Environmental Tracers to Delineate Recharge and Flow ......Environmental Tracers to Delineate Recharge and Flow Processes in the Gibsons Aquifer, British Columbia Presented by: Jessica

Environmental Tracers to Delineate Recharge and Flow Processes in the Gibsons Aquifer, British Columbia

Presented by: Jessica Doyle, UBC M.Sc. Student

Water Technologies Symposium April 12, 2013 – Fairmont Banff Springs

Presentation Overview Project Team Town of Gibsons and Study Objectives Approach to Aquifer Mapping Study Conceptual Hydrogeological Model Environmental Tracers Numerical Groundwater Modeling Future Groundwater Scenarios Aquifer management and sustainability

April 12, 2013 Water Technologies Symposium 2013

Project Team Waterline Resource Inc.

Project Development and Management University of British Columbia

Environmental Tracer Study Numerical Modeling Supervisors: Uli Mayer and Tom Gleeson (McGill)

Gordon GroundH2O (Gibsons) Community Outreach


Gibsons, British Columbia Located on the Sunshine Coast, BC Humid, Mediterranean-like climate 1500 mm precipitation/year

70% during winter months Snow at high elevation


Google Earth 2012

Howe Sound

Strait of Georgia

Home of The Beachcombers!


Town of Gibsons Voted “World’s Most Livable Town” – 2009

International Awards for Liveable Communities. Award program endorsed by the United Nations.

Voted “World’s Best Drinking Water” - 2005 Berkley Springs International Water Tasting Contest

4,300 residents 2/3 rely on groundwater Untreated


Plan for Growth Bedroom community to

Vancouver; Expected population increase

from 4,300 to 10,000 by 2026; 73% (7,300) supplied by

groundwater; Demand up from 2,000 to 4,200

m3/day.


Source: Town of Gibsons Official Community Plan, Neighbourhood Areas, Oct. 2003

Gospel Rock Neighborhood Plan Area

Harbour Plan Area

Upper Gibsons Plan Area

Aquifer Mapping Study - Approach Phase 1 (2011 – 2013)

Data Compilation, field work, initial conceptual model

Phase 2 (2011-12): Refine conceptual model UBC Involved (NSERC)

Environmental Tracers Numerical Modeling

Community Outreach Report (April 2013)


Topo and Study Area Boundary

April 12, 2013 Water Technologies Symposium 2013 Source: Elevation data from Sunshine Coast Regional District, 2012


Bedrock Geology

Source: Bedrock Geology: (Journey and Monger, 1997)


Source: Surficial Geology Modified from (McCammom, 1975)

Surficial Geology

101 wells in BC MOE database

15 monitoring wells

15 Geophysical Soundings


Source: Surficial Geology Modified from (McCammom, 1975)

Geo-model Input

Cross Section A-A’ (NW-SE)


3D Conceptual Model: Bedrock Layer


Mount Elphinstone

Lower Gibsons

Gibsons Creek

Chaster Creek

3D Conceptual Model: Pre-Vashon (Aquifer)


Gibsons Creek

Lower Gibsons

Chaster Creek

Mount Elphinstone

3D Conceptual Model: Vashon Till/Basal Capilano


Mount Elphinstone

Gibsons Creek

Lower Gibsons

Chaster Creek

3D Conceptual Model: Capilano Layer


Mount Elphinstone

Gibsons Creek

Lower Gibsons

Chaster Creek

Aquifer Extent


UBC Research Use environmental tracers to delineate recharge locations and

processes into the Gibsons aquifer Integrate tracer results into a numerical groundwater flow

model to calculate recharge rates Model future groundwater scenarios to predict and guide

sustainable groundwater use for future growth


Environmental Tracers Groundwater samples

analyzed for: Chlorofluorocarbons (CFCs) Sulfur-hexafluoride (SF6) Tritium (3H) Noble Gases (He, Ne, Ar, Kr, Xe) Stable Isotopes (18O, 2H)

Limitations with CFCs/SF6 method Discuss noble gas, tritium results


(Newman et al., 2010)

Atmospheric Noble Gases

Concentrations based on Henry’s Law; Function of temperature, elevation (pressure) and salinity at time of

recharge

Take measured gas concentrations to solve for unknown recharge parameter – temperature Assume: Salinity = 0 mg/L, Elevation (ground elevation at each well).


Naturally occurring; Dissolve into

groundwater at time of recharge;

Tritium/Helium Dating Tritium (3H) in atmosphere

from thermonuclear testing in the 1950’s and 60’s

3H decays to tritogenic helium (3He) 3He determined in noble gas

analysis t1/2 = 12.3 years

3H/ 3He ratio = apparent groundwater age


WL10-01 MW06-2 WL10-02 MW06-1

TW #2 TW

#1

“Mountain Block”

“Bench”

3H/3He Ages and Noble Gas Temperatures


Mountain Block Recharge (MBR) Tracer results suggest significant amount of MBR

How much? How do we assess recharge along the mountain where

there is no physical information? No wells, drill holes, bedrock permeability info, water table

depth, etc…

Approach Noble gas temperatures to estimate recharge elevation Recharge elevation as a calibration target in numerical

model April 12, 2013 Water Technologies Symposium 2013

Elevation vs. Temperature

MW06-1A

MW06-1A

MW06-2A

MW06-2A

MW06-2B

MW06-2B

WL10-01

WL10-01

WL10-02

WL10-02

TW#1

TW#1

TW#2

TW#2

TW#3

TW#3

TW#4

TW#4

Chaster

Chaster

Strata

Strata

0

200

400

600

800

1000

1200

2 3 4 5 6 7 8 9 10

Elev

atio

n (m

ASL)

Temperature (°C)

MW06-1AMW06-2AMW06-2BWL10-01WL10-02TW#1TW#2TW#3TW#4ChasterStrata

Max recharge elevation Min recharge temp

Min recharge elevation Max recharge temp


Atmospheric Lapse Rate (-6.5˚C/1000m)

2˚C below atmospheric lapse rate

Recharge Elevation Calibration Targets

Recharge ranges used in model calibration process

Also calibrated to observed water levels


100

300

500

700

900

1100

Elev

atio

n

Upper Mountain

Mid-Mountain

Bench

MODFLOW Model Domain


N 45˚

MODFLOW Model Grid


N 45˚

Boundary Conditions


Zones of Hydraulic Conductivity


Layer 1

Layer 2

Layer 3

Layer 4

Layer 5

N 45˚

Hydraulic Head Calibration


Recharge Elevation Calibration


Groundwater in the Gibsons Aquifer consists of two recharge end members: 55% MBR

Pre-modern, cold (>50 years, ~5C) that recharges high up on Mt. Elphinstone flows through bedrock fractures and into the aquifer

45% Bench Modern, warm water (

Can the Gibsons Aquifer Supply Enough Water for Future Growth – Sustainably? Predictive modeling shows that the Aquifer can

sustainably supply up to 4,200 m3/day, BUT Current wells can only supply up to 3,500 m3/day based

on calculated sustainable yield If any climate change or variability leads to more than

5% decrease in recharge– begin to deplete aquifer, May lead to salt water intrusion


Conclusion Environmental tracer results improved our understanding

groundwater recharge to the Gibsons Aquifer – MBR! Also provided calibration targets in mountain where no physical

data exists

Numerical modeling suggests two end-members of recharge; 55% MBR 45% Bench

Predictive modeling suggests that the Gibsons Aquifer can support growth to full built out, however the Town needs to take measures to decrease water use if climate change or variability results in decrease recharge


Thank You - Questions?


Contact: [email protected]

Aquifer Recharge


Where ? Capilano Fluvial

deposits? Recharge

Windows - creeks, holes in the Vashon Till

Fault system ? How much?

Water Chemistry

Group 1: Gibsons Aquifer, Gibsons and Chaster Creek

Group 2: Capilano Aquifer and Charman Creek

Group 3: Upper Reaches of Gibsons Deep aquifer


Stable Isotopes


-85

-83

-81

-79

-77

-75

-73

-71

-69

-67

-65

-13 -12.5 -12 -11.5 -11 -10.5 -10 -9.5 -9

δD v

s V

SM

OW

δ18O vs VSMOW

Global Meteoric Water Line

TW#1

TW#2

TW#3

TW#4

WL10-01

WL10-02

MW06-1A

MW06-2A

MW06-2B

STRATA

CHASTER

FDLW

MW06-1A dup

Charman Creek

Chaster Creek

Gibsons Creek

Springs

Victoria Precipitaion (20 masl)

Saturna Island Precipitation (178 masl)

Estimate of Local Meteoric Water Line

Charman

Groundwater

Chaster Creek and Gibsons Creek

Numeric Engines MODFLOW – 2000

Visual MODFLOW 2009.1

Finite Difference Solver

PCG-2 Steady State – long

term averages


http://wi.water.usgs.gov/glpf/images/cs_st_model_modflow_grid.jpg

Hydraulic Head Calibration



Recharge Elevation Calibration

Town of Gibsons Growth and Future Groundwater Use


4,535 4766 5009

5,657

6,400

7,242 7,034

8,559

10,743

2,601

2,675 3,140

3,732 3,906 4,182 4,473

0

2000

4000

6000

8000

10000

12000

1981 1986 1991 1996 2001 2006 2011 2016 2021 2026

Low Growth (1%)

Medium Growth (2.5%)

High Growth (4%)

Measured Population by CanadianCensus

Current = 2,000 m3/day

3,000 m3/day

Full Build-Out = 4,200 m3/day

Environmental Tracers to Delineate Recharge and Flow Processes in the Gibsons Aquifer, British Columbia Presentation Overview Project TeamGibsons, British ColumbiaHome of The Beachcombers!Town of GibsonsPlan for GrowthAquifer Mapping Study - ApproachTopo and Study Area BoundarySlide Number 10Slide Number 11Slide Number 12Slide Number 133D Conceptual Model: Bedrock Layer3D Conceptual Model: Pre-Vashon (Aquifer)3D Conceptual Model: Vashon Till/Basal Capilano3D Conceptual Model: Capilano LayerSlide Number 18UBC ResearchEnvironmental Tracers Atmospheric Noble GasesTritium/Helium Dating3H/3He Ages and Noble Gas TemperaturesMountain Block Recharge (MBR)Elevation vs. TemperatureRecharge Elevation Calibration TargetsMODFLOW Model DomainMODFLOW Model GridBoundary ConditionsZones of Hydraulic ConductivityHydraulic Head CalibrationRecharge Elevation CalibrationModeling ResultsCan the Gibsons Aquifer Supply Enough Water for Future Growth – Sustainably?ConclusionThank You - Questions?Aquifer RechargeSlide Number 38Stable IsotopesNumeric EnginesHydraulic Head CalibrationRecharge Elevation CalibrationTown of Gibsons Growth and Future Groundwater Use

Documents

Environmental Tracers to Delineate Recharge and Flow ......Environmental Tracers to Delineate Recharge and Flow Processes in the Gibsons Aquifer, British Columbia Presented by: Jessica