Michael Kemp Maureen Brooks Jeremy Testa

Box Model Analysis of theCorsica River2005–2006

Box Model Boundary

Sycamore Point

Possum Point

Cedar Point

The Sill

CONMON

WWTP

Box 2

Corsica River Study Site

SONE

Box 3

Box 1

Single Box ModelPrecipitation – EvaporationRunoff,

River Flow

Waste-water

Outflow

Non -AdvectiveExchange

Chester RiverCorsica River

Qww

Qr

Qp-e

Qout

ECh-Co

Water Balance: Qout = Qr + Qp-e + Qww

Salt Balance: ECh-Co = (Qout) [SCo/(SCh-SCo)]

SChesterSCorsica

Caveates in this Analysis

Analyses generated thus far are very preliminary because they are based on incomplete data.

Stream flow & nutrient loading rates estimated using tentative data & untested assumptions on weighting & extrapolation.

Point-source and atmospheric inputs taken from different years, with “interpolation” to common year.

Weighted extrapolation from USGS gauged site.

Many observed patterns are very clear and may be robust (i.e., strong signal showing through noise of questionable data.

Single Box Model: Water-Transport

1

116

1.2

118.2

1040

Chester RiverCorsica River

(103 m3 d-1)

2005

70.2

1

68

1.2 275

2006

2005: April to October Transports2006: May to October Transports

Single Box Model: DIN Transport

20

364

21

25

23

Chester RiverCorsica River

(kg d-1)

402

= 265 mol m-2 h-1

(net uptake)

6

2005

20

211

21 77

323

= 214

2006

Single Box Model: DIP Transport

0

556

506

756

438

Chester RiverCorsica River

133

= 0.11 mol m-2 h-1

(net release)

0

323

506

1080

3772

= 3.28

4023

(kg d-1)

Single Box Model: Biogeochemical Rates

Net DIN Production (mol N m-2 h-1):

Net DIP Production (mol P m-2 h-1):

Denitrification (mol m-2 h-1):

Net Ecosystem Prod. (g C m-2 y-1):

Water Residence Time (FFW, d):

2005 2006

-265 -214

0.11 3.28

267 266

-1 -37

85 145

Chester River

21

276

5

37

55Box 1 Box 2

24

772

1588

(kg d-1)

209 943

= 601 mol m-2 h-1

(net uptake)

= 683 mol m-2 h-1

(net uptake)

21

161

5

4

3

6

105

1551

185 167

= 530 = 144

DIN Transport in 2-Box Model

Chester River

1.4

1.2

0

1.1

1.8Box 1 Box 2

2.3

92.4

00.4

0.3 91.4

= 4.14 mol m-2 h-1

(net uptake, release)

= 36.9 mol m-2 h-1

(net release)

1.4

0.7

0

2.9

5.1

2.5

11.8

00.2

5.9 6.1

= 7.7 = 2.5

(kg d-1)

DIP Transport in 2-Box Model

DIN Transport in 3-Box Model

Corsica River

14.5

92.5

2.1

3.9

4.6

Box 1 Box 23.6

12.4

15.722.8

OutputBox 3

Precip Non-point

Non-Advective

Non-point

Point

3.8

(-100.6) (-43.9) (-28.1)

9.1

5.2

17.3

Chester River

Net Flux

(kg d-1)

Monthly Net Fluxes of DIN & DIP: 1-Box

-400.00

-350.00

-300.00

-250.00

-200.00

-150.00

-100.00

-50.00

0.00

May June July August September October

DIN

NO23

NH4

-2.00

-1.00

0.00

1.00

2.00

3.00

4.00

May June July August September October

DIP

DIP Flux

DIN Flux

May Jun Jul Aug Sep Oct

DIN Flux

-1000.00

-800.00

-600.00

-400.00

-200.00

0.00

200.00

400.00

May June July August September October

um

ol

m-2 h

-1

Box 1

Box 2

DIP Flux

-4.00

-2.00

0.00

2.00

4.00

6.00

8.00

10.00

May June July August September October

um

ol m

-2 h

-1

Box 1

Box 2

DIN Flux

DIP Flux

May Jun AugJul Sep Oct

Monthly Net Fluxes of DIN & DIP: 2-Box

Box 1Box 2

Box 1Box 2

DIN-700

-600

-500

-400

-300

-200

-100

0

Box 1 Box 2 Box 3

um

ol

m-2 d

-1

DIP

0

2

4

6

8

10

12

Box 1 Box 2 Box 3

um

ol

m-2 d

-1

Mean Net Fluxes of DIN & DIP: 3-Box

Box 1 Box 2 Box 3

Box 3Box 2Box 1

DIN Flux

DIP Flux

Key preliminary conclusions

1) Consistent high rates of net DIN uptake within Corsica (retention or transformation?)

2) Net DIP production within Corsica indicates system heterotrophy (mining P from sediments or transforming PP inputs?)

3) Corsica appears to import substantial DIN from

Chester (transported to middle of estuary, Box 2)

4) Clear regional trends in transport and net fluxes

Problems

1) ~Sparse WQ data – difficult to represent concentration distribution along salinity gradient.

2) Need diffuse source water flow and nutrient loading (TN, NH4, NO3, TON, TP, DIP) for major tribs.

3) Need more point-source loading rates.

4) Need time-series atmospheric loading rates.

5) Need algorithms for estimating water flow and nutrient loading in non-monitored years.

Spatial Distribution of Water Depths

Hypsograph of distribution of system area and volume at various water depths

Implications for benthic production with improved water clarity?

Small increase in Secchi (0.7-1.0 m) yields large increase in photic bottom from 40-90%