a methodology for defining homogeneous water bodies in transitional and coastal waters s.b. bricker ...

A methodology for defining A methodology for defining homogeneous water bodies in homogeneous water bodies in transitional and coastal waterstransitional and coastal waters

S.B. Bricker

http://www.noaa.gov

Gulf of Mexico AllianceGovernors’ Action plan

Implementation and Integration WorkshopSt. Petersburg, Florida

July 10-12, 2007

http://www.noaa.gov/

Problem definition and ContextProblem definition and ContextEcosystem division into waterbodies for monitoring and

management of coastal systems:

Required by Water Framework Directive and useful for

fulfilment of other legislation such as US Clean Water Act

Methodology should be based on sound scientific

grounding and also meaningful for managers

Must bring together both natural and human criteria

Objectives: to develop and test a Objectives: to develop and test a

methodology for different types of estuarine methodology for different types of estuarine

and restricted coastal systems.and restricted coastal systems.Ferreira, J. G., A. M. Nobre, T. C. Simas, M. C. Silva, A. Newton, S.B. Bricker, W. J. Wolff, P.E. Stacey, A. Sequeira. 2006. A methodology for defining homogeneous water bodies in estuaries – Application to the transitional systems of the EU Water Framework Directive. Estuarine Coastal and Shelf Science 66: 468-482.

MethodologyMethodology

Semi-quantitative methodology that divides estuaries and inshore coastal waters into a meaningful set of water bodies, bringing together

the following criteria:

Morphological classification Salinity based

classification

“Natural” water body division

Natural characteristics

Pressure classification

“Human” water body division

Human dimension

State classification

Normalised to tidal

excursion?

Final water body divisionYes

No

Normalised to tidal excursion?No

Yes

Case studiesCase studies

Depth (m)> -5

0-3

3> 5

LimitsNo data0 2000 m

Depth (m)> -5

0-3

3> 5

LimitsNo data0 2000 m

Mondego Estuary - a tubular Mondego Estuary - a tubular

ecosystem ecosystem

Depth (m)> -5

0

-3

3> 5

LimitsNo data

0 4000 m

Depth (m)> -5

0

-3

3> 5

LimitsNo data

0 4000 m

Ria Formosa - a dendritic ecosystem Ria Formosa - a dendritic ecosystem

MethodologyMethodology - morphological criteria -- morphological criteria -

a) Tubular estuary

S1 S2 S3 S4S1

S2S4

S6S1 S2 S3 S4

S3 S5S5

S6

b) Tubular with island c) Complex topographya) Tubular estuary

S1 S2 S3 S4S1

S2S4

S6S1 S2 S3 S4

S3 S5S5

S6

b) Tubular with island c) Complex topography

1. Draw cross-sectional profile

i

ii

z

wlog

wi: Mean width of section i (m)

zi: Mean depth of section i (m)

21

1,

1,

ii

ii

ii

i,I+1: Aggregation factor (no units);

: Absolute difference between si and si+1(no units).

2. Calculate the adimensional shape factor for each section

3. Aggregate longitudinally into water bodies using a threshold value of

0 5 km

N

WB 1WB 2 WB 3

WB 4

Water body limit

1 Section limit

Bathymetry-50

>5

5% 14%

56%

20% 10%2%

3%

16%

4%9% 7% 0%

3%

2% 3%

7%WB 5

WB

0 5 km

N

WB 1WB 2 WB 3

WB 4

Water body limit

1 Section limit

Bathymetry-50

>5

5% 14%

56%

20% 10%2%

3%

16%

4%9% 7% 0%

3%

2% 3%

7%WB 5

WBWBMondego Estuary

MethodologyMethodology - morphological criteria -- morphological criteria -

Cross-sections sketchCross-sections sketch

Cross-sections sketchCross-sections sketch

Morphological sectionsWater body limitsMorphological sectionsWater body limits

Two possibilities for drawing cross-sections:

• meaningless division of intertidal areas• large set of small water bodies

In shallow systems with branched channels and large intertidal areas it is biased to define cross-sections:

Instead it is proposed that the division of dendritic systems is made using a heuristic criterion, e.g. drainage patterns evidenced by the bathymetry:

Ria Formosa

Whole system + intertidal Intertidal only

MethodologyMethodology - salinity criteria and - salinity criteria and naturalnatural harmonization- harmonization-

Salinity WB’s

Mixing zone

Seawater zone

Morphological WB’s

Natural WB’s

0 5 km

WB1

WB3WB5

WB2WB division

WB1/WB2

WB1/WB4

WB4/WB5

WB3/WB5

NWB2/WB3

WB4

WB

Salinity WB’s

Mixing zone

Seawater zone

Morphological WB’s

Natural WB’s

0 5 km0 5 km

WB1

WB3WB5

WB2WB division

WB1/WB2

WB1/WB4

WB4/WB5

WB3/WB5

NWB2/WB3

WB4

WB

Salinity zonation based on the NOAA National Estuarine Inventory:

• Tidal fresh zone (0 – 0.5)• Mixing zone (0.5 – 25)• Seawater zone (> 25)

Salinity zones are interpolated using annual average values over the water column for each sampling station.

Combination of the morphology and salinity dividers into a set of ‘natural’ water bodies:

• In cases where both limits are close together a centerline is defined between

• In other cases potentially lead to more water bodies

Bathymetry

Sado catchment division into sub-basins

Sado estuary division into pressure water bodies

CORINE Land cover:ForestAgriculture areasShrubsArtificial areasMineral extractionSalt pansPaddy fieldsSalt marshesStreams

N

0 10 km

Bathymetry




Bathymetry




N

0 10 km

MethodologyMethodology – human pressure criteria -– human pressure criteria -

Steps for the definition of water bodies according with Steps for the definition of water bodies according with pressure criteria:pressure criteria: Selection of the significant pressure (and representative variables) Assessment and partitioning of loads Normalization, analysis and aggregation: Extend section of eachsub-basin to the estuary

Normalise N and P loading for each sub-basin

Determine the limiting nutrient (using Redfield ratio)

Use of a similarity index to aggregate contiguous lengths of the shoreline with similar pressure

21

1,

1,

ii

ii

ii

i,I+1: Aggregation factor (no units);

i: N load normalised per length of shoreline (kg Nutrient y-1 m-1);

: Absolute difference between i and i+1(kg Nutrient y-1 m-1).

Gulf of Mexico Region: Influencing FactorsGulf of Mexico Region: Influencing Factors

From: Bricker, S., B. Longstaff, W. Dennison, A. Jones, K. Boicourt, C. Wicks and J. Woerner. 2007. A Decade of Change: Effects of Nutrient Enrichment in the Nation’s Estuaries early 1990s to 2000s - National Estuarine Eutrophication Assessment Update. NOAA Coastal Ocean Program Decision Analysis Series No. 26. National Centers for Coastal Ocean Science, Silver Spring, MD.

MethodologyMethodology – state criteria -– state criteria -

3.7 – 4.54.5 – 5.05.0 – 6.06.0 – 7.07.0 – 8.0

DO (mg L-1) percentile 103.7 – 4.54.5 – 5.05.0 – 6.06.0 – 7.07.0 – 8.0

DO (mg L-1) percentile 10

Chl a (g L-1 ) percentile 901.2 – 2.52.5 – 5.05.0 – 7.57.5 – 10.8


0 5 km

N



0 5 km0 5 km

N

State assessmentNo problem for both parameters (Chl a < 5 AND D.O. > 5)No problem for one parameter (Chl a > 5 OR D.O. < 5)Problem for both parameters (Chl a > 5 AND D.O. < 5)

State assessmentNo problem for both parameters (Chl a < 5 AND D.O. > 5)No problem for one parameter (Chl a > 5 OR D.O. < 5)Problem for both parameters (Chl a > 5 AND D.O. < 5)

• Selection of appropriate parameters Selection of appropriate parameters • Data analysisData analysis

The 90th and 10th percentile cut-off points for chl a and D.O. were used as indicators of typically elevated (chl a) and low (D.O.) values *

* Bricker, S.B., Ferreira, J.G. & Simas, T. 2003. An Integrated Methodology for Assessment of Estuarine Trophic Status. Ecological Modelling, 169: 39-60.

Gulf of Mexico Region: Eutrophic Condition SymptomsGulf of Mexico Region: Eutrophic Condition Symptoms


Methodology – Methodology – human harmonization

State divider

Pressure dividerWB1

WB2WB3

0 5 km

N

Human WB’s

State divider

Pressure dividerWB1

WB2WB3

0 5 km0 5 km

N

Human WB’s

N

Pressure division:

State divider:

Human WB’s0 10 km

N

Pressure division:

State divider:

Human WB’s0 10 km0 10 km

Combination of the pressure and state dividers into a set of ‘human’ water bodies:

In each the straight forward combination of both criteria correspond to the human dimension water bodies

MethodologyMethodology – final definition of water – final definition of water bodies -bodies -

The final definition of water bodies for an estuary is obtained by combining and harmonizing the natural and human components:

Human WB’s

Natural WB’s

Final WB’s

NWB1

WB2

WB4 WB3

0 5 km

Human WB’s

Natural WB’s

Final WB’s

NWB1

WB2

WB4 WB3

0 5 km0 5 km

Gulf of Mexico Region: Future OutlookGulf of Mexico Region: Future Outlook


Final commentsFinal comments

Method divides coastal systems into meaningful set of water bodies integrating natural characteristics and management criteria

Final definition will usually be a policy decision, this approach scientifically informs the decision-making process

Significant challenges in the definition of water bodies to be used as “operational” units of the WFD, e.g. “natural” pressures such as harmful algal blooms. Science must play a key role in informing decision-makers on what may be identified as human influence responsive to management measures.

Appropriate time for scientific discussion of issues i.e. technical definition, guidance and harmonisation in both EU and US

Provides contribution to and promotes increased flow of scientific information to support coastal management

http://www.eutro.org

http://www.eutro.org/



a methodology for defining homogeneous water bodies in transitional and coastal waters s.b. bricker ...

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