SCALING IMPLICATIONS OF VARIABLE
FROZEN SOIL INFILTRATION ON RUNOFF
GENERATION
JR Janowicz1, JW Pomeroy2 and DM Gray
1
Water Resources Branch, Environment Yukon
Whitehorse, YT
2
Centre for Hydrology, University of Saskatchewan
Saskatoon, Saskatchewan
U OF S LOGO
HERE
C OF HYD LOGO HERE
STUDY OBJECTIVES
• To quantify the spatial variability of parameters
governing infiltration to frozen soil and
infiltration excess (runoff) in cold regions
• To examine whether point scale relationships
for infiltration and runoff associated with
frozen soils can be upscaled using mean
parameters
• To propose a method for calculating cold
regions runoff generation from basins with
complex physiography
INFILTRATION TO FROZEN SOILS
unlimited
measured
120
Infiltration (mm)
100
1:1
80
0.3
0.4
0.5
0.6
0.7
60
40
20
0.9
0
0
30
60
90
120 150 180
Snow Water Equivalent (mm)
restricted
•Early work by U of S
came up with 3 classes of
infiltrability
•Unlimited
•Restricted
•Limited
PARAMETRIC RELATIONSHIP
Zhao & Gray (1999)
INF = CS
2.92
0
(1 − S I )
1.64
 273.15 − TI 


 273.15 
−0.45
t 0.44
• INF = Infiltration (cm)
• SI = initial soil saturation (mm3/mm3)
(water + ice; 0-40 cm)
• C = bulk coefficient
• S0 = surface saturation (mm3/mm3) • TI = initial soil temp (0K)
(vol soil moisture / porosity)
• t = time (hrs)
SCALING PRINCIPLES
•Consider Interrelationships Between Parameters
INF = CS
2.92
0
(1 − S I )
•INF = f (SWE, SI)
•S0, TI, t = f (SWE)
•S0, TI = f (SI)
1.64
 273.15 − TI 


 273.15 
−0.45
t 0.44
DURATION OF SNOWMELT
• Controls infiltration
opportunity time, runoff
generation, streamflow
• Can be simply described as a
function of SWE and melt
rate, M.
• Approximates the infiltration
opportunity time, t0, when
melt is continuous at high
latitudes
• Spatially variable because
SWE and M are spatially
variable.
SWE
t0 ≈ T =
M
WATER STORAGE POTENTIAL
•Northern mineral soils often overlain by organic layer
•Organic layers will hold water to water storage potential
5 – 25 cm
Wsp = 0.6φ (1 − S I ) z w
Wsp = water storage potential (mm)
Φ = porosity
SI = initial soil
saturation, θ/Φ
θ = average volumetric
moisture content
zw = depth of organic layer (mm)
•drain rapidly down slopes
•ponds on poorly drained sites
NORTHERN RUNOFF GENERATION
•
•
•
Occurs through organic matter layers
and over frozen mineral soils
Primarily snowmelt driven (mineral
soils thawed during major rain events)
Complex process Subarctic
mountainous terrain has highly
variable:
–
–
–
–
–
•
snow accumulation,
melt rate,
organic layer thickness,
degree of saturation,
ice layers
Runoff is further complicated by
– variable contributing area,
– poorly defined drainages,
– large storage terms.
WOLF CREEK ECOSYSTEMS
2200
2000
Elevation (m)
1800
Alpine
Granger
1600
1400
1200
Buckbrush
1000
800
Forest
600
0
20
40
60
% Area Below
80
100
FOREST
•Thick Spruce Canopy (20 m)
•Level Undulating Terrain
SUBALPINE TAIGA
•Shrub Alder & Willow (2 m)
•Moderate (150) Undulating Hillslope
ALPINE TUNDRA
•Moss, Grass, Lichen
•50 % Level; 50% Shallow Slope (100)
GRANGER SUB-BASIN - NORTH FACING
Drift
•Shrub Alder & Willow (2 m)
•Steep Undulating Slope ( 250)
GRANGER SUB-BASIN - SOUTH FACING
•Shrub Alder & Willow
•Steep Undulating Slope ( 250)
GRID SURVEY
100 m
5 X 5 m grid
441 points
Met Station
GRID SURVEY - GRANGER SUB-BASIN
10 X 20 m grid
258 points
420 m
100 m
GRID DATA COLLECTION
•Soil moisture - TDR – fall (prior to freeze-up)
•SWE – Mount Rose – spring (max snowpack)
•Porosity - soil particle size
VARIATION IN RUNOFF
COMPONENTS
Snow Accumulation (SWE)
1200
200
1000
150
800
hours
mm
250
100
Infiltration Opportunity Time
600
400
50
200
0
0
Granger
40
Shrub Tundra
Sparse Tundra
Spruce Forest
Granger
200
Infiltration
35
140
120
20
mm
mm
25
15
Sparse Tundra
Spruce Forest
Infiltration Excess
(Potential Runoff)
180
160
30
Shrub Tundra
R = SWE - Inf
100
80
60
40
10
5
20
0
0
Granger
Shrub Tundra
Sparse Tundra
Spruce Forest
Granger
Shrub Tundra
Sparse Tundra
Spruce Forest
GRANGER FALL SOIL MOISTURE
AND SPRING
SWE
Volumetric Water Content %
100
5 0
4 0
50
3 0
2 0
1 0
0
0
50
100
North Face
150
200
250
300
Valley Bottom
35 0
1
400
South Face
0
100
5 0 0
50
3 0 0
1 0 0
0
0
50
100
150
200
25 0
300
350
400
Snow Water Equivalent mm
0
ORGANIC STORAGE & SOIL
INFILTRATION
Water Storage Potential mm
100
9 0
7 0
5 0
50
4 0
3 0
2 0
0
1 0
0
50
North Face
100
150
200
250
Valley Bottom
300
3 50
400
South Face
1
0
100
9 0
7 0
5 0
50
4 0
3 0
2 0
0
0
5 0
100
150
200
25 0
300
350
400
Frozen Soil Infiltration mm
1 0
1
0
INFILRATION EXCESS
(SNOWMELT RUNOFF)
5 0 0
100
4 0 0
3 0 0
50
2 0 0
1 5 0
1 0 0
0
0
50
100
150
North Face
200
250
300
350
Valley Bottom
South Face
100
50
0
0
50
100
150
200
250
300
400
350
400
1
0
CONCLUSIONS
• Infiltration and runoff can be calculated from mean parameters
(SWE, θ, Φ, M) within a landscape type – no ‘scaling
problem’ evident.
• Substantial difference in infiltration and runoff with landscape
type
– SWE determined by windflow change
– Melt rate determined by slope and aspect
– Soil moisture determined by drainage
– Organic layer thickness determined by slope and aspect
• Water storage potential in organic layer and infiltration to
frozen mineral soils are not primarily drainage controlled but
are controlled by slope and aspect through their influence on
melt energy and soil and organic layer properties
• Snowmelt runoff is not primarily topographically controlled
but is controlled primarily by accumulation of wind-blown
snow and melt energetics and secondarily by soil moisture.
WOLF CREEK – 15 YEARS
1993 - 2008
Thank You