Land Surface Land Surface Hydrological Processes Hydrological Processes

and Modellingand ModellingJohn PomeroyJohn Pomeroy11, Raoul Granger, Raoul Granger22, Newell Hedstrom, Newell Hedstrom22, Tom Brown, Tom Brown11, ,

Alain PietroniroAlain Pietroniro22, Lawrence Martz, Lawrence Martz11, Robert Armstrong, Robert Armstrong11 and Logan Fangand Logan Fang11..

Centre for Hydrology, University of Saskatchewan and Centre for Hydrology, University of Saskatchewan and National Water Research Institute, Environment CanadaNational Water Research Institute, Environment Canada

OverviewOverview

?? OBJECTIVEOBJECTIVETo better understanding, describe and model the To better understanding, describe and model the evolution of hydrological drought on the prairies, evolution of hydrological drought on the prairies, from frozen and unfrozen land surface fluxes, to soil from frozen and unfrozen land surface fluxes, to soil moisture and surface water storage to streamflow moisture and surface water storage to streamflow generationgeneration

?? FOCUS FOCUS –– evaluation and drought sensitivity ofevaluation and drought sensitivity of?? Snowmelt RunoffSnowmelt Runoff??Areal EvaporationAreal Evaporation?? Small Basin Hydrological ModellingSmall Basin Hydrological Modelling

Much of the Much of the prairie does prairie does

not not contribute contribute

runoff:runoff:NonNon--

contributing contributing Areas for Areas for

River FlowRiver Flow

Grain Grain Stubble to Stubble to

Trap Trap Blowing Blowing

SnowSnow

Stubble Field (25 cm tall)

0102030405060708090

100

Snow Evaporation Accumulation Blowing SnowTransport

% o

f Sn

ow

fall

Prince Albert

Yorkton

Regina

Swift Current

Fallow Field

0

10

20

30

40

5060

70

80

90

100

Snow Evaporation Accumulation Blowing SnowTransport

% o

f Sno

wfa

ll

Prince Albert

Yorkton

Regina

Swift Current

0 30 60 90 120 150 180Snow Water Equivalent (mm)

100

0

20

40

60

80

120Restricted

Unlimited

0.30.40.50.60.7

0.9

1:1

Empirical Model of Infiltration into Empirical Model of Infiltration into Frozen Soils Frozen Soils -- Prairie EnvironmentPrairie Environment

Infiltration(mm)

Saturation

Effect of Thawed Soils on Effect of Thawed Soils on Prairie Spring RunoffPrairie Spring Runoff

0

0.2

0.4

0.6

0.8

1

1.2

1.4

95 100 105 110 115 120 125Julian Date

Dai

ly F

low

, m

3 /s

ObservedFrozen SoilUnfrozen Soil

Snowmelt Runoff in a Prairie EnvironmentSnowmelt Runoff in a Prairie EnvironmentLogan Fang, M.Sc. StudentLogan Fang, M.Sc. Student

?? Implement spatially distributed model of snowmelt runoff Implement spatially distributed model of snowmelt runoff based on SWE and snowmelt infiltration (INF): based on SWE and snowmelt infiltration (INF): ?? snowmelt runoff = SWE snowmelt runoff = SWE -- INFINF

?? Assemble modules in CRHM (Cold Region Hydrological Model Assemble modules in CRHM (Cold Region Hydrological Model Platform) using meteorological data from St. Denis, Bad Lake, otPlatform) using meteorological data from St. Denis, Bad Lake, otherher?? Key modules including PBSM (Prairie Blowing Snow Model), EBSM Key modules including PBSM (Prairie Blowing Snow Model), EBSM

(Energy(Energy--Budget Snowmelt Model), and GrayBudget Snowmelt Model), and Gray’’s parametric equation for s parametric equation for snowmelt infiltrationsnowmelt infiltration

?? Find appropriate aggregation techniques for runoff calculation.Find appropriate aggregation techniques for runoff calculation.

?? Examine the drought condition sensitivities of snowmelt runoff Examine the drought condition sensitivities of snowmelt runoff ?? low snowfalllow snowfall?? low soil moisturelow soil moisture

Flowchart for Calculating Snowmelt RunoffFlowchart for Calculating Snowmelt Runoff

GrangerGranger--Gray General EquationGray General Equation

GG = relative evaporation = ratio of actual to saturated = relative evaporation = ratio of actual to saturated surface E (dimensionless)surface E (dimensionless)

G is related to the Relative Drying power, D;G is related to the Relative Drying power, D; DD = E= Eaa/(E/(Eaa + + QQaa) (dimensionless)) (dimensionless)

EGQ GE

Ga a?

??

??

??

? ?? ?G D D? ? ?1 0 793 0 2 4 902 0 006. . exp . .

Surface ResistanceSurface Resistance

0

200

400

600

800

1000

1200

1400

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

Drying Power, D

Su

rfac

e R

esis

tan

ce, r

s (

s/m

)

Grass

Jack Pine

Relationship between Relationship between rrss/r/raa and Gand GNative Grass

0.01

0.1

1

10

100

1000

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0G

r s/r

a, s

/m

MeasuredTheoretical

Estimating surface resistance, Estimating surface resistance, rrss, using The , using The GG--D relationshipD relationship

Regenerating Pine

-100

0

100

200

300

400

500

600

700

184 184.25 184.5 184.75 185

Decimal Date 2000

Flux

, W/m

²

0

50

100

150

200

250

300

r s, s

/m

Net Rad.

rs, measured

rs calc f(D)

Spatial Variability of Evaporation in a Spatial Variability of Evaporation in a Prairie LandscapePrairie Landscape

Robert Armstrong, Ph.D. StudentRobert Armstrong, Ph.D. Student

?? Test and compare observational and modelling methods of Test and compare observational and modelling methods of estimating evaporation estimating evaporation –– including remote sensingincluding remote sensing

?? Assess feasibility of remotelyAssess feasibility of remotely--sensed, distributed estimates of sensed, distributed estimates of evaporation over a heterogeneous prairie landscapeevaporation over a heterogeneous prairie landscape

?? Examine the spatial variability of soil, vegetation and Examine the spatial variability of soil, vegetation and atmospheric parameters and the effects of spatial variability onatmospheric parameters and the effects of spatial variability onlarger scale estimates of evaporation (i.e. linear and nonlarger scale estimates of evaporation (i.e. linear and non--linear linear relationships)relationships)

?? Suggest improved methods to estimate spatially aggregated Suggest improved methods to estimate spatially aggregated evapotranspiration.evapotranspiration.

Evaporation MethodologyEvaporation Methodology

Prairie landscape units

Data:atmospheric, soil,

vegetation and remotely-sensed

Test, compare (modify?) methods of estimating evaporation (Granger-

Gray, Penman-Monteith, remote sensing)

Spatial variability and effects of scale

Distribute evaporation across landscape (e.g. wet, normal, drought)

Aggregation Methodology

IssuesIssues?? Complex Terrain Complex Terrain

?? TopographyTopography?? VegetationVegetation?? SoilsSoils

?? DataData?? Archives need QA/QCArchives need QA/QC?? Algorithm development and Algorithm development and

testing will require testing will require new field new field datadata

?? ParameterisationParameterisation?? Supplement surface Supplement surface

observations with assimilated observations with assimilated datadata

CCold old RRegions egions HHydrological ydrological MModelodel?? Object oriented, modular modelling platform in Windows Object oriented, modular modelling platform in Windows

(C++)(C++)?? Library of basin, process and data modules Library of basin, process and data modules –– user friendly user friendly

interfaceinterface?? Ability to write new modules from within the modelAbility to write new modules from within the model?? User assembles & User assembles & ‘‘compilescompiles’’ the model using the CRHM the model using the CRHM

platform platform –– make what you wantmake what you want?? Applied to Applied to HHydrological ydrological RResponse esponse UUnitsnits

?? Scaling problems minimised within HRU (~process scale, internallScaling problems minimised within HRU (~process scale, internally y uniform response)uniform response)

?? Characteristic sequences of water flow between HRU governs the bCharacteristic sequences of water flow between HRU governs the basin asin responseresponse

?? Water and snow fluxes from HRU to HRU and outside of basin.Water and snow fluxes from HRU to HRU and outside of basin.?? Parameters set Parameters set aprioriapriori. No calibration. No calibration?? Visualisation, mapping and sensitivity tools, GIS interface for Visualisation, mapping and sensitivity tools, GIS interface for

inputs and outputsinputs and outputs

Cold Regions Hydrological Model Cold Regions Hydrological Model Process ModulesProcess Modules

?? Developed from research at University of Developed from research at University of Saskatchewan and NHRC over several decadesSaskatchewan and NHRC over several decades

?? Radiation (slopes, estimation procedures)Radiation (slopes, estimation procedures)?? Blowing snow (snow transport & sublimation)Blowing snow (snow transport & sublimation)?? Interception (rain and snow)Interception (rain and snow)?? Snowmelt (open & forest, advection, energy balance & Snowmelt (open & forest, advection, energy balance &

degree day options)degree day options)?? Infiltration (frozen and unfrozen soils)Infiltration (frozen and unfrozen soils)?? Evaporation (unsaturated surfaces)Evaporation (unsaturated surfaces)?? Soil moisture balance (with groundwater interaction)Soil moisture balance (with groundwater interaction)?? Routing (hillslopes, subRouting (hillslopes, sub--surface and streamflow)surface and streamflow)

Cold Regions Hydrology Model Cold Regions Hydrology Model --Prairie Basin Water Balance Prairie Basin Water Balance

-500

-400

-300

-200

-100

0

100

200

300

400

500Fallow Stubble Coulee Basin

mm

wat

er e

quiv

alen

t

SnowfallRainfallRunoffSublimationDrifting SnowEvaporation

With 30% Summer Fallow

Changed to Changed to Continuous Continuous Grain Grain CroppingCropping

-400

-300

-200

-100

0

100

200

300

400

500Stubble Coulee Basin

mm

wat

er e

qu

ival

ent

Snowfall

RainfallRunoffSublimationDrifting SnowEvaporation

- 4 0 - 2 0 0 2 0 4 0 6 0

rainfa l l

s n o w fal l

e va p o r a t i o n

drift

s u b l i m a t i o n

s n o w m e l t

in f i l t ra t ion

runof f

% C h a n g e

CRHM Use for DRICRHM Use for DRI

?? Hydrological evolution and feedbacks in Hydrological evolution and feedbacks in droughtdrought

?? Hydrological Drought Indices based on small Hydrological Drought Indices based on small basin soil moisture, streamflow and slough levelsbasin soil moisture, streamflow and slough levels

?? Scaling methodology and process test bedScaling methodology and process test bed?? Evaluate prairie land surface parameterisations Evaluate prairie land surface parameterisations

and aggregation for MESHand aggregation for MESH?? Test prairie hydrology routing for MESHTest prairie hydrology routing for MESH