Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Soil And Water > Extra Reading > Flashcards

Extra Reading Flashcards

(66 cards)

Start Studying
1
Q

Hydrophobicity:

Commonly associated with fungal mycelia

A

Savage et al, 1969

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Hydrophobicity:

Bug fires vaporise more organic compounds creating a stronger, more continuous hydrophobic layer.

A

Tiedemann et al, 1979

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Hydrophobicty:

Stronger in coarser textured soils.

A

Huffman et al, 2001

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Infiltration:

Infiltration capacity is a control of surface runoff.

A

Horton, 1933

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Infiltration:

Wind action and differential temperatures aid in re-opening soil pores after rain.

A

Horton, 1933

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Infiltration:

Increase of infiltration capacity immediately following cultivation of soils.

A

Horton, 1940

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Infiltration:

Rough surfaces may have lower infiltration capacities.

A

Horton, 1940

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Infiltration:

4 tension disc experiment on loamy soils.

TDR measured water at depth of 2cm below tension disc, with varying hydraulic head.

Measuring transport of contaminants.

A

Simunek et al, 1999

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Unsaturated zone:

Part of the soil where water contents are less than the soil porosity.

A

Nielsen et al, 1986

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Unsaturated zone:

Surface and ground waters are linked by the unsaturated zone

A

Nielsen et al, 1986

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Hysteresis:

Enhanced by presence of rapped air, soil shrinking and swelling and rates of wetting and drying

A

Davidson et al, 1966

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Hysteresis:

Keeps water contents higher in the initially wetted part of the soil, while reducing wetting front in the drier soil

A

Dracos, 1984

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Unsaturated zone:

Temperature effects viscosity and surface tension.

A

Nielsen et al, 1986

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Preferential flow:

In well structured soils, water moves along cracks

A

Bouma, 1991

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Preferential flow:

Sandy soils create ‘fingers’

A

Hillel, 1987

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Preferential flow:

Dyes used to trace flows but are destructive and you cannot do repeats.

A

Ehlers, 1975

Flury et al, 1994

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Preferential flow:

Penetration depth is deeper in wet soils

A

Flury et al, 1994

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Preferential flow:

Structure must be considered when pesticides are used.

Poor structure, sandy soils are more susceptible.

A

Flury et al, 1994

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Influences on water movement in soils

A

Soil bulk density
Soil strength
Soil OM
Soil chemical properties

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Processes that slow infiltration capacity…

A 
Deterioration of soil structure
Crust formation
Detachment of particles(blocked pores) 
Clay swelling
Air entrapment below wetting front
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Factors influencing infiltration…

A

Topography
Macropores
Hysteresis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Effects of soil properties on infiltration…

A

Water content - infiltration is faster on initially dry soil

Soil texture - reduced infiltration on fine textured soils - associated with porosity.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Infiltrability depends on…

A 
Time of event
Initial soil water content
Hydraulic conductivity
Soil surface
Presence of impeding layers.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What is field capacity and what is the UK matric potential value used for it?

A

The water content of the soil after it has been saturated and allowed to drain against gravity for 48 hours… Half wet, half dry.

Matric potential -5kPa

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Factors effecting field capacity...
``` Texture Type of clay-montmorillonite has high fc. Organic matter Depth of initial wetting Impeding layers Evaportranspiration ```
26
What is bulk density... Including the equation.
The mass of dry soil per unit of volume (including pore space) Pb = Ms/Vt Where ms is mass of solids and vt is total vol.
27
What happens to bulk density when the ground is compacted?
There is less pore space, therefore the bulk density is higher.
28
Why does bulk density increase with depth?
Pressure.
29
What is the bulk density of clay like?
Clays have low bulk density because of their many micropores In agricultural soils: 1.00-1.60gcm3
30
What is the bulk density of sands like?
Sands have a higher bulk density because all the partials lie close. In agriculture soils: 1.20-1.80gcm3
31
Pore sizes...go. Luxmoore 1991
Micropores: 100 micrometers
32
What is soil water potential?
Potential energy possessed by water held in any position within the soil. The difference in energy levels determines direction and rate of flow. High energy state when pore sizes are small.
33
What is water flow in soils caused by?
``` OM Chemistry Topography Structure Stoniness Horizons Compaction ```
34
What is runoff influenced by?
``` Soil type Cracks Type of rock OM content Vegetation Topography Type or rainfall/intensity ```
35
What is overland flow?
If the rate of water supply at the soil surface exceeds the infiltration capacity. Laminar flow=shallow/gentle Turbulent flow=erosive
36
What is through flow?
Lateral downslope movement within the soil profile. ``` Diffuse flow (slow) Macropore flow (fast) Pipe flow (much larger scale) ```
37
What is groundwater flow?
Need knowledge of parent material including pressure, density, viscosity and homogeneity.
38
What is Channel precipitation?
Less than 5% contribution to runoff.
39
Environmental implications of runoff...
``` Pesticide pollution soil loss flooding decrease in soil quality Landslides Toxic waste ```
40
What does hydrograph separation enable you to do?
Enables separation of runoff compartment from baseflow compartment. From where runoff begins to the corresponding point on the regression limb.
41
What are the two main hydrographic separations in runoff?
Theoretical separation Experimental separation - using tracers to find water source (isotopic and geo chemical separation)
42
Factors effecting the shape the hydrograph
Climate - rainfall intensity. Regression limb would be more gradual and slow for snow. Topography - size/shape of basin. Slope of land. Ponding/storage Geology.
43
What is tortuosity?
The average ratio of the actual roundabout path to the straight flow path. Wiggly line : straight line
44
Pressure cell for measuring matric potential
Good to -98kPa, takes a long time to reach equilibrium, works by applying positive air pressure
45
Pressure plate for measuring matric potential
Good to -1500kPa, often used in labs, unsuited for large cores and determination at the wet end of the range
46
Psychrometer to measure matric potential
Psychrometer: Range -98 to -3000kPa, measures contribution of matric and osmotic potential
47
Tensiometer to measure matric potential
Good to -85kPa, inexpensive and quick can measure whole profile but slow to respond/equilibrate, requires excellent soil contact
48
How does a tensiometer work?
Water is drawn into soil through porous cup until the pressure in the cup & soil are in equilibrium (Bouma, 1981)
49
Advantages of using a tensiometer to measure unsaturated hydraulic conductivity
* Inexpensive * Quick * Variable length so can measure whole profile * Can be used to control irrigation schedules for crops
50
Disadvantages of using a tensiometer to measure unsaturated hydraulic conductivity
Doesn’t measure matric potential as low as PWP, effective up to -85kPa • Slow to respond/equilibrate • Requires excellent soil contact
51
Unsaturated hydraulic conductivity decreases as:
Volumetric water content decreases Tortuosity increases Cross-sectional area of water flow decreases Drag forces increase
52
Advantages of TDR - measuring unsaturated hydraulic conductivity
Fast, precise, non-destructive measurement (Roth et al., 1990) •Minimal calibration • Continuous measurement/automation – rapid results
53
Disadvantages of TDR - measuring unsaturated hydraulic conductivity and porosity
Measurement area only a few cm’s beyond probe | Problems with clay soils and organic soils
54
Neutron probe to measure soil water content. Porosity.
Measures how fast neurons are converted to slow neutrons is dependant on soil water content
55
Advantages of neutron probe
Non destructive High precision
56
Disadvantages of neutron probe
Expensive Health hazard - need training
57
What can be used to measure the water content of a soil
Oven drying: 105 degrees for 8 hours Neutron probe Time domain reflectometry
58
What would you use to hydrostatic (positive pressure potential) of saturated soils
Piezometer Open tube in soil Bottom is perforated to allow soil water to enter Digital reading
59
What would you use to matric potential of unsaturated soils
Tensiometer Water drawn into soil through porous cup until pressure in the cup and soil in equilibrium
60
Name the two flow types in saturated flow
Steady state flow - intensity does not change Transient flow - does change with time, realistic USE DARCYS LAW TO MEASURE
61
Darcy's law
The flow of water in soils is proportional to the hydraulic conductivity (ease of flow) The flow of water is dependant on the differences in hydraulic potential between two locations in the soil The rate of flow is equal to hydraulic conductivity multiplied by hydraulic head.
62
Limitations of Darcy's law
Steady flow - flux must remain constant Uniform medium - assumption Preferential flow - no account for horizons and a change in flow due to structure etc.
63
How can hydraulic conductivity be measured
Calculated using a permeameter, hydraulic head needs to stay constant Remember lab work.
64
Factors control Ksat
Porosity Tortuosity Pore size distribution - poiseuilles law - total flow rate is proportional to R4. A sand with large pores may have a higher Ksat than clay with small pore.
65
Measuring infiltration
Double ring infiltration-2 rings with water ponded inside, measurement of rate from inside ring, outside used to reduce lateral flow. Sprinkle infiltrometers-excess water is sprayed on the surface at a measured rate and runoff independently collected. Pop for catchments studies Tension disc infiltrometer-water held at tension. Determines unsaturated hydraulic conductivity Pressure ring infiltration.
66
Hydrophobicity: caused by leaching of hydrophobic compounds, such as aliphatic hydrocarbons from the litter and humus layers.
Huffman et al, 2001

Soil And Water (1 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions