4. WHAT IS THE HYDROLOGICAL CYCLE ?
The hydrological cycle is the system which
describes the distribution and movement of
water between the earth and its
atmosphere. The model involves the
continual circulation of water between the
oceans, the atmosphere, vegetation and
land.
Now see little video of Hydrological cycle.
6. SOURCES OF GROUND WATER
1. Wells
2. Spring
3. Infiltration galleries
4. Karez
7. 1.WELLS
It is a deep hole, generally cylindrical, that is
dug of drilled into the ground to penetrate
an aquifer within the saturated zone.
Recharge the addition of new water to the
saturated zone.
The water table in an unconfined aquifer
rises in wet seasons and falls in dry
seasons as water drains out of the saturated
zone into rivers.
8.
9. 2.SPRING
A spring is a flow of ground water at the
ground surface
Springs Types:-
1. Stratum spring
2. Valley spring
3. Fault spring
4. Artesian spring
5. Deep seated spring
11. 3.INFILTRATION GALLERIES
An infiltration galleries is a horizontal
conduit having permeable boundaries so
that ground water can infiltrate into the
same.
Three layers of graded around gallery are:-
I. 16 cm ballast(25 to 50mm size) around pipe.
II. 16 cm large pebbles (12 to 24mm size) as
intermediate layer.
III. 24 cm fine pebbles (3 to 10mm size) as the
outer layer.
14. 4.KAREZ
A Karez is an underground tunnel driven
into the hill side to tap water from the
underground spring.
Karez channels are in use in Baluchistan
and West Pakistan
16. OCCURANCE OF GROUND WATER
It is depended upon following features:-
I. The porosity of the rocks.
II. The permeability of the rocks.
17. 1.POROSITY
I. Porosity is quantitative measures of the
voids present in the rock.
II. Porosity = volume of voids x100/ total
volume of metrical
III.It is classified 5 to 20% medium and less
then 5% small.
18. POROSITY VALUES OF FEW ROCK FORMATIONS
Sr.No Types of rock Formation Porosity %
1 Granite, Quartzite 1.5%
2 Shale, slate 4%
3 Lime stone 5-10%
4 Sand stone 10-15%
5 Sand and gravel 20-30%
6 Only gravel 25%
7 Only sand 35%
8 Clay and soil 45%
19. 2.PERMEABILITY
Permeability is defined as the property of
rock or unconsolidated sediment to permit
flow of ground though it.
Gravels are high permeable.
Clays are less permeable.
Granite rocks are impermeable.
20. COEFFICIENT OF PERMEABILITY(K)
Sr.No Types of soil K,(cm/sec)
1 Clean gravel 1.0 and greater
2 Clean sand (coarse) 1.0 - 0.01
3 Sand (mixture) 0.01 - 0.005
4 Fine sand 0.05 - 0.001
5 Silty sand 0.002 - 0.0001
6 Silt 0.0005-0.00001
7 Clay 0.000001 and smaller
21. ZONES OF UNDERGROUND WATER
With respect to existence of water at
different depths, the earth’ s crust can be
divided into two major zones namely.
i. Zone of rock flowage.
ii. Zone of rock fracture.
23. ZONE OF ROCK FLOWAGE
The depth of the zone of rock flowage is not
accurately known, but is generally estimated
as many miles.
Interstices are generally absent in this zone,
because the stresses are beyond the
elastic limits, and the rocks remain in the
state of plastic flow.
Water present in this zone is known as
internal water.
24. ZONE OF ROCK FRACTURE
It this zone, the stresses are within the
elastic limits, and depends upon porosity.
The maximum depth of this zone below the
ground surface, varies in the range of about
100m to 1000m or more.
The zone of rock fracture.
i. Zone of aeration.
ii. Zone of saturation.
25. TERMS RELATED TO GROUND WATER
1.Aquifer:
An aquifer may be defined as geological
formation that contains sufficient permeable
materials which permits storage as well as
movement of water through it under ordinary field
conditions.
2.Aquiclude:
An aquiclude may be defined as geological
formation of relatively impermeable material which
permits storage of water but it is not capable of
transmitting water in sufficient quantity.
26. TERMS RELATED TO GROUND WATER
3.Aquitard:
A geological formation that has poor
permeability, but through which seepage is
possible, and hence, it does not yield water freely to
wells. It may transmit vertically appreciable
quantities of water to from adjacent aquifers.
4.Aquifuge:
An aquifuge may be defined as a geological
formation of relatively impermeable material which
neither contains nor transmits water.
27. TERMS RELATED TO GROUND WATER
4.Porosity (n):
Porosity of soil or a rock may be defined as the
ratio of volume of voids to the volume of the
material.
5.Coefficint of Permeability (K):
The coefficient of permeability is defined as the
velocity of flow which will occur through the total
cross-sectional area of the soil under a unit
hydraulic gradient.
28. TERMS RELATED TO GROUND WATER
6.Coefficint of Transmissibility (T):
The coefficient of transmissibility is defined as
the rate of flow of water in (m.cu/day) through
vertical strip of aquifer of unit which (1m) and
extending the full saturation height under a unit
hydraulic gradient, at a temperature of 60 F.
29. TYPES OF AQUIFERS
Aquifers are mainly of two types:
UNCONFINED AQUIFER CONFINED AQUIFER
30. UNCONFINED AQUIFER
Unconfined aquifer is one in which water
table forms the upper surface of the zone of
saturation.
It is known as water table aquifer or
Phreatic aquifer or non artesian aquifer.
31.
32. CONFINED AQUIFER
Confined aquifer is one in which ground
water is under pressure greater then
atmospheric pressure by overlying relatively
impermeable strata.
It is known as artesian aquifer or pressure
aquifer.
33.
34. DIFFERENCE BETWEEN
CONFINED AND UNCONFINED AQUIFER
In confined aquifer
water is stored below
impermeable layer at
pressure higher than
the atmospheric
pressure
It is also called artesian
aquifer.
In unconfined aquifer
water is stored in the
top pervious soil layers.
It is known as water
table aquifer or
Phreatic aquifer or non
artesian aquifer.
Confined aquifer Unconfined aquifer
36. GEOLOGICAL CONTROLS
OF GROUND WATER MOVEMENT
Ground water movement in the zone of
aeration takes place under the influence of
gravity. But the factors influencing water
movement in the zone of saturation are of
different kinds. Most of them are geological
and are as follows:-
1. Permeability of rocks.
2. Attitude of bedding
3. Buried river channels and unconformities.
4. Hydraulic gradient.
37. GROUND WATER EXPLORATION
“Ground water Prospecting” means
searching for the ground water.
Ground water investigations are of three
kinds:-
1. Geological investigations.
2. Geophysical investigations.
3. Hydrological investigations.
38. 1.GEOLOGICAL INVESTIGATIONS.
It is the most important and e main deciding
factor. The other two provide only
supplementary information
Geological investigations, comprises of the
following:-
i. Study of rock types.
ii. Study of topography.
iii. Study of weathering.
iv. Study of geological structures.
v. Study of intrusive rocks.
vi. Geological mapping.
39. 2.GEOPHYSICAL INVESTIGATIONS
It is the based on the fact that rock
formation differ in their in gravitational,
magnetic, seismic and radioactive behavior.
The sub-surface geophysical methods
involve recoding variations in temperature,
resistivity, conductivity, spontaneous
potential and response to gamma radiation
and acoustic waves with increasing depth
40. 3.HYDROLOGICAL INVESTIGATIONS
In the hydrological investigations the
following studies are made:-
i. Study of depth of water table.
ii. Study of surface water table.
iii. Study of springs and seepage.
iv. Quality of water.
v. Study of rainfall and climate.
vi. Pumping tests.
