Drought, Climate Variability and Water Resources in Western Canada

J.W. Pomeroy, K.R. Shook, R.N. Armstrong, X. Fang J.W. Pomeroy, K.R. Shook, R.N. Armstrong, X. Fang Centre for HydrologyCentre for Hydrology

University of Saskatchewan, University of Saskatchewan, Saskatoon, CanadaSaskatoon, Canada

www.usask.ca/hydrologywww.usask.ca/hydrologyjohn.pomeroy@usask.cajohn.pomeroy@usask.ca

Canadian Rocky

Mountains are the

Headwaters for much of

North America

Canadian Prairies

Rocky Mountains

Canadian Rocky Mountains

Cold alpine and sub-alpine climate

Rivers Draining the Rocky Mountains Supply Prairie Cities and Irrigation

Canadian Prairie Agriculture:mostly dryland grain farming & pasture

Precipitation on average 350 mmGrain Growing– 125 mm soil water

reserves needed from snowmelt

– 175 mm spring rainfall needed

– Roughly 300 kg/ha increased wheat yield for each extra 25 mm of water added

Cold, continental, semi-arid climate

Canadian Prairie Drought of 1999-2004 Most Expensive Natural Disaster in Canadian History

$5.8 billion decline in GDP 2001-2002$3.6 billion drop in agricultural production, 2001-200241,000 jobs lostBritish Columbia & Alberta forest firesSaskatchewan dust storms

OBJECTIVE OF DRI –the Drought Research Initiative

To better understand the physical characteristics of and processes influencing Canadian Prairie droughts, and to contribute to their better prediction, through a focus on the recent severe drought that began in 1999

www.drinetwork.ca

DRI THEMES1. Quantify the physical features,

flows of water and energy into and out of the region, and storage and redistribution within the region

2. Improve the understanding of processes and feedbacks governing the

formation, evolution, cessation and structure of the drought

3. Assess and reduce uncertainties in the prediction of drought4. Compare the similarities and differences of current drought

to previous droughts and those in other regions5. Apply our progress to address critical issues of importance

to society

1. QUANTIFY THE DROUGHT

Saskatoon

Swift Current

Calgary

Red Deer

Lethbridge

Drumheller

Medicine Hat

Gem

Olds

Verlo

Tyner

Orton

Hague

Cluny

Bruno

Warner

Warman

Ponoka

Instow

Elnora

Barons

Vanscoy

Swanson

Sibbald

Pakowki

Okotoks

Enchant

Duchess

Cypress

Blucher

Stettler

Mud Lake

Irricana

Elkwater

Conquest

Cessford

Shaunavon

Saskatoon

Pine LakeInnisfail

Gull Lake Duck Lake

Cavendish

Carseland

Big Stone

Oldman Dam

High River

Hand Hills

Del Bonita

Sylvan Lake

Dickson Dam

Smith Coulee

Many Springs

Buffalo LakeBuffalo Lake

Buffalo North

Sounding Creek

Crestomere Lake

Kirkpatrick Lake

Forty Mile Coulee

Legend

Observation Well Location

0 30 60 90 12015Kilometers

Observational Networks

GRACEsatellite

Wells in South Saskatchewan

200 mSurface Storage Change

2. UNDERSTAND THE DROUGHTV

ertic

al S

cale

Storage of Water

Drought

Non-drought

Horizontal Flux of Water

Non-drought

Drought

3. SIMULATE AND PREDICT THE DROUGHT

AGCM3 200 km

CRCM4 45 km

CLASS, MESH 15 km

CPM, CRHM 1 km

Global Climate model

Land Surface Hydrology Models

GEM 15 km

NWP Model

Hydrological Process Models

GEM-LAM 2.5 km

Cloud-Resolving ModelRegional Climate Model

Global Reanalysis

Forcings and Initial conditions

Regional Analysis & obs

Process Parameterizations

(for LDAS)

LDAS

LDAS data flow

Canadian Prairie Runoff GenerationSnow Redistribution to Channels

Spring melt and runoff

Water Storage in Wetlands

Dry non-contributing areas to runoff

Runoff Non-Contributing Areas to Streamflow a Prairie Characteristic

Prairie Streamflow – very seasonal

0

5

10

15

20

25

01-Jan

31-Jan

02-Mar

01-Apr

01-May

31-May

30-Jun

30-Jul

29-Aug

28-Sep

28-Oct

27-Nov

27-Dec

Stre

amflo

w m

3 pe

r se

cond

Average 1975-20061995 High Year2000 Low Year

Smith Creek, Saskatchewan

Drainage area ~ 450 km2

No baseflow from groundwater

Hydrological drought can be viewed as the absence of prairie runoff……

Sparse Prairie Streamflow Network for Drought Analysis

Burn et al., 2008 Inadequate coverage to characterise prairie runoff

How to Characterise Hydrological Drought for the Prairies?

River flows reflect Rocky Mountain, but not Prairie hydrological conditions.Streamflow network is very sparse.Modelling required to create a hydrological drought “surface” for the Prairies over small first order basins.

Cold Regions Hydrological Model (CRHM) Drought Hydrology Simulation

Create “virtual” representative basin models, which can produce simple exceedence probability drought indicesAllows comparison of basin response to drought conditions and to historical variabilityRequires high resolution driving data over entire Prairies for normal (1961-1990), non-drought (1962-1987) and drought periods (1999-2004)– Snowfall, rainfall– Temperature– Humidity– Wind speed

CRHM Prairie Module StructureGarnier and Ohmura’s radiation module

Observationmodule

Sunshine hourmodule

Interception module

PBSM

Gray and Landine’s

Albedo module

EBSM

All-wave radiation module

Gray’s snowmelt infiltration module, Green-Ampt infiltration

Granger’s evaporation module, Priestley and Taylor

evaporation module

Wetland moduleMuskingum

routing module

Global radiation

Max. sunshine

Temperature, WindspeedRelative HumidityVapour PressurePrecipitation

Sunshine hour

Rainfall Snowfall

SWE

albedo

snowmeltShort- and long-wave radiation Snow INF

Rain INF Runoff

Evap in recharge and rooting zones

Walmsley’s windflow module

Adjusted windspeed

Long-wavemodule

Canopy effect adjustment for

radiation module

Adjusted short- andlong-wave radiation

Runoff

Impact of Wetland Change on Streamflow in a Wet Year

Scenarios of Smith Creek Spring Discharge near Marchwell

0

5

10

15

20

25

30

01-Mar 10-Mar 19-Mar 28-Mar 06-Apr 15-Apr 24-Apr 03-May 12-May 21-May 30-May

1995

Daily

Mea

n Di

scha

rge

(m3 /s

) "Normal Condition"high natural wetland extentminimum wetland extent

1995 Flood: Record High Discharge Volume

Scenarios of Smith Creek Spring Discharge near Marchwell

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

11-Feb 20-Feb 29-Feb 09-Mar 18-Mar 27-Mar 05-Apr 14-Apr 23-Apr 02-May

2000

Daily

Mea

n Di

scha

rge

(m3 /s

)

"Normal Condition"high natural wetland extentminimum wetland extent

2000 Drought: Lowest Discharge Volume on Record

Impact of Wetland Change on Streamflow in a Drought Year

Drought Hydrology SimulationsDrought Hydrology SimulationsStation locations & Prairie Station locations & Prairie ecozoneecozone

Summer Growing Season Climate Normals Summer Growing Season Climate Normals (1971(1971--2000)2000)

Dry southwestern zone is suited for pasture rather than dryland farming

CRHM Surface Water CRHM Surface Water Drought ModellingDrought Modelling

CRHM was used to create CRHM was used to create ““virtualvirtual”” model model of typical prairie upland basinof typical prairie upland basinModel was run over climate normal period Model was run over climate normal period (1961(1961--1990)1990)Output during drought period was Output during drought period was compared to normal period and spatially compared to normal period and spatially interpolatedinterpolated

CRHM model of small upland CRHM model of small upland prairie stream basinprairie stream basin

HRU1 HRU2

HRU3HRU3

Small stream basin CRHM model

HRUsHRUs 1 and 2 alternate 1 and 2 alternate between cropped and between cropped and fallowfallowHRU3 is grassedHRU3 is grassed

Prairie Spring Discharge 2001 Drought

Prairie Spring Discharge 2005 Wet Year

Spatial Variation of Prairie Soil Moisture Spatial Variation of Prairie Soil Moisture (Drought (Drought vsvs Wet)Wet)

Drought Wet

Mean for normal period 332 mm

Drought period: distribution wide, variance large, median > mean

Wetter period: distribution loses low soil moisture, variance smaller, median < mean

Probability density of soil moisture

Spatial Variation of Evapotranspiration Spatial Variation of Evapotranspiration (Drought (Drought vsvs Wet)Wet)

Drought Wet

• Mean for normal period 352 mm• Drought period: distribution wide, variance large, median >> mean• Wetter period: distribution symmetric, variance greatly reduced

Probability density of evapotranspiration

Climate Change Impacts

Virtual basin model also useful for estimating climate change impacts on Prairie hydrologyClimate warming has a strong effect on cold season hydrological processes.

Prairie Streamflow & Climate Change First more, then less

Three most reliable climate change scenarios suggest increases in annual prairie winter temperature and precipitation from the 1961-1990 average: – 2050 +2.6 ºC and +11% – 2080 +4.7 ºC and +15.5%

Using these scenarios in the virtual upland basin results in a 24% rise in 2050 spring runoff, but a 37% drop by 2080, compared to conditions in the mid 1970s.

Prairie Climate Change – Winter Snow

Winter Snow Accumulation at Bad Lake, SK

0

10

20

30

40

50

60

70

01/1

0/19

74

15/1

0/19

74

29/1

0/19

74

12/1

1/19

74

26/1

1/19

74

10/1

2/19

74

24/1

2/19

74

07/0

1/19

75

21/0

1/19

75

04/0

2/19

75

18/0

2/19

75

04/0

3/19

75

18/0

3/19

75

01/0

4/19

75

15/0

4/19

75

29/0

4/19

75

SWE

(mm

)

Normal SWE (Winter of 1974/75)

SWE (Winter of 2049/50)

SWE (Winter of 2079/80)

Prairie Climate Change – Spring Runoff

Spring Runoff from Creighton Tributary at Bad Lake, SK

0

10

20

30

40

50

60

70

01/1

0/19

74

15/1

0/19

74

29/1

0/19

74

12/1

1/19

74

26/1

1/19

74

10/1

2/19

74

24/1

2/19

74

07/0

1/19

75

21/0

1/19

75

04/0

2/19

75

18/0

2/19

75

04/0

3/19

75

18/0

3/19

75

01/0

4/19

75

15/0

4/19

75

29/0

4/19

75

Runo

ff (m

m)

Normal Spring Runoff (Spring of 1975)

Spring Runoff (Spring of 2050)

Spring Runoff (Spring of 2080)

ConclusionsPrairie streamflow is inherently unreliable in drought,– Hydrological droughts migrate across the Prairies.– Drought increases the variability of soil moisture,

evapotranspiration and snowpackFuture climate change likely to first increase then decrease spring snowmelt runoff from prairie drainages.– Flooding– Shortages

If droughts also increase, this means greater use will need to be made of mountain-derived river water supplies for agriculture

Thanks!

The gracious invitation of ISACS-3 and financial support of National Natural Science Foundation of China made this presentation possible.