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1. Integrated
Groundwater/Surface Water Modelling
to Assess Irrigation Demand
and Drought Response
in a Southwestern Ontario Watershed
Dirk Kassenaar, E.J. Wexler
Peter J. Thompson, Michael Takeda
CWRA Montreal
May 25, 2016

2. Presentation Outline
1. Introduction: Understanding Irrigation Demand
2. Integrated SW/GW Modelling
3. Pilot Watershed: Whitemans Creek Tier 3/ Low Water Response Project
4. GSFLOW Code modifications and conceptual testing
5. Simulation of farm operations in Whitemans Creek
6. Conclusions
Integrated Simulation of Irrigation Demand - Introduction 2

3. Agricultural Water Use
 Agricultural irrigation is growing in response to:
▪ An increase in climate variability
▪ Contract farming: “supply chain” management and production certainty
▪ Advances in precision agriculture
• “Irrigation is next frontier in precision agriculture” (Farm Press, Oct, 2014)
 Irrigation operations are frequently driven by dynamic soil moisture
▪ Highly adaptive water use
 We need a method to simulate “soil moisture-based irrigation water use”,
including:
▪ Losses of irrigation water to ET or runoff to streams
▪ Return flows – irrigation water that re-infiltrates
▪ Effect of precipitation events on recently irrigated crop land
Integrated Simulation of Irrigation Demand - Modelling Approach 3

4. Integrated SW/GW Modelling: Advantages
 Better estimate of groundwater recharge and feedback
(rejected recharge)
 Better representation streamflow and head-dependent
leakage
 Better representation of SW/GW storage.
 Better representation of cumulative effects of takings.
 Better calibration: input total precipitation, calibrate to
total flows (no baseflow separation)
 It’s just better...
Integrated Simulation of Irrigation Demand - Modelling Approach 4
California Department of Water Resources

5. USGS GSFLOW
 USGS integrated GW/SW model
▪ Based on MODFLOW-NWT and PRMS
(Precipitation-Runoff Modelling System)
▪ Fully-distributed: Cell-based representation
▪ Excellent balance of hydrology, hydraulics and GW
▪ Open-source, proven and very well documented
5- Modelling Approach

6. Irrigation Module for GSFLOW
 Earthfx Inc. has developed a new irrigation module for GSFLOW
 The general technical approach is based on work by the USGS for the
simulation of water use in California’s Central Valley
▪ The MODFLOW-OWHM code includes the “Farm Process” module
▪ OWHM, however, is only a groundwater model, and therefore does not represent the
soil zone, runoff processes and total streamflow routing
▪ GSFLOW is a complete and integrated representation of the hydrologic processes
that drive irrigation demand
 The implementation of this new soil-moisture irrigation demand module is
currently being tested in the Whitemans Creek Watershed with funding support
from the Ontario MNR, MOECC and Grand River Conservation Authority
Integrated Simulation of Irrigation Demand - Modelling Approach 6

7. PILOT WATERSHED -
WHITEMANS CREEK
Integrated Simulation of Irrigation Demand – Watershed Overview 7

8. Study Area
 Whitemans Creek watershed is
located southwest of Cambridge,
Ontario
Integrated Simulation of Irrigation Demand - Modelling Approach 8

9.  Numerous groundwater-fed wetlands.
 Streams are deeply incised in southeast.
 Fluctuations in shallow water table affects
recharge, runoff, ET, and groundwater
discharge to streams.
 Main branch of Whitemans Creek is a
cold-water stream supporting Brown,
Brook, and Rainbow trout.
 Uplands of watershed generally classed as
warm-water reaches.
 Main valley serves as a continuous habitat
corridor from GR Valley into Oxford County.
Wetlands and streams in the Whitemans
Creek subwatershed
Natural Features
Integrated Simulation of Irrigation Demand - Watershed Overview 9

10. Current Land Use
10Integrated Simulation of Irrigation Demand - Watershed Overview
(SOLRIS v2, 2015)

11. Agricultural Usage
11
 Corn, sod farms, tobacco, mixed..
 Water usage can vary
considerably by crop type (sod vs.
hay/pasture).
 Includes significant irrigated
water use in Norfolk Sand Plain
Integrated Simulation of Irrigation Demand - Watershed Overview

12. Integrated Simulation of Irrigation Demand - Geologic & Hydrostratigraphic Model 12
Conceptual Hydrostratigraphic Model

13.  Wisconsinan glaciation (85,000 to 11,000 years ago)
 Regional Till Sheets (minor tills in report)
▪ Canning Till – very stiff clay till; overlies discontinuous “pre-
Canning” tills and “pre-Canning” sands.
▪ Catfish Creek Till - stony, over-consolidated, sandy silt to silty
sand till; outcrops at Bright.
▪ Tavistock Till – major unit; outcrops in north and to west of
Whitemans; clayey silt till.
▪ Port Stanley Till - major unit; outcrops in middle of study area;
stiff clayey silt to silt till; sandier to north.
▪ Wentworth Till – Outcrops to east near Bethel Rd; silty sand till;
overrides outwash and Lake Whittlesey deposits.
 Erie Phase Deposits
▪ Waterloo Moraine-age deposits; overlie Catfish Creek and Maryhill
Tills.
 Grand River Outwash
▪ Ice recession during Mackinaw phase.
▪ Difficult to distinguish from overlying Lake Whittlesey sands.
 Lacustrine Deposits
▪ Associated with Glacial Lake Whittlesey
▪ Source of the fine sands of Norfolk sand plain
Integrated Simulation of Irrigation Demand - Geologic & Hydrostratigraphic Model 13
Quaternary Geology

14. Simulated Streams
Integrated Simulation of Irrigation Demand - GW Model Construction/Calibration 14
 1,767 km of simulated stream channels.
▪ 15,729 Reaches (GW Cell Interactions)
 Properties assigned by Strahler Class
▪ Manning’s Roughness, 8-Point Cross Section, Bed
Conductances
▪ Class 1 represents 842 of 1767 km

15. Simulation Results: Long Term Average ET (WY1976-WY2010)
Integrated Simulation of Irrigation Demand – PRMS (Hydrologic Submodel) 15
Potential Actual

16. Simulated Runoff
Integrated Simulation of Irrigation Demand – PRMS (Hydrologic Submodel) 16

17. Long Term Average Recharge Comparison
Integrated Simulation of Irrigation Demand – PRMS (Hydrologic Submodel) 17
PRMS
(248 mm/year)
GAWSER
(243 mm/year)

18. 18
Actual ET
Integrated Simulation of Irrigation Demand – Preliminary GSFLOW Model Calibration
 Animation shows daily Actual ET from the
PRMS submodel for WY2007, a relatively
dry year
 AET response is sinusoidal but varies
spatially depending on available soil
moisture
 AET is reduced in the dry years because
of basin-wide limitations in available soil
moisture
Animation Link

19. 19
Water Levels
Integrated Simulation of Irrigation Demand – Preliminary GSFLOW Model Calibration
 Animation shows transient water levels
from the MODFLOW submodel in Layer 3
for WY2007
 Groundwater response appears muted
because of contour interval places but
change is in range of 1-2 metres
Animation Link

20. 20
Streamflow
Integrated Simulation of Irrigation Demand – Preliminary GSFLOW Model Calibration
 Animation shows transient streamflow for
WY2007
 Results show:
▪ Streamflow response to dry year
▪ Where streamflow is intermittent
▪ Location of reaches which might be more
sensitive to drought
 Simulated flows at locations of active and
historic gauges can be compared to
observed.
 Animation Link

21. 21
Streamflow
Integrated Simulation of Irrigation Demand – Preliminary GSFLOW Model Calibration
 Animation shows transient streamflow
for WY2007
 Results highlight an area of the
watershed with relatively low
permeability surface materials.
Animation Link

22. WATER USE
Whitemans Creek Tier 3
Integrated Simulation of Irrigation Demand - Water Use 22

23.  Significant agricultural water takings:
▪ Over 95% of reported takings
▪ Takings vary by crop, season, and
antecedent rainfall/ET
 Need historic consumptive use for model calibration.
 Need to predict future usage for drought analysis.
Integrated Simulation of Irrigation Demand - Water Use 23
Water Use - Overview

24.  Permits to take Water:
▪ Permit ID can be assigned to multiple sources (e.g., 2 different wells).
▪ Sources have generic names (e.g., “Well 1”, “Pond”).
▪ Locations linked to Permit ID, no link to WWIS Well ID.
▪ Sometimes source locations plot close enough to existing wells to assign.
▪ Maximum Permitted Taking often well in excess of actual.
 Water Taking Reporting System
▪ Self reporting compliance poor in 2009; improves in subsequent years.
▪ WTRS data linked to Permit ID/Source; no locations or names.
▪ Queries to match PTTW to WTRS partly successful; varies by year.
• 65% matched in study area; 62% in Whitemans in 2012
• Does (38%) non-reporting equal no usage ?
▪ Taking not always separated by source; is taking amalgamated?
WTRS Sources matching PTTW Sources
Integrated Simulation of Irrigation Demand - Water Use 24
Reconciling Provincial Data

25. Simulated SW Use
Integrated Simulation of Irrigation Demand - GW Model Construction/Calibration 25
 A total of 70 surface water permits
with 92 sources simulated in the
model
 Surface water permits processed to
assign location of source streams:
▪ Represented using MODFLOW-SFR package
▪ Script used to assign takings (diversions) to
closest simulated stream segment
▪ All ponds assumed to be online with no
mitigative storage effects

26. Groundwater Permits –
by Primary Purpose
Agricultural Groundwater Permits –
by Sub-Purpose
Integrated Simulation of Irrigation Demand - Water Use 26

27. Annual Takings for Groundwater Permits –
2012
Annual Takings for Agricultural GW Permits
– 2012
Integrated Simulation of Irrigation Demand - Water Use 27

28. Analysis of
WTRS data
provides
Insights
Daily Takings
for Agriculture
by Crop Type
(2012)
Integrated Simulation of Irrigation Demand - Water Use 28
Variation in Water Use by Crop

29. Daily Takings for
Wet vs. Dry Year
(2011-2012)
at a Sod Farm
Integrated Simulation of Irrigation Demand - Water Use 29
Variation in Water Use by Year

30. Daily Takings for
Agriculture
Sod Farm 1 vs.
Sod Farm 2
(2012)
Integrated Simulation of Irrigation Demand - Water Use 30
Variation in Water Use by Location

31.  Model calibration runs for GSFLOW Model
based on daily taking data from
PTTW/WTRS.
 470 GW takings
 Well locations and aquifers determined by
matching PTTW to WWIS data.
Integrated Simulation of Irrigation Demand - Water Use 31
Use of PTTW/WTRS Data

32. Water Use - Conclusions
 Data compiled from multiple sources.
 WTRS data provides good snapshot of recent takings.
 Daily data used in model calibration phase.
 WTRS provides targets for development/calibration of irrigation
submodel.
Integrated Simulation of Irrigation Demand - Water Use 32

33. SOIL MOISTURE DEMAND-
BASED IRRIGATION MODULE
Earthfx GSFLOW Code Extension
Integrated Simulation of Irrigation Demand - Streamflow Data 33

34. Irrigation Demand Submodel - Methodology
 Need to predict water use under drought or future development conditions
▪ Simply using maximum permitted rate does not help us understand real crop needs
under future drought conditions.
 Proposed method to estimate water use requires daily takings:
▪ GSFLOW/PRMS daily estimate of soil moisture used to “trigger” irrigation.
▪ Irrigation starts when available soil moisture falls below trigger
▪ Trigger can be defined based on soil and crop type
▪ Irrigation water can be lost to ET, runoff or returned to the GW system
 Predictive irrigation submodel can be calibrated with actual WTRS data.
▪ PTTW/WTRS data used estimating historic use for model calibration.
Integrated Simulation of Irrigation Demand - Water Use 34

35. Irrigation Demand Submodel – Code Features
 Each farm represented by multiple PRMS cells (fully distributed)
▪ Each farm can have multiple crop types and unique moisture content triggers
▪ Each well is linked to a Farm ID with max pumping rate
▪ Farm SW diversions can take a defined percentage of current daily streamflow
 Soil moisture calculated on a daily basis in PRMS and used to trigger GW
pumping or SW diversion
 Total GW well pumping or SW diversion per farm passed back to PRMS
▪ PRMS adds pumped volume to precipitation (for spray irrigation) or to net
precipitation after interception (for drip irrigation) over farm cells.
▪ PRMS calculates runoff and infiltration in usual manner
Integrated Simulation of Irrigation Demand - Water Use 35

36. Integration of Irrigation Module
 Low moisture levels in soil
zone reservoir can trigger
spray irrigation from either GW
pumping wells or SW
diversions.
 With drip irrigation, water is
added to the recharge zone
Integrated Simulation of Irrigation Demand - Climate Data 36
Groundwater Model
MODFLOW NWT
PRMS
GWPumping
SWPumping

37.  Simple problem with streams lakes and multiple irrigated
and non-irrigated farms
 Farm wells and SW diversion used for irrigation
 Different triggers used for each well
 Different irrigation types (drip/spray)
 Animation shows soil moisture in farm vicinity, farm well
pumping, and streamflow
Animation Link
Simple Submodel Testing
Integrated Simulation of Irrigation Demand - Water Use 37

38. Sub-model Testing
 Example shows one Water Year (Oct 1-Sept 30)
▪ Soil moisture on irrigated farm fields
▪ Groundwater levels as blue contours
▪ Pumping wells shown as small circles
 Fall-winter: Water levels stable – no pumping
▪ Irrigation starts in late May
 Soil moisture represented as color – pumping
adjusted to maintain moisture levels
 GW drawdown cones grow over the summer and
recover in the fall after irrigation stops
Animation Link
Integrated Simulation of Irrigation Demand - Water Use 38

39. Whitemans Test Simulation
 Testing of GSFLOW Farm Process module
in the Whitemans Creek model
Integrated Simulation of Irrigation Demand - Water Use 39

40. Whitemans Simulation
 Farm wells linked
to classified crop
areas.
Integrated Simulation of Irrigation Demand - Water Use 40

41. Soil Moisture Animation link
 Example shows
Integrated Simulation of Irrigation Demand - Water Use 41

42. Whitemans Simulation: Soil Moisture vs Pumping
 Example compares soil
moisture in an irrigated
field vs a field outside
of the farm.
 Pump comes on when
moisture levels drop –
Irrigated field never
dries out
Integrated Simulation of Irrigation Demand - Water Use 42

43. 43
Conclusions
Integrated Simulation of Irrigation Demand - Conclusions & Next Steps
 Predicting and simulating cumulative water use under future drought conditions
requires an understanding of farm irrigation processes and triggers
 The new GSFLOW irrigation module developed by Earthfx integrates farm
water management practices into a comprehensive and fully integrated SW/GW
model
 Historic climate and WTRS data can be used to develop farm-specific water use
practices and triggers.
▪ Alternatively, standard or best management practices could be represented in the
model to simulate and evaluate improved water use and informed permit renewal