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Plot scale. What this section will address. Plot scale. Hillslope scale. Catchment scale. Outline. From core to plot Quick review of flow and transport in porous media Problems with the notion of linear upscaling of soil core information Plot scale changes with depth - PowerPoint PPT Presentation
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FE 537
Oregon State University
Plot scalePlot scale
FE 537
Oregon State University
What this section will addressWhat this section will address
A
B
C
Plot scale
Hillslope scale
Catchment scale
FE 537
Oregon State University
OutlineOutline
From core to plotFrom core to plot Quick review of flow and transport in porous Quick review of flow and transport in porous
media media Problems with the notion of linear upscaling of Problems with the notion of linear upscaling of
soil core informationsoil core information
Plot scale changes with depthPlot scale changes with depth Some experimental dataSome experimental data
Preferential flow changes with depthPreferential flow changes with depth Some experimental dataSome experimental data
SummarySummary Plot scale conceptualization and how this links Plot scale conceptualization and how this links
to the hillslope scaleto the hillslope scale
FE 537
Oregon State University
From core From core to plotto plot
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Oregon State University
Our so-called Our so-called subgrid subgrid parameterizationparameterization
Jan Hopmans, UC Davis
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Oregon State University
The stepsThe steps
Sherlock et al., 2000
How does measurement uncertainty in thesesteps affect estimation of K(h)?
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Oregon State University
What’s important conceptuallyWhat’s important conceptually
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How we define this quantitativelyHow we define this quantitatively
Source: Mike O’Kane
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Oregon State University
Just to be clearJust to be clear
Source: Mike O’Kane
FE 537
Oregon State University
So for unsaturated conductivity…So for unsaturated conductivity…
Water potential cmH2O
0 -100 -200
Hydra
ulic
conduct
ivit
y m
m/h
r
1000
100
10
1
Water is the conducting medium!
FE 537
Oregon State University
Intact field soil very different to admixtures of sand/silt/clay
But wait, structure trumps texture!But wait, structure trumps texture!
0
0.1
0.2
0.3
0.4
0.5
1 10 100 1000 10000 [cm]
Wate
r conte
nt
[-] Sand
Loess
Clay
Photo by Jim Kirchner
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Oregon State University
Preferential flowPreferential flow
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Oregon State University
If Darcy were alive today…If Darcy were alive today…
Merde!q K
Hz
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Two common strategies to deal with thisTwo common strategies to deal with this
Source: Brent Clothier, WISPAS Newsletter 2008
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Oregon State University
Darcy revisitedDarcy revisited
It’s not that Darcy does not apply (almost It’s not that Darcy does not apply (almost all of the time)all of the time)
It’s just that a different physics kicks in It’s just that a different physics kicks in during brief windows in timeduring brief windows in time Days or weeks of Darcian bordom, punctuated Days or weeks of Darcian bordom, punctuated
by all (macropore) hell breaking loose!by all (macropore) hell breaking loose! Think of it as a struggle between the Think of it as a struggle between the
Newtonian vs Darwinian world viewsNewtonian vs Darwinian world views read John Harte’s 2002 paper in Physics Today (on read John Harte’s 2002 paper in Physics Today (on
merging the Newtonian and Darwinian world views) merging the Newtonian and Darwinian world views)
FE 537
Oregon State University
surface,topsoil
soil
soil base
matrix
soil pipes
highly permeable layers
Peter Kienzler, ETH Zurich
The plot scale paradox
While large pore space makes up only a small percent of the total porosity, they control almost all the flow at or near saturationAlmost all our theory is for the matrixWe‘ve learned about as much as we ever will for
pure textural mixtures and re-packed field soils
FE 537
Oregon State University
Not a new ideaNot a new idea
The curse of preferential
flow
1898 - Some 104 years ago
Courtesy Brent Clothier
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Oregon State University
Plot scale Plot scale changes with changes with
depthdepth
FE 537
Oregon State UniversityPhoto: Markus Weiler UBC
At depth
Deep percolation
Lateral flow
Transpiration
Evaporation
Infiltration
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Oregon State University
Hydrology’s most basic equationHydrology’s most basic equation
nZr ds/dt = I(s, t) - E(s, t) - L(s, t)
Where: n is porosity, Z is soil depth, s is the relative soil moisture content, I is infiltration, E is evaporation and L is leakage
Rodriguez-Iturbe (2000, WRR) notes that “although apparently simple, this presents serious challenges when the terms in the RHS are considered dependent on the state s.
FE 537
Oregon State University
Changes with depthChanges with depthone of your benchmark papersone of your benchmark papers
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Some data from the same siteSome data from the same site
Data from WS10, HJA, Kevin McGuire
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Ksat changes with depth!Ksat changes with depth!
Saturated hydraulic conductivity with exponential curve fits. The dashed lines indicate the envelope for most data observations.
Data from WS10, HJA, Kevin McGuire
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Oregon State University
Drainable porosityDrainable porosity
Data from WS10, HJA, Kevin McGuire
Drainable porosity Drainable porosity = saturated water = saturated water content – water content – water content at field content at field capacitycapacity
Change in Change in drainable porosity drainable porosity will directly alter will directly alter the depth function the depth function of drainable of drainable storage in the soil storage in the soil
Relates to ground Relates to ground water table water table fluctuations fluctuations
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Oregon State University
Why such changes with depth?Why such changes with depth?
0
20
40
60
80
100
120
140
0 5 10 15 20
Knocks / 5 cm
So
il d
ep
th (
cm
)
FE 537
Oregon State University
.. and for many nutrients.. and for many nutrients
Data from forest soils (Hagedorn et al., 2001)
Also distinct depth distributions
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Oregon State University
The preferential flow – matrix linkThe preferential flow – matrix link
Soil matrix changes Soil matrix changes with depth conspire with depth conspire with vertical with vertical preferential flow:preferential flow:
Drainable porosityDrainable porosityBulk densityBulk densityHydraulic Hydraulic
conductivityconductivityPore size Pore size
distributiondistribution
z
?
Peter Kienzler, ETH Zurich
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Oregon State University
A now common mechanismA now common mechanism
New water bypass New water bypass flow to depthflow to depth
Transient saturation Transient saturation at soil-bedrock at soil-bedrock interfaceinterface
Lateral pipeflow of old Lateral pipeflow of old water due to limited water due to limited storage and headstorage and head
Bedrock surface Bedrock surface control of mobile watercontrol of mobile water
Rapid recession after Rapid recession after rainfall endsrainfall ends
Important coupling of Important coupling of unsaturated and unsaturated and transient saturated transient saturated zones.zones.
<0
<0
ddZdZ
Storm Rainfall
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Oregon State University
Why this is important for runoff Why this is important for runoff generation?generation?
Water cannot enter the pipe drain when it is placed above the level of the water table (i.e. water will not flow from a position of low potential in the soil to a position of higher potential). Water will only enter the drain when it is placed within the saturated zone (below the water table) and if there is sufficient hydraulic head.
Remember this when we move to the hillslope scale…(McLaren and Cameron, 1994)
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Oregon State University
Kitihara-san’s Lab at FFPRI in Japan
R
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More detail on More detail on preferential preferential flow changes flow changes with depthwith depth
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It’s network-like and it’s ubiquitous
A network of connected macropores and fissures that rapidly transmits water & solutes through the rootzone
Courtesy Brent Clothier
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Oregon State University
A quick case study to illustrate thisA quick case study to illustrate thisSprinkling experiments on undisturbed soils: Sprinkling experiments on undisturbed soils: the work of Weiler and Naefthe work of Weiler and Naef
electric linearactuator
nozzles
tensiometer and TDR probes
overland flowmeasurement
pump and control
gutter
covered dry plot wind protection
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Oregon State University
Sprinkling and dye tracing Sprinkling and dye tracing experimentsexperiments
Markus Weiler, Freiburg University
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Oregon State University
Horizontal dye pattern
unstained
stones
macropores
low concentration
medium concentration
high concentration
Stained areas with
Legend
Dep
th
8 cm
De
pth
0
50 cm
High rainfall intensity
Dry soil
15 cm
57 cm
MappingMapping
Markus Weiler, Freiburg University
FE 537
Oregon State University
Soil water content and preferential Soil water content and preferential flowflow
Soil water content measurementVertical dye pattern
unstained
stones
macropores
low concentration
medium concentration
high concentration
Stained areas withLegend
1.0
Depth (m)
Flow process
Surface initiation (water repellency)
High interaction (permeable matrix)
High rainfall intensity
Dry soil
Markus Weiler, Freiburg University
FE 537
Oregon State University
An animationAn animation
1.0
Depth (m) Dye pattern Water content change
High rainfall intensity Dry soil
Markus Weiler, Freiburg University
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Oregon State University
Matric potential and preferential Matric potential and preferential flowflow
Matric potential measurement Vertical dye pattern
unstained
stones
macropores
low concentration
medium concentration
high concentration
Stained areas withLegend
1.0
Depth (m)
0 10 20 30 40 50 60 70 80 90 100-20
-15
-10
-5
0
5 82 cm
98 cm
30 cm
18 cm
Tim e (m in)
Mat
ric
po
ten
tial (
kPa
)
Duration of sprinkling experiment
Flow process
Subsurface initiation (saturated matrix)
Low interaction (saturated matrix)
Markus Weiler, Freiburg University
Recall Weyman, Burt and others from your reader….
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Oregon State University
Other sitesOther sites
1.0
Depth (m) Dye pattern Water content change
High rainfall intensity Dry soil
Markus Weiler, Freiburg University
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Oregon State University
Other sitesOther sites
1.0
Depth (m) Dye pattern Water content change
Low rainfall intensity Dry soil
Markus Weiler, Freiburg University
FE 537
Oregon State University
Other sitesOther sites
1.0
Depth (m) Dye pattern Water content change
Low rainfall intensity Wet soil
Markus Weiler, Freiburg University
FE 537
Oregon State University
Infiltration in macroporous soilsInfiltration in macroporous soils
Macropore Flow Initiation
Water supply to the macropores
Interaction
Water transfer between macropores and the surrounding soil matrix
Markus Weiler, Freiburg University
FE 537
Oregon State University
How do macropores influence How do macropores influence runoff processes?runoff processes?
Activated macropore rapid infiltration
Storage Fast Subsurface Flow
Overland Flow
Runoff reaction
Markus Weiler, Freiburg University
FE 537
Oregon State University
The preferential flow – matrix link revisitedThe preferential flow – matrix link revisited
Soil matrix changes Soil matrix changes with depth conspire with depth conspire with vertical with vertical preferential flow:preferential flow:
Drainable porosityDrainable porosityBulk densityBulk densityHydraulic Hydraulic
conductivityconductivityPore size Pore size
distributiondistribution
z
?
Peter Kienzler, ETH Zurich
FE 537
Oregon State University
A now common mechanismA now common mechanism
New water bypass New water bypass flow to depthflow to depth
Transient saturation Transient saturation at soil-bedrock at soil-bedrock interfaceinterface
Lateral pipeflow of old Lateral pipeflow of old water due to limited water due to limited storage and headstorage and head
Bedrock surface Bedrock surface control of mobile watercontrol of mobile water
Rapid recession after Rapid recession after rainfall endsrainfall ends
Important coupling of Important coupling of unsaturated and unsaturated and transient saturated transient saturated zones.zones.
<0
<0
ddZdZ
Storm Rainfall
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Oregon State University
Implications for modelingImplications for modeling
Traditional conceptual runoff models
Saturated storage
Unsaturated storage
What undergraduate textbooks will state
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Saturated storage
Unsaturated storage
A process prerequisite
Implications for modelingImplications for modeling
FE 537
Oregon State University
The use of qualitative, conceptual models can overcome the
shortcomings of quantitative models. Conceptual models consider the sum interaction of all processes, even if
not known, that result in a particular phenomenon
(Pilkey and Pilkey-Jarvis, 2007).
FE 537
Oregon State University
One exampleOne example
b
znznd exp)( 0
1
1)(
m
o D
zKzK
wtTtqSSF )()( Weiler and McD, 2004 JoH
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ConclusionsConclusions
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Oregon State University
This sectionThis section
Peter Kienzler, ETH Zurich
From core to plotFrom core to plot Quick review of flow and transport in porous media Quick review of flow and transport in porous media Problems with the notion of linear upscaling of soil Problems with the notion of linear upscaling of soil
core informationcore information Plot scale changes with depthPlot scale changes with depth
Some experimental dataSome experimental data Preferential flow changes with depthPreferential flow changes with depth
Some experimental dataSome experimental data SummarySummary
Plot scale conceptualization and how this links to Plot scale conceptualization and how this links to the hillslope scalethe hillslope scale
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Next sectionNext sectionFrom vertical to lateral flowFrom vertical to lateral flow
z
Saturated vertical hydraulic conductivity
Q Q Qs
% Saturation Downward percolation
Lateral subsurface flow
Often an impeding horizon or soil-bedrock contact