Water Quality Issues
Polluted
runoff Many human activities have the potential to
influence the water quality in the watersheds and
the Sanctuary by contributing pollutants to runoff.
All public and private land-uses, including urban
and rural development, recreation and wildlife,
industrial, and agricultural activities may affect
water quality within these rivers and streams.
Individually insignificant sources of polluted
runoff build upon each other as the water travels
downstream. Throughout the country there is
increasing recognition that addressing these
scattered "nonpoint" sources of pollution is
critical to maintaining the health of natural
resources and local communities. However, because
of the complexity of the variables that affect
nonpoint source pollution, including weather,
climate, substrate, terrain, land use, etc., no
single unified solution exists. Addressing polluted
runoff requires a long-term collaborative effort
among all the people who live and work in a
region's watersheds. Addressing current water quality problems in the
region's watersheds becomes particularly important
as we look to a future with the expectation of
increasing population and intensity of human land
use activities along the Central Coast. This
increased intensity stems from continuing
urbanization in many coastal watersheds.
Simultaneously, many parts of the region are
experiencing an increase in agricultural land-use
activities. Agricultural
impacts The aspects of agriculture that potentially
impact water quality include erosion and
sedimentation, offsite transport of chemical
fertilizers and pesticides, and microbial
contamination. Stormwater, flooding, irrigation,
and leaching can all mobilize substances that are
beneficial while on-site, but become pollutants as
they concentrate in neighboring streams, rivers,
wetlands, and nearshore waters. Though each
individual farm or ranch may contribute a
relatively small amount of pollutants, the
cumulative effects through the length of a
watershed can be damaging. At the same time, the
offsite movement of sediments, pesticides and
nutrients can represent a long-term economic loss
to the grower. Many farmers, ranchers and forest landowners
have already adopted a variety of management
measures to reduce polluted runoff. Expanding and
strengthening the conservation practices already
begun by the industry can help protect our natural
resources and sustain the long-term economic
viability of agriculture. It can also improve the
public perception of agricultural conservation
issues, and increase recognition of the value that
agriculture provides the Central Coast region. Some management practices that address these
issues may have long-term economic benefits for the
grower or rancher, as well as improving habitat for
fish and wildlife and reducing offsite damage to
public trust resources. Costs for other practices
may exceed any economic benefit to the agricultural
landowner or operator, though the benefit to the
public may be considerable. The WQPP encourages
increased support for the development and
implementation of economically feasible management
improvements, and the development of incentives
which allow implementation of marginally economic
practices where substantial benefits to natural
resources may justify public investment. Although this document focuses on strategies to
protect water quality from potential adverse
impacts of agricultural land management, the
program recognizes the importance of maintaining
agricultural use of the lands for the long-term
health of the watersheds. Relative to the extensive
paved surfaces of urban areas, effectively managed
agricultural lands can act to slow and capture
stormwater runoff, provide sites for recharge,
water storage and wildlife habitat, and reduce the
impact of flood events. These lands also enrich the
quality of life for watershed residents and
visitors, providing green, aesthetically pleasing
landscape, and jobs and tax revenues that sustain
local communities. An overview of nonpoint source issues in the
Central Coast region is provided below. This
section is based on a review of existing data and
literature, as well as additional information
provided by participants at agricultural workshops.
Additional information on the literature cited is
provided in the backnotes on page 56. Although the
WQPP is addressing a much wider set of issues which
impact water quality, including urban runoff and
marinas and boating activities, only those issues
which have an agricultural component are discussed
here. Soil management practices can have an effect on
wetlands and waterways, fish populations, levels of
toxic pollutants in water and sediment, and the
economic viability of farm, range and forest lands.
The most significant impacts in this region are
caused by the accumulation of soils washed into
surface waters by rain, particularly by winter
storm events and periodic extensive floods.
Although some natural level of sedimentation occurs
in all watersheds, and flooding can overwhelm the
most prudent land management, both offshore
activities and land use practices can significantly
increase the rate of erosion and sedimentation.
Erosion occurs not only from agricultural areas,
but from urban and rural development as well,
including rural roads. These non-agricultural
sources of erosion are included in the WQPP's Urban
Runoff plan and in Section 6 of this document. Transport of sediment is a natural function of a
healthy hydrological system, but excessive
sedimentation is a concern for the rivers, wetlands
and harbors that border the Sanctuary. Although
several studies have focused on specific sediment
sources and problems, additional research is needed
to fully understand all the functional variables in
the various watersheds. Excessive sedimentation may
smother riverine, estuarine and marine habitats,
killing benthic (bottom-living) organisms, reducing
colonization, interfering with feeding, covering
spawning grounds important to fish such as
steelhead and salmon, and reducing the number of
plants emerging in wetlands. It can also fill
wetland areas, reducing their natural ability to
"treat" and slow runoff water as it makes its way
to the sea, and cause perennial wetlands to evolve
toward seasonal wetlands. Increased sediment in
streams can result in sediment deposition in the
stream channels, which can lead to severe
streambank instability and increased flooding
downstream. Sedimentation is also a main transport
mechanism for persistent pesticides (see below)
that adhere to soil particle surfaces.1 Anadromous fish (like steelhead and salmon) that
spend part of their lives in the ocean and make use
of local rivers to reproduce are particularly
susceptible to human activities in the watersheds.
Heavy sediment loads from rural developments and
roads, agricultural activities, and urban areas can
cause habitat degradation that contributes to fish
population decline by burying the coarse gravel
beds where they would normally deposit their eggs.
Recently both the Coho salmon and steelhead
populations on the Central Coast have been listed
as threatened/ endangered species by the National
Marine Fisheries Service and the State of
California, increasing the level of interest in
restoring and protecting the spawning habitat of
these fisheries.2 Soil loss from farms, range and forest lands
also has a variety of economic effects. Over the
long term, reduced agricultural productivity
through topsoil loss can be a significant economic
loss to the agricultural landowner and manager,
particularly in upland areas where soil layers are
thin. Added to this are the costs of reduced water
retention and percolation, and increased on-farm
maintenance to control erosion or dispose of
sediments. There are costs to all sectors of the
community from sediments being in the wrong place
(e.g., cleanup and disposal of sediments deposited
on public roads, in channels and harbors). In
addition, downstream transport of soils which
contain relict loads of banned or discontinued
persistent pesticides adsorbed to their surfaces
has impeded dredging of sediment in areas such as
Moss Landing Harbor, increasing annual dredging
costs and making appropriate disposal of the
dredged materials difficult. Control of excessive
erosion and runoff is one of the most important
issues for agricultural land management in the
region's watersheds, since it can result not only
in reduced sedimentation, but reduced transport of
other contaminants as well. Elevated nutrient concentrations, particularly
nitrates, are also of concern in several areas
surrounding the Sanctuary. Nutrients can enter
surface and groundwater from agricultural and urban
sources, including agricultural and urban
fertilizer application, human septage, waste from
livestock and domestic pets, and from numerous
natural sources including plant decomposition and
wildlife. Elevated levels of nutrients from mixed
sources have been reported in the Elkhorn Slough
and Salinas River watersheds, Moro Cojo Slough, and
in the Pajaro River and its tributaries including
Llagas Creek and Watsonville Sloughs. Long-term
monitoring studies indicate a marked seasonal
increase in surface water nitrate concentrations in
the Elkhorn Slough watershed since the 1970's, and
very high year-round levels in the lower portions
of the Salinas River in the 1990's.3 Concentration of nutrients in surface waters may
result in the rapid growth of aquatic plants and
plankton, decreasing biological diversity, clogging
waterways and flood control channels, and leading
to the depletion of oxygen in the water. Algal
blooms have been observed in the Pajaro River and
several tributaries, and in the Watsonville Slough
System. Nutrient inputs can also cause algal blooms
in coastal waters, leading some scientists to
consider nutrients a contributing factor in the
national and global rise in toxic "harmful algal
blooms". Although surface waters are the primary
focus of the WQPP, it is important to note that
nutrients may also infiltrate groundwater supplies
and may have public health consequences. There may
be some supplementary benefits to groundwater
quality from activities undertaken in connection
with the Water Quality Protection Program.4 Elevated ammonia concentrations can result from
urban, agricultural and natural nutrient sources,
and may be toxic to fish. Data for the Watsonville
Sloughs System, which receives runoff from
agricultural lands, urban sources, and small
acreage rural ranchettes, are routinely in excess
of chronic ammonia toxicity limits for sensitive
fish species. Additional recent data from the
Pajaro watershed indicate high ammonia levels in
several subwatersheds further upstream. Because
there is no direct application of either anhydrous
ammonia or aqua ammonia on agricultural lands in
these subwatersheds, the presence of ammonia is the
result of breakdown products from either
agricultural or nonagricultural sources such as
human or animal waste. Accurate source
identification will therefore be necessary for
development of effective controls.5 Old-generation Pesticides Elevated levels of contamination from persistent
pesticides such as DDT, aldrin, chlordane,
dieldrin, toxaphene, endosulfan, etc. have been
reported from sediment and/or shellfish tissue for
the Old Salinas River Channel, Salinas River
Lagoon, Moro Cojo Slough, Moss Landing Harbor,
Elkhorn Slough, and Watsonville Sloughs, and in
aquatic toxicity tests for subwatersheds draining
to the Pajaro Lagoon. For several of these
persistent compounds, the studies of the
Watsonville Sloughs and Salinas River/Old Salinas
River areas report some of the most severe
pesticide contamination in the state. A recent
study of sediments in the mid-portions of Monterey
Bay also found DDT, probably related to discharges
from the Pajaro and Salinas Rivers, but at
relatively low levels.6 Although most of these persistent pesticides are
currently banned (except for endosulfan and
dacthal), they remain present in the soil and are
transported in surface runoff, through the movement
of sediment, to the water bodies and tributaries
surrounding the Sanctuary. Their impact on water
quality is generally not an issue related to
current pesticide practices, but a sedimentation
issue to be addressed through management practices
that reduce controllable sediment sources. Many of
the watershed and rivermouth concentrations exceed
the levels of these compounds at which biological
impacts have been observed in other areas. The degree of overall impact of these compounds
is uncertain in this region, but the high
concentrations occurring at some sites raise
significant concerns. Many of these compounds are
fat-soluble and tend to accumulate and persist in
fatty tissues of animals, especially shellfish and
other aquatic species. Shellfish and other
bottom-living organisms accumulate these pesticides
as they feed, and other animals accumulate them by
consuming contaminated fish or shellfish. DDT may
accumulate in the tissue of predatory birds and has
reportedly caused reproductive failure locally
through weakening of eggshells. DDT found in
tissues and eggshells is assumed to be the cause of
near-complete reproductive failure of a breeding
population of Caspian Terns in Elkhorn Slough in
1996. These terns reportedly hunt in the
Watsonville Sloughs area as well as in Elkhorn
Slough. Elevated levels of DDT have also been found
in the tissues of sea otters in the Monterey Bay
region, although it is not yet known what, if any,
impact this may be having on the population.7 Although currently used compounds generally
decay more rapidly than the historically-used
organochlorine pesticides, some more persistent
compounds still in use can accumulate in fairly
high concentrations locally, particularly in
rivers, lagoons, sloughs, and harbors where
sediment deposition rates are high. Dacthal and
endosulfan have been detected in sediments and
tissues of local estuarine and freshwater animals
at concentrations that cause concern. Dacthal is no
longer manufactured, and its current use is limited
to depletion of existing inventories. Due to its
persistence in the environment, the use of
endosulfan is restricted near all waterways. The
Monterey County Agricultural Commissioner, for
example, has prohibited its use on lands that may
drain into the Salinas River or Elkhorn
Slough.8 New-generation Pesticides Most of the newer organophosphate and carbamate
pesticides currently in use are not regularly
monitored in the region's watersheds or coastal
waters. A study in the Salinas Valley found no
offsite migration of currently used pesticides from
two parcels with appropriate management practices
in place, although surface water runoff was minimal
during the sampling period. Sediment monitoring for
a few of the currently-used new generation
pesticides did not find detectable levels in
Monterey Bay. However, limited data available from shellfish
studies in the Salinas, Elkhorn and Pajaro
watersheds indicate that chlorpyrifos, diazinon,
and oxydiazinon may bioaccumulate, suggesting a
certain degree of persistence in the environment.
Diazinon has also been found in the subwatersheds
draining to the Pajaro Lagoon. Additional
monitoring should be conducted to determine the
distribution and fate of a wider range of
currently-used compounds to ensure that the newer
pesticides are functioning as designed to be
non-persistent and non-bioaccumulatable and do not
run off into waterways. It also should be
recognized that chlorpyrifos, diazinon and
oxydiazinon are also used for non-agricultural uses
such as urban/rural landscape maintenance, and
their use in these urban areas is not subjected to
the degree of supervision, regulation or reporting
imposed on agricultural uses.10 Data from the state's pesticide use reporting
system indicates that total pounds of pesticide
applied in the Central Coast region (and other
areas of the state) increased over the time period
from 1991 to 1995. It is important to recognize
that total pounds of pesticide applied does not
provide a measure of pesticide load in the
environment, and it is currently not known what, if
any, environmental impacts there may be in the
region's waterways. Potential factors contributing
to the 1991-1995 increase included changes in
weather patterns, increases in agricultural acreage
and total crop production, greater pest problems,
increased compliance with reporting requirements,
lack of alternative pesticides due to suspended or
canceled pesticides or to increases in pest
resistance, increased intensity of use, and changes
in reporting requirements of organic products. In
addition, some of the increase may have been due to
shifts from the few remaining old-generation,
persistent, broad-spectrum pesticides still in use
to new-generation products that break down more
readily and must be applied more often, and are
highly pest-specific, requiring more chemicals to
do the job previously done by one. Note that the
1996 Summary of Pesticide Use Report Data indicates
that total pounds applied in 1996 statewide were
somewhat less than the previous year (though still
higher than the total pounds applied during the
years 1991 to 1994).11 The limited water quality monitoring data that
are available do not suggest a crisis situation
with currently-used pesticides. More adequate
monitoring for these compounds in the watersheds
should be developed to detect any potential
problems. Microbiological contamination also occurs in
some watersheds from mixed sources including urban
runoff, confined animal facilities, rural
ranchettes, poorly functioning septic systems, and
wildlife. Elevated concentrations of coliform
bacteria have been reported for Watsonville
Sloughs, stemming from mixed sources. Coliform
bacteria are relatively harmless microorganisms
that live in the intestines of animals and aid in
the digestion of food. Fecal coliform bacteria are
a subgroup of this collection of bacteria which are
associated only with the fecal material of
warm-blooded animals. The presence of fecal
coliform in water sources indicates fecal
contamination, which in turn indicates possible
contamination by pathogens or disease-producing
bacteria or viruses. Elevated concentrations of
coliform bacteria from mixed sources in Elkhorn
Slough have resulted in the loss of a significant
shellfish culturing industry. There have also been
localized problems in some watersheds along the San
Mateo Coast apparently due to bacterial
contamination in creeks from nearby rural
ranchettes. Existing limited microbiological data
from these reports do not allow quantification of
the relative contribution of urban, agricultural
and wildlife sources.12 Although the studies cited above present
significant information on water quality issues,
the lack of adequate long-term monitoring data for
watershed and coastal areas was identified as a
concern by workshop participants. There are a
number of federal, state and local monitoring
programs operating within the region (including
State Mussel Watch and the Toxic Substances
Monitoring Program), as summarized in Tetra Tech's
1995 report. Most of these programs have a limited
focus and generally work independently of other
monitoring efforts. The need for coordinated monitoring and
databases which can provide readily accessible and
understandable information to characterize the
health of the Sanctuary and its watersheds was
identified and addressed in WQPP's Action Plan II.
Work has been initiated by the Central Coast RWQCB
in conjunction with the California Department of
Fish and Game (CDFG), municipal dischargers, the
Sanctuary, and others to develop a coordinated
regional monitoring program. The program includes
development of a centralized database which can
incorporate data from the various government
monitoring programs in the region. In addition to
collecting data from existing monitoring programs,
the RWQCB has recently received funding to collect
water quality data in various central California
watersheds on a 5-year, rotational basis. This will
not only provide baseline data for establishing
water quality trends, but will allow for the
detection of pollution problems and for the
evaluation of various conservation measures
implemented by both point and nonpoint source
dischargers, including agricultural management
practices. In parallel with the RWQCB's effort to
coordinate regional governmental monitoring
programs is an effort led by the Coastal Watershed
Council and the Center for Marine Conservation, in
association with the Sanctuary's WQPP. The
Sanctuary Citizen Watershed Monitoring Network is
coordinating and providing training for the
existing volunteer monitoring programs in the
Sanctuary's watersheds. Data collected from
approximately 20 citizen monitoring programs will
be displayed in a standardized database, and linked
to the RWQCB's database of monitoring programs.
These volunteer groups are being provided with
standardized training and sampling protocols to
ensure collection of high quality data. Trainers
also emphasize the need to sample from public
access locations and to work on private lands only
with the permission of the landowner. In addition, grower self-monitoring is addressed
in Sections 1 and 2 of this document. Water quality
data generated from agricultural self-monitoring,
compiled by the Farm Bureaus at a subwatershed
level to protect the privacy of the individual
landowners, will eventually be linked into the
coordinated regional monitoring program. These
three related monitoring efforts will help resource
managers further evaluate the overall health of the
waters that drain into the Sanctuary. The
self-monitoring data will also provide valuable
information to growers and ranchers regarding the
effectiveness of management practices. The need for more adequate monitoring data,
especially for sediments, was of particular concern
to the participants in the WQPP's agricultural
workshops in Half Moon Bay, due to a relative lack
of information for the San Mateo Coast. The
recommendation for additional monitoring in this
area led to the development of a proposal for a
joint project by the San Mateo County Resource
Conservation District, the Sanctuary and the San
Mateo County Farm Bureau which includes sediment
characterization, monitoring and outreach on source
control for the Pescadero watershed. This project
was recently funded by the San Francisco Regional
Water Quality Control Board and work will begin in
1999. Notes for "Water
Quality Issues" Section
The Sanctuary is adjacent to over 400 miles of
California's coastline and includes Elkhorn Slough,
one of the region's key wetland areas. This coastal
area contains 11 major watersheds, ranging from
forest and grazing lands to heavily agricultural
and urbanized areas. The Sanctuary's watersheds
receive rainfall, runoff from urban and rural
lands, and return flows from irrigation which
travel downhill to streams, rivers, wetlands,
harbors and ultimately out to the Sanctuary. This
runoff can pick up a variety of potential
pollutants such as sediments, oils and grease,
nutrients, pesticides, and pathogens, which can
then be carried to the surrounding rivers and
wetland areas that sustain many Sanctuary species.
Polluted runoff is also known as "nonpoint source
pollution" because the pollutants come from a
variety of sources, rather than a single "point"
source, such as industrial effluent discharged from
a pipeline.
The character of pesticides in use has changed over
the last two decades, from persistent
broad-spectrum compounds to products that decay
rapidly and are generally applied to specific
groups of target organisms. Many organochlorine
pesticides that are now banned were used
extensively in the past during an era in which
their persistence and toxicity to non-target
organisms was unknown. These now-banned pesticides
were used throughout various watersheds, primarily
for agricultural pest control but also for urban
and rural uses such as mosquito abatement,
structural fumigation, urban park and residential
garden pest control. Many of these compounds have
persisted in the soil longer than anticipated,
adhering to fine soil particles on site, or moving
downstream with eroding sediments to be deposited
elsewhere.
The newer generation pesticides decompose more
readily. Potential impacts of currently used
pesticides are extensively evaluated in the course
of product registration by the U.S. Environmental
Protection Agency and the California Department of
Pesticide Regulation. Current pesticide use in the
State of California is closely regulated, with 100%
use reporting to the Agricultural Commissioner's
office required for most pesticide use. However,
monitoring for these compounds in the region's
streams, rivers, wetlands and harbors is both
difficult and expensive, and there is currently
little data on their distribution and fate
throughout the watersheds, due to funding
constraints of the monitoring programs and
difficulties in keeping up with new compounds as
they are introduced.9
References regarding effects of excessive
sedimentation: Mathias & Moyle, 1992; Jurik,
et al., 1994; Questa Engineering, 1995.
References regarding sediment as transport
mechanism for persistent pesticides:
Kleinfelder, 1992, 1993; Werner, et al.,
1993.
Reference regarding increase in surface water
nitrate concentrations in the Elkhorn Slough
watershed and in the lower portions of the
Salinas River: Caffrey, et al., 1997.
Reference regarding "harmful algal blooms":
Anderson, 1999.
Reference regarding nitrates in groundwater
supplies: Monterey County Water Resources
Agency, 1990.
Reference regarding no offsite migration of
pesticides in two parcels in the Salinas Valley:
Kleinfelder, 1993.
Reference regarding total pounds of pesticide
applied during 1996: CDPR, 1999.
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Last modified on: August 6,
1999