San Francisco Bay Water Quality Index by kch10832

VIEWS: 35 PAGES: 21

									                                San Francisco Bay
                                Water Quality Index
             INDICATOR ANALYSIS AND EVALUATION
A. Background
San Francisco Bay is a large
dynamic estuary, connected to large                                        Suisun
rivers and small ephemeral streams,           San Pablo
urban and agricultural watersheds,                                          Bay
and the Pacific Ocean. The Bay is
                                                Bay
also an unusual "inland" estuary,
consisting of four interconnected
embayments or subregions, each of              Central
which differs with respect to the
amounts and sources of freshwater               Bay
inflow, and the levels of
urbanization along its shores (Figure
1). Water quality in the Bay, and its
effects on the animals and plants                         South
that live in the estuary and people                        Bay
who enjoy those resources, is
strongly influenced by inputs from
each of these connections.

Assessing and monitoring water
quality in such a large and complex
ecosystem is challenging. Transport
                                         Figure 1. San Francisco Bay consists of four inter-
of many contaminants into the Bay        connected embayments. For indicator analysis,
coincides with periods of high           each embayment was considered as a subregion of
freshwater inflow, episodic and          the Bay.
often short-duration events in
California's Mediterranean climate (see Freshwater Infow Index). Dispersal of
contaminants within the Bay is driven by multiple freshwater inflows, strong tidal
influences, and the complicated topography of the Bay. The list of contaminants detected
in Bay waters continues to grow: new chemicals replace those found to be too harmful to
use while older chemicals, discharged into the Bay or its tributaries years ago, still seep
into Bay waters. Water quality standards, identifying contaminant concentrations that are
harmful to aquatic life or human health, have been established for a number of
contaminants found in the Bay but, for many chemicals, no guidelines exist.




The Bay Institute Ecological Scorecard                      San Francisco Bay Water Quality Index
October 17, 2003                                                                           Page 1
B. Indicators
The Water Quality Index measures the levels of contamination of San Francisco Bay
waters for several classes of toxic compounds and other adverse water quality conditions
that are harmful to aquatic life and impair ecosystem function. The Index has five
indicators, each based on a class of contaminants or water quality conditions:

1. Trace elements – Trace elements include elements, such as arsenic, and metals,
including mercury and copper. Typically these contaminants enter Bay waters during
high flow events or are re-suspended from Bay sediments. For many aquatic organisms,
exposure to high levels of dissolved metals or other trace elements can be lethal or
adversely affect reproduction or early development. Toxicity of a number of these
contaminants is dependent on other water quality characteristics, primarily hardness
(concentration of calcium carbonate, CaCo3, mg/L); for example, toxic effects of some
dissolved metals are reduced in hard water compared to soft water. In addition, for the
protection of aquatic life, different water quality standards may apply for fresh and salt
waters. A number of trace elements, principally mercury and selenium, bioaccumulate in
aquatic organisms in the Bay's food web.

2. Pesticides – Pesticides, herbicides and fungicides used throughout the San Francisco
Bay Area and its upstream watersheds enter Bay waters as runoff and their concentrations
in Bay waters often peak following rainfall events. These compounds, which are
intended to control terrestrial pests, can be equally harmful or lethal to aquatic organisms.

3. PCBs – Polychlorinated biphenyls (PCBs) are a class of man-made chemicals
developed in the 1920s and used extensively in a variety of industrial applications. By
the 1970s, the health risks associated with PCBs were identified and publicized and,
following direction by the U.S. Congress in 1976, the US EPA banned the manufacture
of these compounds in 1978. PCBs are resistant to degradation and persist for many
years in the environment. In addition, PCBs bioaccumulate in the food web and are
stored in the body fat of animals and humans.

4. PAHs – Polycyclic aromatic hydrocarbons (PAHs) are a group of chemicals that occur
naturally in coal, crude oil, and gasoline. Most PAHs enter the environment from
incomplete burning of oil, wood, garbage or coal, where they can persist for months of
years. Identified health effects of PAH exposure include cancer and adverse reproductive
and developmental effects. Present water quality standards for PAHs are for the
protection of human health based on consumption of exposed aquatic organisms.

5. Dissolved oxygen – Low dissolved oxygen concentrations can kill fish and
invertebrates and exclude many aquatic animals from large areas of habitat. Oxygen
depletion usually results from high rates of microbial and/or algal respiration that exceed
the capacity of the water body to replenish oxygen through phytoplankton photosynthesis
and diffusion from the air. Excessive inputs of organic material and nutrients, for



The Bay Institute Ecological Scorecard                       San Francisco Bay Water Quality Index
October 17, 2003                                                                            Page 2
example from poorly treated sewage discharges or surface runoff, can accelerate
respiration rates and trigger localized and regional oxygen depletion.

Individual contaminants in each of the indicators are shown in Table 1.

Sediment Contamination – Pollutants are not only present in the Bay's open waters but
are also found in the sediments on the Bay's bottom, particularly near the mouths of
tributary streams. Contaminant-laden sediments are reintroduced to the Bay's open
waters when shipping channels or other areas are dredged; as a result of tidal action;
and/or during peak rainfall events. Thus, sediments can be a source of continued
contamination to Bay waters as well being directly toxic to benthic (bottom-dwelling)
organisms. Sublethal contamination of benthic organisms is also an important pathway
for bioaccumulation and biomagnification of contaminants in the food web. Future
versions of the San Francisco Bay Water Quality Index will include an indicator for
sediment quality to assess the condition of Bay sediments and changes in contamination
levels through time.

C. Methods and Calculations

1. Data sources

The Indicators were calculated for
each year using data from the San
Francisco Estuary Regional
Monitoring Program for Trace
Substances (RMP)1, which has
conducted two or three surveys per
year since 1993, sampling 26
stations distributed throughout Bay
(Figure 2). Half of the stations are
located in areas of the Bay that are
predominantly salt water and half in
more estuarine areas with lower and
more variable salinities. Additional
data for dissolved oxygen
concentrations and for general
evaluation of long-term trends in
Bay water quality were obtained
from the U. S. Geological Survey               Figure 2. Regional Monitoring Program water sampling
Ecology and Contaminants Project.2             station in San Francisco Bay.

1
  More information on the RMP can be obtained at www.sfei.org and at www.sfei.org/rmp/index/html.
RMP water quality data can be downloaded at www.sfei.org/rmp/data/rmpwater.htm.
2
  More information on the USGS Ecology and Contaminants Project can be obtained at
http://wwwrcamnl.wr.usgs.gov/tracel/. Water quality data from this program are available for download at
http://sfbay.wr.usgs.gov/access/wqdata.

The Bay Institute Ecological Scorecard                               San Francisco Bay Water Quality Index
October 17, 2003                                                                                    Page 3
2. Water Quality Standards

The concentrations of dissolved oxygen or contaminants assessed by each indicator were
evaluated in relation to water quality standards established for the protection of aquatic
life and human health by the U.S. Environmental Protection Agency (USEPA), California
Toxics Rule (CTR), California Regional Water Quality Control Board (RWRCB), San
Francisco Bay Region), and the California Department of Fish and Game (CDFG) (Table
1).3 Water quality standards for the protection of aquatic life identify levels of
contaminants that can be directly harmful to exposed plants and animals. Standards for
the protection of human health are intended to prevent unacceptable accumulation of
contaminants in aquatic organisms such that consumption of the organisms by human
would be safe. Although the RMP monitors more than 120 contaminants, water quality
standards have been established for only 41 chemicals and for dissolved oxygen. For a
number of contaminants, concentrations deemed safe for the protection of aquatic life or
human health differ between fresh water (defined as having salinity<5 ppt more than 75%
of the time) and salt waters (salinity>5 ppt more than 75% of the time). For samples
collected from the intermediate and variable salinity estuarine waters of the Bay, the most
protective of the salt and fresh water standards was applied. For several dissolved metals
with toxicities dependent on water hardness (concentration of calcium carbonate, CaCo3,
in mg/L), the applicable standard was calculated based on hardness of the measured water
sample.

3. Calculations

Each indicator was calculated using methods developed by the British Columbia Ministry
of the Environment, Lands and Parks (Zandbergen and Hall, 1998)4 and adopted by the
Canadian Council of Ministers of the Environment (CCME, 2001). Using this method,
calculation of each indicator incorporated three different measurements:

    Scope (how many?) - the number of contaminants that exceeded water quality
    standards

    Frequency (how often?) - the proportion of samples for each contaminant that
    exceeded water quality standards

    Amplitude (how much?) - the amount by which the samples exceeded water quality
    standards




3
  For more information on water quality standards used for the Water Quality Index see
www.epa.gov/ost/standards/wqslibrary/ca/131.38.pdf, www.swrcb.ca.gov/%7erwqcb2basinplan.htm, and
www.sfei.org/rmp/index/html.
4
  Zandbergen and Hall (1998) is available at http://www.cciw.ca/33-4/33-4-519.htm.

The Bay Institute Ecological Scorecard                          San Francisco Bay Water Quality Index
October 17, 2003                                                                               Page 4
Scope was calculated as:
      Scope = [(number of failed variables/total number of variables)]*100
      where "failed variables" are the contaminants considered in the indicator that
      exceeded the standard.

Frequency was calculated as:
      Frequency = [(number of failed tests)/(total number of tests)]*100
      where "failed tests" are the samples tested for each contaminant considered in the
      indicator that exceeded the standard.

Amplitude was calculated in three steps as:

         a) Excursioni = [(failed test valuei)/(objectivei)]-1
            where "i" is each sample test.

                          n
         b) NSE = [Σ excursioni)/(number of tests)]
                        i=1
               where NSE is the normalized sum of the excursions.

         c)    Amplitude = {NSE/[(0.01(NSE) + 0.01]}
               where amplitude scales the NSE to a 100-point scale.

Each of these three measurements yielded results in a 100-point scale, with high values
indicating greater contamination than low values.

The indicator5 was calculated from the Scope, Frequency and Amplitude results as:

         Indicator = 100 – {[sqrt(scope2 + frequency2 + amplitude2)]/1.732}
         where "sqrt" is the square root.

This final calculation also yielded results in a 100-point scale but, in contrast to its
component metrics, high Indicator values corresponded to low levels of contamination
(i.e., good water quality) and low values indicated high levels of contamination (i.e., poor
water quality).

Calculations were conducted using a Microsoft Excel macro, CCME Water Quality
Index 1.0, available on request from the Canadian Council of Ministers of the
Environment.6 For the PCBs and Dissolved oxygen indicators, data from stations in each
of the Bay's four embayments, or subregions (i.e., South, Central, San Pablo, and Suisun

5
  Although we use the result of this calculation as the "indicator", this value is referred to as the "CCME
Water Quality Index" by the Canadian Council of Ministers of the Environment (CCME, 2001).
6
  For further scientific information contact on the CCME Water Quality Index, see http://www..ec.gc.ca or
contact Environmental Canada, Guidelines and Standards Division, 351 St. Joseph Blvd., Hull, QC K1A
0h3, email: ceqg-rcqe@ec.gc.ca.

The Bay Institute Ecological Scorecard                                 San Francisco Bay Water Quality Index
October 17, 2003                                                                                      Page 5
Bays), were partitioned and contaminants in each region were treated individually.
Therefore, for these indicators, the "Scope" calculation yielded information on the
number of subregions in the Bay in which the water quality standard was exceeded. For
reference and validation of the collective Indicator results, expressed as the Water
Quality Index, an additional calculation using the CCME Water Quality Index 1.0 Excel
calculator was made using the data from all contaminant categories and all subregions
(see F. Alternative Calculation of the Water Quality Index).




The Bay Institute Ecological Scorecard                   San Francisco Bay Water Quality Index
October 17, 2003                                                                        Page 6
Table 1. Water quality standards for the protection and aquatic life and/or human health
used for calculation of Water Quality Indicators. RWRCB=Regional Water Resources
Control Board, San Francisco Basin Plan; USEPA=U.S. Environmental Protection
Agency; CTR=California Toxics Rule; CDFG=California Department of Fish and Game.
      Contaminant                Standard           Source              Comments
Dissolved oxygen (mg/L)                     >5.0 mg/L        RWRCB
Trace elements*                                                            * Fresh water and salt water
  Ag (silver)**                              <1.9 ug/L       USEPA         standards differ and the lower
  As (arsenic)                               <36 ug/L                      of the two standards was
  Cd (cadmium)**                           <2.2-9.3 ug/L                   used for estuarine water
  Cr VI (chromium VI)                       <11-50 ug/L                    samples.
  Cu (copper)**                              <3.1 ug/L                     ** Ag, Cd, Cu, Ni, Pb, and Zn
  Hg (mercury)                           <0.012-0.025 ug/L                 toxicities are dependent on
  Ni (nickel)**                               <8 ug/L                      water hardness, therefore
  Pb (lead)**                              <2.5-8.1 ug/L                   standards were calculated
  Se (selenium)                             <5-71 ug/L                     based on hardness in the
  Zn (zinc)**                                <81 ug/L                      measured water sample.
Pesticides
  Alpha-HCH                                <13000 pg/L       USEPA,        * Water quality standard for
  Beta-HCH                                 <46000 pg/L       CTR, and      diazinon for the protection of
  Chlorpyrifos                             <5600 pg/L         CDFG         aquatic life developed by
  Diazinon*                                <40000 pg/L                     California Department of Fish
  Dieldrin                                  <140 pg/L                      and Game (Menconi and
  Endosulfan I                              <8700 pg?l                     Cox, 1994).
  Endosulfan II                            <8700 pg/L
  Endosulfan sulfate                     <240000000 pg/L
  Endrin                                   <2300 pg/L
  Gamma-HCH                                <63000 pg/L
  Heptachlor                                <210 pg/L
  Heptachlor oxide                          <110 pg/L
  Hexachlorobenzene                         <770 pg/L
  Mirex                                    <1000 pg/L
  p,p∧-DDD                                  <840 pg/L
  p,p∧-DDE                                  <590 pg/L
  p,p∧-DDT                                  <590 pg/L
                                                              USEPA
PCBs (total, pg/L)                          <170 pg/L
                                                             and CTR
PAHs
  Acenaphthene                            <270000 ng/L       USEPA,
  Anthracene                             <110000000 ng/L     CTR, and
  Benz(a)athracene                          <49 ng/L         RWRCB
  Benzo(a)pyrene                            <49 ng/L
  Benzo(b)fluoranthene                      <49 ng/L
  Benzo(k)fluoranthene                      <49 ng/L
  Chrysene                                  <48 ng/L
  Dibenz(a,h)anthracene                     <49 ng/L
  Fluorathene                             <370000 ng/L
  Fluorene                               <14000000 ng/L
  Indeno(1,2,3-cd)pyrene                    <49 ng/L
  Pyrene                                 <11000000 ng/L




The Bay Institute Ecological Scorecard                                 San Francisco Bay Water Quality Index
October 17, 2003                                                                                      Page 7
D. Evaluating Results and Grading
For each indicator, the grading scale followed the "ranking" scale recommended by the
CCME (2001). That scale also used five categories or levels that corresponded to
specific levels of water quality impairment (Table 2). The Water Quality Index was
calculated as the "grade point average" of the component indicators, and was reported as
a Grade (i.e., A-F) and a Score (i.e., the grade point average is expanded to a 100 point
scale using a multiplication factor of 25).

Table 2. Grading scale and rationale used for the all Water Quality Indicators.
     Indicator                                                                        Grade
(100-point scale)                        Ecological condition                         point       Grade
                         Excellent: water quality is protected with virtual
       95-100                                                                            4           A
                                absence of threat or impairment; conditions
                                very close to natural or pristine levels
                         Good: water quality is protected with only minor
       80-94                                                                             3           B
                                degree of threat or impairment; conditions
                                rarely depart from natural or desirable levels
                         Fair: water quality is usually protected but
                                 occasionally threatened or impaired;
       65-79                                                                             2           C
                                 conditions sometimes depart from natural or
                                 desirable levels
                         Poor (marginal*): water quality is frequently
       45-64                                                                             1           D
                                threatened or impaired; conditions often
                                depart from natural or desirable levels
                         Very poor (poor*): water quality is almost always
        0-44                                                                             0           F
                                threatened or impaired; conditions usually
                                depart from natural or desirable levels
* The CCME identifies the two lower levels with the terms "marginal" (for a grade of D) and "poor" (for a
grade of F), rather than "poor" and "very poor" as is used for indicators in other Scorecard Indexes.




The Bay Institute Ecological Scorecard                                  San Francisco Bay Water Quality Index
October 17, 2003                                                                                       Page 8
E. Results
Indicator 1. Trace elements

The RMP monitors 14 trace elements in the Bay. These contaminants occur in Bay
waters in both particulate and dissolved forms, but water quality standards apply only to
dissolved trace elements and have been established for only ten of the monitored
elements. Toxicity of the several of the dissolved metals depends on other water quality
conditions, principally hardness and salinity. Figure 3 shows the results of the Trace
elements indicator calculations.


    100
     75
             Scope                                                                  Grade
            how many?
     50
                                         100                                          A
     25
      0
                                         80
                                                                                      B
    100
            Frequency                                                                 C
     75
            how often?                   60
     50                                                                                   D
     25
                                         40
      0
    100
                                                 Trace Elements
     75
        Amplitude                        20                                               F
        how much?
     50
     25
                                          0
       0                                       1993   1995    1997       1999       2001
           1993 1995 1997 1999 2001


  Figure 3. The Trace Elements Indicator measures the concentration of dissolved trace
  elements in Bay waters in relation to the water quality standards for the protection of
  aquatic life. The Indicator is calculated from three metrics. Scope measures the number of
  contaminants and regions of the Bay in which concentrations were were above the
  standards. Frequency measures the proportion of water samples in which standards were
  not met. Amplitude measures the magnitude of each exceedence, the amount by which the
  measured concentration for a contaminant exceeded the standard.



Water quality standards for most toxic trace elements found in the Bay were met in
most water samples collected at most stations in the Bay.
From 1993-2001, an average of 10% (range: 2-18%) of all water samples exceeded the
standard for one or more trace elements. In 2001, 10% of samples failed for at least one
contaminant.




The Bay Institute Ecological Scorecard                        San Francisco Bay Water Quality Index
October 17, 2003                                                                             Page 9
Copper, mercury, selenium, and
                                                                                                                        salt water: 0.025 ug/L
nickel concentrations exceeded




                                         Mercury (ug/L)
                                                                          0.01
water quality standards in some                                                                                               fresh water: 0.012 ug/L

years (Figure 4).
                                                                   0.001
Water quality standards for copper
were exceeded in all years.                                                                                                         no data 2000-2001
                                                            0.0001
Mercury concentrations (measured                                10                         fresh water: 5 ug/L
for only 1993-1999) exceeded




                                                     Selenium (ug/L)
standards in 1994, 1997 and 1998.                                                      1
Selenium concentration standards
                                                                                0.1
were exceeded in each of the last
five years of the survey. Nickel                                          0.01
standards were exceeded at least                                                       6
once in most years.                                                                    5                                fresh and salt water: 3.1 ug/L




                                                                       Copper (ug/L)
                                                                                       4
Trace element contamination                                                            3
was most severe in South and                                                           2
                                                                                       1
San Pablo Bays.
                                                                                       0
Water quality exceedences for the
                                                                                              1994          1996     1998           2000         2002
four problem trace elements
                                                                           South Bay               Central Bay      San Pablo Bay          Suisun Bay
occurred exclusively in South and
San Pablo Bays (Figure 4). No                    Figure 4. Concentrations of mercury, Selenium, and
exceedences were measured in                     copper in the four subregions of the San Francisco Bay
                                                 from 1993-2001. Each point is the contaminant
either Central or Suisun Bays.                   concentration measured at a single station during a
                                                 survey. Each line is the linear regression of the
Concentrations of most of the                    contaminant concentrations over time from a subregion.
problem trace element                            Note that mercury and selenium graphs use a log scale
                                                 on the Y axis.
contaminants are declining
(Figure 4).
Mercury concentrations in South and San Pablo Bays declined significantly from 1993 to
1999 (regression, p<0.001, both subregions). Copper concentrations declined in all
regions except San Pablo Bay (p<0.01, all subregions except San Pablo). Selenium
concentrations have declined in areas except South Bay (p<0.001, all subregions except
South Bay). In South Bay, selenium concentrations increased significantly during the
nine-year period (p<0.001).




The Bay Institute Ecological Scorecard                                                                     San Francisco Bay Water Quality Index
October 17, 2003                                                                                                                         Page 10
Indicator 2. Pesticides

The RMP monitors 29 pesticides or pesticide breakdown products in the Bay but water
quality standards have been established for only 17 of these contaminants. Figure 5
shows the results of the Pesticides indicator calculations.



   100
     75
            Scope                                                                   Grade
           how many?
     50
                                         100                                          A
     25
     0
                                         80
                                                                                      B
   100
           Frequency                                                                  C
     75
           how often?                    60
     50                                                                                   D
     25
                                         40
     0
   100
                                                 Pesticides
     75
        Amplitude                        20                                               F
        how much?
     50
     25
                                          0
      0                                        1993   1995     1997      1999       2001
          1993 1995 1997 1999 2001

   Figure 5. The Pesticides Indicator measures the concentrations of pesticides in Bay
   waters in relation to the water quality standards for the protection of aquatic life. The
   Indicator is calculated from three metrics. Scope measures the number of contaminants
   and regions of the Bay in which concentrations were were above the standards.
   Frequency measures the proportion of water samples in which standards were not met.
   Amplitude measures the magnitude of each exceedence, the amount by which the
   measured concentration for a contaminant exceeded the standard.



Water quality standards for most pesticides found in the Bay were met in most
water samples collected at most stations in the Bay.
From 1993-2001, an average of 31% of all water samples exceeded the standard for one
or more pesticides. In 2001, only 17% of samples had pesticide concentrations greater
than the water quality standard. The percentage of water samples containing pesticide
concentrations in excess of water quality standards was substantially lower in 2000 and
2001 (mean: 14%), the last two years for which data were available, than in any year
between 1993 and 1999 (mean: 36%). However, fewer water samples were collected in
2000 and 2001 (18 samples/year compared to an average of 45 samples/year).




The Bay Institute Ecological Scorecard                         San Francisco Bay Water Quality Index
October 17, 2003                                                                             Page 11
Concentrations of diazinon,                               10000
                                                                                                            p,p -DDE
dieldrin, heptachlor epoxide, or
                                                                1000
DDT compounds exceeded water
quality standards in all years                                  100
(Figure 6).
Dieldrin and DDE (a compound                                      10
                                                                1000
related to DDT) exceeded water                                                                   Heptachlor epoxide
quality standards in all years.                                 100




                                         Concentration (pg/L)
Standards for Diazinon and
                                                                 10
Heptachlor epoxide were exceeded
in most years.                                                    1
                                                                1000
                                                                                                            Dieldrin
Pesticide contamination was most
                                                                100
severe in South, San Pablo Bays,
and Suisun Bay.                                                  10
Most pesticide exceedences
                                                                  1
occurred in South and San Pablo
Bays (Figure 6). For most of the                  100000                                                    Diazinon
problem pesticides, the highest                           10000
contaminant concentrations
                                                                1000
occurred in South and Suisun Bays.
Concentrations of heptachlor                                    100
epoxide were significantly higher in                                    1994     1996     1998       2000       2002
Suisun Bay than all other subregions                        South Bay     Central Bay     San Pablo Bay       Suisun Bay
while Diazinon concentrations were
highest in South Bay. (Kruskal-          Figure 6. Concentrations of mercury, Selenium, and
                                         copper in the four subregions of the San Francisco Bay
Wallis, p<0.05, both tests). DDE         from 1993-2001. Each point is the contaminant
concentrations were equally high in      concentration measured at a single station during a
South, San Pablo and Suisun Bays.        survey. Each line is the linear regression of the
                                         contaminant concentrations over time from a subregion.
                                         Note that mercury and selenium graphs use a log scale
Concentrations of most of the            on the Y axis.
problem pesticides have not
declined (Figure 6).
Diazinon, Dieldrin and DDE concentration did not significantly change during the nine-
year 1993-2001 period. In contrast, concentration of heptachlor epoxide declined
significantly in all areas of the Bay (regression, p<0.05, all subregions).




The Bay Institute Ecological Scorecard                                          San Francisco Bay Water Quality Index
October 17, 2003                                                                                              Page 12
Indicator 3. PCBs

The RMP has identified 56 different polychlorinated biphenyls in San Francisco Bay
waters. However, water quality standards for protection of aquatic life and human health
(based on consumption of aquatic organisms exposed to PCB in fresh and salt water) for
these chemicals apply to the summed concentration of all isomers and congener
compounds (U.S. EPA and CTR). Figure 7 shows the results of the PCBs indicator
calculations.



    100
     75                                                                               Grade
     50
            Scope
                                         100                                            A
     25
      0
           how many?
                                          80
                                                                                        B
    100
                                                                                        C
     75
                                          60
     50                                                                                     D
     25    Frequency
           how often?                     40
      0
    100
                                                 PCBs
     75
                                          20                                                F
     50
     25    Amplitude                      0
      0
           how much?                           1993    1995      1997      1999       2001
          1993 1995 1997 1999 2001

   Figure 7. The PCB Indicator measures the concentration of PCBs in Bay waters in
   relation to water quality standard for the chemical. The Indicator is calculated from three
   metrics. Scope measures in how many regions of the Bay PCB levels exceeded the
   standard. Frequency measures the proportion of water samples in which the standard
   was exceeded. Amplitude measures the magnitude of each exceedence, the amount by
   which the measured PCB concentration exceeded the standard.


PCB concentrations in San Francisco Bay exceeded water quality standards in every
year, in every subregion of the Bay, and at nearly every sampling station.
From 1993-2001, most water samples exceeded the standard by more than three-fold,
with a median PCB concentration of 471 ng/L (compared to the standard of 170 ng/L).
In South Bay, all but one water sample collected over the nine-year period exceeded the
standard, while in Suisun Bay nearly 35% of all samples were in compliance with the
PCB standard. In 2001, PCB concentrations in San Francisco Bay exceeded water
quality standards for the protection of human health by nearly three-fold.




The Bay Institute Ecological Scorecard                           San Francisco Bay Water Quality Index
October 17, 2003                                                                               Page 13
PCBs concentrations were highest in South Bay, intermediate in San Pablo Bay, and
lowest in Central and Suisun Bays.
From 1993-2001, median PCB concentrations in South Bay, 1172 ng/L, were
significantly higher than those measured in all other areas of the Bay (Kruskal-Wallis
ANOVA, p<0.05) (Figure 8). San
Pablo Bay PCB concentrations,
                                        10000
472 ng/L, were lower than South
Bay but significantly higher than




                                         PCBs (ng/L)
levels measured in either Central         1000
or Suisun Bays.

PCB concentrations are                                 100           water quality
                                                                      standard
declining in most areas in the                                        (31 ng/L)

Bay.                                                                1994             1996     1998       2000    2002
In Central, San Pablo and Suisun                             South Bay        Central Bay        San Pablo Bay   Suisun Bay

Bays, PCB levels significantly
declined from 1993 to 2001                      Figure 8. PCB concentrations in the four subregions of
(regression, p<0.05, all tests)                 the San Francisco Bay from 1993-2001. Each point is
                                                the PCB concentration measured at a single station
(Figure 8). South Bay PCB levels
                                                during a survey. Each line is the linear regression of
have not declined (regression,                  the contaminant concentrations over time from a
p>0.5).                                         subregion. Note that the Y axis uses a log scale.




The Bay Institute Ecological Scorecard                                                San Francisco Bay Water Quality Index
October 17, 2003                                                                                                    Page 14
Indicator 4. PAHs

The RMP has identified 25 different polycyclic aromatic hydrocarbons in San Francisco
Bay waters. However, water quality standards have been established for only 12 of these
individual PAH compounds. Figure 9 shows the results of the PAHs indicator
calculations.



    100
     75
            Scope                                                                  Grade
           how many?
     50
                                         100                                         A
     25
      0
                                         80
                                                                                     B
    100
           Frequency                                                                 C
     75
           how often?                    60
     50                                                                                  D
     25
                                         40
      0
    100
                                                 PAHs
     75
        Amplitude                        20                                              F
        how much?
     50
     25
                                          0
      0                                        1993   1995   1997      1999       2001
          1993 1995 1997 1999 2001


   Figure 9. The PAHs Indicator measures the concentration of polycyclic aromatic
   hydrocarbons in Bay waters in relation to the water quality standards for the
   protection of aquatic life and human health. The Indicator is calculated from three
   metrics. Scope measures the number of contaminants and regions of the Bay in
   which concentrations were were above the standards. Frequency measures the
   proportion of water samples in which standards were not met. Amplitude measures
   the magnitude of each exceedence, the amount by which the measured concentration
   for a contaminant exceeded the standard.


Concentrations of PAHs in Bay waters exceeded water quality standards in four of
nine years.
Water quality standards for at least one of the 12 PAH compounds for which standards
have been established were exceeded in 1995, 1996, 1997 and 2001. In 2001, one water
sample from the South Bay had concentrations of two PAH compounds,
benzo(b)fluoranthene and benz(a)anthracene, that exceeded standards for those
chemicals.




The Bay Institute Ecological Scorecard                       San Francisco Bay Water Quality Index
October 17, 2003                                                                           Page 15
South and San Pablo Bays had
the highest levels of PAH                                    1000
pollution (Figure 10).




                                         Total PAHs (ng/L)
Total PAH concentrations were                                100
highest in South Bay, intermediate
in San Pablo Bay lowest in Central
                                                              10
and Suisun Bays (Kruskal-Wallis,
p<0.05, all tests).
                                                               1
                                                                           1994      1996       1998      2000    2002
PAH concentrations in Bay                                           South Bay     Central Bay     San Pablo Bay   Suisun Bay
waters did not change during the
nine-year survey period                   Figure 10. Total PAH concentrations in four subregions of
                                          San Francisco Bay from 1993-2001. Each point is the
(regression, p>0.1, all tests)            total PCB concentration measured at a single station
(Figure 10).                              during a survey. Each line is the linear regression of the
                                          contaminant concentrations over time from a subregion.
                                          Note that the Y axis uses a log scale.




The Bay Institute Ecological Scorecard                                                 San Francisco Bay Water Quality Index
October 17, 2003                                                                                                     Page 16
5. Dissolved oxygen

Current water quality standards for dissolved oxygen in Bay waters require a minimum of
5 mg/L of dissolved oxygen. However, availability of oxygen for aquatic animals is
more closely related to the % saturation of oxygen in the water, which is a function of
water temperature and salinity as well as dissolved oxygen concentration. Oxygen
saturation levels below 60-80% can be harmful to many aquatic animals and, in cooler
and fresher Bay waters, oxygen concentrations above the minimum standard of 5 mg/L
may be still be inadequate for the protection of aquatic life. Figure 11 shows the results
of the Dissolved oxygen indicator calculations.



   100
    75
            Scope                                                                      Grade
           how many?
    50
                                         100                                             A
    25
     0
                                         80
                                                                                         B
   100
           Frequency                                                                     C
    75
           how often?                    60
    50                                                                                      D
    25
                                         40
     0
   100
                                                 Dissolved Oxygen
    75
       Amplitude                         20                                                 F
       how much?
    50
    25
                                          0
      0                                        1993    1995      1997      1999       2001
          1993 1995 1997 1999 2001


   Figure 11. The Dissolved Oxygen Indicator measures the concentration of dissolved
   oxygen in Bay waters in relation to the water quality standard for the protection of aquatic
   life. The Indicator is calculated from three metrics. Scope measures the number of
   regions of the Bay in which dissolved oxygen levels fell below the standard. Frequency
   measures the proportion of water samples in which the standard was not met. Amplitude
   measures the magnitude of each exceedence, the amount by which the measured
   dissolved oxygen concentration was below the standard.



Dissolved oxygen concentrations were above the minimum standard in all areas of
the Bay except the South Bay.
In several years from 1993 and 2001, dissolved oxygen concentrations fell below the
standard at the San Jose, Sunnyvale and Coyote Creek stations near the southern end of
South Bay. In 2001, one water sample, collected at San Jose, failed to meet the minimum
standard for dissolved oxygen.



The Bay Institute Ecological Scorecard                           San Francisco Bay Water Quality Index
October 17, 2003                                                                               Page 17
Dissolved oxygen concentrations




                                                 Dissolved oxygen (mg/L)
in South Bay were lower than                                               14
levels measured in other                                                   12
subregions of the Bay.                                                     10
South Bay oxygen concentrations                                             8
were consistently and significantly                                         6
lower than those measured in all                                            4                                                 water quality
other regions of the Bay (Kruskal-                                          2
                                                                                                                               standard
                                                                                                                               (31 ng/L)
Wallis, p<0.05 all tests) (Figure 12).
                                                                                       1994      1996       1998      2000           2002
Oxygen concentrations were highest
                                                                                South Bay     Central Bay     San Pablo Bay          Suisun Bay
in Suisun Bay and, from 1993-2001,
only one sample, collected in 1998,                      Figure 12. Dissolved oxygen concentration measured in
failed to meet the higher dissolved                      the in four subregions of San Francisco Bay from 1993-
                                                         2001. Each point is the dissolved oxygen concentration
oxygen standard (7 mg/L) set by the
                                                         measured at a single station during a survey.
RWQCB for Bay-Delta waters west
of Antioch.

Dissolved oxygen levels varied seasonally.
Throughout the Bay, higher oxygen concentrations were measured during the spring, the
result of high rates of photosynthesis during the spring phytoplankton bloom (see Food
Web Index) (Figures 12 and 13). Low dissolved oxygen conditions usually occurred
during the summer months.

From 1993-2001, overall
                                          14 Regional Monitoring Program
dissolved oxygen conditions in            12     (South Bay, 1993-2001)
the Bay have not changed.
                                         Dissolved oxygen (mg/L)




                                          10
                                               water quality standard
However, based on the longer data          8          (5 mg/L)
record from the USGS Ecology               6
and Contaminants Project,                  4
                                           2
dissolved oxygen conditions in the
South Bay have improved during            14 USGS Ecology and Contaminants Project
                                                  (South Bay, 1971-1978, 1993-2001)
the past thirty years (Figure 13).        12
                                          10
The USGS program, which                    8
samples more frequently and at             6
stations that are farther from shore,      4
measured consistently low                  2
dissolved oxygen in the South Bay               1972        1976      1980      1995 2000
throughout the 1970s (including
                                       Figure 13. Dissolved oxygen concentration measured at
one year in which oxygen
                                       South Bay sampling stations by the RMP and the USGS
concentrations fell to zero            Ecology and Contaminants Program.
following a uncontrolled release of
inadequately treated sewage into the Bay, not shown in Fig 13, but see SFEI, 2003).
Since 1993, the USGS program has not reported any samples with oxygen concentration
below the minimum standard.



The Bay Institute Ecological Scorecard                                                             San Francisco Bay Water Quality Index
October 17, 2003                                                                                                                 Page 18
6. Water Quality Index
                                         Score                                                                                                            Grade

The San Francisco Bay Water                   100                                                                                                               A
Quality Index aggregates the                                75                                                                                                  B
results of the Trace elements,
Pesticides, PCBs, PAHs, and                                 50                                                                                                  C
Dissolved oxygen indicators
                                                            25                                                                                                  D
(Figure 14).
                                                                        0                                                                                       F
Between 1993 and 2001, water
quality in the open waters of the              1993       1995     1997       1999     2001
Bay was fair (Grade = C) to good
                                        Figure 14. The Water Quality Index aggregates the
(Grade = B). Although the Water         results of the Trace elements, Pesticides, PCBs, PAHs,
Quality Index has fluctuated            and Dissolved oxygen indicators.
slightly from year to year, it has
not significantly increased or decreased during the nine-year period for which indicator
data were available (regression, p>0.05).

F. Alternative Calculation of the Water Quality Index
In the above analysis, the Water
Quality Index was calculated from                                                                                                               CCME Rank
                                                                      (value calculated from three metrics)




separate analyses of several classes                                                                          100                                     Excellent
                                          Water Quality Index




of contaminants, each class equally                                                                                                                       Good
weighted despite different numbers                                                                            80
                                                                                                                                                            Fair
of constituent contaminants. An
                                                                                                              60
alternative approach to calculate                                                                                                                     Marginal
the Index uses the CCME Water                                                                                 40                                           Poor
Quality Index calculator for all of
the contaminants monitored in the                                                                                   1994    1996     1998      2000         2002
Bay, a method that weights each                                                                                                                           Grade
individual contaminant equally.
                                          Water Quality Index Score
                                                                      (expanded grade point average)




                                                                                                              100                                            A
Figure 15 shows the Water Quality                                                                                                                     (excellent)
                                                                                                              80                                              B
Index calculated using this                                                                                                                               (good)
alternative method and compares it                                                                            60
                                                                                                                                                              C
with the Water Quality Index                                                                                  40                                            (fair)

calculated as the grade point                                                                                                                                 D
                                                                                                              20                                      (very poor)
average of the five Indicators.                                                                                0
                                                                                                                                                              F
                                                                                                                                                      (very poor)
Both approaches yielded similar
                                                                                                                    1994    1996     1998      2000         2002
results: San Francisco Bay water
quality from 1993-2001 was                     Figure 15. Comparison of San Francisco Bay Water
generally fair to good and the small           Quality Index calculated using the CCME Water Quality
year-to-year variations in pollution           Index and all Bay contaminants (upper panel) and the
                                               Index calculated as the grade point average of the five
levels were consistent between the             Indictors (lower panel).
two calculation methods.


The Bay Institute Ecological Scorecard                                                                                     San Francisco Bay Water Quality Index
October 17, 2003                                                                                                                                         Page 19
G. Long-term Trends in Bay Water Quality
Although the earliest data from the San Francisco Estuary Regional Monitoring Program
for Trace Substances (RMP) are from 1993, the U. S. Geological Survey has been
conducting both monitoring and focused special studies on Bay water quality since the
1970s. Because the USGS monitoring studies are less comprehensive than the RMP with
respect to the diversity of contaminants, the Water Quality Index indicators were
calculated using only the RMP data. However, the USGS results were used to evaluate
long-term trends in Bay water quality for selected contaminants.

Concentrations of ammonia                                                          30




                                                         Ammonia nitrogen (mg/L)
nitrogen and copper declined                                                       25                             Ammonia nitrogen
substantially during the late                                                      20
1970s and early 1980s (Figure                                                      15
16).                                                                               10
Following implementation of                                                         5
                                         Concentration

advanced wastewater treatment,                                                      0

concentrations of ammonia
nitrogen and copper in effluents                                                   150                                    Copper
                                                         Copper (ug/L)




discharged into South Bay declined                                                 120

substantially. Excessive nitrogen                                                  90

inputs can promote bacterial and                                                   60

algal blooms that can result in                                                    30
periodic and localized dissolved                                                    0
oxygen depletion. Since the 1970s,                                                       1970   1975      1980     1985      1990     1995

incidences of low dissolved                    Figure 16. Ammonia nitrogen and copper concentrations
oxygen in the South Bay have also              in wastewater effluent discharged into South Bay.
been reduced (see Dissolved                    Redrawn from U. S. Geological Survey, “San Francisco
oxygen indicator and Fig. 13).                 Bay Program: Lessons learned for managing coastal
                                               water resources”, http://water.usgs/wid/html/sfb/html.




The Bay Institute Ecological Scorecard                                                                 San Francisco Bay Water Quality Index
October 17, 2003                                                                                                                     Page 20
H. References
CCME (2001) Canadian water quality guidelines for the protection of aquatic life.
CCME Water Quality Index 1.0 User's Manual. In: Canadian environmental quality
guidelines, 1999, Canadian Council of Ministers for the Environment, Winnipeg.

Cloern, J. E., S. N. Luoma, and F. H. Nichols (1995) San Francisco Bay Program: lessons
learned for managing coastal water resources. U.S. Department of Interior, U. S.
Geological Survey, Fact Sheet FS-053-95.
This article is available at http://water.usgs.gov/wid/html/sfb.html.

Menconi, M. and C. Cox (1994) Hazard assessment of the insecticide diazinon to aquatic
organisms in the Sacramento-San Joaquin river system. Administrative Report 94-2.
California Department of Fish and Game. Rancho Cordova, CA.

San Francisco Estuary Institute (SFEI) (2003) The Pulse of the Estuary: Monitoring and
Managing Contaminants in the San Francisco Estuary. SFEI Contribution 74. San
Francisco Estuary Institute, Oakland, CA.

Zandbergen, P. A. and K. J. Hall (1998) Analysis of the British Columbia Water Quality
Index for watershed managers: a case study of two small watersheds. Water Qual. Res. J.
Canada 33: 519-549.
This article is available at http://www.cciw.ca/33-4/33-4-519.htm.




The Bay Institute Ecological Scorecard                    San Francisco Bay Water Quality Index
October 17, 2003                                                                        Page 21

								
To top