Lecture Panel 10 Flashcards

1
Q

Infiltration

A

movement of water from the soil surface into the soil

-inputs from precipitation and snowmelt

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2
Q

Redistribution

A

Movement of infiltrated water within the unsaturated zone

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3
Q

Exfiltration

A

Evaporation of water vapour from the upper layers of the soil (output)

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4
Q

Vegetative Uptake

A

Soil water is absorbed by plant roots and subsequently released during transpiration

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5
Q

Interflow

A

Soil water is carried down slope within the unsaturated zone

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6
Q

Percolation and groundwater recharge

A

Soil flows downward through porous soil into the saturated zone and creates ground water recharge

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7
Q

Capillary rise

A

Movement of water upward from the saturated zone to the unsaturated zone due to surface tension

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8
Q

Why is it important to understand infiltration and redistribution?

A

to determine the water budget

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9
Q

What is Darcy’s Law

A
Tells you discharge (Q) from a tube of saturated soil 
Q=-KAdh/dl
A= area
K= hydraulic conductivity
dh= change in head
dl= change in length
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10
Q

Specific discharge

A

q=Q/A=-Kdh/dl

can say this is apparent velocity (v=L/t) of saturated flow

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11
Q

Anisotropic unsaturated flow

A

flow rate differs depending on direction, due to grain shape and orientation

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12
Q

How are hydraulic conductivity and water content related?

A

directly proportional - but the rates differ by soil texture

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13
Q

Darcy’s law for unsaturated flow

A

Pressure head and connectivity are functions of moisture:

q = -K*(1+dpsi/dz)

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14
Q

Infiltration rate

A

rate water enters soil

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15
Q

infiltration capacity

A

maximum rate at which water can enter soil

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16
Q

Water input rate

A

precipitation rate

17
Q

Time to ponding

A

time at which input rate exceeds infiltration capacity

18
Q

5 moisture zones during infiltration

A
  1. saturated zone
  2. transition zone
  3. transmission zone
  4. wetting zone
  5. wetting front
19
Q

saturation zone

A

during infiltration - near the surface, extending up to 1.5 cm down

20
Q

transition zone

A

during infiltration - about 5cm thick and located below the saturated zone. rapid decrease in water content

21
Q

transmission zone

A

during infiltration - water content varies slowly with depth and time

22
Q

wetting zone

A

during infiltration - where sharp decrease in water content is observed

23
Q

wetting front

A

during infiltration - region of very steep moisture gradient. this represents the limit of moisture penetration into the soil

24
Q

infiltration and runoff over time during storm

A

infiltration starts out very fast and efficient, then can’t hold anything more due to saturation of the top layers. runoff is reciprocal

25
Factors controlling infiltration
- water input rate - hydraulic conductivity of the surface - -soil organic layers - -frost - -swelling or drying - -rain compaction - -in-washing of sediment - -human modification - initial water content - -wetter soils have higher unsaturated hydraulic conductivity but will also fill up faster - slopes - soil chemistry - water chemistry - -K at 30C almost 2x at 0
26
Rings for infiltration rate measurement
ring in soil, water in ring at constant head - we keep water level constant, and since we are just barely avoiding runoff we know we are at max infiltration rate - issues are ring deforms soil, not nature conditions - can use two rings to stop lateral spread
27
Rainfall simulator
device for measuring infiltration with attempted realism
28
Hortons early infiltration insight
infiltration begins at some rate of, and exponentially decreases until it reaches some constant rate, fc