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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
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