Ground water harvesting

1. GROUND WATER
EXTRACTION –
TYPES OF WELLS
SUBMITTED BY,
RISHAV RAY
MSC SEM 2
DEPT. OF ENVIRONMENTAL STUDIES, VISVA BHARATI,
SHANTINIKETAN

2. A) WHAT IS GROUNDWATER?
Ground water is the water found underground in the cracks
and spaces in the soil, sand and rock. It is stored in and
moves slowly through geological formation of soil, sand and
rocks called aquifers. The largest use of groundwater is to
irrigate crops
The area where the water fills the aquifer is called the
saturated zone. The top of the zone is water table zone. The
water table may be located only a foot below grounds surface
or it can set hundreds of feet down. It is an important

3. component in many industrial processes and a source of
recharge for lakes, rivers and wetlands.
B) HOW GROUNDWATER MOVES?
#most of the groundwater within a few hundred meters of
the land surface is in motion. However, groundwater flows so
slowly that its movements are measured in centimeters per
day or meters per year.
======================x======================

4. #water form a rain shower soaks into the soil by infiltration.
Fine clay particles may make the soil less permeable than
underlying coarser regolith or rock. Low permeability and
mobility, molecular attraction between water and fine particles
cause a part of water to be retained in the soil.
#movement of groundwater in the saturated zone termed
percolation is similar to flow of water that occurs when a
saturated sponge is squeezed gently.
#recharge of groundwater occurs when rainfall and snowmelt
enters the ground in recharge areas or recharge zones, places
where precipitation infiltrates and percolates downward through
soil layers to reach the saturated zone. Water continues to
move slowly along its flow path towards zone where discharge
occurs.
C) SOURCES OF GROUNDWATER
People generally obtain groundwater either from natural springs
or from wells reaching down to a body of water underground
.1. SPRINGS-flow of water that emerges naturally at ground
surface. Porous sand overlies a relative impermeable clay
aquiclude, water percolating downward through the sand will

5. flow laterally when it reaches the underlying clay and emerge
as a spring at a point.
2. WELLS-supply water if it intersects the water table. When
water pumped from a new well, rate of withdrawal may
initially exceed the rate of local ground water flow. If the
source of a groundwater supply is, non-homogenous rock or
sediment amount of water yielded by wells may vary.
3. AQUIFERS- A body of highly permeable rock or regolith
lying in zone of saturation. Bodies of gravel and sand
generally are good aquifers.
Unconfined-upper surface coincides with water table and in
contact with atmosphere.
Confined-bounded by aquicludes.
D) Subsurface distribution of water-
Groundwater distribution may generally be categorized into
zones of aeration and saturation.
a) Soil-water zone-It begins at the ground surface and
extends downwards through the major root band. Total depth
is variable and dependent on soil type and variable and
dependent on soil type and vegetation. Water that is drained
from a soil by gravity is known as specific yield, which is

6. expressed as the ratio of volume of water that can be
drained by gravity to the gross volume of soil
b) Intermediate zone-Belt extends from bottom of soil water
zone to the top of capillary fringe and may vary from non-
existence to several hundred centimeters to thickness.
C)Capillary zone-extends from water table to a height
determined by capillary rise that can be generated in the soil.
D) Saturated zone-Groundwater fills the pore spaces
completely and porosity is there for direct measures of a
storage volume. Due to molecular and surface tension forces.
Groundwater basins-physio-graphic hydrological unit
containing one large or several connected and interrelated
aquifers.
Springs-Conc. Discharge of ground water at surface.
E) GROUNDWATER MOVEMENT
It is in constant motion although the rate at which it movies
is generally slower that it would move in a stream as it has
to pass through the intricate passageways between free
spaces in the soil. Groundwater moves downward due to pull

7. of gravity. It can also move upward when it flows from high
pressure to low pressure areas.
i)Movement in the zone of aeration-
Rainwater soaks into the soil where some of it is evaporated,
some adheres to grains in the soil by molecular attraction,
and plant roots absorb a portion, while some seeps down into
saturated zone.
ii) Movement in the saturation zone-
In the saturation zone, water percolates through the
interconnected pore spaces, moving downward by the forces
of gravity and upward toward zones of lower pressure.
iii) Recharge and discharge areas-
Earth surface can be divided into areas where some of the
water failing on surface seeps into saturated zone and other
areas, where water flows out of saturated zone onto surface.
Areas where water flows out of saturated zone onto surface.
Areas where water enters the saturated zone are called
recharge areas, because saturated zone is recharged with
groundwater beneath these areas. Recharge areas are greater
than discharge areas.
F) GROUNDWATER YIELD-

8. Development of groundwater supplies is accomplished mainly
through wells or infiltration galleries. Response of the head is
an aquifer due to pumping one or more wells is dealt in well
hydraulics. By testing wells, storage coefficients of aquifers,
future decline of groundwater can be calculated .Aquifers
performance test is categorized into two type’s equilibrium and
non-equilibrium tests.
SOIL FORMATION AND
TEXTURE
RADIUS OF INFLUENCE
Fine sand formation with
some clay and silt
100-300
Fine to medium sand
formation ,fairly clean and
free from clay and silt
300-600
Coarse sand and fine gravel
formation free from clay and
silt
600-1000
Coarse sand and gravel, no
clay or silt
1000-2000
Maximum quantity of water that is actually available from
groundwater basins on a perennial basis is limited by possible

9. deleterious side effects that can be caused by pumping and
by operation of the basin.
{.}UNCONFINED AQUIFER-
Flow towards a well in an unconfined aquifer or a water table
aquifer is determined based on assumption. Dupuit implicitly
assumes that a concentric boundary of constant head
surrounds a well, for otherwise, no steady flow can occur.
{.}CONFINED AQUIFER-
Water in the observation well rises above the top of aquifer
due to pressure and water level in the test well might rises
above the roof level of an aquifer at steady flow conditions.
G) METHODS OF GROUNDWATER YIELD
Wells are constructed to extract appreciable quantities of
groundwater. Wells also serve another purpose like surface
exploration and observation, artificial recharge and other
domestic purposes. Shallow wells generally less than 15m in
depth are constructed by digging, boring drilling or jetting.
Various characteristics of aquifers need to be explored

10. thoroughly before deciding the use of groundwater for large-
scale application such as irrigation and other requirements.
These are-
1} Depth of water table
2} status of aquifer
3} thickness and spatial distribution of aquifer
4} groundwater movement
5} quality of groundwater
6} various properties of aquifers materials- texture,
permeability and porosity.
The various methods of subsurface exploration are divided into
major groups –
.Direct method- done by anger boreholes
.Indirect method- includes geological mapping, serial
photography, resistivity method, seismic method and tracer
method.

11. H) TYPES OF WELLS-
I) OPEN WELLS-
Simplest device to raise the groundwater is to construct open
wells and lift water by manual and mechanical means such as
pumps, Persian wheels, etc, usually shallow and unliked and
are feasible only when water table is near the ground surface.
When water table is deep, sunk wells with liking are
constructed to prevent the collapse of sidewalls. These can be
constructed upto 20m depth or more depending upon the
nature of strata and position of water table. In open wells, no
strainer to artificial obstruct the flow of sand and silt under
increased drawdown head. Yield is therefore limited.

12. FIGURE OF AN OPEN WELL

13. II) TUBE WELLS-
Wells having perforated tubes or pipes in holes bored into the
ground to tap water from one or more aquifers. These can be
categorized into shallow and deep tube wells.
*SHALLOW TUBE WELL-tube well is termed shallow when it
lifts water from an aquifer lying nearer the ground surface
mostly under the free water table conditions
*DEEPTUBE WELLS-these not only draw water from nearest
aquifer,but pierce through others. Aquifers lying several
hundred meters below the ground surface.

14. FIGURE OF A DEEP TUBE WELL

15. I) GROUNDWATER FOR DOMESTIC PURPOSES-

16. .Dug wells- oldest and most common method pf extracting
groundwater. Depth can be 20m or less. Depending on
position of water table, diameter ranges from 1-10m
.Bore wells-when water table is at a shallow depth in an
unconsolidated aquifers, bore wells can furnish small quantities
of water at minimum cost.
.Driven wells-consists of series of connected pipes by repeated
impacts into ground below table (water). Water enters the well
through lower end of the well which is referred as to driving
point.
======================X=========================

17. REFERENCES-
1)SOIL AND GROUNDWATER POLLUTION FROM
AGRICULTURAL ACTIVITIES (
T.V.RAMCHANDRA)
GROUNDWATER HYDROLOGY ANDYIELD (PG
NO-64-96)
2)www.wikipedia.org
3) researchgate
4)slideshare

18. THANK YOU