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Integrated Modelling: Insights and Blind Spots


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Integrated Modelling: Insights and Blind Spots

  1. 1. 1 Integrated Modelling: Insights and Blind Spots Dirk Kassenaar Earthfx Inc.
  2. 2. 2 Blind Spots ► “The only thing worse than being blind is having sight but no vision” Hellen Keller (1880-1968) ► We all have a blind spot at our optic nerve connection.  Your blind spot is only 20 degrees off your main center of vision line!  Our brain “post-processes” it away.
  3. 3. 3 Modelling Blind Spots ► Why are blind spots common in integrated modelling?  Each discipline (Hydrology, Hydraulics and Hydrogeology) has traditionally “simplified” the others in order to solve their problems.  Those simplifications become blind spots when developing an integrated model ► The temptation is to defer addressing the blind spots until an “integration” phase late in the model development project.
  4. 4. 4 Insights and Blind Spots ► The only thing worse than being blind is having sight but no vision” ► Blindness: Uncoupled modelling  Historic simplifications prevent us from true understanding ► Sight: Integrated modelling  Better, but not enough if historic blind spots are not addressed ► Vision: Knowing where to look  Insights are usually located in the blind spots  Integrated modelling starts at the conceptualization phase ► Know, and address, the blind spots early in the modelling process
  5. 5. 5 Earthfx SWP Fully Integrated Models ► Every project is an opportunity, for both the client and consultant ► Our goal at Earthfx was to complete Tier 3 studies using the best available modelling technology ► We would like to thank our SWP clients for their vision.
  6. 6. 6 Model Selection ► Blindness: My code is better than your code  My code is fully-integrated, fully distributed, physically-based, multi- processor, open-source with fully-automated parameter-estimation and a “use-friendly” interface. ► Insight: The difference between model codes is generally less important than the skill and vision of the modelling team  Insight: All integrated models work in humid glacial terrain  However: Mackay Watershed: 70 percent of the study area is muskeg on discontinuous permafrost (need a good frozen ground module).
  7. 7. 7 GW/SW Partitioning ► Blindness: Attempting to quantify and partition the GW and SW components of flow ► Insight:  Water does not care what we call it: Stop trying to classify it and put it into fixed buckets.  Water moves seamlessly and continuously between domains  Anything we do in the watershed will move water from one bucket to another in any case….
  8. 8. 88 Aquifer Head vs. Stream Stage • GW/SW discharge reverses during each storm event • Baseflow separation? Good luck.. • GSFLOW Simulated Hydrograph at Oro-Hawkstone stream gauge Storm Event Reversal: Stream level higher than aquifer Dry period: Aquifer level higher than stream = GW discharge
  9. 9. 9 GW Recharge ► Blindness: GW Recharge rates are strongly correlated with surficial geology ► Insight: Groundwater feedback dominates  Surficial geology is important only where there is no GW interaction ► E.g. the top of the ORM  GW feedback dominates event runoff response ► Even the SW modellers think so: They referred to the “contributing area” to understand event response  Attempting to estimate recharge without assessing fluctuating water table feedback is nearly impossible.
  10. 10. 10 GW Feedback: Dunnian Runoff ► Runoff that occurs off fully saturated soils  Occurs when the water table is at or near surface  Not sensitive to surficial material K ► Can create runoff from saturated gravels  Spatially controlled: Tends to occur in stream valley areas  Seasonally controlled: Tends to occur in spring when WT is high ► Not sensitive to rainfall intensity or model time step Unsaturated zone StreamStream Gravity drainage Recharge Ground-water flow
  11. 11. 11 How common is Dunnian Runoff? ► Portions of York Region where Dunnian rejected recharge occurs  Depth to water table less than 2 m  Also on ORM south flank: flowing wells, springs and headwater seeps
  12. 12. 12 Surface Discharge and Time-varying GW Feedback ► The “contributing area” that generates true runoff depends on the time-varying position of the water table ► Milton Tier 3: Dunnian response area varies seasonally between 5 and 25% of the watershed area
  13. 13. 13 Unsaturated Flow ► Blindness: The SW and GW systems are linked by 1-D vertical flow through the unsaturated zone. ► Insight: A singular focus on the “unsaturated zone” is wrong  New Runoff Conceptualization: Event mobilized GW discharge  New research focus: “The Critical Zone”  New models: MODFLOW-NWT: Designed specifically for the simulation of shallow interface flow
  14. 14. 14 Trouble: The “Old Water Paradox” ► Hydrologists are re-evaluating basic SW processes  Jeff McDonnell, 2011 Birdsall-Dreiss Lecture Rainfall Event Increase in Streamflow Deuterium isotope profile shows that event streamflow is predominantly “old” water (i.e. water that has been subject to ET processes) Conclusion: Storm event streamflow is mobilized shallow groundwater! Time
  15. 15. 15 More Trouble… ► Garth van der Kamp, Research Scientist (Groundwater and surface water interactions), National Hydrology Research Centre, Saskatoon, SK ► Slide from Garth’s IAH 2012 World Congress Keynote Presentation: ► Conceptual flownet models are wrong – fail to recognize exponential decrease in K ► Active flow in the shallow zone dominates ► Agreement with the event mobilized groundwater theory
  16. 16. 16 NSF “Critical Zone” Conceptual Model ► In 2001 the US National Science Foundation (NSF) began work on a new “framework” for shallow earth science research  More comprehensive approach than just GW/SW, unsat flow, etc.  Includes water, climate, vegetation (carbon cycle), energy processes ► New terminology: the “Critical Zone”  Definition: “where rock meets life”  “From the tops of the vegetation down into the groundwater” ► NSF funding of “Critical Zone Observatories” (CZOs)  Multiple research sites set up to study CZ processes 
  17. 17. 17 NSF “Critical Zone” Research Approach
  18. 18. 18 Critical Zone Conceptual Model ► Macropores ► Interflow!! ► Throughflow ► Event mobilized GW ► Soil/rock contact zone interface flow ► Seepage faces ► 1D Richard’s eqn. unsat flow? ► 2D Diffusive wave runoff? from Lin, 2010
  19. 19. 19 Integrated Modelling is Different ► Integrated modelling forces us to address the blind spots (assumptions and simplifications) we make about the “other” (SW or GW) system ► Integrated modelling is better for GW modelers, because:  It allows the use of measured fluxes (precip and total streamflow)  Forces us to fully address transient response, storage and the wide range of GW flow rates ► Integrated modelling is better for SW modelers, because:  Storm response (runoff generation) can be include water table feedback and event mobilized shallow system storage  Integrated modelling is physically based and distributed (no “lumped” parameters)
  20. 20. 20 Next: Integrated Modelling at the Engineering Scale
  21. 21. 21 Flow Schematic between multiple excavations 21 (With Average Takings) 11,175 m³/day 4,048 m³/day 10,675 m³/day
  22. 22. 2222 Overland Flow Simulation (With Average Accumulating Overland Runoff)
  23. 23. 23 Integrated Assessment of Offsite Discharge ► Whether it is GW or SW discharging from the quarry pit does not matter ► Integrated assessment:  No blind spots or pre-conceived assumptions  No need to partition the assessment of impact
  24. 24. 24 Conclusions ► Integrated Modelling is different; It requires:  Integrated data management ► Data silos and barriers will only hide the relationships and response lag between the systems ► You cannot build an integrated model without an integrated database See: Sitefx 6.0 and VIEWLOG 4.0  Integrated Conceptualization: Start now.  Integrated calibration ► Don’t become attached to your initial uncoupled calibration estimates! ► Consider re-conceptualization, even late in the integrated calibration  An integrated and balanced modelling team ► The skill, multi-disciplinary knowledge, and ability of the SW and GW experts to address their “blind spots” is far more important than the choice of model code
  25. 25. 25 Integrated Modelling: Final Insight ► Blind Spot: Process flow charts are a good way to communicate the concepts of integrated modelling ► Insight: FAIL  A good conceptual cartoon always helps  Look at those clouds!