GLACIER MODELING Glacial Runoff and Hydrology Modeling Irina Overeem
Canadian Prairie Hydrology and Runoff Generation
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Canadian Prairie Hydrology and Runoff Generation John Pomeroy Centre for Hydrology, University of Saskatchewan, Saskatoon www.usask.ca/hydrology
description
Canadian Prairie Hydrology and Runoff Generation. John Pomeroy Centre for Hydrology, University of Saskatchewan, Saskatoon www.usask.ca/hydrology. Prairie Hydrology. - PowerPoint PPT Presentation
Transcript of Canadian Prairie Hydrology and Runoff Generation
Canadian Prairie Hydrology and Runoff
Generation
John PomeroyCentre for Hydrology,
University of Saskatchewan, Saskatoon www.usask.ca/hydrology
Prairie Hydrology Major river flow is primarily from mountain runoff, but
prairie runoff supplies smaller rivers, streams, wetlands, and lakes
Prairie Runoff forms in internally drained (closed) basins that are locally
important but non-contributing to river systems that drain the prairies, OR
drains directly to small prairie rivers (Battle, Souris, Assiniboine) >80% of runoff during snowmelt period
Redistribution of snow to wetlands and stream channels in winter is critical to formation of runoff contributing area
Drainage of small streams and wetlands ceases completely in summer when actual evaporation* consumes most available water.
Baseflow from groundwater often nonexistent. Prairie streams are almost completely ungauged and
often altered by dams, drainage, water transfers, etc*evaporation used here as transpiration + evaporation + sublimation
Prairie Hydrological Cycle
Prairie Runoff GenerationSnow Redistribution to Channels
Spring melt and runoff
Water Storage in Wetlands
Dry non-contributing areas to runoff
Non-Contributing Areas to Streamflow a Prairie Characteristic
Prairie Hydrology – don’t blink
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 sec
ond
Average 1975-2006
1995 High Year
2000 Low Year
Smith Creek, Saskatchewan
Drainage area ~ 450 km2
No baseflow from groundwater
Information Needed to Estimate Runoff
Snow accumulation and redistributionMelt rate Infiltration to frozen soils Infiltration excess forms runoff
>80% of all runoff is snowmelt runoff
Blowing Snow: Transport, Sublimation and Redistribution of Snow
Pomeroy and Gray, Wat Resour. Res. (1990)Pomeroy and Male, J Hydrol. (1992)Pomeroy, Gray and Male, J Hydrol. (1993)Pomeroy and Gray, NHRI Science Report No. 7 (1995)
Effect of Blowing Snow Sublimation on Prairie Snow Supply (losses, mm SWE)
Location Stubble-field Fallow-fieldCalgary 19.7 37.5Peace River 6.6 7.6Swift Current 28.2 37.8Prince Albert 24.9 29.6Regina 39.4 48.1Yorkton 18.6 28.6Portage 23.5 33.8Winnipeg 27.4 36.5
Pomeroy and Gray, NHRI Science Report No. 7 (1995) 1970-1976 hourly simulations
Distribution of Blowing Snow over Landscapes
Blowing snow transport, and sublimation relocate snow across the landscape from sources to sinks depending on fetch, orientation and area.
Source
Sink
Stubble Field Grassland Brush TreesFallow
Field
Shelterbelts on Prairies
Winkler, Manitoba
Conquest, Saskatchewan
Transport to shelterbeltsdepends on upwind fetchand vegetation roughness
Spatially Distributed Snow Redistribution
Snow mass balance equation
St Denis, Saskatchewan
Results – Spatially distributed SWE
Fang and Pomeroy, Hydrol Proc, in preparation
Spatially distributed SWE cont’
Spatially distributed SWE cont’
Spatially distributed SWE cont’
Spatially distributed SWE cont’
Spatially distributed SWE cont’
Spatially distributed SWE cont’
Spatially distributed SWE cont’
Spatially distributed SWE cont’
Spatial Pattern of Blowing Snow Sublimation
Simulations vs. Snow Surveys
Snowmelt
Degree Day Method has problems in open environments with late melt, & in forests.
Energy Balance snow CAN be estimated using reliable and readily applicable methods
Coupled Mass and Energy Equations for Snowmelt
MELT of SWE = QM/(w Lf Bi)
Melt Energy QM = Q* - QE – QH – QG – dU/dt Q* Net radiation (+ to snow surface) QE Evaporative energy (+ away from snow surface) QH Sensible energy (+ away from snow surface) QG Ground heat flux (+ downward from snow) dU/dt Internal energy change (+ loss from melt)
-200-100
0100200300400500600700
0:00 4:00 8:00 12:00 16:00 20:00 24:00Time
Radiation(W/m²)
Incoming SWNet SWNet RadNet LW
Diurnal Variation in Radiative Fluxes - clear day near Saskatoon
Empirical atmospheric transmittance equations
Qsi can be calculated directly if the atmospheric transmittence is known
Many similar relationships, all give similar results:
Bristow and Campbell and Walter et al. Annandale
All use a simple relationship between daily atmospheric transmittance and the range of daily air temperatures
Edmonton 1979-2000
Snowpack Albedo Decay
CRHM Snowmelt Simulation
Infiltration to Frozen Soils
Frozen soils can be permeable, but show reduced infiltration compared to unfrozen conditions
‘Frozen’ means a frost depth of at least 0.5 m Simple grouping of soil types
Three classes of infiltrability:
unlimited Inf=SWE restricted Inf=0 limited Inf = f(SWE, Saturation)
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
Gray’s Model of Infiltration into Frozen Soils - Prairie Environment
Infiltration(mm)
Saturation
Effect of Thawed Soils on Prairie Spring Runoff
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0.2
0.4
0.6
0.8
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1.2
1.4
95 100 105 110 115 120 125Julian Date
Dai
ly F
low
, m
3 /s
ObservedFrozen SoilUnfrozen Soil
Local Scale Prairie Runoff Because of frozen soils and rapidly melting
snowcovers in the spring, 80% - 90% of prairie runoff is produced from snowmelt
Snowmelt runoff is strongly controlled by snow drift location and size, soil moisture and mid winter thaws.
In wet years, there is often excess water to dryland cereal grain growing needs.
Hydrological computer simulations may tell us something about the reliability and behaviour of local prairie water supplies
Prairie hydrological modelling requires consideration of the following:
Cold Regions Hydrological Model
1. Transport of water in liquid, vapour and frozen states (runoff, percolation, evaporation, sublimation, blowing snow);
2. Coupled mass and energy balances; 3. Phase change in snow & soils (snowmelt, infiltration in frozen
soils, soil freezing and thawing);4. Snow and rain interception in forest canopies;5. Episodic flow between soil moisture, groundwater, ponds and
streams.6. Variable storage, drainage and contributing area7. Land use change
CRHM Module Development
Data from multiple sites Interpolation to the HRUs
Infiltration into soils (frozen and unfrozen)
Snowmelt (prairie & forest) Radiation – level, slopes Evapotranspiration Snow transport Interception (snow & rain) Sublimation (dynamic & static) Soil moisture balance Sub-surface runoff Routing (hillslope & channel) Advection
DATA ASSIMILATION
SPATIAL PARAMETERS
Basin and HRU parameters are set. (area, latitude, elevation, ground slope, aspect)
PROCESSES
Creighton Tributary, Bad Lake as a typical Prairie Basin
Moderately well drained plateau of grains and fallow drains into a couleeSemi-arid to sub-humid climateTypical drainage and landcover for much of southern prairies
Snowmelt Runoff over Frozen SoilsBad Lake:Semi-arid SW Saskatchewan
Soil moisture is FALL soil moisture
Snowmelt runoff isSpring
Physically basedInfiltration equations(Zhao & Gray, 1999)
Cold Regions Hydrological Model
Bad Lake – Creighton Tributary Water Balance
-500
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-100
0
100
200
300
400
500Fallow Stubble Coulee Basin
mm
wat
er e
quiv
alen
t
SnowfallRainfallRunoffSublimationDrifting SnowEvaporation
With 30% Summer Fallow
Pomeroy, De Boer, Martz (2007)
Changed to Continuous
Grain Cropping
-400
-300
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-100
0
100
200
300
400
500Stubble Coulee Basin
mm
wat
er e
quiv
alen
t
SnowfallRainfallRunoffSublimationDrifting SnowEvaporation
-40 -20 0 20 40 60
rainfall
snowfall
evaporation
drift
sublimation
snowmelt
infiltration
runoff
% Change
Prairie Streamflow & Climate Change “first more, then less”
Three most “reliable” climate change scenarios for hydrology 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
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40
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01/1
0/19
74
15/1
0/19
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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
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01/1
0/19
74
15/1
0/19
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29/1
0/19
74
12/1
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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)
Conclusions Prairie hydrological processes that control water
balance and runoff generation have been largely quantified and described and model requirements are known, but have not been widely implemented in models.
Major unknowns are the changing contributing area and its interaction with surface storage terms in poorly defined drainages.
