Comparison of the South Florida Water Management Model (SFWMM) with the

Simple Refuge Stage Model (SRSM) for the A.R.M. Loxahatchee National Wildlife Refuge

Michael G. Waldon mike_waldon@fws.gov

William (Ben) Roth, Ehab A. Meselhe

Center for Louisiana Inland Water StudiesEcological Engineering Analysis & Modeling

University of Louisiana - Lafayette

ACKNOWLEDGMENTSThe South Florida Water Management District provided SFWMM files. Their cooperation & assistance are gratefully acknowledged.

Background – SFWMMSouth Florida Water Management Model

• Model domain is South Florida• 2x2 mile grid with other features• User specifies – rain, ETP• Calibration uses historic flows• Model outputs – stages, flows• Often applied in comparing alternatives• Regulatory flows calculated in predictive

mode

SFWMM –WCA-1

Source: SFWMD

Background – SRSMSimple Refuge Stage Model

• Model domain is WCA-1• Based on water budget• 2 compartments – Canal & Marsh• Constant surface area• Flow between canal & marsh calculated• Originally in Excel; Now Madonna• User specifies – rain, ETP, inflow, water supply• Model outputs – stage, regulatory outflow

SRSM Water Budget

Qin

P P

QMC

ET Qout GC ET

Canal Marsh

GM

Canal Stage = EC Marsh Stage = EM

AC = 1,000 acres AM = 139,000 acres

OBJECTIVES

• Set up SRSM run as similar as possible to a SFWMM simulation

• Compare model projections over the 36-year period of simulation

• Examine sensitivity of Refuge stage to inflow, outflow, & management assumptions using SRSM

SRSM IMPLEMENTATION

• SFWMD provided input & output files for SFWMM ECP Base model run

• Used historic rainfall & ET data• Inflow was from SFWMM• Outflows

– Regulatory release– Water supply

Outflow – Regulation Schedule

14

15

16

17

18

1-Jan

1-Feb

1-Mar

1-Apr

1-May

1-Jun

1-Jul

1-Aug

1-Sep

1-Oct

1-Nov

1-Dec

Stag

e (ft

)

MANDATORY (REGULATORY) RELEASE

WATER SUPPLY RELEASE

SFWMM S-10 CFS

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

-0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.6

Canal - A1 Floor (ft)

CFS

Model Projections

14.0

14.5

15.0

15.5

16.0

16.5

17.0

17.5

18.0

18.5

Jan-65Jan-66Jan-67Jan-68Jan-69Jan-70Jan-71Jan-72Jan-73Jan-74Jan-75Jan-76Jan-77Jan-78Jan-79Jan-80Jan-81Jan-82Jan-83Jan-84Jan-85Jan-86Jan-87Jan-88Jan-89Jan-90Jan-91Jan-92Jan-93Jan-94Jan-95Jan-96Jan-97Jan-98Jan-99Jan-00Jan-01

Mar

sh s

tage

(ft)

SRSM SFWMM

Historic S-10 CFS

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

-2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5

Canal - A1 Floor (ft)

CFS

SFWMM & Historic Water Supply(thousand acre-ft/year)

0

20

40

60

80

100

120

140

160

180

200

1965196619671968196919701971197219731974197519761977197819791980198119821983198419851986198719881989199019911992199319941995199619971998199920002001200220032004200520062007

ECPBASE Historic

Average days per yearmeeting condition

Above Above Below BelowSource HistRR HistWS 17 ft 17.5 ft 16 ft 15.5 ftSFWMM 110 44 89 15SRSM 101 32 90 7SRSM X 84 27 106 13SRSM X 98 31 100 20SRSM X X 81 26 117 25

Observed 58 10 50 0.2

0

20

40

60

80

100

120

140

160

180

0.5 0.75 1 1.25 1.5 1.75 2

Inflow Multiplier

Day

s pe

r yea

r

<15.5 <16 >17 >17.5

SRSM – Sensitivity to Inflow

Conclusions: Findings relevant to Everglades restoration

• Marsh stage sensitive to water supply demands• Marsh stage sensitive to regulatory releases• Simplified modeling is efficient, & is one of multiple

tools used to evaluate impacts of alternatives• There is value in having multiple models based on

different assumptions & levels of complexity• Comparison of alternative models

– increases credibility– identifies model limitations– identifies areas needing investigation & improvement

Questions?