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Defining Restored Bay Water Quality from the Perspective of Fish, Crabs, Oysters and Underwater Grasses: Chesapeake Bay Dissolved Oxygen, Water Clarity and Chlorophyll a Criteria. Impaired Waters and Clean-up Plans.

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slide1

Defining Restored Bay Water Qualityfrom the Perspective of Fish, Crabs, Oysters and Underwater Grasses:Chesapeake Bay Dissolved Oxygen, Water Clarity and Chlorophyll a Criteria

impaired waters and clean up plans
Impaired Waters and Clean-up Plans

Portions of the Chesapeake Bay and its tidal rivers are listed under the Clean Water Act as “impaired waters” largely because of low dissolved oxygen levels and other problems related to nutrient pollution.

Impaired Water

chesapeake 2000 the new agreement
Chesapeake 2000: The New Agreement

In June 2000, the Chesapeake Bay Program partners signed a new agreement to guide the restoration and protection of the Bay through the next decade and beyond.

In Chesapeake 2000, the partners agreed that:

Improving water quality is the most critical element in the overall protection and restoration of the Chesapeake Bay and its rivers.

chesapeake bay watershed partners
Chesapeake Bay Watershed Partners
  • Signatories to the Chesapeake Bay agreement
    • EPA (representing the Federal government)
    • Jurisdictions of MD, PA, VA and DC
    • Chesapeake Bay Commission (representing MD, PA and VA state legislatures)
  • Headwater states
    • DE, NY and WV
    • Memorandum of Understanding linked to water quality goals
slide5

Chesapeake 2000 AgreementWater Quality Protection and Restoration

  • Integrate cooperative Chesapeake Bay
  • Program and statutory Clean Water Act processes.
  • By 2010, correct the nutrient- and sediment-related
  • problems in the Chesapeake Bay and its tidal
  • tributaries and…
  • Remove the Bay and tidal tributaries from the list
  • of impaired waters under the Clean Water Act.
slide6

Chesapeake 2000 AgreementWater Quality Protection and Restoration

  • Define the water quality conditions necessary to
  • protect aquatic living resources.
  • Jurisdictions with tidal waters will use their best
  • efforts to adopt new or revised water quality
  • standards consistent with the defined water
  • quality conditions.
  • Use the standards as the basis for removing the
  • Bay and its tidal rivers from the list of impaired
  • waters.
refined designated uses for chesapeake bay and tidal tributary waters
Refined Designated Uses forChesapeake Bay and Tidal Tributary Waters

A. Cross Section of Chesapeake Bay or Tidal Tributary

Shallow-Water

Bay Grass Use

Open-Water

Fish and Shellfish Use

Deep-Water

Seasonal Fish and

Shellfish Use

Deep-Channel

Seasonal Refuge Use

B. Oblique View of the “Chesapeake Bay” and its Tidal Tributaries

Migratory Fish

Spawning and

Nursery Use

Open-Water

Habitat

Shallow-Water

Bay Grass Use

Deep-Water

Seasonal Fish and

Shellfish Use

Deep-Channel Seasonal Refuge Use

restored tidal water quality means
Restored Tidal Water Quality Means:
  • Fewer algae blooms and better fish food.
  • Clearer water and more underwater Bay grasses.
  • More oxygen and improved habitat for more fish, crabs and oysters.
chesapeake bay water quality criteria
Chesapeake Bay Water Quality Criteria
  • Dissolved Oxygen – for fish, crabs and oysters
  • Water Clarity – light for underwater Bay grasses
  • Chlorophyll a – base of the Bay food chain

Together, these three criteria define the conditions necessary to protect the wide variety of the Bay’s living resources and their habitats.

slide10

Chesapeake Bay Criteria Needed for Protection of the Refined Tidal Waters Designated Uses

Dissolved Oxygen

Chlorophyll a

Water Clarity

Migratory Spawning and Nursery

Shallow Water

Open Water

Deep Water

Deep Channel

dissolved oxygen
Dissolved Oxygen
  • Living things--even those underwater--need oxygen!
  • The amount of oxygen needed in the water depends on the specific needs of the Bay’s living resources.
  • The amounts depend on where and when certain areas are used by different living resources.
oxygen requirements mg l of bay species
Oxygen Requirements (mg/L) of Bay Species

Migratory Fish Spawning & Nursery Areas

6

Striped Bass: 5-6

American Shad: 5

Shallow and Open Water Areas

5

White Perch: 5

Yellow Perch: 5

4

Hard Clams: 5

Deep Water

Alewife: 3.6

3

Bay Anchovy: 3

Crabs: 3

2

1

Spot: 2

Deep Channel

Worms: 1

0

basis for bay dissolved oxygen criteria
Basis for Bay Dissolved Oxygen Criteria
  • 1992 Chesapeake Bay oxygen restoration goal laid basic foundation
  • 2000 EPA marine and 1985 EPA freshwater dissolved oxygen criteria documents
  • Addition of more Bay species effects data
  • Application of larval recruitment model using Bay specific parameters, species
  • Authored by a team of Bay region scientists, state agency and federal agency technical staff
chesapeake bay dissolved oxygen criteria
Chesapeake Bay Dissolved Oxygen Criteria

1. At temperatures >29oC, dissolved oxygen concentrations above instantaneous minimum of 4.3 mg/L will protect shortnose sturgeon.

water clarity
Water Clarity
  • All plants--even those underwater--need light!
  • Water clarity is a measure of the amount of sunlight that penetrates the Bay’s waters and reaches the surface of underwater Bay grass leaves.
  • The amount needed is determined by the specific underwater grasses which grow in different areas of the Bay.
what s blocking the light
What’s Blocking the Light?

Good Water Clarity

Poor Water Clarity

  • Percent of sunlight at the water surface that penetrates the water:
  • 13% in low salinity waters
  • 22% in high salinity waters

Sediment and other particles in the water

+

Algae in the water

+

Algae on the leaves

equals

Very low percentage of sunlight reaching leaves – Bay grasses grow poorly or die.

basis for bay water clarity criteria
Basis for Bay Water Clarity Criteria
  • Two past technical syntheses (1992, 2000) of Chesapeake Bay underwater grasses habitat requirements
  • Focus on light available to the underwater grasses at the leaf surface
  • 18 year+ tidal WQ monitoring database
  • Investments in ecosystem processes modeling
chesapeake bay water clarity criteria

Percent Surface

Light

Low Salinity Habitats

13%

High Salinity Habitats

22%

Chesapeake Bay Water Clarity Criteria
  • The criteria apply to Chesapeake Bay Program segment-specific depths up to two meters.
  • Areas where underwater bay grasses never occurred or where natural factors, such as currents and wave action, prevent its growth are excluded.
  • Water clarity criteria only apply to shallow-water bay grass designated use.
slide21

Watershed partners have adopted a new 185,000 acre Bay grasses restoration goal

Water clarity criteria apply in the shallow water habitats at depths needed to restore grasses to these areas.

New Bay Grasses Restoration Goal

Baltimore

Washington DC

Cambridge

Fredericksburg

Richmond

Norfolk

slide22
Chesapeake Bay Water Clarity Criteria for Application to Shallow-Water Bay Grass Designated Use Habitats

Example: If a state chooses to use Secchi depth for criteria application at 1.5 meter depth, the criteria equivalent to 13% and 22% PLW is 1.1 and 1.4 meters, respectively.

chlorophyll a
Chlorophyll a
  • Chlorophyll a is a measure of the amount of algae in the water.
  • Some algae are good sources of fish food and others are poor sources.
  • Excessive nutrients can stimulate nuisance algae blooms resulting in reduced water clarity, reduced amounts of “good fish food”, and depleted oxygen levels in deeper waters.
chlorophyll a criteria components
Chlorophyll a Criteria Components
  • Based on fish food/algal composition quantification across an array of poor to good water quality conditions
  • Narrative criteria to protect against adverse algal-related impacts on water quality
  • Chlorophyll a concentrations characteristic of a range of water quality conditions and protective against specific water quality impairments have been published
  • Concentration are applied as:
    • Salinity regime based
    • Spring, summer medians
chesapeake bay narrative criteria for chlorophyll a
Chesapeake BayNarrativeCriteria forChlorophyll a

“Concentrations of chlorophyll a in free-floating aquatic plants (algae) shall not exceed levels that result in ecologically undesirable consequences – such as reduced water clarity, low dissolved oxygen, food supply imbalances, proliferation of species deemed potentially harmful to aquatic life or humans or aesthetically objectionable conditions – or otherwise render tidal waters unsuitable for designated uses.”

Source: U.S. EPA. 2003.

chesapeake bay criteria guidance for chlorophyll a criteria
Chesapeake Bay Criteria Guidance for Chlorophyll a Criteria

“EPA expects states to adopt narrative chlorophyll a criteria into their water quality standards for all Chesapeake Bay and tidal tributary waters. EPA strongly encourages states to develop and adopt site-specific numerical chlorophyll a criteria for tidal waters where algal-related impairments are expected to to persist even after the Chesapeake Bay dissolved oxygen and water clarity criteria have been attained.”

Source: U.S. EPA. 2003.

chlorophyll a criteria supporting technical information
Chlorophyll a Criteria: Supporting Technical Information
  • Based on fish food/algal composition quantification across an array of poor to good water quality conditions
    • Phytoplankton growth limiting water quality conditions and and related chlorophyll a concentrations
    • Concentration characteristic of potentially harmful algal blooms
    • Concentrations characteristic of trophic-base conditions
    • Concentrations protective against water quality impairments (water clarity, dissolved oxygen,
    • Methodologies for deriving water body specific chlorophyll a criteria
  • Salinity regime based, focused on spring, summer medians with maximum concentrations addressing algal blooms
slide28

Illustration of Chlorophyll a, Food Quality, and Water Quality Relationships

Scientist’s View

Chlorophyll

Concentration

Biomass of

Edible Phytoplankton

Biomass of

Inedible Phytoplankton

Water Quality Worst Poor Better Best Restored

Poor Water Clarity

Excess Nutrients

Good Water Clarity

Low Nutrients

Corresponding Phytoplankton

Food Value

Poor

Good

slide29

Illustration of Chlorophyll a, Food Quality, and Water Quality Relationships

Simplified View

Oprah’s Tasty Diet Quantity of Food Available to be Eaten

Index

Too Much

Green Stuff

Right Green

Stuff for Fish Food

Filet Mignon (or Fresh Caesar Salad) with a 1952 French Bordeaux wine

McDonald’s Cheeseburgers (and lots and lots of them)

Water Quality Worst Poor Better Best Restored

Poor Water Clarity

Excess Nutrients

Good Water Clarity

Low Nutrients

Corresponding Phytoplankton

Food Value

Poor

Good

slide30

Illustration of Chlorophyll a, Food Quality, and Water Quality Relationships

Simplified View

Where the Bay

and rivers are now

Where the Bay and rivers

will be when chlorophyll a

criteria are met

Water Quality Worst Poor Better Best Restored

Poor Water Clarity

Excess Nutrients

Good Water Clarity

Low Nutrients

Corresponding Phytoplankton

Food Value

Poor

Good

application of numerical chlorophyll a criteria
Application of NumericalChlorophyll a Criteria
  • The narrative criteria describes the various possible impacts on tidal Bay habitats due to too much algae and the wrong types of algae.
  • Supporting target concentrations will be used by the states to establish numerical chlorophyll a criteria to address localized algal-related problems which are expected to persist even after the Chesapeake Bay dissolved oxygen and water clarity criteria have been attained.
criteria implementation procedures
Criteria Implementation Procedures

A detailed set of criteria implementation procedures have been developed addressing:

  • Magnitude
  • Duration
  • Frequency
  • Space
  • Time

For determining criteria attainment.

slide34

Proposed Approach for Defining Attainment

  • Develop an analytical tool that uses available data to account for spatial and temporal variability in criteria exceedence.
  • Develop Cumulative Frequency Diagram (CFD).
  • Develop a precise rule for deciding if a given segment is attaining its designated use.
slide35

Steps for Developing a CFD

Step 1: Interpolate the Bay water quality monitoring data for each sampling event (e.g., cruise)

 Station

slide36

Step 2. Evaluate interpolated WQ monitoring data interpolator cell by cell using the appropriate criterion value

Criterion by Salinity

slide37

Step 3. Identify the cells in a CBP segment / designated use area that exceed the criteria for each sampling event

slide38

Step 4. Repeat Step 3 for each sampling event in assessment period ...

March 1999

April 1999

May 1999

June 1999

March 2000

Apr 2000

May 2000

Assessment Period

slide39

Step 4. …to generate an event by event accounting of %area (%volume) of a segment exceeding the criteria

March 1999

April 1999

May 1999

June 1999

March 2000

Apr 2000

May 2000

Assessment Period

slide40

Step 5. Compile the measures of % area (%volume) exceeding the criteria. This quantifies the SPATIAL EXTENTof the exceedences in a segment for each sampling event.

% Area (%Volume) Exceeding

Example Assessment Over A

Three Year Assessment Period

Month

slide41

Step 6. Sort and rank the measures of % area/volume of criteria exceedence…

% Area (%Volume) Exceeding

Month

Example Assessment Over A

Three Year Assessment Period

Rank

slide42

Step 6. … and calculate the cumulative probability values based on the ranks

% Area (%Volume) Exceeding

Cumulative Probability (Rank/n+1)

Month

Rank

slide43

Step 7. Plot the % area in exceedence vs. cumulative probability over time

Example Assessment Over A

Three Year Assessment Period

April 2000 X=39%, Y=62%

%Time the Given % Area/ Volume is in exceedence

May 1998

X = 65%, Y = 31%

% Area/Volume in Exceedence

slide44

Step 7. Plot the % area in exceedence vs. cumulative probability over time

Example Assessment Over A

Three Year Assessment Period

at least 39% of the area exceeds the criteria in 62% of the sampling events during the three year assessment period

%Time the Given % Area/ Volume is in exceedence

at least 65% of the area exceeds the criteria in 31% of the sampling events during the three year assessment period

% Area/Volume in Exceedence

slide45

100

Percent of Time

90

80

70

60

50

40

30

20

10

0

10

20

30

40

50

60

70

80

90

100

Percent of Space

Definition of Criteria Attainment

CFD Curve

Biologically-Based

Reference Curve

0

slide46

100

Percent of Time

90

80

70

60

50

40

30

20

10

0

10

20

30

40

50

60

70

80

90

100

Percent of Space

Definition of Criteria Attainment

Area of Criteria

Exceedence

Area of Allowable

Criteria

Exceedence

0

more information is available
More Information is Available

The following products are available athttp://www.chesapeakebay.net/baycriteria.htm

  • Ambient Water Quality Criteria for Dissolved Oxygen, Water Clarity and Chlorophyll a for the Chesapeake Bay and its Tidal Tributaries (U.S. EPA 2003)
  • Bay specific dissolved oxygen, chlorophyll a, and water clarity criteria published as EPA regional water quality criteria
  • Baywide implementation guidelines for each of the three criteria
more information is available48
More Information is Available

The following products are available athttp://www.chesapeakebay.net/uaasupport.htm

  • Technical Support Document for the Identification of Chesapeake Bay Designated Uses and Attainability (U.S. EPA 2003)
  • Technical support document providing extensive information on attainability of current and refined tidal water designated uses
  • Detailed documentation on refined tidal designated uses and recommended use boundaries