This document discusses key terms and concepts related to groundwater, including: 1. Storage coefficient, which is the volume of water released from an aquifer per unit change in head. 2. Coefficient of permeability, which is the velocity of flow through soil under a unit gradient. 3. Coefficient of transmissibility, which is the rate of flow through an aquifer under a unit gradient. It also describes unconfined and confined aquifers, and discusses the importance of and methods for artificial groundwater recharge given increasing water usage and falling water tables in many areas.

1. Unit-3
Ground Water
Mr. Dipesh Rajput
Lecturer in Civil Engineering
Dr. S. & S. S. Ghandhy College of Engg. & Tech., Surat
Email: dipesh_rajput2000@yahoo.com
Water Resources
Management (3340604)
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Lecture-4

2.  Out lines
1. Terms Related to Ground Water
2. Steps to Increase Ground Water
3. Natural Recharge
4. Artificial Recharge
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3. 7. Storage Co-efficient (S) :
 The water yielding capacity of a confined aquifer can be
expressed in terms of its storage coefficient .
 Storage coefficient is defined as the volume of water that
an aquifer releases from or takes into storage per unit
surface area of aquifer per unit change in the component
of head normal to that surface.
 Let us consider a vertical column of unit area ( 1m x 1m )
extending through a confined aquifer as shown in Fig . 3.9
.
 Then, the storage coefficient S is the volume of water in
m3 released from the aquifer when the piezometric head
declines by 1 m.
 In most of the confined aquifers, the value of storage
coefficient, S ranges between 0.00005 to 0.005. 3
 Terms Related to Ground Water Conti…..

4. 8. Coefficient of Permeability (K) :
 The coefficient of permeability is defined as the velocity of the flow
which will occur through the total cross-sectional area of the soil
under a unit hydraulic gradient.
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 Terms Related to Ground Water Conti…..

5. 9. Coefficient of Transmissibility (T) :
 Coefficient of transmissibility is defined as the rate of flow of water in (m3/day) through
vertical strip of aquifer of unit width (1m) and extending the full saturation height under
unit hydraulic gradient, at a temperature of 60° F.
T = B. K %3D
where,
T = Transmissibility (m³ / day)
K = Coefficient of permeability (m/day)
B = Thickness of aquifer (m).
10. Water Table (W.T.) :
 Water table is the surface of water level in an unconfined aquifer at which the pressure is
atmospheric.
 It is the level at which water will stand in a well drained unconfined aquifer.
 The water table fluctuates whenever there is recharge or overflow from the aquifer.
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 Terms Related to Ground Water Conti…..

6.  Types of Aquifers
Aquifers are mainly of two types:
1.Unconfined Aquifer
2.Confined Aquifer
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7. 1. Unconfined Aquifer
 Unconfined aquifer is the one
in which water table forms the
upper surface of the zone of
saturation.
 It is also known as water table
aquifer or Phreatic aquifer or
non artesian aquifer.
 The water table is not a
stationary surface but it rises
when more water enters the
aquifer from natural or
artificial recharge, and it drops
when recharge is less and the
previously stored water flows
out towards springs, streams,
wells, etc.
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8. 2. Confined Aquifer
 A confined aquifer is the one in which ground water is confined under pressure
greater than atmospheric pressure by overlying relatively impermeable strata.
 It is also known as artesian aquifer or pressure aquifer.
 A confined aquifer is analogous to a pipeline.
 In a well penetrating such an aquifer, the water level will rise to the level of the
local static pressure or artesian head.
 Confined aquifers have small recharge area as compared with in confined
aquifers.
Flowing Well :
 When a well penetrates a confined aquifer water rises in the well to the level of
local static pressure or artesian head. If this artesian pressure is sufficient to
raise the water above the ground level, a flowing well occurs. Fig. 3.10.
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9.  Artesian Well :
 If however, the water level in such
a well is below the ground level,
but it is above the local water
table it is known as the artesian
well.
 Perched aquifer:
 It is a special type of unconfined
aquifer. It occurs where ground
water body is separated from the
main ground water by a relatively
impermeable stratum of small
aerial extent and by the zone of
aeration above the main body of
ground water.
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10.  Steps to Increase Ground Water
 The various steps to increase / preserve ground water are as follows :
1. Supply of water for limited period instead of unlimited supply.
2. Use of water meter system.
3. Provision of penalty for wastage of water.
4. Artificial recharge should be made compulsory for multi-storeyed buildings.
5. The person or agencies should be rewarded who are engaged in artificial recharge of water.
6. Construction of check dams, khet-talawadi.
7. Controlling extraction of ground water from bore wells by the authorities.
8. Controlling wastage of water by industries.
9. Provision of subsidies for construction works related to artificial recharge.
10. To apprise people regarding importance of water through radio, T.V., Newspapers, etc.
11. Adoption of new techniques of irrigation like sprinkler irrigation and drip irrigation.
12. Tree plantation.
13. Crop rotation.
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11.  Natural Recharge
The following conditions are favourable for natural recharge of
ground water :
1. Sandy or permeable soil
2. Rocky strata with fractures / Faults
3. Perennial rivers
4. Streams
5. Forest land
6. Comparatively level land, with less slope
7. Topography suitable for the construction of artificial recharge
structures.
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12.  Causes of Reduction in Natural Recharge
1. Development of urban area which reduces open land for recharge.
2. Deforestation
3. Reduction in agricultural land
4. Artificial diversion of stream, rivers by men.
5. Living of irrigation canals.
6. Insufficient and irregular rainfall.
7. Construction of flood control structures.
8. Overuse of water by industries situated on river banks.
9. Discharge of polluted water in natural flow of water reduces infiltration
capacity of soil as pores of soil gets blocked with impurities.
10.Use of advance irrigation methods. 12

13.  Artificial Recharge
 The practice of artificially obstructing the flowing rainwater and inducing its infiltration to increase
the ground water reservoir is called artificial recharge.
Necessity :
 Due to rapid industrialisation, population increase, intensive agriculture, urbanisation, etc. the use of
water has been considerably increased.
 For these purpose water is pumped from the ground water sources.
 The aquifers are not recharged at the same rate at which water is pumped out.
 Thus, the water table falls every year.
 If this process is not controlled ground water resources will be emptied, resulting in serious water
problems.
 Thus, there is a keen demand to recharge the ground aquifers by diverting the rain water towards
these aquifers.
 Normally, the aquifers recharge by natural process.
 But, the rate of recharge is less than the rate of withdrawal of water.
 In North Gujarat, in certain areas water table has dropped upto 450 to 600 m below ground level.
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14.  Necessity Conti…….
 The water extracted from deeper sources contains higher concentration of fluorides
and nitrates, which is harmful for the human health.
 In the coastal areas, due to pumping of ground water, the sea water intrusion has
taken place.
 In certain areas due to sea water intrusion, ground water has become salty which is
not suitable for domestic or agricultural purposes.
 As per the report of Indian National Committee on Irrigation and Drainage 1996) India
receives average annual rainfall of about 4060 cubic kilometer, out of which 1880 km3
flows in rivers, 1258 km3 is evaporated.
 Only 432 km3 of water gets accumulated as ground water.
 Thus, only 10% of the rain water infiltrates into the ground and meet the ground water
reservoir.
 Thus, there is a need to divert some portion of 1880 km3 water flows in the rivers to
the ground water resources.
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 Artificial Recharge Conti…..

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