This document discusses applications of integrated surface water/groundwater modeling techniques using the GSFLOW model. It summarizes three case studies: 1) assessing the hydrologic impacts of a large urban development, 2) evaluating interactions between a municipal wellfield and nearby surface water features, and 3) determining linkages between groundwater recharge and surface water features. The case studies demonstrate how GSFLOW can be used as a practical tool to solve complex water resource management problems through integrated modeling of hydrologic and groundwater systems.

1. Applications of Integrated
Surface Water/Groundwater Modelling
Techniques and Perspectives
P.J. Thompson, M.A. Marchildon, E.J. Wexler, J.D.C. Kassenaar
Earthfx Incorporated
GeoMontréal 2013
October 2, 2013

2. Introduction
…demonstrate that integrated modelling is a
practical solution to complex water management
problems…
Case Studies:
1. Large Scale Urban Development
2. Assessment of Municipal Well System in contact
with nearby surface water features
3. Eco-hydrology study of linkages between
groundwater recharge and significant surface water
features

3. Ground water and Surface-water FLOW
GSFLOW:
• Released in 2008
• Free and open source
• Modular
• Fully distributed
• Based on the USGS PRMS and MODFLOW
(Markstrom et.al., 2008)

4. GSFLOW Submodels
Hydrology (PRMS) GW (MODFLOW-NWT) Hydraulics (SFR2)

5. GSFLOW: Multi-Resolution
Climate variables 10:1
Surface hydrology 1:1
Sub-surface 5:1
hydrogeology
Stream networks
Treated as linear segments
independent of grid resolution
( 5 - 200m )
( 10 - 50m )
( 2 - 4 km )

6. NEXRAD (U.S. Based Doppler Weather Radar)
Click for Animation
Environment Canada (AES)
Rain Gauges
NEXRAD
(Buffalo, NY)

7. GSFLOW: High Resolution Land Use
Land Use Class Assigned to 20-m Grid
% Impervious
Based on
Land Use
Class

8. GSFLOW: Cascade flowpaths
• 5m LIDAR digital elevation
model down-scaled to a
10m DEM
• Flowpaths defined using
an 8-directional, steepest
decent algorithm

9. GSFLOW: Cascade flowpaths
• Runoff generated from one
grid cell can infiltrate in an
adjacent cell (i.e., Run-on)
• Infiltration into the soil zone
of one cell is routed to an
adjacent cell (interflow) and
can emerge as surface runoff
(exfiltration)
• Timing is treated explicitly
• Assumption: water runs
downhill

10. GSFLOW: Cascade flowpaths
Q
Q
“Nash (1957) cascade”

11. GSFLOW: Streamflow
• GSFLOW outputs total
streamflow as opposed
to cumulative baseflow
• Water budget
calculated for each
stream cell, reach,
pond and lake
Click for Animation

12. GSFLOW: Calibration
Transient
Groundwater
Calibration to
Monitors
Transient
Surface Water
Calibration to
Stream Flow
Gauges

13. Case Study 1: Large Scale Urban Development
• Large urban
development in
Central Florida
• 1100 km2 Area
• Model centered
on wetland
complex over
karst
Caloosahatchee River
Telegraph
Swamp
Proposed
Site

14. Case Study 1: Large Scale Urban Development
• Complex stormwater
management plan
• Compare Current and
Post-development
conditions
• Analyze changes to
groundwater
recharge, runoff, and
wetland hydroperiod
• Demonstrate that the
storm water
management system
will restore more
“natural” conditions
Proposed Site Plan

15. Case Study 1: Large Scale Urban Development
• Transient Model
Results
• Current
conditions
• Precipitation
• Groundwater heads
• Streamflow
• Lake & Wetland
Stage
Click for Animation

16. Case Study 1: Large Scale Urban Development
• Simulated
Wetland
Hydroperiod
• Current
conditions
• Range between
0-365 days
• Magenta areas
are wet 365 days

17. Case Study 1: Large Scale Urban Development
• Natural stream
network
• No ditching
• Pre-Columbian
vegetation and
land use
estimated from
historical mapping
and photography

18. Case Study 1: Large Scale Urban Development
• Simulated
Change in
Infiltration
• Natural to
Current
Conditions
• (decrease/
increase)

19. Case Study 1: Large Scale Urban Development
Current Simulated
Hydroperiods
Post-Development
Simulated Hydroperiods

20. Case Study 1: Large Scale Urban Development
Natural, Post-development, and Current Conditions• Wetland Stage

21. Case Study 2: Wellfield Interactions with SW
• Study conducted for
Conservation Halton
• Municipal well field supplies
Milton, Ontario, Canada’s
fastest growing city
• Complex reservoir
operations
• Several large quarries above
the escarpment

22. Case Study 2: Wellfield Interactions with SW
• Groundwater model layers follow stratigraphy
• Layers adjusted to preserve continuity
Wellfields

23. Case Study 2: Wellfield Interactions with SW
• Runoff directed to lakes and
streams, flow routed down
stream network
• Groundwater leaks in/out of
lake cell and stream segment
depending on stage and aquifer
head
• Total streamflow is simulated

24. Case Study 2: Wellfield Interactions with SW
OBSERVED PREDICTED
Simulated Stage in Reservoirs
Kelso
Lake
Hilton Falls
Kelso Reservoir Control Structure (Hatch, 2007)

25. Case Study 2: Wellfield Interactions with SW
• Had difficulty matching seasonality
in the wellfield
• Required two-stage lake leakage:
Enhanced leakage around shoreline
when filled
• Lower lake bottom leakage is
reduced by silts and fine sediments
Upper Lake: Summer high stage
Lower lake: Winter holding level
Lake Leakage Out
Lake Leakage In

26. Case Study 2: Wellfield Interactions with SW
OBSERVED PREDICTEDCampbellville – MW2/05B
Kelso
TW3/67
Kelso
TW4/67
Shows influence of high leakage
from lake at summer stageHeads in Wellfield Monitors

27. Case Study 3: Ecohydrology Recharge Assessment
• Study conducted for Lake
Simcoe Region
Conservation Authority
• Detailed assessment of
the linkages between
recharge and significant
surface water features
• Drought assessment
• Model includes all 1st
Order Streams
• 85 Lakes, Ponds, and
Lake/Wetlands

28. Case Study 3: Ecohydrology Recharge Assessment
Backward Particle
Tracking from Features
of Interest to Areas of
Recharge
See Marchildon et al. in the proceedings for a more detail discussion
Stream: Orange pathlines
Wetland: Green pathlines

29. In Summary
• Integrated modelling is rapidly becoming an accepted
strategy to assess complex challenging problems
• Integrated models can assess practical problems
• GSFLOW represents a practical, scalable tool, capable
of solving real-world engineering problems
• Demonstrated application in multidisciplinary
projects
Thanks to:

30. Questions? Click for Animation
Simulated heads and lake stage at Kelso Reservoir
Dry year (2007) and wet year (2008)