1. Michael Kemp Maureen Brooks Jeremy Testa Box Model Analysis of the Corsica River 2005–2006

2. Box Model Boundary Sycamore Point Possum Point Cedar Point The Sill CONMON WWTP Box 2 Corsica River Study Site SONE Box 3 Box 1

3. Single Box Model Precipitation – Evaporation Runoff, River Flow Waste- water Outflow Non - Advective Exchange Chester RiverCorsica River Q ww QrQr Q p-e Q out E Ch-Co Water Balance:Q out = Q r + Q p-e + Q ww Salt Balance:E Ch-Co = (Q out ) [S Co /(S Ch -S Co )] S Chester S Corsica

4. 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.

5. Single Box Model: Water-Transport 1 116 1.2 118.2 1040 Chester RiverCorsica River (10 3 m 3 d -1 ) 2005 70.2 1 68 1.2 275 2006 2005: April to October Transports 2006: May to October Transports

6. 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

7. 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 )

8. 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 0.113.28 267266 -37 85145

9. Chester River 21 276 5 37 55 Box 1Box 2 24 772 15 88 (kg d -1 ) 209943 = 601 mol m -2 h -1 (net uptake) = 683 mol m -2 h -1 (net uptake) 21 161 5 4 3 6 105 15 51 185167 = 530= 144 DIN Transport in 2-Box Model

10. Chester River 1.4 1.2 0 1.1 1.8 Box 1Box 2 2.3 92.4 0 0.4 0.391.4 = 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 0 0.2 5.96.1 = 7.7= 2.5 (kg d -1 ) DIP Transport in 2-Box Model

11. DIN Transport in 3-Box Model Corsica River 14.5 92.5 2.1 3.9 4.6 Box 1Box 2 3.6 12.4 15.7 22.8 Output Box 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 )

12. Monthly Net Fluxes of DIN & DIP: 1-Box DIP Flux DIN Flux May JunJulAugSepOct

13. DIN Flux DIP Flux MayJunAugJulSepOct Monthly Net Fluxes of DIN & DIP: 2-Box Box 1 Box 2 Box 1 Box 2

14. Mean Net Fluxes of DIN & DIP: 3-Box Box 1Box 2Box 3 Box 2Box 1 DIN Flux DIP Flux

15. 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

16. Problems 1) ~Sparse WQ data – difficult to represent concentration distribution along salinity gradient. 2) Need diffuse source water flow and nutrient loading (TN, NH 4, NO 3, 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.

17. 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%