GWE 1-9 Lem 1.pptx

What do you understand by the term
Ground water
 Equivalent terminologies: groundwater, subsurface
water, ground water
 Definitions
 Water occupying all the voids within a geologic stratum
(Todd, 1980)
 All the water found beneath the surface of the
ground (Bear and Verruijt, 1987)
 Practically, all the water beneath the water table (i.e.,
in the saturated zone) and above the water table (i.e.,
in the unsaturated zone, vadose zone, zone of
aeration) are called groundwater.
 Groundwater velocity is very small and depends on
local hydrogeologic conditions , 2 m/year to 2 m/day
are normal (Todd, 1980).

Introduction:
Ground water is commonly understood to mean water
occupying voids with in under ground geological stratum.
The study of Ground water hydrology is equally important of
surface water hydrology.
Out of 2.5% of world fresh water coverage 30% exist as
ground water(0.76 %)
Ground Water Hydrology is the sub division of hydrology
science that deals with occurrence movement distribution
and quality (Chemistry)of water beneath the earth surface .it
involves multi disciplinary scope of applications of biological
mathematical physics different sciences
Therefore, groundwater is very important in terms of
quantity and water use for drinking, even in some
countries for irrigation

Estimates of relative volumes of water various existence

Hydrologic Cycle
Hence Hydrologic cycle refers the constant movement
of water above, on and below the earth surface, ground
water is apart this complex dynamic flow.

 Practically, all groundwater constitutes part of the
hydrologic cycle.
 Sources of groundwater
 Natural recharge: precipitation, stream flow, lakes,
reservoirs, …, etc
 Artificial recharge: Excess irrigation, Seepage from
canals, man-made recharge, …, etc
 Discharge of groundwater
 Natural discharge: flow into surface water bodies
(streams, lakes, and oceans), springs (groundwater
flows to the surface), evaporation from soil and
transpiration from vegetation for near-surface
groundwater
 Artificial discharge: man-made pumping for water
supply (drinking water, irrigation, fishery, …, etc)

Chapter -2
Occurrence/ Existence /of ground water
Ground Water occurs in the subsurface in two broad
zones(vertical cross section)
Unsaturated zone/zone of aeration / vadose zone
Its immediately below the land surface
Voids are filled with water+ air.
Comprises 3 sub zones;
soil part, intermediate and the capillary fringe zone
 Saturated zone

Zones of Aeration and Saturation

 Infiltration
 Percolation
 capillary rise
 Ground water flow
 Seepage
Types of opening in
which ground water
occurs
Pores
Fractures, crevices or
joints
Solution channel,
caverns in lime stone
(karst water)

Groundwater is water, which originates from the infiltration of fluids through
the soil profile and accumulates below the earth's surface in a porous layer.
Porosity is the percentage of open void space in the subsurface material. It is
expressed as a percent.
When a rock is first formed by precipitation, cooling from an igneous melt
induration from loose sediments; or when a soil is first formed by weathering
of rock materials and possibly subsequent biological action, the new entity will
contain a certain inherent porosity known as primary porosity.
This porosity may later be reduced by cementation from precipitates from
circulating groundwater, or from compaction accompanying burial by later
sediments. However, fractures or solution cavities formed in the rock, or root
tubes or animal burrows in soils may later form and are known as secondary
porosity.
the total porosity of a sample will be the sum of the primary and secondary
porosities.
If all the pores in a rock are not connected, only a certain fraction of the pores
will allow the passage of water, andthis fraction is known as the effective
porosity.
Important Hydraulic Properties of Earth Materials and
Groundwater

 Specific yield
 Specific retention
Example
An undisturbed sample of medium sand weight 484.68g.The
core of the undisturbed sample is 6cm in diameter and 10.61
cm high. the sample is oven dried for 24hr at 110oc to remove
the water content. at the end of the 24hr, the core sample
weight 447.32 g. Determine the bulk density, void ratio,
porosity, and saturation percentage of the sample.

The dry weight Wd=447.32g total weight Wt=484.68
Total volume Vt=
The bulk density(density of solid and void together after drying
thus:)
assuming quartz is
predominant mineral in san

Aquifer An aquifer is defined by Davis and DeWiest (1966) as “The natural zone
(geological formation) below the surface that yields water in sufficiently large
amounts to be important economically.”
aquitard is rock material that is low in porosity/permeability. Fluid flow is not
good and the unit may often be termed a "cap rock", not allowing underlying
water to flow upward.
aquiclude is a unit of rock or layer of rock, which is impermeable to fluids. It acts
as a barrier to fluid flow. There probably are no true aquicludes.
Spring is where water flows out without the aid of pumping. It may be caused by
hydrostatic pressure (pressure pushing upward), or the intersection of the
pieziometric surface with the ground surface. Also referred to as an Artesian
System.
Types of Geological formations

Formation
nature
Can store water? Can transmit water?
Aquifer Pervious Yes Yes
Aquitard
＊
Semi pervious Yes Yes but slower than
that in an aquifer
Aquiclud
e
Semi pervious Yes No
Aquifuge Impervious No No

Contents
1. Definitions of aquifer
2. Types of aquifer
3. Hydraulic head
4. Important aquifer parameters /properties
5. Geological formation of an aquifer

 Aquifer, Aquitards, Aquicludes, and Aquifuges are a geological formation
or a group of formations that can/cannot contain water, and that water
can/cannot move within the formation
Formation nature Can store water? Can transmit water?
Aquifer Pervious Yes Yes
Aquitard＊ Semi pervious Yes Yes but slower than that
in an aquifer
Aquiclude Semi pervious Yes No
Aquifuge Impervious No No
＊Aquitard = leaky aquifer
Latin: Aqui  water; -fer  “to bear”, aquifer  “water bearer”
-tard  “slow”; -clude  “to shut or close”; -fuge  “to drive away”
(Todd, 1980)
Natural variation in permeability and ease of transitivity
the geological formation could be

Types of aquifer
 Confined aquifer: Artesian aquifer
an aquifer bounded from above and from below by impervious
formations (aquiclude or aquifuge)
 Unconfined aquifer (phreatic aquifer or water table aquifer): an
aquifer in which water table serves as its upper boundary
 Perched aquifer: An unconfined aquifer which has an
impervious layer of limited areal extent located between the
ground surface and the water table (of the unconfined aquifer)
Confining layer: a geologic formation that is impervious to water,
e.g., unconsolidated soils such as silt and clay; consolidated bed
rock such as limestone, sandstone, siltstone, basalt, granite, …, etc.
The latter rock formations can also be aquifers when only
consolidated formations are considered.
1. Definitions of aquifers
IT is a rock unit of or a formation that has a capacity to yield and transmit
a usable amount of water .

There are two (2) scenarios that may occur with
aquifers:
1. Confined Aquifer -- when an aquifer is bounded by two (2) aquitards
(one above and one below) An aquifer that is sandwiched in between
two impermeable layers or formations that are impermeable is calleda
confined aquifer if it is totally saturated from top to bottom
2. Unconfined Aquifer -- when an aquifer is not bounded on the surface
side by an aquitard so that fluids may flow freely above the aquifer.
The distribution of groundwater is present in several distinct layers or
zones:
a. Soil moisture zone -- usually top soil; much infiltration; much
organic material
b. Zone of aeration (Vadose Zone) -- mostly air but some interstitial
water
c. Capillary fringe -- transition between unsaturated and saturated
zone; top of aquifer
d. Zone of saturation (Phreatic Zone) -- pores completely saturated
with water; main aquifer storage zone

confined (or artesian) aquifer?
 Sealed off
 Transmits water
down from R.A.
 Water confined in
aquifer unless
drilled.
- Water under
hydrostatic
pressure.
- Water rises; well may
flow.

Flowing or Artesian Well Development

an unconfined aquifer
 They are not
sealed
off at any point.
 Recharge can occur
anywhere.
 Water at w.table
under atm
pressure.
 Must pump.

Zones of Subsurface Water
Zone of Aeration
 pores filled with
both air and water
 Water held against
gravity by surface
tension
 Soil water
 Zone of Saturation
 pores filled only
with water
 Water drained
through soil
under influence
of gravity.
 Ground Water

What is the configuration of
the water table?
R = Recharge area
Humid Area
Arid Area
R = Recharge Area

Configuration of Water Table
in a Humid climate

How do springs occur?
 Lateral diversion of flow
 Perching
 Fracture zones
E
E
E
E
E
E
E
e
j

Fundamental physical properties
 Six fundamental physical properties for describing
hydraulic aspects of saturated groundwater flow
in aquifers
 Three fluid properties
 Density, r (M/L3)
 Dynamic viscosity, m (M/LT) (or kinematic viscosity, m/r, L2/T)
 Fluid compressibility, b (LT2/M) (or 1/Pa)
 Three medium properties
 Porosity, n
 Permeability, k (L2/T)
 Matrix compressibility, a (LT2/M) (or 1/Pa)

Properties of an aquifer
 Pore space (voids, pores, or interstices): The portion of a
geologic formation that is not occupied by solid matter (e.g.,
soil grain or rock matrix).
 Effective or interconnected pore space: Pores that form a
continuous phase through which water or solute can move
 Isolated or non-inter connected pore space: Pores that are
dispersed (scattered) over the medium. These pores cannot
contribute to transport of matter across the porous medium.
Also known as dead-end pores.
 Saturated zone: Aquifers in which pore space is completely
filled with water.
 Unsaturated zone: Aquifers in which the pore space is filled
partially with liquid phase (water), and partially with gas
phase.
1. Porosity

Pore space and porosity
Schematic diagrams of various pore space
(After Bear and Verruijt, 1987)

Porosity is a function of the following factors
(a)Grain size distribution: soils with uniformly distributed grains
have larger porosities than soils with non-uniformly
distributed grains
(b)Grain shape: Sphere-shaped grains will pack more tightly and
have less porosity than particles of other shapes(granular)
(c)Grain arrangement: Porosities of well-rounded sediments
range from 26% (rhombohedral packing) to 48% (cubic
packing)
Clays, clay-rich or organic soils have very high porosities because:
 Grain shapes are highly irregular
 Dispersive effect of the electrostatic charge on the surfaces of
certain book-shaped clay minerals causes clay particles to be
repelled by each other, resulting in high porosity.

Unconsolidated deposits (sediments) Porosity
(%)
Gravel 25-40
Sand 25-50
Silt 35-50
Clay 40-70
Rocks
Fractured basalt 5-50
Karst limestone 5-50
Sandstone 5-30
Limestone, dolomite 0-20
Shale 0-10
Fractured crystalline rock 0-10
Dense crystalline rock 0-5
(After Freeze and Cherry, 1979)

 Porosity of rocks (Two porosities)
 Primary: pore space between grains
 Secondary: pore space caused by fracturing
 Sedimentary rocks (Fetter, 1994): Formed by sediments by
digenesis. Sediments are products of weathering of rocks or
chemically precipitated materials. Changes in sediments due
to overlying materials and physiochemical reactions with fluid
in the pore space result in pore space variation.
 Compaction: porosity is reduced
 Dissolution: porosity is increased
 Precipitation (e.g., cementing materials such as
calcite, dolomite, or silica): porosity is reduced

 Limestone and dolomites: Formed respectively by calcium
carbonate and calcium-magnesium carbonate, which were
originally part of an aqueous solution. These rocks may be
dissolved in a zone of circulating groundwater, resulting in
huge caverns that have sizes as large as a building. For
example, the caverns at Carlsbad, New Mexico.
Bottomless Pit Hall of Giants The Big Room

a.Specific yield, Sy
 The ratio of the volume of water that drains from a
saturated aquifer due to the attraction of gravity to the total
volume of the aquifer. This is also called gravity drainage.
b.Specific retention (Sr)
 The volume of water retained in an aquifer per unit area per unit
drop of the water table after drainage has stopped, which is hold
between soil particles by surface tension. Hence, the smaller the
particle size, the larger the surface tension and the larger the
specific retention
 Specific retention is responsible for the volume of water a soil can
retain against gravity drainage.
 Maximum specific yield occurs in sediments in the medium-to-
coarse sand-size range (0.5 to 1.0 mm).

Schematic representation of storativity in confined and
unconfined aquifers
Aquifer remains
saturated in spite of
the decline of
piezometric surface
Aquifer above the original
water table becomes
unsaturated as the water table
declines to a new level

2. Hydraulic conductivity
 Hydraulic conductivity, K [L/T]: It is measurement of
the ease of a particular fluid (Water) passing through
the pore space of a porous medium (i.e., conductive
properties of a porous medium for a particular fluid)
(Hubbert, 1956).
 The proportionality constant in Darcy’s law, which
depends on medium and fluid properties i.e. grain
size, density and viscosity of fluid.
K=kikw K=coefficient of Permeability
Ki = intrinsic permeability (depending rock property)
KW =permeability depending on fluid property

Hydraulic conductivity
 Determination of hydraulic conductivity
 Theoretical calculation
 ki = Cd2  K=kirg/m
 Few estimates are reliable because of the difficulty of
including all possible variables in porous media
 Laboratory measurements
 Permeameter (Fetter, 1994, Sec. 4.5)
 Constant head experiment
 For non cohesive sediments, such as sand and rocks because of
the required duration for experiment is short
 Falling head experiment
 For cohesive sediments with a low permeability, such as clay and
silt
 Field measurements
 Pumping test
 Tracer test

Example: (Fetter, 1994) The intrinsic permeability of a
consolidated rock is 2.7  10-3 Darcy. What is the hydraulic
conductivity for water at 15C?
Solution :
For water at 15C, ( 
3
0.999099 /
0.011404 / 0.011404 1.1404
g cm
g cm s poise cp
r
m

  
Also, g = 980 cm/s2, and 1 darcy = 9.87  10-9 cm2. Hence
( 
( 
3 9 2 3 2
6
2.7 10 9.87 10 / 0.999099 / 980 /
0.011404 /
2.28 10 /
darcy cm darcy g cm cm s
k g
K
g cm s
cm s
r
m
 

    
 
 
It is strongly advisory to perform the multiplication with units
included.

(Aquifer) (Aquitard, aquiclude) (Aquifuge)

 Heterogeneity and anisotropy
 Heterogeneity: K(x1)  K(x2), x1  x2
 Layered sediments, e.g., sedimentary rocks and unconsolidated
marine deposits
 Spatial discontinuity, e.g., the presence of faults or large-scale
stratigraphic features
 Evidences from stochastic studies
 Hydraulic conductivity tends to be log-normally distributed
 Y = log10K has standard deviation in the range 0.5 ~1.5, meaning K
values in most geological formations show variations of 1 – 2
orders of magnitude (Freeze, 1975)
-------------------------------------------------------------------------------------------------------------------------------------------------------------
Freeze, R. A., A stochastic-Conceptual Analysis of One-Dimensional Groundwater Flow in Nonuniform Homogeneous Media, Water
Resources Research, Vol. 11, No. 5, pp.725-741, 1975.

 Anisotropy
 Hydraulic conductivity depends on the direction of
measurement, e.g., Kx  Kz
 Principal directions of hydraulic conductivity: the directions at
which hydraulic conductivity attains its maximum and
minimum values, which are always perpendicular to one
another.
 Four cases
 Homogeneous and isotropic :
 Homogeneous and anisotrpic :
 Heterogeneous and isotropic
 Heterogeneous and anisotropic

3.Transmissivity
 Definition: The rate (Q) at which water is
transmitted through a unit width (Dy = 1) of
aquifer under a unit hydraulic gradient (h=1).
In groundwater hydrology, it is usually
denoted as T
T Kb

 Transmissivity is well defined for the analysis of well
hydraulics (Chapter 4) in a confined aquifer in which the
flow field is essentially horizontal and two-dimensional, in
which b is the (average) thickness of the aquifer between
upper and lower confining layers
 It is, however, not well defined in unconfined aquifer but is
still commonly used. In this case, the saturated thickness is
the height of the water table above the top of the underlying
aquitard (impervious layer) that bounds the aquifer
in which b is the “saturated thickness” of aquifer
( 
( 
h
T
h
Kb
y
Q
y
b
h
K
A
h
K
qA
Q






D
D








Transmissivity
Impervious
b Confined aquifer
Confining layer
T = Kb
Schematic representation of the definition of transmissivity
(Adapted from Freeze and Cherry, 1979)
Note that transmissivities greater than 0.015 m2/s represent good
aquifers for water well exploitation (Freeze and Cherry, 1979)
Impervious
b
Unconfined aquifer
Water table

4. Storage capacity
 Specific storage (specific storativity), Ss (1/L)
 Definition: the amount of water per unit volume of saturated
aquifer released from (or added to) storage per unit decline (or unit
rise) in hydraulic head
water
s
aquifer
V
S
V h
D

 D
 Storativity (Storage coefficient), S: is the amount of water per
unit surface area of saturated aquifer released from (or added to)
storage per unit decline (or unit rise) in hydraulic head normal to
that surface
 Similar to transmissivity, storativity is developed primarily for the
analysis of well hydraulics in a confined aquifer
water
s
aquifer
V
S S b
A h
D
 
D
b is the saturated thickness of the aquifer

Storage capacity
 Storativity of a confined aquifer
 Water released from a confined aquifer is caused by two
mechanisms:
1. Expansion of water due to decline of hydraulic head and
2. Release of pore water due to compaction of soil skeleton that is
again induced by the decline of hydraulic head
 In general, storage coefficients for a confined aquifer are
small, in the range of 0.005 to 0.00005 (Freeze and
Cherry, 1979)

Storage capacity
 Storativity of an unconfined aquifer
 Water released from the storage in unconfined aquifer :
 Primary release: storage from the decline of water table, which is
generally known as specific yield, Sy
 Secondary release: the expansion of water and expel of water
from aquifer compaction
 S = Sy + hSs, h is the saturated thickness of the unconfined
aquifer
 Specific yield of an unconfined aquifer is several orders of
magnitude greater than hSs. The usual range of Sy is 0.01 ~ 0.30
(Freeze and Cherry, 1979)
 It is customarily to approximate the storativity of an unconfined
aquifer by its specific yield.

7.Aquifer storativity
 Storativity
 The amount of water per unit surface area of saturated
aquifer released from (or added to) storage per unit
decline (or unit rise) in hydraulic head normal to that
surface
 Mechanisms
 Elastic expansion of water
 Compaction of solid matrix
 Drainage from pore space between the initial and final
water tables (primarily for unconfined aquifers), i.e.,
specific yield Sy
 Used in two-dimensional, transient groundwater flow
equations
 Definition (for both confined and unconfined aquifers)
( 
( 
( 
water
s
aquifer
b x,y
s
b x,y
V
S S b
A h
S x,y,z dz
D
 
 D


2
(for constant aquifer thickness)
(for variable aquifer thickness)
(Note again that storativity is dimensionless)

 S for confined aquifers
 510-5 ~ 510-3 (Freeze and Cherry, 1979)
 10-4 ~ 10-6 in which 40% from expansion of water and
60% from the compaction of the medium (Bear and
Verruijt, 1987)
 Sy for unconfined aquifers: 0.01 ~ 0.3 (Freeze and
Cherry, 1979)
 Sy is sometimes called effective porosity
 n = Sy + Sr

. Hydraulic head
 Hydraulic head, h (L): For incompressible fluids (density is
constant) it is the sum of potential energy and pressure
energy per unit weight of water. Sum of elevation head (z)
and pressure head (p/g)
p
h z

 
A

z
p/
h
Schematic of hydraulic head, pressure head,
and elevation (potential) head
Arbitrary datum : z = 0
(Laboratory
manometer)
(2)
 
( ( 
  m
N
Nm
Water
of
Weight
Energy
Potential
z
m
N
Nm
s
m
m
Kg
m
N
g
p
p
m
N
Nm
water
of
weight
energy
h










2
3
2
/
/
/
r


Hydraulic head at a point in a groundwater system is expressed as
h = Z + P/ρg
h = Z +Ψ
where Z is the elevation head or the distance of the reference point above a datum plane
(normally mean sea level), P is fluidpr essure at the point exertedb y the column of water
above the point, and ρg is the specific weight of water, γ , or more simply stated
Hydraulic head

Henry Philibert
Gaspard Darcy
(1803–1858)
Figure illustrating tube experiments of Henry Darcy
From experiments Darcy showed that
‘v’ is α to hB-hA =(-Δh) when Δl is held constant
inversly proportional to Δl when hB-hA is held constant
v α -Δh/Δl
v =-KΔh/Δl
Where v=Q/A (specific discharge through the cylinder), K is hydraulic conductivity or
coeifficent of permeability. Permeability is how readily a fluid can flow through a material.
Often referred to as "connected pore space".
Q =-K(Δh/Δl)A=-KiA [:i= Δh/Δl]
Dimensions Q[L3/T], A[L2], v has dimensions of velocity[L/T]

The flow of groundwater is taken to be governed by Darcy’s law, which states that the
velocity of the flow is directly proportional to the hydraulic gradient.
A similar statement in an electrical system is Ohm’s law and in a thermal system, Fourier’s
law. The grandfather of all such relations is Newton’s law of motion.
In that year, Henry Darcy published a simple relation basedon his experiments on the flow of
water in vertical Sand filtres in Les Fontaines Publiques de la Ville de Dijon, namely , v = Ki
= −K dh/dl
Some Similarities of Flow Models

‘v’ has the dimension of velocity and is called Darcian velocity. This term or its
usage is not the same as the true average linear velocity or average pore velocity
or seepage velocity of flow through a porous medium; the latter property is given
as porevelocity = q/ne
where ‘ne’ is the effective porosity
Q as the total volume of flow per unit time through a cross-sectional area A, Darcy’s law
takes the form
Q = Av = -AKi = −AKdh/dl
Hubber (1956) pointed out, K (hydraulic conductivity or coeifficent of permeability) is a
function of the medium and the fluid.
By experimenting darcy’s experimental setup with water and molasses as a fluid
Specific discharge ‘v’ is very low experiments with molasses as fluid compared to
water
how to describe the conductive properties of a porous medium independently from the
flowing fluid?
Ans: Further experiments with ideal porous media

Experimental observation
 Carried out with ideal porous media considering uniform glass beds of diameter ‘d’.
 Various fluid of density ‘ρ’ and dynamic viscosity ‘µ’
 Under constant hydraulic gradient dh/dl
vα d2
vα ρg
vα 1/µ
vα dh/dl
v=-(Cd2 ρg/µ)(dh/dl)
K= Cd2 ρg/µ
K= kρg/µ [where ρ,µ are functions of fluid k= Cd2]
k is the intrinsic or specific permeability
 Intrinsic permeability is strictly a function of the medium and has nothing to
do with the temperature, pressure, or fluidpr operties of a particular
fluidpassing through the medium. It is commonly measured in terms of the
darcy, after Henri Darcy who developed the relationship known today as
Darcy’s Law
1 darcy = [(1 centipoise × 1 cm3/sec)/1 cm2]/(1 atmosphere/1 cm)

Aquifer A : Phreatic
Aquifer B : Confined
Aquifer C : Confined
leakage direction :
from aquifer B to C
leakage direction :
from aquifer B to A
GWLB
GWLC
WB1
WB2
WC1
WA
piezometric surface B :
determined by GWLB,
and water levels at WB1
and WB2 piezometric surface C :
determined by GWLC,
and water level at WC1
The same
aquifer (e.g,
aquifer B) can
be phreatic,
confined, leaky,
or artesian
depending on
the domain of
interest

 Piezometric surface or Potentiometric surface: an
imaginary surface connecting the water levels of a
number of observation wells tapping into a confined
aquifer
 Note that we use water table instead of piezometric
surface for unconfined aquifers
 Artesian aquifer: a confined aquifer whose piezometric
surface is above the ground surface (i.e., water comes
out automatically from a well in an artesian aquifer)
 Double porosity aquifer
 For fractured rocks
 Matrix blocks: low permeability, high storativity
 Fractures: high permeability, low sotrativity
 How it could be

Hydraulic head
 Compressible fluids (density varies with fluid pressure)
 Fluid potential: the energy that is required to change a unit mass
of fluid from the initial state to a new state by varying an
appropriate state variable like:
 Elevation potential: by raising a unit mass of fluid from elevation
0 to z
 Kinetic potential: by accelerating a unit mass of fluid from
velocity 0 to v
 Pressure potential: by increasing pressure of a unit mass of fluid
from p = 0 to p
z
h
p/
Ground surface
Datum z = 0
Piezometer

Laboratory Measurement ofHydraulic Conductivity
constant head permeameter, the hydraulic conductivity obtained from Darcy’s law is
The falling head permeameter, the hydraulic conductivity is obtained by equating

Laboratory test for hydraulic conductivity
1. Constant Head Permeameter
 Basically, redo Darcy's
experiments:
Darcy's Law
Q = KAxc[- Dh/L]
Rearrange, solve for K
K = –[QL] / [AxcDh]
L
Continuous
Supply
Overflow
Volume/ti
me
= Q
Dh
Cross-Sectional Area,
A

Measuring K
Falling Head Permeameter
Stand pipe w/
cross-sectional
Area a
Head falls from h0 at
t0 to h1 to t1
Sample w/cross-sectional
Area Axs
L
h0
h1
Datum: z = 0; P = 0

Field Measurement ofthe Hydraulic Conductivity
Pumping tests
value of K (on a scale of 10 to 103 m) rather than the almost punctual information
(on a scale of 10−2 to 10−1 m) obtained by laboratory tests
Using a dye such as fluorescein or a salt such as calcium chloride can also be used.
If there is a drop of water table h in a distance L between the injection test hole and the
observation bore hole and t is the observed travel time between the two bore holes, the
hydraulic conductivity is obtained by
Tracer tests
n is the porosity of the material

Check list
 Existence of G.W (saturated zone un saturated zone)
 Geological formations(aquifer ,aquitard, aquifuge,
aquiqluid)
 Aquifer
 Definition ,type of aquifer
 Ground water flow parameters such as, porosity specific
yield, specific retention, hydraulic
conductivity(permeability),hydraulic head, transitivity,
storativity, specific storativity

Chapter-3
Ground Water movement
1. Darcy’s law
2. Hydraulic conductivity
3. Aquifer flow and transitivity
4. Flow anisotropic aquifer
5. Ground water flow directions
6. General flow equation

The nature of G.W moment is invariable and governed by hydraulic principles.
G.W moves through the sub surface from areas ( greater hydraulic head to
lower hydraulic head). the rate of the G.W flow movement depends
Slope hydraulic head
Intrinsic aquifer
Fluid property
The theory to express G.W movement established by French Hydraulic Engineer
Henry Darcy first published 1856.the result of his experiment define the basic
empirical principle of ground water flow.
The law stated as “the flow through a porous media is proportional to the area of
Normal flow direction (A) ,the head loss (hL) and inversely proportional
to the length (L) of the flow path.”
His apparatus consisted of sand filled column with an inlet and out let
piezometers measuring hydraulic head the sample was saturated and steady
flow of water was forced through at a discharge rate
Q ~ h and Q ~1/L and from continuity Q ~ A
And thus Q ~ h.A/L
Introducing the proportionality constant K,
Q = -K.h/L.A -----------Darcy Equation
And Expressed in general terms as Q = KAdh/dl

Darcy's experiment, 1856
Datum (z = 0)
h2
h1
l
Q
m3/s
Dh = h2 – h1
Sand column

Darcy's experiment, 1856
Datum (z = 0)
h2
h1
l
Q
m3/s
Dh = h2 – h1
Soil Orientation
Does Not Matter
Sand column

Q is proportional to Dh
Q
A
Q is proportional to sample cross
sectional area, Axs
Q is inversely proportional
to sample length, l
Q
L
Dh
Q

Darcy’s Law
 Combine and insert a constant of proportionality
Q = –K Axc[ Dh/l]
 Axc = sample cross-sectional area [m2]
 perpendicular to flow direction
 K = hydraulic conductivity [m/s]
 Dh/l = hydraulic gradient [-]
 Sometimes written as Q/A = q = –K[Dh/l]
 Where q = specific discharge. “Darcy velocity”
 Hydraulic gradient often written as a differential, dh/dl
Specific Discharge /Dar cy Flux /Darcy Velocity
 It is the discharge Q per cross-section area, A. q= .
Taking the limit as 0 i.e.

D
D


h
k
A
Q
dl
dh
k
h
K
it 

D
D


D

 0
lim

D

D

Darcy’s Law - Units
 Q = -KAxc[dh/dl]
 Solve for K:
Where:
 dh/dl is dimensionless
 Q  [m3 s–1]
 Axc [m2]
 Therefore,
dh
A
Qdl
K
xc

Since the fluid we consider most
frequently (certainly in this
course) is water, we almost
always will be using hydraulic
conductivity (K)


























s
m
m
m
m
s
m
K 2
3
1

K is a property of the porous material
Interstitial Velocity
actual
n
a
A
Q
Q
Q
Q
V





.........
3
2
1
n
A
Q
Va
*

The Darcy velocity (v) or the specific discharge (q) assumes that, flow
occurs through the entire x-section of the material without regard to solids
& pores. Actually, the flow is limited to the pore space only so that is the
average interstitial velocity
va>v
Effect of Geologic Material
Q = –KAxc[dh/dl] •Re-run experiments with different geologic materials
•e.g., grain size
•General relationship still holds – but –
•Need a new constant of proportionality (K)

Effect of Fluid Properties
•Re-run experiments with a different fluid
•e.g., petroleum, trichloroethylene, ethanol
•General relationship still holds – but –
•Need a new constant of proportionality (K)
Q = –KAxc[dh/dl]
K is a property of the fluid
Example
Afield an unconfined aquifer is packed in test cylinder. the length
and the diameter of the cylinder are 50cm and 6 cm respectively.
the field sample is tested for a period of 3 min under a constant
head difference of 16.3 cm. As a result 45.2cm3 of Water is
collected at the outlet. In addition the sample has median grain
size of 0.037cm and a porosity of 0.3.the test is conducted using
pure water 20oc.Determined the hydraulic conductivity of aquifer
sample, Darcy’s velocity, interstitial velocity, and assess the
validity of Darcy’s law(k=1.634cm/min, 23.54m/day v=7.67m/day
va=25.6m/day

Example
Afield sample of medium sand with a median grain size 0.84 mm
will be tested to determine .The hydraulic conductivity using a
constant head permemeater .the sample has length of 30cm .Dia
of 5cm.for pure water at 20oc,estimate the range of piezometeric
head difference to be used in the test if the representative
hydraulic conductivity of sand medium is12m/day. Take Reynolds
No=1
Example
An unconfined aquifer consist of three horizontal layers, each
individual isotropic. the top layer has a thickness of 10cm an
hydraulic conductivity of 11.6m/day .the middle layer has a
thickens of 4.4m and a hydraulic conductivity of 4.5 m/day . the
bottom layer has thickness of 6.2m and hydraulic conductivity of
2.2m/day. Compute the equivalent horizontal and vertical
hydraulic conductivities.

Validities of Darcy law
In general the Darcy’s law holds well for
 i) Saturated & unsaturated flow.
 ii) Steady & unsteady flow condition
 iii) Flow in aquifers and aquitards.
 iv) Flow in homogenous & heterogeneous media v) Flow in isotropic & an
isotropic media.
 vi) Flow in rocks and granular media.
 Vii)Darcy’s law is valid for laminar flow condition as it is governed by the
linter law.
In flow through pipes, it is the Reynolds number(R) to distinguish b/n
laminar flow & turbulent flow.
m
rvD
force
visouse
force
Inertial
NR 

For the flow in porous media,
v is the Darcy velocity
D is the effective grain size (d10) of a
formation/media. D10 for D is merely an
approximation since measuring pore size
distribution a complex research task
NR < 1
and does not go beyond seriously up to NR =10.

Intrinsic Permeability - Ki
 Separate the effects of the fluid and the porous medium
 K = (porous medium property) x (fluid property)
 Porous medium property: Ki = intrinsic permeability
 Essentially a function of pore opening size
 Think of it as a 'friction' term
 K= Ki x (fluid driving force/fluid resisting force)
 Fluid driving force = specific weight
 Fluid resisting force = dynamic viscosity
K = Ki *
Hydraulic Conductivities- K=Kw*Ki
[rg/m]

Intrinsic Permeability - Units
 Write as: Q = –Ki(rg/m)Axc[dh/dl]
 Solve for Ki
Where:
 Q  [m3 s–1]
 Axc [m2]
 r  [kg m–3]
 g  [m s–2]
 m  [kg m–1 s–1]
 Therefore,  
2
2
3
2
3
1
m
m
m
m
s
kg
m
m
s
m
kg
s
m
Ki 












































gdh
A
dl
Q
K
xc
i
ρ
μ

Magnitude of Intrinsic Permeability
 (rg/m) is a large number
For water at 15 oC, rg/m =
999.1 x 9.81/0.0011 = 8,910,155 [1/(m-s)]
 If K = 1 m/s then
Ki = K/(rg/m) = 1.12x10-7 m2
 Therefore we usually use a smaller unit –
1 Darcy = 9.87x10-9 cm2
 This course: typically use hydraulic conductivity
(K)
Contaminant transport, petroleum geology: Ki is important

Effect of Temperature
 Density and viscosity (r and m) for water are a
function of temperature
 K is therefore a function of temperature, but
 Ki is NOT a function of temperature
 More fundamental unit controlling flow

Effect of T on K
K = Ki(rg/m)
0.00E+00
2.00E+06
4.00E+06
6.00E+06
8.00E+06
1.00E+07
1.20E+07
1.40E+07
0 5 10 15 20 25 30 35
Temperature, Celcius
r
g
/m

m-s



Estimating K, Ki
Empirical Relations to Grain Size
 Where K is hydraulic
conductivity in cm/sec
 d10 is the effective grain
size
 10%of the soil by weight is
finer in grain size, 90% is
coarser
 C is an empirical
coefficient
Soil Type C
Very fine sand, poorly sorted 40-80
Fine sand with appreciable fines 40-80
Medium sand, well sorted 80-120
Coarse sand, poorly sorted 80-120
Coarse sand, well sorted, clean 120-150
K is proportional to
the square of grain
size
Hazen's Formula
K = C (d10)2

Kozeney (1927)
Where Ki = intrinsic permeability (in darcies); C = an
empirical constant ~0.5, 0.562, & 0.597 for circular,
square, and equilateral triangular pore openings; n =
porosity; S* = specific surface - interstitial surface areas
of pores per unit bulk volume of the medium.
Kozeny-Carmen Bear (1972)
Where K = hydraulic conductivity; ρw = fluid density; μ
= fluid viscosity; g = gravitational constant; dm = any
representative grain size; n = porosity











180
)
1
(
2
2
3
m
w d
n
n
g
K
m
r
2
*
3
/ S
Cn
Ki 

Constant Head Permeameter Test Protocols
 Good for relatively coarse grained material with
relatively high hydraulic conductivity
 Keep Dh at reasonable field conditions
 (< 1/2 L)
 Be certain that no air is trapped in the sample
 Air bubbles will act as impermeable lenses
 Fill slowly from the bottom to force air upwards
 De-gas water

Constant Head Permeameter Test Design
Design test, so all parameters can be
measured accurately
Design test, so it can be conducted in a
reasonable amount of time

Constant Head Permeameter Test Design
 K = –QL / [ADh] = –(Vol/time)*L / [ADh]
 Solve for time = –(L*Vol) / [KADh]
 Trial Design:
 L = 10 cm long
 Axs = 5 cm2
 Head difference (Dh) = – 5 cm
 K = 10-1 cm/sec (~ coarse sand)
 Volume collected = 100 ml
 Time = 10x100/(0.10x5x5) = 400 s

Constant Head Permeameter /Test Design –
Effect of Grain Size/
 Example:
 L = 10 cm long
 Axs = 5 cm2
 Head difference (Dh) = – 5 cm
 K = 10-1 cm/sec (~ coarse sand)
 Volume collected = 5 ml
0.01
0.1
1
10
100
1000
10000
0 0.2 0.4 0.6 0.8 1 1.2
grain size (mm)
time
for
completion
of
constant
head
test
(minutes)

Falling Head Permeameter Analysis
 Apply to fine grained soils
 Constant head permeameter test inaccurate,
lengthy
 Mass balance – standpipe
Q = dV/dt = a (dh/dt)
 Darcy’s Law – sample
Q = –KAxs(h/L)
 Set Q equal
a (dh/dt) = –KAxs(h/L)
Set datum at outlet
Therefore, houtlet = 0 and
Dh = houtlet – h = –h
At t = to
Dh = houtlet – ho = –ho
At t = t1
Dh = houtlet – h1 = –h1

Falling Head Permeameter Analysis
 Combine mass balance and Darcy’s Law
a (dh/dt) = –KAxs(h/L)
 Separate variables and integrate

 

1
1 t
t
xs
h
h o
o
dt
aL
KA
h
dh
aL
t
t
KA
h
h o
xs
o )
(
ln 1
1


1
1
ln
)
( h
h
t
t
A
aL
K o
o
xs 


Falling Head Permeameter Test Design
 Solve for time =
 Trial Design:
 L = 10 cm
 Axs = 10 cm2
 Stand pipe a = 0.5 cm2
 ho = 20 cm; h1 = 19 cm
 K = 10-3 cm/sec (~ fine sand with silt)
 Time =
1
1 ln
h
h
KA
aL
t
t o
xs
o 

s
6
.
25
19
20
ln
10
001
.
0
10
5
.
0
1 



 o
t
t

Consider a falling head test similar to that we just looked at above. The
head initially starts at 25 cm above the top of the sample. Let's
calculate the length of time it takes for various increments of change
as the test proceeds.
Given:
A = 10 cm2, a = 1 cm2, K = 10–4 cm/sec, L = 10 cm
time = (aL / [KA] ) * ln (ho/h1)
a) from 25 to 24 cm
t = 1 x 10 /(10 x 10–4) x ln (25/24)
t = 408.2 sec (6
.80 min)
b) from 16 to 15 cm
t = 645.4 sec (10.76 min)
c) from 6 to 5 cm
t = 1823.2 sec (30.39 min)
d) from 2 to 1 cm
t = 6931.5 sec (115.5 min)
How long does the 1st cm take?
How long does the 10th cm take?
L
ho
h1

0
20
40
60
80
100
120
140
0 5 10 15 20 25 30
head
time
to
fall
1
cm
The time required to fall a given distance increases
exponentially as head decreases. This is a characteristic shape
for many physical phenomena - where else have you seen this
shape curve????
Another way to think of this same falling head scenario is
to think of Q decreasing with time as driving force
(energy) decreases.

Example of the use of Darcy's Law
w =50 m
h = 25 m
L = 100 m
Pool
h = 20 m
How much water is flowing from the pool into the river per
second over a 50 m stretch?
Dh = –5 m (head decreases in the direction of flow)
l = 100 m
Dh/l = –0.05
Axc = b x w = 2 m x 50 m = 100 m2
K = 10–4 cm/sec
Q = –10–4 cm/sec x 100 m2 x 1002 cm2/m2 x (–0.05) = 5 cm3/s
(114 gal/d)
River
Q = –KAxs( Dh/L)
b = 2 m
K = 10–4 cm/sec
PERPENDICULAR to
the direction of flow!

1.Tracer test
 Field determination of hydraulic conductivity can be made by
measuring the time interval for a water tracer to travel b/n two
observation wells or test holes. The tracer can be a die such as
sodium fluorescing or salt
va = Kh/(nL) But va = L/t K= nL2/ht
limitations.
* The holes need to be close together; otherwise, the travel time interval can
excessively be long. For this requirement, the value of K is highly localized.
* Unless the flow direction is accurately known, the tracer may miss
the d/s hole entirely. Multiple sampling holes may help, but costly.
* If the aquifer stratified with layers having different hydraulic conductivities, the
first arrival of the tracer will result in conductivity considerably larger than the
average for the aquifer
Field Test for hydraulic conductivity

 Example
If the water level in two observation wells 20m apart are 18.4 and
17.1m.tracer injected in the first well arrives at the second
observation well in 167 hour compute hydraulic conductivity of the
unconfined aquifer given porosity of formation 0.25,
Ans: k=11.1m day

 Measurement procedure
1) Drilling of the hole
2) Removal of the water from the hole
3) Measurement of the rate of the rise
4) Computation of the hydraulic conductivity from the
measurement data
2. Auger hole method

3. Pumping test well method
The most reliable method of estimating aquifer hydraulic
conductivity is the pumping test of wells. Based on observations of
water levels near pumping wells an integrated K value over sizable
aquifer section can be obtained.
Transmissivity (T)
 The rate at which water is transmitted through a unit width of aquifer
under a unit hydraulic gradient
 Our last calculation (flux per unit width per unit hydraulic gradient)
 A common unit in hydrogeology
 Q = –KAxs(Dh/l) Axs = b x w
 Q = –K(b x w)(Dh/l) divide both sides by w
 Q/w = –K(b )(Dh/l) divide both sides by –Dh/l
 Q/w/(–Dh/l) = Kb
T = Kb

Transmissivity (T)
 For confined aquifers, b is the aquifer thickness
(may vary in space)
 For unconfined aquifers, b is not as well defined,
since it can also change with position and through
time
 use b as the saturated thickness
 Alternate way of expressing Darcy's Law
 Q = –KAxs(Dh/l)
 Q = –K(b x w)(Dh/l)
 Q = –Tw(Dh/l)
 w is the aquifer width (horizontal dimension
perpendicular to flow)
 Units: (volume/time)/length (gallons/day/foot) or
 Units: length2/time [m2/s]

Gradients in Hydraulic Head
 We measure gradients in
head using piezometers
 We can map these as
shown
 We often observe
changes in head gradient
 What aquifer properties
can cause changes in
these gradients?
190
180
150
100
High Gradient
Low Gradient
Flow
Hydraulic gradient = Dh/l

Head Gradient
 Head profile for homogeneous material
 Slope is constant
Flo
w
DhT

Effect of K on Change in Head Gradient
 Length, L, from A to B and B to C is same
 Width, w,  to the page is constant
 Thickness, b, at A, B & C is the same
 Q1 = Q2 by continuity (mass balance)
 Let K2 = 2K1
 How does head vary? (What is the profile?)
Flo
w
A B C
aquifer 1
low K
aquifer 2
high K
Q1 Q2

Head Profile (Effect of K)
 By continuity, Q1= Q2
 Write Darcy’s Law
–K1A1 (Dh/l)1 = –K2A2 (Dh/l)2
 Cancel like terms, A, l
 Substitute K2 = 2K1
K1 Dh1 = K2 Dh2 = 2K1 Dh2
 Cancel K1; therefore,
Dh1 = 2 Dh2
 Determine Dh1 and Dh2
DhT = Dh1 + Dh2 = 2 Dh2 + Dh2 = 3 Dh2
Dh2 = DhT /3
Dh1 = 2 DhT /3
Flow
A B C
aquifer 1
low K
aquifer 2
high K
Q1 Q2

Change in K can cause Change in Head Gradient
Head loss is
greater in low K
unit
Flo
w
A B C
aquifer 1
low K
aquifer 2
high K
DhT /3
2 DhT /3

Effect of b on Change in Head Gradient
 Length, L, from A to B and B to C is same
 Width, w,  to the page is constant
 Hydraulic conductivity, K, is the same
 Q1 = Q2 by continuity (mass balance)
 Let b2 = 2b1; therefore A2 = 2A1
 How does head vary? (What is the profile?)
Flo
w
A
B C
aquifer 1
Small b
aquifer 2
Large b

Head Profile (Effect of b)
 By continuity, Q1= Q2
 Write Darcy’s Law
–K1A1 (Dh/l)1 = –K2A2 (Dh/l)2
 Cancel like terms, substitute A2 = 2A1
A1 Dh1 = A2 Dh2 = 2A1 Dh2
 Therefore,
Dh1 = 2 Dh2
 Determine dh1 and dh2
DhT = Dh1 + Dh2 = 2 Dh2 + Dh2 = 3 Dh2
Dh2 = DhT /3
Dh1 = 2 DhT /3
Flow
A
B C
aquifer 1
Small b
aquifer 2
Large b

Changes in b can cause Changes in Head
Gradient
Head loss is
greater for
smaller thickness
dhT /3
2dhT /3
Flo
w
aquifer 1
Small b
aquifer 2
Large b

Flow Across Layers – Effective K
Flo
w
A B C
aquifer 1 aquifer 2
dh1
dh2
l1 l2
l
dh1 + dh2 = dhT

Flow Across Layers(vertically
different layer)
Effective K
 Continuity: Q1= Q2
 Head: dh1 + dh2 = dhT
 Flow path: l1 + l2 = l
 Darcy’s Law – solve for Keff
2
1
2
1
l
l
dh
dh
A
K
l
dh
A
K
Q eff
T
eff



 )
(
)
(
2
1
2
1
dh
dh
A
l
l
Q
Keff



1
1
1
AK
Ql
dh 
1
1
1
l
dh
A
K
Q 

















2
2
1
1
2
2
1
1
2
1 )
(
K
l
K
l
l
K
l
K
l
l
l
Keff
• Darcy’s Law – solve for dh1 and
dh2
• Substitute
Flow
A B C
aquifer 1 aquifer 2
dh1
dh2
l1 l2
l
Flow

Flow Along Layers(horizontal different
aquifer) – Effective K
Aquifer 1
Aquifer 2
b1
b2
dhT
B
Head loss in each layer
is the same
l

Flow Along Layers
Effective K
 Continuity: Q1+ Q2 = QT
 Head: dh1 = dh2 = dhT
 Flow area: b1w + b2w = A
 Darcy’s Law – solve for Keff
L
dh
w
b
b
K
Q T
eff
T )
( 2
1 

l
h
w
b
K
Q T
D
 1
1
1
T
T
eff
wdh
b
b
L
Q
K
)
( 2
1 

1 1 1 1 1 1 2 2
1 2
( )
eff
K b K b K b K b
K
b b B
 
 

• Darcy’s Law – solve for Q1
• Substitute Q1+ Q2 = QT
aquifer 1
aquifer 2
b1
b2
dhT
B
Head loss in each layer
is the same
L

Vertical vs Horizontal K
 Vertical flow – across layers
 Horizontal flow – along layers
 Example
 K1 = 1 and K2 = 100 m/d
 b1 = 2 and b2 = 2 m
 Find Keff for horizontal and
vertical flow
b1
b2
b3
B

 Vertical flow – across layers
 Horizontal flow – along
layers
b1
b2
b3
B
]
m/d
[
98
.
1
100
2
1
2
4
)
(
2
2
1
1
2
1


















K
b
K
b
b
b
Keff
]
m/d
[
5
.
50
4
2
100
2
1
)
( 2
1
1
1
1
1








b
b
b
K
b
K
Keff

 Vertical effective conductivity is
dominated by the layer having
the lowest K
 Horizontal effective
conductivity is dominated by
the high K layer
 Horizontal effective K is much
larger than the vertical effective
K
b1
b2
b3
B

Ground water flow direction
Flow net
Flow net is a net work flow lines and equipotential lines intersecting
at right angles to each other
Flow lines The imaginary path which a particle of water follows in
its course of seepage through a saturated soil mass. OR (An
imaginary line that traces the path that a particle of groundwater
would follow as it flows through an aquifer.)
equipotential lines:contour that joins which has equal hydraulic
head. it intersect flow lines at 90o OR (Potential of groundwater ϕ
= h = mechanical energy (pressure energy + elevation energy)
per unit mass of groundwater. Equipotential lines are always
perpendicular to the direction of h, no matter the isotropy of the
medium)

Flow Net Theory
1. Streamlines Y and Equip. lines  are .
2. Streamlines Y are parallel to no flow
boundaries  parallel to constant head
boundaries.
3. Grids are curvilinear squares, where
diagonals cross at right angles.
4. Each stream tube carries the same flow.

Assumption for construction of
Flow net
 The aquifer is homogeneous
 The aquifer is fully saturated
 The aquifer is isotropic
 There is no change in the potential field with time.
 The soil and water are incompressible
 Flow is laminar, and Darcy’s law valid
 All boundary conditions are known

Boundary conditions Vs flow lines
Boundary conditions vs flow lines and equipotential lines
 No-flow boundary (Neumann):
Adjacent flow lines are parallel to this boundary, and
equipotential lines are perpendicular to this boundary
 Constant-head boundary (Dirichlet):
Adjacent equipotential lines are parallel to this boundary. Flow
lines will intersect the constant-head boundary at right angles
 Water-table boundary:
It is a line where head is known. If Dupuit assumption is valid,
equipotential lines are vertical and flow lines are horizontal. If
there is recharge or discharge across the water table, flow lines
will be at an oblique angle to the water table.
142

Boundary conditions Vs flow lines
DMM 2011 GWH GW Motion 143
Three BC’s vs flow lines and equipotential lines

Boundaries such as impermeable formations,
engineering cut off structures

Recharging or discharging
surface water body

The following procedure helps to draw the flow net by trial and error
procedure. (Forchiemer Solution)
 Draw carefully the boundaries of the region to scale and sketch a few
stream lines on the drawing
 Identify the components of flow nets which are regarded as the boundaries
of the flow region (at least two in many flow nets).
 Begin and end stream lines at equipotential surface and they must intersect
these equipotential surface at right angles.
 As a first trail, use not more than four to five channels.
 Follow the principle of ‘Whole’ to part.
 All the flow and equipotential lines should be smooth and there should be
no any sharp transition b/n straight and curved lines.
There are many methods in use for the construction of flow
nets.
Some of the important methods are:
• Analytical methods
•Electrical analog methods
•Scaled model method
•Graphical method

Flow in relation to GW Contours
 Contour maps of water levels (both unconfined and confined
aquifers) are made in the majority of hydro geologic investigations
and, when properly drawn, represent a very powerful tool in
aquifer studies
 At least several data sets collected in different hydrologic season
should be used to draw GW contour maps for the area of interest.
In addition
 Recordings from piezometres, monitoring and other wells,
 Record elevations of water surface in the nearby surface streams,
lakes, seas, ponds and other bodies including cases when these
bodies seem “too far” to influence GW flow pattern.
 Gather information about hydro-meteorological conditions in the
area for preceding months paying attention to the presence of
extended wet or dry periods. All of this information is essential for
making a correct contour map.

Ground water flow direction
 The direction of GW flow in a localized area of an aquifer can
be determined if at least three recordings of water table
(piezoelectric surface) elevations are available.

GWE 1-9 Lem 1.pptx

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