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Introduction to Vadose Zone Hydrology
CE/ENVE 320 – Vadose Zone Hydrology/Soil Physics
Spring 2004
Course objectives
• CE/ENVE 320-03 provides theoretical and experimental
foundation for understanding and quantifying physical and
hydrological properties of soils and other porous media.
• The course covers key hydrological processes taking place at
or near the Earth’s surface, emphasizing mass and energy
exchange, transformation and transport in partially-saturated
porous media at multiple scales.
• Coupling with atmospheric processes and the role of plants in
the hydrological cycle will be studied.
• We will examine modern measurement methods and analytical
tools for interpretation of hydrological information.
• The course provides conceptual and practical basis for
addressing vadose-zone related science and environmental
engineering challenges.
Syllabus (Spring 2004)
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Instructor: Dani Or (CAST 313, 486-2768)
Time:
MW 4:30-6:00 pm (Lec.)
Location:
CAST 206 (and 105, 4 Lab sessions)
Lab Inst. - Jon Drasdis (CAST 203, 486-3211)
Office Hrs: M 2:00-3:00 pm
Text:
Grades:
Classnotes – Vadose Zone Hydrology/Soil Physics, by Or
D., J.M. Wraith, and M. Tuller will be available (PDF) to
registered students on the course webpage:
www.engr.uconn/edu/~environ/dani/courses/VDZ-320/
Supplemental book: Environmental Soil Physics, by: D. Hillel
• 35% on Homework assignments (due Monday)
• 15% on each of three exams (and quizzes)
• 15% on lab reports
• A>90%; B=80-89%; C=70-79%; D=60-69%; F<60%
• Lab reports are due beginning of the following lab session
Policies and expectations
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Use office hours or contact instructor for
assistance – PRIOR to last week of semester.
No late HW returns.
Exams are open book
Engineers and scientists are expected to use ALL
information available and make assumptions regarding
missing information - never “get stuck” due to lack of
information – check, estimate, approximate, and assume.
Pay attention to “rules of thumb” to develop a sense for
estimating properties to within an “order of magnitude”.
Check if results make sense – no negative volumes, please!
Use SI units to report results & HW (scientific currency).
Dimensional inspection - a key step to happiness !
Course content and schedule
Week 1 to 4 (Section 1):
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Physical Properties of Soils and Other Porous Media –
Units and dimensions, definitions and basic mass-volume
relationships between the solid, liquid and gaseous phases;
soil texture; particle size distributions; surface area; soil
structure. New addition – Clay behavior (Hillel Chapter 4)
Soil Water Content and its Measurement - Definitions;
measurement methods - gravimetric, neutron scattering,
gamma attenuation; and time domain reflectometry; soil
water storage and water balance.
Demo Lab #1 : Soil bulk density; water content measurement
methods -gravimetric, TDR, Neutron Probe.
Please mark your calendars - NO CLASS on February 4th (Wed.)
Course content and schedule
Week 1 to 4 (Section 1):
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Soil Water Retention and Potential (Hydrostatics) - The energy
state of soil water; total water potential and its components;
properties of water (molecular, surface tension, and capillary rise);
modern aspects of capillarity in porous media; units and
calculations and measurement of equilibrium soil water potential
components; soil water characteristic curves definitions and
measurements; parametric models; hysteresis.
New addition – Capillarity in angular pores and adsorption
Lab #2: Determination of SWC curves using pressure plates, flow
cells, and dew point psychrometer. Combining measurements and
fitting SWC.
Course content and schedule
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Water Flow in Porous Media – laminar flow, saturated and
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Soil-Plant-Atmospheric Relations – radiation and energy balances,
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unsaturated flow, hydraulic properties, infiltration.
evapotranspiration, evaporation from soil surface and groundwater.
Solute Transport in Soils – transport mechanisms, breakthrough
curves, solutions for steady flow, salinity balance.
Temperature and Heat Flow in Porous Media - soil thermal
properties; steady state heat flow; nonsteady heat flow; estimation of
thermal properties; engineering applications.
Soil Gaseous Phase and Exchange Processes – effective gaseous
diffusion; water vapor flow; gaseous fluxes and their measurement.
Questions/comments regarding the syllabus, policies, etc.?
Scope of Vadose Zone Hydrology (1)
• Soils are among the most complex systems found in
nature where physical, chemical, and biological processes
taking place simultaneously.
• Vadose zone hydrology/soil physics is concerned with the
application of physical principles to characterization of soil
properties and to understanding of processes occurring in
this life-supporting thin crust of the Earth surface.
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It has been estimated that globally, soil contains
approximately 2.6x1029 prokaryotic cells (compared to
1.2x1029 in ocean water and sediments); concentrated in
a relatively small volume on the earth skin (soil volume
1.2x1014 m3 vs 1020 m3 for open ocean) making the
unsaturated zone the richest compartment of prokaryotic
life on Earth (Whitman et al., 1998, PNS). (Additionally,
consider most vegetation and crops on Earth)
Where is the Vadose Zone?
The vadose zone
Vadose Zone Hydrology – Profile Scale
Scope of Vadose Zone Hydrology (2)
The study of physical properties of soils and other porous
media; particle and pore size distribution, water retention and hydraulic
conductivity, thermal capacity and conductivity, soil strength, etc.
The measurement, prediction, & control (manipulation) of
physical processes taking place in & through the vadose zone;
water infiltration & redistribution, solute & contaminant transport, heat flow, etc.
The study and control of physical conditions and processes
affecting water resources, plant growth, and remediation
activities concerning atmospheric influences at the top
boundary, and groundwater at the lower boundary; e.g., solar
radiation, precipitation, evapotranspiration, recharge capillary rise, etc.
(In the next few slides we illustrate some of the processes and
applications of vadose zone hydrology)
Agricultural Water Management
Knowledge of physical soil properties and processes is required
for agricultural soil water management (design of drainage
systems, irrigation scheduling).
Excess water in a coastal Area in Texas
Irrigated field in Southern Idaho
Importance for reducing soil erosion
Physical soil properties govern many
dynamic processes, such as erosion.
Knowledge of physical properties
allows estimation of erosion potential
and establishment of active measures
for prevention of soil erosion.
Soil erosion damage
Surface Runoff & Colloid-Facilitated Transport
Soil erosion and the presence of clay minerals enhance surface
runoff and associated transport of agrochemicals with the
sediment into surface and subsurface water resources.
Soil Water Management - Nutrients
Water running off agricultural fields carries sediment and
nutrients into streams and creeks.
Eutrophication
The transport of excess nutrients and sediment into water bodies
can cause algae blooms, resulting in the death of many aquatic
organisms.
Land use - Soil Compaction Management
Heavy harvest machinery, grazing, or recreational use often
lead to compaction of soils.
Knowledge of soil physical soil properties and processes is
required for management of our natural resources.
Skid trails from logs often initiate erosion.
Importance for Soil Compaction
Poor drainage in a compacted logging road.
Soil Compaction due to Recreational Use
Intensive recreational use of forest soils also leads to soil compaction.
Military land use and related issues
 Landmine detection and
clearing is critically
dependent on knowledge of
soil properties and
hydrological conditions in
the shallow vadose zone.
 Military land use and
trafficability rely on
knowledge of soil
properties and
hydrological conditions.
Importance for water resource management
Shrinkage cracks in dry clay soils, biological macropores, or
fracture networks in basalt may lead to fast preferential
transport of chemicals and contamination of drinking water
resources.
Importance for Engineering Applications
Certain soils and earth materials (e.g., clays) are often used for
engineering applications, such as containment of hazardous
waste sites or earth dams.
Clay Liners for Waste Isolation
Importance of Soil Physics – Engineering
Lack of knowledge of soil physical properties and processes
might lead to disastrous events like the failure of the Teton Dam
near Rexburg in 1976.
Teton Dam Failure – Flood in Rexburg
Watershed Studies of Runoff Production - Panama
● Watershed studies of runoff
production mechanisms
(Rio Chagres, Panama –
Prof. Ogden) – rely on
vadose zone hydrological
information (e.g., infiltration)
Contaminant transport - Hanford Site
The Hanford Site located at the Columbia River in southeastern
Washington is the world’s largest cleanup operation.
Nuclear waste left from the Manhattan project leaks through
corroded tanks and migrates towards the Columbia river.
Hanford Site
Bio- and Phytoremediation
• Stimulation of microorganism-based transformation by plant exudates and
leachates, and by fluctuating oxygen regimes.
• Slowing of contaminant transport from the vegetated zone due to adsorption
and increased evapotranspiration.
• Plant uptake, followed by metabolism or accumulation.
(http://www.wes.army.mil/el/phyto/ )
Advanced Life Support Systems in Space - NASA
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Behavior and distribution of liquids in
plant growth media under zero gravity
is essential for design of advanced life
support systems (ALS) part of NASA’s
future space missions.
O2
CO2
The International System of Units SI
All physical quantities are measured and expressed in units.
We will use the international system of units (SI system) for all
calculations throughout this course.
The SI system contains seven basic units for length, mass, time, electric
current, temperature, amount of substance, and luminous intensity.
Other physical quantities are expressed in derived units. Force, for
example, is expressed by a derived unit Newton (kgm x m/s2).
Table 1-1: Base Units in the Systeme International (SI) and their Prefixes
Dimension/Property
SI Unit
Symbol
Length
Meter
m
Mass
Kilogram
kg
Time
Second
s
Electric current
Ampere
A
Temperature
Kelvin
K
Amount of substance
Mole
mol
Luminous intensity
candela
cd
Derived SI-Units
VELOCITY: Rate at which position changes with time
SI Unit = [m/s]
Distance per Time
v
s
t
[ L]
 [L T 1 ]
[T ]
ACCELERATION: Rate of change of velocity with time
SI Unit = [m/s2]
Velocity per Time
v
a' 
t
[L T 1 ]
 [L T 2 ]
[T ]
FORCE: (Newton’s second law of motion)
SI Unit = Newton [nt] or [N]
Mass times Acceleration
F  m  a ' [M ]  [L T 2 ]
Derived SI-Units
PRESSURE:
SI Unit = Newton/m2 [nt/m2] = Pascal [Pa]
Force per Unit Area
F
P
A
[M LT 2 ]
 2 1

[
M
T
L ]
2
[L ]
WORK:
SI Unit = Newton m [nt m] = Joule
Force times Distance

M L
W  F  s   2  [ L]  M L2 T 2
T 

The International System of Units SI
Table 1-1 continued: Base Units in the Systeme International and their Prefixes
Fraction
Prefix
Symbol
Multiple
Prefix
Symbol
-1
deci
d
10
deca
da
-2
centi
c
102
hecto
h
-3
milli
m
103
kilo
k
-6
micro
µ
106
mega
M
-9
nano
n
109
giga
G
-12
pico
p
1012
tera
T
10
10
10
10
10
10
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A dimension is a qualitative expression of a physical quantity or an attribute. It
may be a basic dimension such as length [L], time [t], or mass [M], or a derived
dimension such as volume [L3], or density [ML-3].
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Dimensional inspection is an important step in verifying the validity of an
equation; the dimensions of all terms must be consistent.
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Writing the equation in dimensional form only, leaving out real values (numbers),
enables algebraic manipulation of dimensions, i.e., dimensions may be divided,
multiplied, and cancelled to simplify the dimensional equation in terms of basic
dimensions.
Dimensions and Unit Conversion
Example 1-1: Dimensions and Unit Conversion
Dimensions: Find the dimensions of pressure in basic units
Solution: Pressure is force divided by the area of its action. The dimensions of force are
-2
2
[MLt ] and those of area are [L ]. Thus, the dimensions of pressure are
F [MLt 2 ]
1  2
P 

[
ML
t ]
2
A
[L ]
Units: Convert a pressure of 2.7 kg/cm2 into SI units (Pa = N/m2)
kg  100 2 cm2  9.806 N 

  264762 Pa  264.7 kPa
2.7
 2.7
2
2 
2

kg
cm
cm  m


kg
http://www.digitaldutch.com/unitconverter/