Climate change and potential impact Climate change and potential impact on Coastal aquifers in ATLANTIC on Coastal aquifers in ATLANTIC

CANADA: CANADA: Initial FindingsInitial Findings

Brian HansenBrian Hansen11, Calvin Beebe, Calvin Beebe11, Grant Ferguson, Grant Ferguson1 ,1 ,Nathan GreenNathan Green22, Kerry , Kerry MacQuarrieMacQuarrie22, Eric Mott, Eric Mott22, Karl Butler, Karl Butler2 , 2 , Trina IvanyTrina Ivany--AdamsAdams33, Gavin , Gavin KennedyKennedy4, 4, George SomersGeorge Somers5 ,5 ,Don JardineDon Jardine66

11Saint Francis Xavier UniversitySaint Francis Xavier University22 University of New Brunswick University of New Brunswick 33 Newfoundland and Labrador Dept. of Environment and ConservationNewfoundland and Labrador Dept. of Environment and Conservation44 Nova Scotia Environment Nova Scotia Environment 55 Prince Edward Island Dept. of Environment, Labour and JusticePrince Edward Island Dept. of Environment, Labour and Justice66 DEJardine Consulting Ltd.DEJardine Consulting Ltd.

IntroductionIntroduction•• A significant number of coastal communities in A significant number of coastal communities in

Atlantic Canada rely on groundwater as a Atlantic Canada rely on groundwater as a source of potable water.source of potable water.

•• Climate change can be expected to result Climate change can be expected to result changes to the hydrologic cycle changes to the hydrologic cycle

•• The implications related to salt water intrusion The implications related to salt water intrusion of coastal have not previously been of coastal have not previously been investigated in this region.investigated in this region.

•• The issue is The issue is •• The issue is The issue is –– Or interest from an academic perspectiveOr interest from an academic perspective–– Has very practical implications for Has very practical implications for

planners, water utilities etc.planners, water utilities etc.

•• Current study conducted under auspices of Current study conducted under auspices of Atlantic Climate Adaptation Solution Atlantic Climate Adaptation Solution AssociationAssociation (ACASA) with participation by:(ACASA) with participation by:

–– Governments of NB, NS. NFLDGovernments of NB, NS. NFLD--LAB PEILAB PEI–– Academic community (St Fx, UNB)Academic community (St Fx, UNB)–– Collaboration with municipal govt.s &First Collaboration with municipal govt.s &First

Nations CommunitiesNations Communities

Sensitivity to Sea Level Rise

(NRCan, 2009) :

•Relief

•Geology

•Coastal landform

•Sea-level tendency

•Shoreline displacement

•Tidal range

•Tidal height

•SWI potential ????

OutlineOutline�� The Nature of Salt Water IntrusionThe Nature of Salt Water Intrusion

�� Selected Case StudiesSelected Case Studies

�� Summerside, PEISummerside, PEI

�� Richibucto, NBRichibucto, NB

�� Other workOther work�� Other workOther work

�� NS (site specific and regional assessment)NS (site specific and regional assessment)

�� NFLDNFLD--L (regional assessment)L (regional assessment)

�� ConclusionsConclusions

Salt Water IntrusionSalt Water Intrusion•• The classical view The classical view

(static conditions:)(static conditions:)–– Salt water is denser than fresh Salt water is denser than fresh

water water

–– In coastal regions a “wedge” In coastal regions a “wedge” of salt water may “intrude” of salt water may “intrude” inland from the coastinland from the coast

–– Theoretically the position of Theoretically the position of the saltwater / fresh water the saltwater / fresh water interface is determined by the interface is determined by the fresh water head (elevation of fresh water head (elevation of the water table above sea the water table above sea level)level)

BUT in reality the extent of saltwater intrusion depends on a variety of site specific factors…..

Site Specific Influences on SWISite Specific Influences on SWI•• Boundary between fresh Boundary between fresh

and saline water and saline water –– Is not sharp (zone of Is not sharp (zone of

diffusion)diffusion)–– Is affected by local geologyIs affected by local geology

•• Groundwater Flow DynamicsGroundwater Flow Dynamics

–– GW is not static, but GW is not static, but –– GW is not static, but GW is not static, but discharges to the oceandischarges to the ocean

–– Sea levelSea level determines a determines a “constant head” boundary for “constant head” boundary for the GW flow regime the GW flow regime

–– Flux of GW toward ocean Flux of GW toward ocean influenced byinfluenced by

•• GW rechargeGW recharge•• GW extractionGW extraction

Prevalence of SWI in Atlantic Prevalence of SWI in Atlantic Canada (current conditions)Canada (current conditions)

•• The occurrence and extent of SWI is highly The occurrence and extent of SWI is highly variable even under conditions of similar geologyvariable even under conditions of similar geology

•• Knowledge of the extent of SWI highly biased Knowledge of the extent of SWI highly biased •• Knowledge of the extent of SWI highly biased Knowledge of the extent of SWI highly biased toward those areas of existing GW exploration toward those areas of existing GW exploration and developmentand development

•• Has not been mapped on a regional scale Has not been mapped on a regional scale (perhaps can’t be accurately?)(perhaps can’t be accurately?)

Approaches to the current Approaches to the current investigationinvestigation

•• Step 1Step 1 Characterize extent and dynamics of SWI (locally)Characterize extent and dynamics of SWI (locally)

•• Step 2Step 2 Develop scenarios for assessment of impacts of CC Develop scenarios for assessment of impacts of CC relative to:relative to:–– Sea levelSea level–– GW rechargeGW recharge–– GW rechargeGW recharge–– GW extraction (not wholly dependant on CC)GW extraction (not wholly dependant on CC)

•• Step 3 Step 3 Simulate GW response to CC with respect to SWISimulate GW response to CC with respect to SWI

•• Step 4 Step 4 Draw conclusions regarding adaptive measures to Draw conclusions regarding adaptive measures to protect coastal GW resourcesprotect coastal GW resources

Selected Case Studies Selected Case Studies -- PEIPEI

Lennox Island

Summerside

•• Summerside Summerside •• located on narrow Isthmus between Northumberland Strait and Gulf located on narrow Isthmus between Northumberland Strait and Gulf

of Saint Lawrenceof Saint Lawrence•• 22ndnd largest city in PEIlargest city in PEI•• Historical problems with saltwater intrusion with older municipal wellsHistorical problems with saltwater intrusion with older municipal wells

•• Lennox IslandLennox Island•• Small, low lying Island located off northSmall, low lying Island located off north--west coast of PEIwest coast of PEI•• Serviced by municipal water supplyServiced by municipal water supply

Summerside Summerside –– site characterizationsite characterizationTotal depth and screened intervals for observation wells.

Well I.DWell I.D Well Well DepthDepth

Screened Screened Interval (m)Interval (m)

Well #1Well #1 8282..33 mm 7979..33--8282..33

WellWell ##22 4141..88 mm 3838..88--4141..88

WellWell ##33 2424..44 mm NoNo ScreenScreen

WellWell ##44 8383..88 mm 8080..33--8383..88

WellWell ##55 2626..22 mm 2323..22--2626..22

WellWell ##66 1818..33 mm NoNo ScreenScreen

Summerside Summerside –– geochemical characterizationgeochemical characterization

Chloride concentrations (ppm) with depth

and distance from the coast. Dashed line

indicating position of Ghyben-Herzberg

interface as calculated from piezometric

surface.

Piper diagram depicting

relationships between major ions

in solution.

Summerside Summerside –– SWI Climate Change SWI Climate Change ScenariosScenarios

•• Numerical groundwater Numerical groundwater simulations coupled with simulations coupled with various CC scenariosvarious CC scenarios

•• Groundwater modeling using Groundwater modeling using 3D variable3D variable--density flow and density flow and transport model “SEAWAT”transport model “SEAWAT”

SimulationSimulation DescriptionDescription ResultResult

BaseBase--line line simulationsimulation

Calibrated to represent Calibrated to represent present conditionspresent conditions

Position of the Position of the interface: 0 interface: 0

Total fresh SGD: Total fresh SGD: 0.18 m day0.18 m day--11

HadCM3 A1B1HadCM3 A1B1 --139 mm increase in 139 mm increase in annual rechargeannual recharge--0.59 m linear rise in 0.59 m linear rise in seasea--levellevel

Position of the Position of the interface: +20 minterface: +20 mTotal fresh SGD: Total fresh SGD: 0.24 0.24 m daym day--11

HadCM3 A1BHadCM3 A1B --33 mm increase in 33 mm increase in Position of the Position of the transport model “SEAWAT”transport model “SEAWAT”

•• Simulations run and calibrated Simulations run and calibrated to baseline conditionsto baseline conditions

•• Simulations run for various CC Simulations run for various CC scenarios considering:scenarios considering:–– Changes in sea levelChanges in sea level

–– Changes in groundwater Changes in groundwater rechargerecharge

–– Changes in groundwater Changes in groundwater extraction rate extraction rate

HadCM3 A1BHadCM3 A1B --33 mm increase in 33 mm increase in annual rechargeannual recharge--0.48 m linear rise in 0.48 m linear rise in seasea--levellevel

Position of the Position of the interface: 0 interface: 0 Total fresh SGD: Total fresh SGD: 0.19 0.19 m daym day--11

HadCM3 A2HadCM3 A2 --29 mm increase in 29 mm increase in annual rechargeannual recharge--0.38 m linear rise in 0.38 m linear rise in seasea--levellevel

Position of the Position of the interface: 0 interface: 0 Total fresh SGD: Total fresh SGD: 0.19 0.19 m daym day--11

HadCM3 B1HadCM3 B1 --31 mm increase in 31 mm increase in annual rechargeannual recharge--0.48 m linear rise in 0.48 m linear rise in seasea--levellevel

Position of the Position of the interface: 0 interface: 0 Total fresh SGD: Total fresh SGD: 0.19 0.19 m daym day--11

PumpingPumping -- Pumping rate of 70 Pumping rate of 70 L/s for 50 yearsL/s for 50 years

Position of the Position of the interface:interface:--1000 m1000 mTotal fresh SGD: 0Total fresh SGD: 0

MultiMulti--ensemble ensemble approachapproach

--33 mm increase in 33 mm increase in annual rechargeannual recharge--1 m linear rise in sea1 m linear rise in sea--levellevel

Position of the Position of the interface: 0 interface: 0 Total fresh SGD: Total fresh SGD: 0.19 0.19 m daym day--11

Summerside simulation results:Summerside simulation results:

Conclusions:Conclusions:

–– Sea level rise Sea level rise is alone is is alone is unlikely to unlikely to have much have much

Base line

simulation

Effect of sea level

rise have much have much impact on SWIimpact on SWI

–– Managing GW Managing GW withdrawal withdrawal rates is rates is importantimportant

rise

Effect of

increased

GW

withdrawals

Lennox Island InvestigationsLennox Island Investigations

•• Based on existing Based on existing hydrogeological hydrogeological data.data.

•• Numerical model Numerical model

Data

collection

Numerical •• Numerical model Numerical model simulations for simulations for

–– Rising sea levelRising sea level

–– Increased GW Increased GW extraction ratesextraction rates

Numerical

modelling

predictions

Lennox IslandLennox Island•• Sea Sea –– level rise is level rise is

predicted to have predicted to have little impact on the little impact on the encroachment of the encroachment of the SW / FW interfaceSW / FW interface

•• At existing GW At existing GW extraction extraction

current

One century

of sea level

riseextraction extraction rates, water supplies rates, water supplies are not at riskare not at risk

•• Substantial increases Substantial increases in GW extraction in GW extraction rates could prove rates could prove problematicproblematic

rise

2 X

municipal

supply

Selected Case Studies Selected Case Studies –– Richibucto, New Richibucto, New BrunswickBrunswick

•• Municipal wells experiencing Municipal wells experiencing increased chloride levels over the increased chloride levels over the past decadepast decade

•• Site characterized by geophysical Site characterized by geophysical survey and borehole information to survey and borehole information to supplement existing hydrogeological supplement existing hydrogeological informationinformation

•• Numerical simulations (SEAWAT) Numerical simulations (SEAWAT) •• Numerical simulations (SEAWAT) Numerical simulations (SEAWAT) examiningexamining–– Sea level changeSea level change–– Recharge changeRecharge change–– GW extraction changeGW extraction change

•• CC scenariosCC scenarios–– A1B &A2 emission scenariosA1B &A2 emission scenarios–– Mean deviations in climate indicies Mean deviations in climate indicies

by Environmental and Sustainable by Environmental and Sustainable Development Research CentreDevelopment Research Centre

Regional map of the study area bounded by the tidal St. Charles and Richibucto Rivers, showing model boundaries, location of monitoring and pumping wells and location of cross-section

Geophysical characterization of Geophysical characterization of salinity distribution in vicinity of the salinity distribution in vicinity of the Richibucto well fieldRichibucto well field

Estimate of the true resistivity structure obtained by inversion with horizontal smoothing constraints.

Figure shows the location of PW1 and suggests presence of four layers with possible upconing through the lower sandstone under the well.

Richibucto Model DomainRichibucto Model Domain

Cross-section of model domain showing grid discretization, shale layers (shaded grey and labelled C1-C4), well locations and surface waters (constant head above cells).

Richibucto Richibucto -- Simulation resultsSimulation results

Conclusions:Conclusions:

•• Declining recharge Declining recharge most significant at most significant at shallow to shallow to intermediate depthsintermediate depths

•• Increased pumping Increased pumping most significant near most significant near well fieldwell field

Base line conditions. The source of the shallow zone of elevated TDS is the Richibucto harbour, while the deeper salt water wedge represents intrusion from the Northumberland Strait.

well fieldwell field

•• SeaSea--level rise least level rise least significant, primarily significant, primarily affects deeper affects deeper portions of the portions of the aquifer.aquifer.

wedge represents intrusion from the Northumberland Strait.

Spatial changes in TDS at yr. 2100 compared to the initial conditions. Dashed concentration contours = absolute TDS for initial conditions, solid concentration contours =absolute TDS at end of the simulation.

Nova Scotia:Nova Scotia:Regional sensitivity and site specific studiesRegional sensitivity and site specific studies

•• Field programs:Field programs:–– PugwashPugwash

–– WolfvilleWolfville–– WolfvilleWolfville

•• Regional Regional assessmentassessment

–– Geochemical Geochemical considerationsconsiderations

Newfoundland and Labrador:Newfoundland and Labrador:Reconnaissance of SW Nfld. Potential for SeaReconnaissance of SW Nfld. Potential for Sea--water water intrusion intrusion –– public supply wellspublic supply wells

•• Baseline survey as a Baseline survey as a foundation for future workfoundation for future work

•• MethodsMethods–– Well selection and Well selection and

characterizationcharacterization–– Well selection and Well selection and

characterizationcharacterization–– Geochemical Geochemical

characterizationcharacterization•• Conductivity profilesConductivity profiles•• Age dating (tritium)Age dating (tritium)•• Seawater indicators (Br Cl)Seawater indicators (Br Cl)

•• Limited evidence of sea Limited evidence of sea water intursionwater intursion

ConclusionsConclusions

•• Climate change impacts alone will not cause a Climate change impacts alone will not cause a significant change in SWIsignificant change in SWI

•• Anthropogenic influences regarding GW Anthropogenic influences regarding GW extraction (related or not to cc) are far more extraction (related or not to cc) are far more significantsignificantsignificantsignificant

•• Extent and severity, as well as the key factors Extent and severity, as well as the key factors influencing, SWI vary even on a small scale influencing, SWI vary even on a small scale

–– Emphasis should be on Emphasis should be on

•• better delineation and understanding of SWI better delineation and understanding of SWI •• sensitivity to management of GW extraction.sensitivity to management of GW extraction.

THE ENDTHE END

Questions?Questions?