Plot scale

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Oregon State University

Plot scalePlot scale

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What this section will addressWhat this section will address

A

B

C

Plot scale

Hillslope scale

Catchment scale

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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

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From core From core to plotto plot

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Our so-called Our so-called subgrid subgrid parameterizationparameterization

Jan Hopmans, UC Davis

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The stepsThe steps

Sherlock et al., 2000

How does measurement uncertainty in thesesteps affect estimation of K(h)?

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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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Just to be clearJust to be clear

Source: Mike O’Kane

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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!

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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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Preferential flowPreferential flow

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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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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)

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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

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Not a new ideaNot a new idea

The curse of preferential

flow

1898 - Some 104 years ago

Courtesy Brent Clothier

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Plot scale Plot scale changes with changes with

depthdepth

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Oregon State UniversityPhoto: Markus Weiler UBC

At depth

Deep percolation

Lateral flow

Transpiration

Evaporation

Infiltration

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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.

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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.


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Drainable porosityDrainable porosity


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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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

)

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.. and for many nutrients.. and for many nutrients

Data from forest soils (Hagedorn et al., 2001)

Also distinct depth distributions

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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

?


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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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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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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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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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Sprinkling and dye tracing Sprinkling and dye tracing experimentsexperiments

Markus Weiler, Freiburg University

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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


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Soil water content and preferential Soil water content and preferential flowflow

Soil water content measurementVertical dye pattern

unstained

stones

macropores

low 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


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An animationAn animation

1.0

Depth (m) Dye pattern Water content change

High rainfall intensity Dry soil


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Matric potential and preferential Matric potential and preferential flowflow

Matric potential measurement Vertical dye pattern

unstained

stones

macropores

low 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)


Recall Weyman, Burt and others from your reader….

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Other sitesOther sites

1.0


High rainfall intensity Dry soil


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1.0


Low rainfall intensity Dry soil


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1.0


Low rainfall intensity Wet soil


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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


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How do macropores influence How do macropores influence runoff processes?runoff processes?

Activated macropore rapid infiltration

Storage Fast Subsurface Flow

Overland Flow

Runoff reaction


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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

?


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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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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

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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).

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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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This sectionThis section


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

Plot scale

Documents

Transcript of Plot scale