FATHOM Model for Florida Bay: Overview and Calibration/Verification Exercise

Transcription

1 FATHOM Model for Florida : Overview and Calibration/Verification Exercise October 2-3, 13 Frank Marshall, Bill Nuttle, Jack Cosby Flux Accounting and Tidal Hydrology at the Ocean Margin The FATHOM Model Version 6.

2 G. E. P. Box Essentially, all models are wrong, but some models are useful. Box, G. E. P., and Draper, N. R., (1987), Empirical Model Building and Response Surfaces

3 Outline of Presentation Overview of FATHOM Update on FATHOM calibration/verification (calver) project Coupling FATHOM to hydrologic models

4 What is FATHOM? Dynamic, spatially explicit, mass-balance salinity and water quality model of Florida Accounts for water and salt budgets in each of 4 well-mixed basins Designed to investigate circulation, salinity, and water quality responses in Florida to runoff, climate, and tides, given the bathymetry

5 Model Structure The banks and shoals effectively divide Florida into a network of interconnected basins Exchange between the basins is limited / controlled by the shallow banks and the presence of islands in the bay. Based on bathymetric data for the bay, 4 distinct basins form the basic structure and domain of the FATHOM model. Transfer of water and solutes between basins is controlled by the bathymetry of the banks.

6 FATHOM groups Model Goodnessof-fit Observed flows as input Simulated vs Observed Salinity

7 Model Goodness-offit observed flow inputs Region Region Region Salinity (psu) Joe Fathom 13 SERC Salinity (psu) Long Sound Fathom 7 SERC 8 4 Region Salinity (psu) Little Blackwater Sound Fathom 8 SERC Salinity (psu) Manatee Fathom 6 SERC Salinity (psu) Little Madeira Fathom 14-1 SERC 11 Salinity (psu) Barnes Sound Fathom SERC Efficiency % All Seasons Wet Seasons Dry Seasons Salinity (psu) Blackwater Sound Fathom 9 SERC Ave sim-obs All Seasons Wet Seasons Dry Seasons

8 Model Goodness-offit observed flow inputs Region Region Region Salinity (psu) Duck Key Fathom 47 SERC Salinity (psu) Park Key Fathom 1 SERC 23 4 Region Salinity (psu) Terrapin Fathom -26 SERC Salinity (psu) Whipray Basin Fathom 34 SERC Salinity (psu) Butternut Key Fathom SERC 24 Salinity (psu) Garfield/Rankin Fathom 37 SERC Efficiency % All Seasons Wet Seasons Dry Seasons Ave sim-obs All Seasons Wet Seasons Dry Seasons

9 Model Goodness-offit observed flow inputs Region Region Region Salinity (psu) Captain Key Fathom 19 SERC Salinity (psu) Porpoise Lake Fathom 29 SERC Region Salinity (psu) Murray Key Fathom 42 SERC Salinity (psu) Johnson Key Basin Fathom 39 SERC Salinity (psu) Peterson Keys Fathom 3 SERC Salinity (psu) Rabbit Key Basin Fathom 38 SERC Efficiency % All Seasons Wet Seasons Dry Seasons Salinity (psu) Twin Key Basin Fathom 32 SERC Ave sim-obs All Seasons Wet Seasons Dry Seasons

10 Applications of FATHOM Using Model-Produced Inputs ENP CESI project used SFWMM calver flows as input 12 SFWMD Florida MFL -year review used SFWMM calver flows as input and other CERP alternatives Results: FATHOM salinity output had some issues For these reason this calver exercise was commissioned

11 Progress To-date: FATHOM Florida Salinity Model Calibration and Verification Concept: Improve boundary conditions, freshwater distribution, and bathymetry before updating Manning coefficient Steps: Assemble SFWMM cal/ver data (completed) Improve western boundary conditions regressions (completed) Review freshwater input distribution along north shore (completed) Review treatment of shallowest depth classes (bathymetry) (completed) Review Manning s N between basins, modify as needed (9%) Use calibrated model in example run (%) Document upgrades (%)

12 Step 1: Assemble SFWMM calver data SFWMM calver data stage and flow: For model goodness-of-fit evaluations: data used to match availability of USGS creek flows Other data used: SERC salinity, USGS creek flows, ENP stage, wind, sea surface elevation, rain (Flamingo, Tavernier, Royal Palm)

13 Step 2: Improve western boundary New Models conditions regressions R 2 for previous model SERC = (1.47*p33_depth) - (.2*T21lag2) - (2.31 * kwwatlevlag2), R 2 =.7 (.6) SERC26 = (.1*T21lag2) - (-1.91*kwwatlevlag2) - (1.*p33_depth) - (1.62*P33_depthlag3), R 2 =.74 (.6) SERC27 = (.2*T21lag2) - (1.13*kwwatlevlag3) - (1.83*P33_depthlag1) + (1.8*kwwatlev), R 2 =.6 (.) SECR28 = (3.3*P33_depthlag2) + (.*vwndmialag1) - (.33*vwndkwlag1), R 2 =.6 (.42)

14 Step 3: Review freshwater input distribution along north shore Reconnaissance trip to verify locations and conditions for freshwater inputs to Florida Analyzed and interpreted Google Earth satellite imagery Reviewed and analyzed USGS observed creek flow data Evaluated SFWMM calver structure data total SFWMM flows are about ½ of USGS observed total flows for 1996-

15 Step 3, cont.: Flows from SFWMM are only similar for seasonal patterns to observed flows total SFWMM flows are about ½ of observed flows LMDBQ1 LMDBQ2 LMDBQ S197 JOEBQ2 JOEBQ1 Reg 3 Reg 4 Reg Reg 2 Reg 1 1 Reg 6 Reg 11 Reg 9 Reg 8 Reg 7 FATHOM Runoff Regions (for model inputs)

16 Step 3, cont.: SFWMM was calibrated to stage, not flow; so SFWMM calver stage data is best SFWMM output Best flow data are USGS observed creek flows Therefore - MLR models of observed creek flows prepared from observed stage data MLR-modeled flows were used with SFWMM calver stage data to produce calver flow simulations, which were input to FATHOM

17 USGS Creek Flows Monitoring began in 1996 at: Highway Creek Trout Creek Mud Creek Taylor River Mouth McCormick Creek These data used for MLR model development Monitoring at other stations began in 1999 and later Data from used for model development

18 Observed USGS Flow Data Receiving Water USGS Flow Station SFWMM X X X X X X X X SERC Data X X X X X X X X X X X X X X X X X X X Manatee Manatee X X X X X X X X X Long Sound Highway Creek X X X X X X X X X X X X X X X X Long Sound Oregon Creek X X X X X X X X X X X Long Sound Stillwater Creek X X X X X X X X X X X X X Long Sound Highway Creek X X X X X X X X X X X Little Madeira Homestead X X X X X X Little Madeira Taylor River Mouth X X X X X X X X X X X X X X X X Joe JB_1e X X X X X X X X Joe JB_2E X X X X X X X X X X X Joe JB_c X X X Joe JB_8w X X X X X X X X X X X Eagle Key Basin Mud Creek X X X X X X X X X X X X X X X X Deer Key Basin Trout Creek X X X X X X X X X X X X X X X X Rankin Lake Alligator Creek X X X X X Terrapin Mccormack Creek X X X X X X X X X X X X X X

19 Flow Models - WHC Highway Creek (WHC) is one of 4 Long Sound inputs Region 2 WHC (cfs) = *CP + 7.*EVER *G *NP6-4.9Ever6lag1 R 2 =.64, RMSE = 32 cfs, N = 16

20 Flow Models Trout Creek Trout Creek is Joe discharge to Deer Key Basin (Region 3) Trout Creek (cfs) = *EVER *P3-9.3*NP *P *cplag1-31.4*Ever7lag1-6.2*G3273lag *NP46lag3 R 2 =.71, RMSE =17 cfs, N = 16 NOTE: Y-axis scale is different than others

21 Flow Models Mud Creek Mud Creek is input to Eagle Key Basin (Region ) Mud Creek (cfs) = *CP *P3-21.1*NP *NP62lag2-4.9*P33lag1-33.6*P37lag2 R 2 =.8, = 26 cfs, N = 16.

22 Flow Models Taylor River Mouth Taylor River Mouth is one of 2 inputs to Little Madeira (Region 6) tr_mouth (cfs) = *E *EVER *P3-28.3*NP62 -.9*P33lag1 R 2 =.8, RMSE =.3 cfs, N = 16

23 Flow Models McCormick Creek McCormick Creek is input to Terrapin (Region 8) McCormick Creek (cfs) = *E *P3-4.6*P *R *P33lag1 R 2 =.62, RMSE = 37.7 cfs, N = 16.

24 Step 3: Regional Flow Inputs Factors were used to simulate some regional flows based on observed post 1996 data Region 1 inputs (S197) direct use of SFWMM calver data Long Sound (Region 2) = 2.4*WHC Joe (Region 3) assumed to be equal to Trout Creek flow to begin, and adjusted based on FATHOM salinity output Little Madeira (Region 4) = 1.7*Taylor River Mouth Region = Mud Creek Terrapin (Region 8) = Mccormack Creek Rankin Lake (Region 11) = 1.*McCormack Creek Regions 3, 7,9,, and 12 have no inflows

25 Modeling Issues with Observed and Model-Produced Flows - Observed USGS data include many negative flow values - MLR flow models from stage as independent variable also produce negative flows - FATHOM cannot handle negative flows - So: all negative flows are set equal to before input to FATHOM Note scale difference

26 Step 4: Review treatment of shallowest depth classes became part of Step

27 Step : Review Manning s N between basins, modify as needed Used best available information on flows to set N USGS observed data Concept for variation of N by depth class ( depth classes: Un-calibrated N distribution:. for all depth classes Shallowest shoals: highest resistance to flow, highest N, lowest flux (flow per unit time) Deepest shoals: lowest resistance to flow, lowest N, highest flux Mid-depth transition from high N to low N values New distribution

28 Manning Equation Coefficient Manning Equation Coefficient Depth (ft) Region 1 Region 2 Region

29 Final Step Used best Manning s N distribution FATHOM used in iterative fashion Flows modified until salinity was reasonably similar to observed salinity (1996-) In the end, total calver flows = 1.4 * USGS flows

30 Region

31 Region

32 Region

33 Region

34 Region

35 ern Region

36 Observed vs Simulated Calver, 1996, N=6 Region Basin SERC station Observed Average FATHOM Average R-sq RMSE Mean Absolute Error Little Blackwater Sound Blackwater Sound Barnes Sound Manatee s Long Sound Joe Little Madeira Terrapin Rankin Lake Whipray Basin Duck Key Basin Park Key Basin Butternut Key Basin Captain Key Basin Porpoise Key Basin Peterson Key Basin Rabbit Key Johnson Key

37 Work Remaining After finalizing details (i.e. some additional runs to improve goodness-of-fit), use SFWMM input for a CERP run Compare output to observed data Can FATHOM detect change?

38 Work Remaining Current FATHOM Documentation Appendix B to be updated

39 Other Potential Model-Produced Inputs TIME stage BISECT flows, stage RSM / RSNSM MIKE SHE Paleo data Others?

40 Coupling FATHOM with TIME Flows TIME flows for primary creeks used like observed input data with best Manning s N values (depth-class distribution) Output compared for 1996-

41 MAE: USGS = 6. Calver = 7.2 TIME = 4.9 MAE: USGS = 4.2 Calver = 4.1 TIME = 4. MAE: USGS = 6.4 Calver = 4.9 TIME = 4. MAE: USGS =.4 Calver = 4. TIME =.4

42 Unresolved Issues for future work Better fix for negative flows Expand FATHOM domain upstream until flow is essentially unidirectional Requires re-programming of FATHOM new code, not too difficult Extension of calver stage data to allows for 9 years of data comparison instead of 4 Revisions to evaporation may be needed

43 Overall Summary of Work Boundary salinity models upgraded Input flows upgraded Manning N upgraded Negative flows handled Comparisons to previous SFWMM coupled out put indicates that these upgrades have significantly improved FATHOM output using SFWMM input data

44 Summary some details Low confidence in SFWMM flows do not recommend using them Stage-to-flow models worked much better use these To better handle negative flows, structural improvements to the model are necessary Additional improvements may be possible with final iterations, review of output, and analysis by other members of team (Nuttle, Cosby)

45 Initial Findings region only responds to Long Sound flows Region responds mostly to outputs from Joe and Little Madeira, may respond slightly to flows from McCormack and Alligator Creeks; also rainfall Region responds (ex: Whipray Basin) mostly to flows from McCormack and Alligator Creeks ern Region also appears to respond somewhat to flows from McCormack and Alligator Creeks

46 THANKS! Flux Accounting and Tidal Hydrology at the Ocean Margin The FATHOM Model Version 6.