1

Integrated Modelling: Insights and Blind Spots

Dirk Kassenaar Earthfx Inc.

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

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

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

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

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

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

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

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

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

U n s a t u r a t e d z o n e

S t r e a m S t r e a m

G r a v i t y d r a i n a g e

R e c h a r g e

G r o u n d - w a t e r f l o w

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

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

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

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

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

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

http://www.criticalzone.org

17

NSF “Critical Zone” Research Approach

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

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

Next: Integrated Modelling at the Engineering Scale

21

Flow Schematic between multiple

excavations

21

(With Average Takings)

11,175 m³/day

4,048 m³/day

10,675 m³/day

22 22

Overland Flow

Simulation

(With Average Accumulating

Overland Runoff)

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

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

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!