when are integrated hydrologic models needed? sam bellamy ... · sam bellamy and gordon macmillan....

When are Integrated Hydrologic Models Needed?

Sam Bellamy and Gordon MacMillan

Presentation Overview

1) What are integrated models?

2) When does modelling scope benefit from an integrated

model?

3) Why would an integrated model detract from the

modelling effort in some cases?

Background

Water resources community is still catching up to

modern software and hardware

o Wide divergence on opinion and practice of modelling

o Divergence of opinion on integrated modelling

Background

Water resources community is still catching up to modern software and hardware

o Wide divergence on opinion and practice of modelling

o Divergence of opinion on integrated modelling

Software providers and people excited about integrated models often claim you need to use integrated models because:

o Recharge to aquifers originates from surface

o There is a surface water receptor

o There is valuable stream flow and climate data available to calibrate model

o You can avoid using artificial recharge boundary




model?



Matrix and Integrated Models

Using integrated models since 2009

o Applied to Ontario’s source water

protection program

o Applied to spills in northern

Alberta (typically 1 to 2 week

timeline to support spill response)

o Developed a Provincial Technical

Guide on Integrated Modelling

• Technical guidance on completing

integrated modelling studies

• Compared different integrated

model codes: MIKE SHE, HydroGeoSphere, and GSFLOW




model?



Detailed representation of the surface water system

Crude approximation of the groundwater system

Surface Water Models

Surface Water Models

Quaternary

Geology/SoilsDEM

Land

Cover

Channel

Characteristics

Climate

(Precip, Temp)

SW

WithdrawalsHydrologic Model

Continuous

Simulation

Streamflow ET RunoffGroundwater

Recharge

Soil Water

Content

Streamflow

Detailed representation of the groundwater system

Crude approximation of surface water processes

Groundwater Models

Groundwater Models

Geology

DEM

Watercourses

Hydrogeologic

Characteristics

GW

Recharge

Boreholes(Water &

Oil/Gas)

GW

Withdrawals

Groundwater Model

Steady State

/ Transient

Simulation

Groundwater

DischargeFlow Paths

Groundwater

Elevations

Water Levels

Interbasin

Flow

Baseflow

Estimates

Includes dynamic, physical representations of both the surface and groundwater systems.

Allows for feedbacks and interactions between the systems to be modelled

Integrated Models

Integrated Models Improve

Understanding of System

More complete representation of the hydrologic system

o Runoff characteristics can be influenced by depth to water table

o Gaining/losing stream reaches are influenced by river stage and

groundwater heads

More Complete Watershed

Characterization

Allows one to investigate year-to-year variability

Provides a quantification of flows within and between

subwatersheds

(mm/yr)Integrated Water Budget Estimates

Wetland Assessment

Allows one to ID the hydrologic processes

supporting critical features

Impact Assessment

Allows one to assess level of impact as it relates to

the complete streamflow regime

Example, pre/post impact from increased

groundwater withdrawals and land development

Integrated Models

Explicit representation of

both systems requires

increased effort

Computational burden is

high and limits the model

domain to a small area

(relative to groundwater

models)

Less nimble than sticking

with a single system

Provides additional

constraints on calibration

Allows for overland and

groundwater flow

Can account for non-linear

interactions between

systems

Advantages Disadvantages




model?



Required Model Prediction

Available Data

Regional Data but

Sparse Local Data

Local Structure and

Parameter Data

Time Series Data

from Project

Operations

Time Series Data

from Multiple

Projects

Requir

ed P

recis

ion o

f Pre

dic

tion First Approximation

Comparable to Known Threshold

Predictions Close to Known Threshold

Project Specific Risk Assessment

Modelling Scope Decision Matrix


Interdependence between Systems

Low Sensitivity Between

Systems

Moderate Sensitivity Between Systems

High Sensitivity Between

Systems

Requir

ed P

recis

ion o

f Pre

dic





Modelling Tool Decision Matrix

Use Integrated Model? - Example 1

PROJECT ACTIVITY

Pumping groundwater from a shallow supply well near a Lake that intersects the pumped aquifer. Water demand is required for 20 years.

QUESTIONS AND CONCERNS

What is long term deliverability in the well?

Will there be groundwater – surface water interaction?

If so are effects of groundwater withdrawal acceptable?


Setting: - large surface water body

- incises the Ethel Lake Aquifer

- Ethel Lake Aquifer is fully saturated

Ethel Lake Aquifer


Setting: - large surface water body

- incises the Ethel Lake Aquifer

- Ethel Lake Aquifer is fully saturated

0

0.5

1

1.5

2

2.5

3

3.5

4

0 0.2 0.4

Dra

wdow

n (

m)

Time (d)

Drawdown vs Time

Theis Aquifer

Constant head boundary


Response to long term pumping:- Capture results in a new dynamic equilibrium

- Aquifer properties don’t change over time

- Water level in lake doesn’t decrease from pumping

= Low Sensitivity between

Systems




Systems



Systems

Requir

ed P

recis

ion o

f Pre

dic






Exam

ple

1




Systems



Systems

Requir

ed P

recis

ion o

f Pre

dic






Assume

percentage of

pumping

2D numerical or

analytical

element model

2D or 3D

numerical

model

Integrated

model?


Integrated model?: - could improve model calibration

- better represent connection to/from lake

- large increase in effort

Challenges

- Adapt to new geology

- Quantify uncertainty

- Communicate work


PROJECT ACTIVITY

Clear land for construction activities and withdraw water

from shallow aquifer.

QUESTIONS AND CONCERNS

What is long term deliverability in the well?

Will development affect stream flows (peak, timing…)?

If so are effects acceptable?


Setting: - near surface water table

- heavy vegetation

- site will require re-grading


= High Sensitivity between Systems




Systems



Systems

Requir

ed P

recis

ion o

f Pre

dic






Change in GW

Discharge


Simultaneously assess effects of groundwater withdrawal

and land use changes on groundwater levels, groundwater

discharge and streamflow

Drawdown

Change in

Streamflow


Simultaneously assess effects of groundwater withdrawal

and land use changes on groundwater levels, groundwater

discharge and streamflow




Systems



Systems

Requir

ed P

recis

ion o

f Pre

dic






Assume

percentage of

runoff and

pumping

Coupled models

Coupled models

or an integrated

model

Integrated

model

Presentation Summary

Integrated models should be seen as a tool in a modeller’s toolkit (which also includes separate SW and GW models).

Selection of the most appropriate tool is dependent on the complexity of the study site, the question being asked, and time/resourcing constraints

o Don’t use a sledgehammer to hang a picture!

Integrated models add value when:

o Contributes to better understand setting

o Outcome of interest is a linked process

o Groundwater – surface water interaction is non-linear

Integrated models don’t add value when:

o Outcome of interest is driven by one domain

o Linear interaction between groundwater - surface water

o Precise predictions are not required

Any Questions?

Gordon MacMillan

Principal Hydrogeologist

403.513.2280

[email protected]

when are integrated hydrologic models needed? sam bellamy ... · sam bellamy and gordon macmillan....

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