waters for not supporting beneficial
uses for warm and cold freshwater habitat.
One of the main sources of diazinon in the SJR was
identified as the pesticides used on orchards during
the dormant season (December through February)
to protect crops from overwintering pests. Runoff
from these areas following winter storms contrib-
uted diazinon to nearby waterbodies.
Project Highlights
A collaborative effort that included both voluntary
and regulatory approaches motivated the agricul-
tural community in the SJR watershed to reduce
diazinon use. Beginning in the 1990s, a number
of grants and research projects by the University
of California (UC) and others supported the devel-
opment of diazinon management practices and
encouraged participation by local growers.
San Joaquin River
Restored Segments
SanJoaquin
River Watershed
Figure 1. Reducing pesticide use improved two
impaired segments in the SJR (noted in yellow).
In 1994 watershed partners initiated the Biologically
Integrated Orchard System (BIOS) project, a
community-based pollution prevention program
that uses biological methods to replace chemical
farming practices. Participating growers adopted
whole-system management approaches to reduce
the use of diazinon and other pesticides, while
also adopting practices to increase production
and improve crop quality. For example, BIOS uses
biological controls, cover crops, and maintenance of
natural areas and hedgerows to provide habitat for
beneficial insects to control pests.
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Figure 2. A navel orangeworm trap
helps control pests in an almond
tree.
Beginning in 2002, the
CV-RWQCB began to
regulate discharges from
agricultural lands through its
Irrigated Lands Regulatory
Program (ILRP). The ILRP
allows growers to attain
regulatory compliance
through coalition groups.
In the San Joaquin Valley,
the Westside San Joaquin
River Watershed Coalition
and East San Joaquin Water
Quality Coalition organized
to educate growers about
water quality problems and
management practices,
monitored water quality,
and served as intermediar-
ies between regulators and
growers. The work of the
coalitions was critical in moti-
vating growers to implement
practices to reduce diazinon
discharges.
In 2003 the CV-RWQCB
adopted a diazinon total
maximum daily load (TMDL).
The TMDL, along with the
reductions required through
the ILRP, played a key role in
motivating the agricultural
community to implement
BMPs. In 2003 the U.S.
Environmental Protection
Agency (EPA) developed a
special label for products con-
taining diazinon, which noted
that users must implement
practices to reduce diazinon runoff. In 2004 EPA
canceled all nonagricultural uses of diazinon; in 2006
the California DPR adopted dormant spray regula-
tions that require that users implement protective
practices when applying dormant orchard sprays.
The diazinon-reduction practices used in CWA sec-
tion 319(h) projects in the Central Valley also helped
to solve other pesticide problems in the area. For
example, in 2009 the Sustainable Cotton Project,
a farm-based program dedicated to sustainable
farming practices and integrated pest manage-
ment (IPM), helped orchard growers near the SJR
to adopt biologically based techniques, including
using pest traps (Figure 2) and scouting for pests
and beneficial insects (Figure 3).
Results
Figure 3. Field scout Luis Gallegos
uses a sweep net to look for pests.
Implementing the diazinon TMDL, ILRP require-
ments, DPR regulations, diazinon label changes and
BIOS project reduced diazinon runoff in the SJR. By
2010 data showed that diazinon levels in two reach-
es of the SJR (totaling 17 stream miles) once again
met water quality standards. As a result, California
removed both reaches—the 3-mile Stanislaus River
to Delta reach and the 14-mile Bear Creek to Mud
Slough reach—from the state's 2010 list of impaired
waters for diazinon. Additional reaches will likely be
removed from the impaired waters list when more
data become available.
Polluted runoff from both agricultural and urban
areas continues to affect the water quality of
the SJR. The State Water Quality Control Board,
CV-RWQCB and DPR continue to work on these
problems through the ILRP, as well as by develop-
ing pesticide regulations and providing funding and
technical assistance to support collaborative efforts
to address toxicity problems.
Partners and Funding
Partners include the DC IPM program, particu-
larly Dr. Frank Zalom, and members and staff of
the BIOS project of the Community Alliance with
Family Farmers. BIOS received funding from EPA
Region 9, DC Sustainable Agriculture Research and
Education, the U.S. Department of Agriculture's
(USDA) Sustainable Agriculture Research and
Education Program, the USDA Environmental
Quality Incentives Program and the Kellogg
Foundation. Other cooperating entities include the
East Merced Resource Conservation District and
the USDA Natural Resources Conservation Service.
The BIOS project strengthened partnerships by
working directly with farmers and promoting
information sharing among farmers, pest control
advisors, researchers and extension personnel,
as well as the ILRP, Coalition for Urban/Rural
Environmental Stewardship, Westland Water
District, UC Cooperative Extension, DPR, California
Dried Plum Board, Almond Board of California and
local resource conservation districts.
In 1994 $181,200 in CWA section 319(h) funding
was allotted to the BIOS program. In 2009 the
Sustainable Cotton Project received an $834,046
CWA section 319(h) grant for which project partners
invested more than $585,000 in matching funds.
CWA section 319(h) grant funds also supported CV
RWQCB project implementation staff costs.
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U.S. Environmental Protection Agency
Office of Water
Washington, DC
EPA841-F-13-001C
January 2013
For additional information contact:
Holly Grover
Central Valley Regional Water Board, Region 5
HGrover@waterboards.ca.gov • 916-464-4747
Wilson Yee
U.S. Environmental Protection Agency, Region 9
yee.wilson@epa.gov • 415-972-3484
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