Models, Muddles, & Management

in Narragansett Bay, RIChris Deacutis

NBEP, URI Coastal Institute

May 18, 2011 http://www.nbep.org/http://www.nbep.org/

Narragansett Bay Watershed

Watershed Area = 4,421 km2

Bay Surface Area =

497 km 2

Watershed:Surface Area ~ 9:1

Vs. Casco Bay

Watershed 2,551 km2

Surf Area 518 km2

Ratio ~ 5:1

3 Major River Basins :

Taunton ; Blackstone ; Pawtuxet

Rivers

Annual Mean Mo. Flow =

104 m3/sec

61% of drainage basin in MA

N-S Pollution Gradient STP

Last

Dam

Lynn Carlson, Brown U.

GIS labN-S Pollution Gradients

August 20, 2003 – Western Greenwich Bay

T. Ardito, NBEP

July 6, 2006

Upper half of Bay - serious hypoxia stress

2003 Kill not

“perfect storm” situation

Aug 4, 2009

Aug 14, 2008

http://www.geo.brown.edu/georesearch/insomniacs/

Blackstone River WWTFs incl. Worcester, MA = 2nd

Lrgst srce N load after Direct Discharges to upper

Bay.

WasteWater Treatment Facilities = 68-73% of loadTot. Diss.Inorganic Nitrogen (DIN) load to Narragansett Bay

2

93

5

Agri

WWTF

Backgrnd

Narragansett Bay P Sources by %

(Roman et al. 2000)

NBC

Bucklin Pt

Worcester

UBWPAD

NBC Fields Pt

Cranston

Pryor et al .

200723

4

73

Atmos

Agri

WWTF

Narragansett Bay N Sources by %

(Roman et al. 2000)

Incl.stormwtr

Other options to calculate Other options to calculate

approximate target for N load ?approximate target for N load ?

URI Mar. Ecosystem Res Lab (MERL) URI Mar. Ecosystem Res Lab (MERL)

exp 1980’s added sewage as DIN at exp 1980’s added sewage as DIN at

various levels (Nixon, various levels (Nixon, OviattOviatt & others)& others)

Politicians Demand Action ! Politicians Demand Action !

Problem: Available hydrodynamic model available does NOT Problem: Available hydrodynamic model available does NOT

reproduce many aspects of Providencereproduce many aspects of Providence--SeekonkSeekonk--Upper Bay Upper Bay

area (most impacted zone) area (most impacted zone) Top of the Bay (major WWTF + River inputTop of the Bay (major WWTF + River input

Upper Bay area below #1 WWTFUpper Bay area below #1 WWTF

TN = 5 mg/L ~ 72% WWTF reduction to Prov.TN = 5 mg/L ~ 72% WWTF reduction to Prov.--Seekonk w/ MA UBWPAD (but Seekonk w/ MA UBWPAD (but

only 58% at design flow) ; ~ 58% w/o MA (28% at design)only 58% at design flow) ; ~ 58% w/o MA (28% at design)

~ 42% (53% w/Worc.MA) Total Load reduction to ~ 42% (53% w/Worc.MA) Total Load reduction to Prov.SeekProv.Seek. ‘95. ‘95--’96 loads (but ’96 loads (but

28% (42%w/MA) at design) 28% (42%w/MA) at design)

W/O treatment = 55% W/O treatment = 55% incrincr load at design flows to load at design flows to ProvProv--Seekonk River areaSeekonk River area

(= 39X MERL)(= 39X MERL)

~ 30% decrease in WWTF

load so far

2014

Projecting a decrease of 50% DIN from WWTF loads from new

permit limits = ~ 35 % decrease Tot DIN to Bay

(BUT > 35% decrease for Upper Bay)

Use of Models - Climate vs Weather • Weather – only short term (days)+ local (Boston vs

Prov.)

• Climate - Long-term (decades & more) affected by major drivers:

– Sunlight Received + Amt. reflected (ice-snow) + amt. heat absorbed / radiated back to space etc.

• Prediction Level Differs !

- Weather - Weather models only able to predict weather conditions max of ~ 1-2 wks due to chaos (nonlinear) behavior

– Climate - Global circulation models (GCM) – target is over wideregion - expect variability yr-to-yr and wider margin of prediction (e.g., ~ avg. annual temp. expect rise ~ +2F over20yrs across wide areas vs will be 60F tomorrow in Prov.)

Mgt Needs : TMDL ? (paper tigers?)

-Driven by WQ criteria standard

violations & “halting violations”

- CWA does not deal with

real world variability well

Model that accurately predicts hrly D.O.

criteria violations? - XXX

Models cannot absolutely replicate

real world - but are useful to give sense

of direction / trend & whether you are

“in the ballpark” you hope for

DO2

N P

N

Land-use

Atmosphericdeposition

N P

Productivity

Temp, Light,

Boundary Conditions

Chl, N, P, Salinity

Phytoplankton

Sediment

organics

.

.

Physics

Surface layer

- - - - - - - - -

Deep layer

- - - - - - - - -

Bottom

sediment

Flux tobottom

Photic zoneheterotrophy

Benthicheterotrophy Denitri-

fication

O2 coupled

stoichiometricallyBZI

ƒ(Chl10d)ƒ[Chl]

ƒ(OM,T) %

Processes of a simplified 2 layer model & basis for

mixing

flushing

Jamie Vaudrey, James Kremer

(UCONN), Mark Brush (VIMS), Dave

Ullman (URI) CHRP October 8, 2009

formulations: (excluding macroalgae...)

Brown, CTD Surveys

salinity

oxygen

Buoy Network

salinity

oxygen

chlorophyll

Nutrient Stations

DIN

DIP

Model uses N , P loads & exchange

between boxes from high res.

ROMS hydrodynamic model

Outputs for each box :

Mean daily Chl a &

Mean daily D.O.

6/1 6/8 6/15 6/22 6/29 7/6 7/13 7/20 7/27 8/3 8/10

Phyto

pla

nkto

n (

ug

Chl / L)

0

10

20

30

40

6/1 6/8 6/15 6/22 6/29 7/6 7/13 7/20 7/27 8/3 8/10

Nitro

ge

n (

mg/L

)

0.0

0.1

0.2

0.3

0.4

0.5

0.6

6/1 6/8 6/15 6/22 6/29 7/6 7/13 7/20 7/27 8/3 8/10

Oxyge

n (

mg/L

)

2

4

6

8

10

12

14

Box 3

Current

Conditions

e.g.

prediction:

N reduced

50%

Phytoplankton

Oxygen

Nitrogen

surface

bottom

surface

bottom

Values = daily avg.

How use daily avgs for Mgt TMDL Needs?

Test sites:

• Bullocks Reach

2003, 2005-07

SURFACE

BOTTOM

y = 0.8193x - 0.2138R² = 0.6508

0

2

4

6

8

10

12

14

0.00 5.00 10.00 15.00

MinO2surf, mg/l

TIMEsurf<2.9 mg/l

TIMEsurf<1.4 mg/l

y = 1.057x - 1.1834R² = 0.9093

0

5

10

15

20

25

30

0.00 2.00 4.00 6.00 8.00 10.00 12.00

MinO2bott, mg/l

TIMEbott<2.9 mg/l

TIMEbott<1.4 mg/l

Bottom Water instantaneous min. DO & time below DO thresholds appears predictable directly from daily mean DO

-Can plug in N load change- see predicted likely min

bottom DO

Mark Brush (VIMS)CHRP October 8, 2009

A suggestion for Casco Bay :

Concentrate on Gradients

-for DO / chl a issues

- look for hot spots using WQ

surveys

-Look into the role of local

hydrodynamics in terms of

geographic orientation &

dominant wind directions on

local FLUSHING

-- Will highlight zones of

greatest sensitivity to nutrient

loads

Kincaid coastal hydrodynamics

lab (URI-GSO): Identified water

retention zones coinciding with

low oxygen hotspots

Develop high resolution

hydrodynamics/ flushing for

the “hot zones to understand

major physical driving

factors- perhaps couple to

simplified ecol. models

High spatial-temporal

hydrodynamic resolution in 2 hotspots:

1) Providence River

2) Greenwich Bay

Success with multiple current meter methods

(tilt meter + ADCP)

Save the Bay

Results of DATA, ROMS Modeling, LAB Modeling point to

Bimodal Flushing of Urban Hotspots (not fully mixed Box Model Flushing)

Channel water flushes ~ 1 day

Shoal bottom water:

can take days to go through cycle,

a week to leave area – tide does not flush !

Edgewood

shoals

channel

Slow flush

Fast flush

Channel tracer flush

< 1 day

Shoal tracer > 5 days

Shoal bottom water floats can take > 6 days to exit the shoal

Cumulative track

No wind NNE-ward wind

Retention in Greenwich Bay: Wind matters at the local level !

Residual flows - distinctly different in the 2 cases. (C Kincaid lab) 10 days of simulation

No sea

breezeApplied sea

breeze

summer 2006 JUSTIN M. ROGERS, M.S. 2008 URI

Slow flushing by ~ 10 X

- commit to long term monitoring at key pts in system

– Need understand key drivers of local hydrodynamics &eco.

- Wind direction, speed & duration- correlated to flushing?

- climate - may affect timing of stratification / hypoxia

- changes in max temp ?- affect nr-shore sp. max temp

limits(e.g., lobster >20 C, metab.up ~50% betw. 20-21.5 C)

Use models to understand which drivers have grtst infl.

on the issue (hypoxia / stratification / flushing etc)

- use nonproprietary models if possible – more users to turn to

for advice & more capable of revisions w/o huge cost

My Suggestions: Use WQ surveys to look for repeated “hot spots” –

then go w/ higher res hydrodynamics to see gyres etc.

– deal w/ input to these areas

Suggestions from LIS special Symposium 5-5-2011 Port

Jefferson, Long Island , NY

Discussion &

Questions