type of Aquifer by Bablu & Vishnu Kumar Barupal

1. FACULTY OF SCIENCE
JAI NARAYAN VYAS UNIVERSITY
JODHPUR
DEPARMENT OF GEOLOGY
PRESENTATION ON:
SUBMITTED TO-
DR. S.R. JAKHAR
ASS. PROF. JNVU
SUBMITTED BY-
BABLU
MSc-semester 3

2. CONTENTS
• INTRODUCTION ABOUT GROUND WATER
• WHAT IS AQUIFER
• WATER TABLE
• TYPES OF AQUIFERS
• EXAMPLES OF AQUIFERS

3. Water Distribution on Earth

4. • Ground Water lies beneath the ground surface, filling
pores in sediments and sedimentary rocks and fractures
in other rock types
• Represents 0.6% of the hydrosphere (35x the water in all
lakes and rivers combined)
– Resupplied by slow infiltration of precipitation
– Cleaner than surface water
– Accessed by wells

5. A saturated
,permeable , geologic
unit that can transmit a
significant amount of
groundwater under an
ordinarily gradient.
Or
Aquifer is body of
saturated rock or
sediment through
which water can move
easily.
Examples: sand stone,
conglomerate, well jointed
limestone, highly fractured
rock etc.

6. The Water Table
• Subsurface zone in which all rock
openings are filled with water is
the saturated zone
• Water table, top of the saturated
zone
– Water level at surface of most
lakes and rivers corresponds
to local water table
• Above the water table is an
unsaturated region called the
vadose zone

8. Unconfined Aquifer
• An aquifer that is bounded from above by a phreatic surface is
called a phreatic or unconfined, aquifer, or a water table aquifer
• Has a water table, and is only partly filled with water.
• Rapidly recharged by precipitation infiltrating down to the
saturated zone

9. AQUITARD-
Rock/sedimen
t that retards
ground water
flow due to
low porosity
and/or
permeability.
e.g.-shale ,
clay,
unfractured
crystalline
rocks
UNCONFINED
AQUIFERS
CONFINED
AQUIFERS

10.  A special case of an Unconfined aquifer.
 This occurs wherever a groundwater body is separated from
the main groundwater by a relatively impermeable stratum of
small areal extent and by the zone of aeration above the main
body of groundwater.
 Commonly produced by thin lenses of impermeable rock (e.g.
Shales or clays) within permeable ones

11. Types of Aquifers
Confined aquifer
overlain by less
permeable
materials
Unconfined aquifer
open to Earth’s surface
and to infiltration
Perched aquifer underlain by
low-permeability unit
Artesian aquifer: water rises in
pipe (maybe to surface)
17.04.c,d.mtb

12. • Confined Aquifer
– Completely filled with water under pressure (hydrostatic head)
– Separated from surface by impermeable confining
layer/aquitard
– Very slowly recharged

13.  CONFINED AQUIFERS
Confined Aquifers, also known as ‘Artesian’ or Pressure
Aquifers.
It occur where groundwater is confined under pressure
greater than atmospheric by overlying relatively
impermeable strata.
In a well penetrating such an aquifer , the water level
will rise above the bottom of the Confining bed , as
shown by the Artesian and Flowing wells in figure on
next slide.
Water enters a confined aquifer in an area where the
confined bed rises to the surface where the confined
bed ends underground, the aquifer becomes
Unconfined.

14. The word Artesian is derived from the French
artesian, meaning “of or pertaining to Artois ,”
the northernmost province of France.
Here the first deep wells to tap confined
aquifers were drilled and investigated, from
about 1750.
The term referred to a well with freely flowing
water, but at present it is applied to any well
penetrating a confined aquifer or simply the
aquifer itself.

15. • Well - a deep hole dug or
drilled into the ground to
obtain water from an
aquifer
– Wells in unconfined aquifers, water
level before pumping is the water
table
– Water enters well from pore spaces
within the surrounding aquifer
creating a cone of depression
– Water table can be lowered by
pumping, a process known as
drawdown
Insert new Fig.
11.8 here

16. ARTESIAN AND FLOWING WELL IN CONFINED
AQUIFER

17. Artesian Wells
– Water may rise to a level above the top of a confined aquifer, producing an
artesian well

19. THE PIEZOMETRICS SURFACE, OR POTENTIOMETRIC
SURFACE OF A CONFINED AQUIFER
 It is an imaginary surface coinciding with the hydrostatic
pressure level of the water in the aquifer.
 The water level in a well penetrating a confined aquifer
defines the elevation of the piezometric surface at that
point.

20. 3.LEAKY AQUIFER
 A leaky phreatic aquifer is a phreatic aquifer that is bounded
from below by a semipervious layer, which is usually referred
to as an aquitard. This is a layer that is much less pervious
than the aquifer overlying it and often is also much thin. It
thus behaves as a “semi-pervious membrane” through which
leakage out of or into the phreatic aquifer from an underlying
saturated region is possible.
 A leaky confined aquifer is a confined aquifer, except that one
or both confining layers are aquitard.
 Pumping from a well in a leaky aquifer removes water in two
ways: By Horizontal flow within the aquifer and By Vertical
flow through the aquitard into the aquifer.

21. In the figure, two leaky aquifers: The upper one is a phreatic-
leaky aquifer, while The Lower one is a confined-leaky aquifer.
They are separated by an aquitard. The piezometric surface is of
the lower leaky-confined aquifer.

22. 4.IDEALIZED AQUIFER
For mathematical calculations of the storage and
flow of groundwater , aquifers are frequently
assumed to be Homogeneous and Isotropic.
A Homogeneous aquifer possesses hydrologic
properties that are everywhere identical.
An Isotropic aquifer is one with its properties
independent of direction.

23. EXAMPLES OF AQUIFERS
GOOD AQUIFERS POOR AQUIFERS
Gravel , sand and deposits Solid rock, Granite
Fractured (broken up) Limestone • Rocks with poor permeability
(water cannot pass through them
easily)
Limestone and Karst Aquifers
Limestone dissolves because rain water is slightly
acidic. Cracks and faults form in the limestone, and
they can grow to be big caves over time.