Dusting Off the Source Water Protection Models: Adaptation and Application of Existing Models to New Projects

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Dusting Off the Source Water Protection Models:

Adaptation and Application of Existing Models to New Projects

M. Takeda, P.J. Thompson, Dirk Kassenaar, E.J. Wexler

Earthfx Incorporated, Toronto, Ontario, Canada

Presented by

Michael Takeda Earthfx Inc.

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1) Introduction

2) Source Protection Plan

3) The Role of Numerical Models

4) Opportunities for Model Re-Application

5) Consideration of Limitations

6) Closing Summary

Dusting Off the Source Water Protection Models: Adaptation and Application of Existing Models to New Projects

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Presentation Outline

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Source Water Protection

Walkerton Tragedy ► E.coli in municipal drinking water supply.

► 7 people died, 1000’s became ill

► Traced to runoff from farm discharging to wetland

► As a result, Clean Water Act was introduced which required Source Water Protection Studies to be undertaken across Ontario

► Water Quality Assessment

► Water Quantity Assessments

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Source Water Protection Studies

Tier 1 Water Budget Studies ► Screening level studies to identify “stressed watersheds”

(total use > 25% of available water)

Tier 2 Water Budget Studies ► Numerical models to confirm watershed stress analysis

Tier 3 Water Budget Studies ► Detailed integrated groundwater and surface water modelling

"The first barrier to the contamination of drinking water involves protecting the sources of drinking water."

Justice Dennis O'Connor (2002)

► Assess “water quantity threats” to municipal water supply using a tiered approach.

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Integrated GW/SW Models

Integrated Models: • Represent hydrologic system,

groundwater system, and interactions between them

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The Role of Numerical Models

Earthfx Detailed Water Budget Studies ► Five Tier 3 Source Water Protection Studies:

(Four complete, one starting up)

► Two Lake Simcoe Protection Plan Studies

Multi-watershed Scale ► Attempts to explain the transient movement

of water though the surface and subsurface systems on a watershed scale.

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Presentation Objective

What are the potential opportunities for further application of the Drinking Water Source

Protection Models?

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Opportunities for Model Re-Application

Ecologically Significant Groundwater Recharge

Areas (ESGRA) Analysis

Assessment of Impacts of Large Scale Urban

Development

Climate Change Assessment

Pit and Quarry Applications

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ESGRA Analysis

What is an ESGRA? ► ESGRAs are identified as areas of land that sustain sensitive features like cold

water streams and wetlands.

► Not related to volume of recharge; rather they are linked by pathways through which GW recharge reaches a given feature.

► ESGRA analysis is an ideal application to understand flow system linkages and volumetric recharge (in a relative sense).

SGRA vs ESGRA? ► SGRAs are “areas where the rate of recharge is greater than a factor 1.15 of

the average recharge across the area”. [1]

► Based on amount of recharge volume, not specific flow systems and linkages.

► SGRAs have potential to miss areas of local significance.

[1] Ontario Ministry of Environment, 2009, Technical Rules: Assessment Report, Clean Water Act (original release 2006).

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ESGRA Analysis

► Establish a linkage between a recharge area and environmental feature - Pathway exists through the groundwater system

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ESGRA Analysis: Approach

► Step 1: Model Construction: Hydrology: Need to simulated wetlands and streams. As

well as best estimate of recharge and runoff.

Hydrogeology: Need detailed simulation of the shallow subsurface.

Scale and structure of model should be appropriate for target(s) of analysis.

Focus of Discussion:

► Use Particle Tracking to link eco-features to recharge areas.

► Use cluster analysis to identify particle endpoint groupings and significance.

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ESGRA Analysis: Particle Tracking

► Particles released in the wetland (green area)

► Particles tracked backwards through the flow system

► Black dots show endpoints where GW recharge occurred

► Select red lines illustrate flow paths from wetland to recharge area

► In this case, the wetland received recharge from three areas

Example of backward particle-tracking from a significant feature (Bluffs Creek West Wetland, Oro Creeks North Subwatershed)

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ESGRA Analysis: Particle Tracking

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(Examples from CLOCA ESGRA Study 2014)

Bowmanville Creek –

Hampton Branch

Harmony-Farewell Iroquois Beach Wetland Complex

Backward Tracking Endpoints

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ESGRA Analysis: Cluster Analysis

► Need for a defensible methodology to delineate Ecologically Significant Groundwater Recharge Areas (ESGRAs).

► Methodology is objective, unbiased, and consistent

► Also, transferable for use in other study areas.

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ESGRA Analysis: Cluster Analysis

► ESGRAs are areas of relatively high particle endpoint density

Endpoint density is assumed to represent largest contributors of recharge to ecological systems of interest.

► Assume each pathline endpoint is representative of a normally distributed recharge feature.

► Kernel density processing converts endpoints (black dots) into a continuous “Cluster frequency distribution”

► Optimal values determined through sensitivity analysis.

𝑓 𝐻 𝑥 =

1

𝑛ℎ 2𝜋 𝑒

−12

𝑑𝑖ℎ

2𝑛

𝑖=1

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► Particle tracking is a powerful means to link the recharge area to features of interest and therefore assign eco-significance.

► Particle tracking provides visual insights into both the shallow and deep flow system.

► The methodology is automatic, objective, unbiased, consistent, and transferable for use in other study areas and different models.

The function is independent of how the particle end points are generated.

This makes it an ideal application for existing Source Water Protection Models.

Analysis can be relatively inexpensive.

► Extends insights and understanding of hydrologic/hydrogeologic system from previous modelling work to focus on specific features of interest and/or conservation objectives.


ESGRA Summary

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Development



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Climate Change Analysis

► The Water Budget drought assessment component of the Source Water Protection program has driven the analysis of water supply sustainability in Ontario.

Study watersheds

► Simulation of recent droughts provides an excellent foundation for climate change analysis. Insights into the complex behaviour at both

the watershed and tributary scale

An excellent “stress test” for the model

A good understanding of the system, and a framework for climate change assessment.

► Conducted using the integrated GSFLOW Ramara-Whites-Talbot Model built for the LSPP water budget drought assessment.

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► Many different climate models exist with range in predictions.

In general:

► 2 to 4C temp. increase by 2050. About double the global estimate.

► More extreme warm temp expected (versus mean annual temp changes) More heat waves and droughts.

► Annual precip will increase up to 10% in S. Ontario, but Summer and fall total rainfall may

decrease by up to 10%,

Winter precip may increase up to 10% in south,

Less precipitation as snow; more lake effect snow, and

Rainfall intensity and frequency of intense events to increase.


Climate Change in Ontario

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Climate Change Analysis

► Applied the recommended approach “Change Field Method” as per MNR guidelines (EBNFLO & Aquaresources, 2010).

► Infilled hourly CC data available through the Aquamapper website (climate.aquamapper.com).

► Hourly simulations spanning 29-years were completed for 10 scenarios.

► Hydrologic/hydrogeologic impacts assessed based on GSFLOW model outputs.

► All results equally valid.

► Step 1: Model Construction:

Integrated model needed to capture interactions between GW/SW system during climate change scenarios.

http://climate.aquamapper.com/

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Climate Change Inputs

► Shift in Monthly Temperature

◄ Shift in Monthly Precipitation

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Climate Change Results – Snow Depth

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Climate Change Results - Streamflow

► Reduced snow depth in winter due to increased rainfall (temps).

► Depletes reservoir for spring freshet.

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Climate Change Results - GW Recharge

► Reduced snow depth in winter due to increased rainfall (temps).

► GW recharge is similarly affected (dampened).

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Climate Change Results

Drought Period

► More flow in winter months

► Spring freshet is earlier

► Less sustained groundwater recharge

► Reduced drought resilience

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Climate Change Results

Drought Period

► Results were sensitive to underlying geology

► Streams fed by aquifers with higher storage are more resilient to drought under climate change

Drought Period

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Climate Change Analysis: Summary

► Linking the climate to the geology is required to understand how storage and the connection to subsurface affects streamflow

► Understanding how the subwatersheds and specific stream reaches respond to drought (which is more extreme) helps inform mitigation and adaptation strategies moving forward

► Integrated models built for drought or low flow analysis are well suited for climate change assessment. Logical extension of the SWP program work.

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Development



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Large Scale Urban Development

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Proposed Site Plan

► Complex stormwater management plan

► Compare Current and Post-development conditions

► Analyze changes to groundwater recharge, runoff, and wetland hydroperiod

► Evaluate goal of storm water management system: to restore more “natural” conditions

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► Model was developed to assess impacts of the proposed development on water budget elements.

► Objectives, scale, methodology has many similarities to Source Water Protection studies:

Integrated GW/SW model simulating transient response to seasonal and year-to-year variation (similar to Tier 3 Assessment).

Regional scale to represent hydrologic system.

Comparison of post-development and current conditions to evaluate impacts of development.

► Simulation of small-scale design elements (stormwater management infrastructure) was critical to the assessment.

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Impacts on Wetland Stage

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Current Simulated Hydroperiods

Post-Development Simulated Hydroperiods

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Impacts on Wetland Stage

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Natural, Current Conditions, and Post-development

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► Transient Model results showing behaviour of system under current conditions.

► Figure shows:

Precipitation

Groundwater heads

Streamflow

Lake & Wetland Stage

► Tier 3 models represent regional-scale understanding of hydrologic/hydrogeologic setting

Can be used to address local-scale problems

Click for Animation

https://youtu.be/tQCUu1AVsIE?t=2m40s

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Development



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► Application for pits and quarries requires evaluation of potential impacts to other stakeholder (as per Aggregate Resources Act, Planning Act, etc.).

Groundwater and surface water.

Ecological features and communities.

Quarry geometry and infrastructure can be successfully incorporated into a model – Why not a Tier 2/3 model?


Pits and Quarry Applications

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► They can be some of the most prominent features in the watershed!



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► Permits can be listed as surface water only, groundwater only, or mixed groundwater-surface water taking.

► But realistically – they are both.

► Evaluating potential impacts of quarries should reflect this.



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► Also have water management infrastructure.

► Can be highly transient and complex.

Let fill during winter?

Process Takings?

Siltation Ponds?

High-flow bypasses?

► What are the impacts of these operations on natural system?

Seasonally?

In a drought?



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► Use a passive system representation.

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Passive System Representation

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► Ditching that drains both groundwater and surface runoff from topographically controlled cascade.

► Sumps that collect ditched water and control groundwater heads.

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Simulated and Observed Quarry Discharge

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► It’s difficult to assess impacts of proposed and existing pit and quarry operations on GW/SW resources and ecological features.

► Represent alteration of both hydrologic and hydrogeologic systems.

► Source Protection Models are developed with groundwater/surface water interactions in mind – as well as regional perspective on hydrologic system


Pits and Quarry Applications - Summary

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Water Management

Climate

GW/SW System

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► A model is developed to solve a specific problem.

► The ability of the model to solve a new problem depends upon:

the relatedness of that problem to the original purpose of the model; and

the versatility of the model itself.

► Limitations of the models and scope of the proposed application must always be taken into consideration, and – when required – addressed.

Boundary Conditions

Grid/Mesh Refinement

Layer geometry and parameterization etc.

► Ultimately, model needs to be capable of solving the question being asked.


Consideration of Limitations

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► Numerical models have been a vital tool in meeting the requirements of the Drinking Water Source Protection Program.

► Represent extensive work consolidating knowledge and understanding of various hydrologic and hydrogeologic process in each of the study watersheds.

► Value of these models can extend beyond initial SPP objectives with continued adaptation and re-application to new studies:

ESGRA Analysis


Assessment of Impacts of Urban Development (and mitigation alternatives)



Closing Summary

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Thank you


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Engineering

Dusting Off the Source Water Protection Models: Adaptation and Application of Existing Models to New Projects