Integrated Modeling of Regional Basins: Thirteen Years of Hard Lesson Learned

1. Integrated Modeling of Regional Basins: Thirteen Years of Hard Lesson Learned Mark A. Ross, Patrick D. Tara, and Jeffrey S. Geurink University of South Florida

2. Integrated Model: Coupled Comprehensive Surface-Groundwater Model (Specifically: Experience with coupled HSPF-MODFLOW model known as FHM, ISGW, or IHM)

3. FHM (HSPF/MODFLOW) Integration Pathways Process Coupling 1. DTWT 2. Hydr. heads (streams, wetlands & lakes) 3. Base flow 4. SW/GW ET 5. Irrigation fluxes 6. Variable SY (vadose moist.) Hydrologic Cycle Interception Transpiration Precipitation Interflow Infiltration & Impervious Lens Percolation Evaporation Evaporation Surface water Runoff storages & stream flows Groundwater Flow Water Table Baseflow Leakage Bays, Gulf, Unconfined Aquifer and Oceans Aquitard (Confining Unit) Confined or Artesian Aquifer

4. FHM Chronology • 1989 FHM development • 1993 FHM ver 1.2 used in mine reclamation • 1995 ISGW proprietary version used for public water supply investigations, FHM District-scale application • 1995-1997 FHM peer-reviewed, adapted for USFWS water rights investigations • 1995-1998 period of W-C Fl water wars, numerous models • 1997-2000 several FHM version updates for regional W-C Fl regional investigations, ISGW peer reviewed • 2001-2002 major re-write of FHM/ISGW->IHM (Interra, Aquaterra, USF)

5. Early Problems(Limitations) • Computers (286s) • Model components (HSPF & MODFLOW) • Data utilities (GIS, database programs) • Digital data (no digital quads) • Client perspectives/interest (“recharge generator”) • User acceptance (“too much time & money”) Consequence: Limited Discretization

6. Bill Williams National Wildlife Refuge R 16 W R 18 W R 17 W 95 Lake Havasu T 11 N River N R 18 W R 16 W R 17 W

7. Cibola National Wildlife Refuge R 21 E R 24 W R 23 W T 1 S T 2 S N IMPERIAL NATIONAL WILDLIFE REFUGE

8. Las Vegas National Wildlife Refuge R 16 E R 17 E T 16 N T 15 N N

9. Rattlesnake Creek Study

10. Model Simulation Results Rattlesnake Creek

11. USFWSApplicationsLessons Learned • Need does not justify model where there is no data • Streamflow separation (runoff/baseflow) very important to do but problematic • Component pre-calibration very important • Size and discretization barriers remained • Need much better data utilities

12. Mid 90s “Water Wars”West-Central Florida • Many model applications, similar stream flow performance & gross ET, wildly varying resultant models (recharge), conclusions • Wide variability in model parameterization resulted from inadequate data, understanding and characterization of processes • Need for detailed basin-scale study, tie down internal fluxes and storages

13. Saddle Creek Study(Data Collection, Far-field and Near-field Models) N e a r F i e l d M o d e l 1 0 0 1 0 2 0 3 0 4 0 5 0 6 0 M i l e s D i s t g e n . s h p N S a d d l e C r e e k B a s i n O u t l i n e N o F l o w B o u n d a r y W E G e n e r a l H e a d B o u n d a r y H y d r o g r a p h y S C o n s t a n t H e a d C e l l I n a c t i v e C e l l F a r F i e l d A c t i v e C e l l

14. Saddle Creek Gauging Stations

15. Station 17 Calibration

16. Saddle Creek StudyLessons Learned • Extensive basin-scale data collection helped refine model calibration and resultant internal fluxes • Real important to characterize time/space scale of rainfall • Needed to understand the mechanism of runoff, especially role of variable saturated areas (VSAs) • Variable specific yield (SY) very important process

17. SWFWMD Southern District Model HSPF, MODFLOW pre-calibration, 1st phase of integrated model

18. SWFWMD Southern District ModelLessons Learned • Importance of including all hydrography explicitly • Strong parameterization and model performance constraints by DTWT resulted in greatly improved calibration (streamflow and aquifer behavior) • Indicated much higher GW ET fraction in shallow watertable settings than previously considered – resulting in model concept changes • Importance of irrigation fluxes and deep aquifer discharges zones

19. Alafia Subbasins

20. Alafia ModelLesson • Need to explicitly characterize connected and unconnected hydrography for each basin • Depart from basin calibration, move to land use calibration

21. Alafia Micro-Scale Field StudyPreliminary Results • Runoff dominated by saturation excess (VSAs) • Air entrapment plays a strong role • Water table fluctuations are very rapid • Baseflow timescale may be controlled by ET timescale not water table drainage • SY is highly variable (.2 – 2 m) controlling water table fluctuation • Vadose zone moisture maintenance pronounced, thus significant GW ET (watertable depths < 2 m)

22. New IHM Model Developments • New code integration structure, HSPF and MODFLOW run concurrently, greatly enhanced capability and enhanced run speed • Integration and all other timesteps completely user defined • Landforms explicitly modeled (more distributed parameterization)

23. Old Model Structure

24. New Model Structure

25. TBW Connected &Unconnected Hydrography DICRETIZATION MODFLOW: 20,000 grids (1/4 mi) 150,000 river reaches 3 aquifer layers HSPF: 172 non-connected reaches 172 storage attenuation 73 routing reaches 172 basins 5 landform categories 320,000 landuse polygons

26. Three-Layer Soil Moisture Model

27. Important Spatial & Temporal Scales(Shallow Aquifer Coastal Plain Systems)

28. Overall Conclusions & Recommendations • Understand the hydrologic processes and water budget magnitudes before beginning • Ensure adequate data to support model • Commit to the data pre-analysis • Understand the limitations and long-term commitments • Attention to internal fluxes and storages will ensure fully constrained, unique solution

29. Integrated Model Commitments • Enormous data requirements • Complete surface water dataset • Complete groundwater dataset • Data pertaining to the integration • Different timescales and space scales • Considerable data analysis prior to calibration • More difficulty in calibration • Users must possess both SW and GW expertise

30. Root Capillary Zone