Validation of a Hydrological Model Using Stable Isotope Tracers

1
Validation of a Hydrological Model Using Stable
Isotope Tracers

• Tricia Stadnyk1
• St.Amour, Natalie2 Kouwen, Nicholas1 Edwards,
  Tom2 Pietroniro, Alain3 Gibson, John4
• 1 Civil Engineering and 2Earth Sciences,
  University of Waterloo, Waterloo, ON, N2L 3G1,
  Canada
• 3 NHRC, Environment Canada, 11 Innovation Blvd,
  Saskatoon, SK, Canada
• 4 National Water Research Institute, Water
  Climate Impacts Research Centre, Victoria, BC,
  Canada

2
Overview

• Objective
• Modelling Background
• Isotope Mixing-Model
• Hydrological model
• Tracer module
• Study Site
• Fort Simpson, NWT
• Results
• Modelled results v. isotope data
• Conclusions

http//www.fortsimpson.com/
3
Objective

• Objective
• To validate the partitioning of water in a
  hydrological model using d18O and d2H isotopes
• Flowpaths
• Water balance
• Source separation and sensitivity analyses
• Source area protection

• How?
• Add tracers to hydrological model partition
  flowpaths
• Compare tracer output to measured stable isotope
  data

4
Isotope Mixing Model

• 2-component mixing model approach

Freshet period
Rain-free period
Post-freshet period
5
Source Separation

• d2H v. d18O plots produced for all 5 basins

St.Amour et al., 2004
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Hydrological Model

• The WATFLOOD Hydrological Model
• Developed over the past 30 years by Dr. Nicholas
  Kouwen
• Primary application is flood forecasting and
  flood studies
• Long time sequences for climate studies
• Model very large areas (1,700,000km2) and smaller
  areas (20km2)
• Optimal use of gridded data sources
• Land cover, DEMs, Radar data
• Universally applicable parameter sets
• Quick turn around time
• Simulation time for Ft. Simpson runs 2min for
  4mths _at_ 10x10km
• Pick-up truck version

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Hydrological Modelling
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Tracer Module Components
Tracer 0 Baseflow separation
Tracer 1 Sub-basin separation
Tracer 2 Land-cover separation
Tracer 3 Rain-on-stream tracer
Tracer 4 Flow-type separation - surface -
interflow - baseflow
Tracer 5 Snow-melt as a fn(flow-type) - surface
surface melt - interflow melt drainage -
baseflow interflow melt drainage
Tracer 6 Glacial Melt - surface - interflow -
baseflow
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Baseflow Tracer Model

• Add tracer to groundwater flow system
• Mass IN Conc qlz Dt
• Calculate mass of tracer leaving grid (iterative)
  ? ROUTING
• Tracer storage balance
• S2 S1 (In Out) / 2
• Calculate tracer concentration in lower zone
• Mass STORED / Lower Zone Storage
• Calculate tracer mass in stream
• Mass OUT ConcQstreamDt ConcEvap Dt
• - corrected for evaporative losses to preserve
  mass
• Mass OUT Mass IN (for next grid)
• Mass balance _at_ end of Dt ? In Out
  DStorage
• Route twice for wetlands 1. Mass in
  wetland
• 2. Mass in channel

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Study Site
http//atlas.gc.ca/site/english/maps
http//www.fortsimpson.com/

• Near to community of Fort Simpson, NWT
• Confluence of MacKenzie and Liard Rivers
• Inter-relationship via spring melt
• 5 river basins studied
• Ranging from 202 - 2,050km2

http//www.fortsimpson.com/
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Basin Delineation

• Jean-Marie R.
• 1,310 km2
• Martin R.
• 2,050 km2
• Birch R.
• 542 km2
• Blackstone R.
• 1,390 km2
• Scotty R.
• 202 km2

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Meteorological Data
Hamlin, 1996

• Collected by Water Survey Canada (WSC)

• 1995 snow course survey locations

• Temperature stations

• The Lone Rain Gauge

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Landcover Data

• Wetland dominated
• Permafrost region
• Thick glaciolacustrine and deltaic sediment
• 65 organic peat 1-8m deep
• Most vegetation is transitional
• NW-W ? relief
• Martin steepest (0.7 gradient)
• Scotty flattest (0.2 gradient)

Red/Orangemixed/decid. Greenconifer Yellowtrans
itional Light bluewetland Dark bluewater
Töyrä, Jessika, 1997
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Results
El Niño
St.Amour et al., 2004

• Simulations from April to August 1997?1999
• Isotopes identified problems with wetland
  coverage
• Hydraulically connected v. disconnected
• Model modified to account for wetland coverage
  disconnected
• Accuracy of simulation determined by
• Simulated Q ?? Measured Q
• Nash-Sutcliffe coefficient (R2) and Dv
• Modelled GW ? GW-d18O and GW-d2H
• Proportionality plots

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Wetland Hydraulic Connections

• E.g. Birch river 25 wetland coverage (from DEM)

• ?? Only 20 of the wetlands are directly
  connected to the channel
• Based on curve fit proportioning of GW from
  isotope data

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1997 Results
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1998 Results
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1999 Results
? Same parameters as for 1997 ?? Good
recession curve match ?? No longer El Niño
effects ?? Melt modelled correctly
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Conclusions

• Reliable precipitation is critical in producing
  reasonable streamflows (duh!)
• At least 1 rain gauge per basin!!
• Wetland hydraulic connections connected?
• We can use isotopes to help identify how much
  does interact
• Show seasonal interactions and releases (i.e.
  Deltas)
• Incorporation of isotopes are invaluable for
  hydrologic modelling!!
• Flowpath separation validation
• Older GW versus Newer event water
• Snowmelt quantity timing
• Evaporative losses
• Validation of hydrographs
• Flow quantity water balance
• Source area indicators

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Acknowledgements

• Natural Sciences and Engineering Research Council
  (NSERC) for funding
• Natalie St. Amour for the isotopic flow
  separations and for all of the isotope work!
• Dr. Nick Kouwen for assistance with WATFLOOD
  modelling
• Drs. Nick Kouwen and Tom Edwards for their
  supervision and relentless work load ? and of
  course the travels