Groundwater:

GROUNDWATER
Developed By : Prof. A. K. Baile
Assistant Professor of Engineering Geology

Contents
Here’s what you’ll find in this presentation :
Introduction
Advantages of groundwater
Hydrological cycle
Sources of groundwater
Vertical distribution of groundwater
Porosity
Permeability
Classification of rocks based on porosity & permeability
Artificial recharge of groundwater

INTRODUCTUON
FORMS OF WATER
01
Liquid, Solid & Vapour
02
03
04
What is the differnece between
Hydrology & Hydrogeology?
Study of Surface & Subsurface
Water deals about :
Ouccurrence, Distribution, Movement
and chemistry of all water
Water + Soil & Rock = Groundwater

Advantages of
Groundwater
Why under-groundwater
is more advantageous
than the surface
water??????
The insufficient availability of surface water potential
Seasonal changes affect the surface water
The surface water quality may be deteriorates
Always threat of pollution
The groundwater is free from weed seeds plant
organisms, turbidity and bacterial pollution.
Uniform in quality
Dams & Canals systems
Silting problems
Liable to destruction by enemy
Possibility of leakage of surface water
The Earthquake & Landslide
 Area Submerged under the impounded surfacewater

Hydrological Cycle
 Evapo-transpiration
 Condensation
 Precipitation
 Infiltration
 Percolation
 Runoff

•Major Source
(Meteoric Water)
SOURCES OF
GROUNDWATER
•Minor Source: a) Connate water
b) Magmatic water

VERTICAL DISTRIBUTION OF GROUNDWATER
 Zone of Areation:
 Soil Moisture
zone
 Intermediate
Zone
 Capillary Fringe
● Zone of saturation

Porosity: Percentage of open spaces in a
given volume of rock or sediment
Total volume of voids in the sediments
Porosity= ______________________________
Total volume of Sediments

Porosity:
A B
Amount of Cement
Sorting
A B
A
B

Permeability
The ability of water to flow through soil.
Permeability depends on soil
composition (size and sorting)
Large Particles Small Particles Sorted Particles Unsorted Particles

Large Particles Small Particles
Sorted Particles Unsorted Particles
• More permeable
• Water flows
easily from space
to space
• Less permeable
• It’s hard for
water to find a
path through the
soil
• More permeable
• Plenty of open
spaces that
connect to each
other
• Less permeable
• Small particles fill up
the spaces leaving
little room for water
to move

Classification of rocks based on porosity &
permeability
02
Neither Absorb
NOR transmit
Water
Porosity &
Permeability
Ex. Sandstone Ex. Granite Ex. Clay, Shales &
Mudstones
Ex. Clay Lenses
Interbedded with Sand
Aquiclude
Aquifer Aquifuges Aquitard
Only Porous Less Porosity &
Permeable

Types of Aquifer
 Unconfined Aquifer
 Confined Aquifer
 Perched Aquifer
 Semiconfined or leaky
Aquifer
Aquiclude
Aquiclude

Importance of groundwater studies in Civil
Engineering works
Subsurface water conditions are significant for three major
aspects of civil engineering works;
Subsurface water may pose a problem to construction,
It may be an erosive agent that degrades the foundation of the
structure and
Subsurface water may be critical to the functioning of the
structure. Developed By : Prof. A. K. Baile

Problems Created in Constructions
Tunnel and other underground structures
•Data/ information
•the type of vegetation growth on the site
•the subsurface water survey
• Ground water and seepage pressures
Water Table and Tunnel
Water Tables and Reservoir
Groundwater and Dam
Building Foundations and Failure of Pavements
Importance of groundwater studies in Civil
Engineering works

 Digging pits and shafts
 Construction of percolations dams
i.e. Seepage tank
 Injection or recharge Wells
 Incidental or unplanned recharge
 Induced recharge
 Spreading Methods
Artificial recharge of
groundwater

Site Investigations:
Surface Investigations
 Geological & Geo-botanical
Investigations
 Lithological Control
 Igneous Rock
 Sedimentary Rock
 Metamorphic Rock
 Structural Control
 Fractured & Faulted Zones
 Subsurface Barriers
 Weathered & Vesicular Zone
 Stratigraphic Control

Site
Investigations: Sub- Surface Investigations
 Geophysical Surveys
 Electrical Resistivity Survey
 Ohm’s Law
R= V/I
 Potential, Current & Resistance are measured.
 Instruments Used
• Aquameter
• D. C Potentiometer
• The megger and D. Resistivity meter

ARTIFICIAL RECHARGE
OF GROUND-WATER
CONTENT
• Concept of Recharge
• Need for Artificial Recharge
• Purposes and Principles of Artificial Recharge
• Advantages of Artificial Recharge
• Artificial Recharge Techniques And Designs

Groundwater levels are declining across the country as our withdrawals exceed
the rate of aquifers to naturally replenish themselves, called recharge. One method
of controlling declining water levels is by using artificial groundwater.
Natural recharge,
Artificial recharge
•Concept of Recharge

•Need of Artificial Ground water Recharge
Natural replenishment of ground water reservoir
slow process
exploitation of ground water resources
Resulted
declining ground water levels and depletion of ground water
 Artificial recharge efforts are basically aimed at augmentation of the natural movement of surface water
into ground water reservoir through suitable civil construction techniques.

•Purposes and Principles of Artificial Recharge
Replenish ground water resources in depleted aquifers,
Conserve water for future use,
Control of salt-water encroachment,
Filtration of water,
Control of land subsidence.

•IDENTIFICATION OF AREAS FOR RECHARGE
 Where ground water levels are declining due to over-exploitation
 Where substantial part of the aquifer has already been.
 Where availability of water from wells and hand pumps is
inadequate during the lean months .
 Where ground water quality is poor and there is no alternative
source of water

•SOURCES OF WATER FOR RECHARGE
Precipitation (rainfall) Large roof areas Canals from large reservoirs
Diversion of Natural streams
Properly treated municipal and industrial wastewaters

•ADVANTAGES OF ARTIFICIAL RECHARGE
No large storage structures needed to store water.
Structures required are small and cost-effective
 Enhance the dependable yield of wells and hand pumps
Negligible losses as compared to losses in surface storages
Improved water quality due to dilution of harmful chemicals/ salts
No adverse effects like inundation of large surface areas and loss of crops
No displacement of local population
Reduction in cost of energy for lifting water especially where rise in ground water level is substantial
Utilizes the surplus surface runoff which otherwise drains off

Assessment of the available sources of water would require
consideration of the following factors:
• Available quantity of water
• Time for which the water would be available
• Quality of water and the pretreatment required
• Conveyance system required to bring the water to the recharge site

Spreading Methods • Basin method
• Channel Method
• Ditch and Furrow method
• Flooding method
• Irrigation method
Digging pits or Shafts
• Vertical Shafts
• Lateral Shafts
Injection Well • Recharge Well
Induced Recharge • Pumping Well
METHODS OF ARTIFICIAL RECHARGE

Spreading Methods
BASIN METHOD
 Suitable for Irregular Ground Surface.
 Most Effective water Depth in the basin is 1.25m
 A portion of the flood Water can be stored in the
basin
 Not required much land surface preparation,
 Construction of bund is very simple

CHANNEL SPREADING
Constructing small ‘L’ shaped bunds within a stream channel
This is not useful where rivers/ streams are prone to flash floods
A small flowing channel flows through a relatively wide valley

Spreading Methods
CHANNEL METHOD
Constructing small ‘L’ shaped bunds within a stream channel
This is not useful where rivers/ streams are prone to flash floods
A small flowing channel flows through a relatively wide valley

Spreading Methods
DITCH AND FURROW METHOD
 construction of shallow, flat-bottomed and closely spaced ditches or
furrows.
 Adequate slope to maintain flow velocity and minimum deposition of
sediments
 The widths of the ditches are typically in the range of 0.30 to 1.80 m.

Spreading Methods
FLOODING & IRRIGATION METHOD
 Ideal for lands adjoining rivers or irrigation canals;
 Reduce the evaporation losses;
 The least expensive;
 Very low maintenance costs.

Digging pits or Recharge Shafts Methods
These are the most efficient and cost effective structures to recharge the aquifer
directly. These can be constructed in areas where source of water is available either
for some time or perennially. Following are the site characteristics and design
guidelines:
To be dug manually if the strata is of non-caving nature
If the strata is caving, proper permeable lining in the form of open work, boulder lining
should be provided
The diameter of shaft should normally be more than 2 m.
In the areas where source water is having silt, the shaft should be filled with boulder,
gravel and sand to form an inverted filter.
The injection pipe should be lowered below the water level

The main advantages of this technique are as follows:
It does not require acquisition of LARGE PIECE OF LAND.
There are practically NO LOSSES OF WATER.
OPERATIONAL DUG WELLS can be converted into recharge shafts.
Technology and design of the recharge shaft is SIMPLE.
The recharge is FAST.

VERTICAL SHAFT METHOD
VERTICAL SHAFT WITHOUT INJECTION WELL

VERTICAL SHAFT METHOD VERTICAL SHAFT WITH INJECTION WELL

Injection Well Methods
VERTICAL SHAFT METHOD VERTICAL SHAFT WITH INJECTION WELL

Induced Recharge
Induced recharge involves pumping
water from an aquifer, which is
hydraulically connected with surface
water to induce recharge to the ground
water reservoir. Once hydraulic
connection gets established by the
interception of the cone of depression
and the river recharge boundary, the
surface water sources starts providing
part of the pumping yield

THANK YOU

Groundwater:

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