Hydrogeology

Hydrogeology
By
Pramoda G
Faculty in Geology
YCM

Hydrogeology
Hydrologic cycle.
Ground Water – Introduction, origin, types, occurrence,
movement of ground water,
Hydrologic properties of rocks: Porosity; permeability;
specific yield; specific retention, hydraulic conductivity,
transmissivity, storage coefficient.
Water bearing geologic formations – Aquifers (confined,
unconfined & perched), aquiclude, aquifuge, aquitard.
Well hydraulics: Steady, unsteady and radial flow,
Darcy’s Law and Its’ applications.
Water table and its fluctuations; causative factors and their
measurements;
methods of pumping test and analysis of data.

Hydrographs, water table contour maps, hydrostratigraphic
units.
Groundwater chemistry - Physical, chemical and
biological properties of groundwater. Water quality,
drinking water standards,
Groundwater quality map of India.
Artificial recharge of groundwater; problem of over
exploitation of groundwater;
sea water intrusion in coastal aquifiers; remedial
measures.
Interpretation of hydrogeomorphic units using satellite
imageries.
Radio isotopes in hydrogeological studies.
Water budget equation and Groundwater management

Hydrology is study of water in the broadest sense. It
encompasses the occurrence, distribution and circulation
of water, its physical and chemical properties and its
relation to living things.
What is Hydrogeology?????
Hydrogeology (hydro- meaning water, and -
geology meaning the study of the Earth) is the
area of geology that deals with the distribution
and movement of groundwater in the soil and
rocks of the Earth's crust.

Hydrological cycle / water cycle.
It is the normal water recycling system on Earth.
Continuous movement of water on, above and
below the surface of the Earth.
The storage and movement of the water between the
Biosphere, Lithosphere, Atmosphere and Hydrosphere is
called Hydrological cycle

“Due to solar radiation, water evaporates, generally from the
sea, lakes, etc. Water also evaporates from plant leaves through
the mechanism of transpiration. As the steam rises in the
atmosphere, it is being cooled, condensed, and returned to the
land and the sea as precipitation. Precipitation falls on the
earth as surface water and shapes the surface, creating thus
streams of water that result in lakes and rivers. A part of the
water precipitating penetrates the ground and moves
downward through the incisions, forming aquifers. Finally, a
part of the surface and underground water leads to sea. During
this trip, water is converted in all phases: gas, liquid, and solid.
As mentioned above, water always changes states between
liquid, vapor, and ice, with these processes happening in the
blink of an eye and over millions of years.

THE STAGES OF THE CYCLE
ARE:
1) Evaporation
2) Transpiration
3) Interception
4)Condensation
5) Precipitation
6) Run-off

EVAPORATION
During part of the
water cycle, the sun
heats up liquid water
and changes it to a gas
by the process of
evaporation. Water
that evaporates from
Earth’s oceans, lakes,
rivers, and moist soil
rises up into the
atmosphere.

Saturation humidity :At any given temperature, the air can only hold a
certain amount of moisture, which is referred to as the saturation
humidity.
Relative Humidity : The ratio of the measured humidity
(gmwater/m3air) to the saturation humidity. Evaporation ceases when
100% relative humidity is reached

Transpiration is the process by which plants lose
water from their leaves. The water rises in to the
air. (In other words, it’s like plants sweating.)
TRANSPIRATION
The combined loss of water to the
atmosphere via the processes of
evaporation from free water or soil
moisture and transpiration (total water
loss) is called evapotranspiration.

Evapotranspiration includes:
a) Evaporation from open water bodies (ocean, lakes, rivers,
and ponds).
b) Evaporation from bare soil.
c) Transpiration from vegetation (aquatic, terrestrial,
riparian).

When the water in the clouds gets too heavy, the water falls back
to the earth. This is called precipitation.
Precipitation

PRECIPITATION TYPES
1.Orographic
2.Convection
3.Stratiform
Stratiform precipitation occurs
when large air masses rise
diagonally as larger-scale
atmospheric dynamics force them
to move over each other.

CONDENSATION
Water vapour in the air gets cold and changes back into
liquid, forming clouds. This is called condensation.

When rain falls on the land, some of the water is absorbed into
the ground forming pockets of water called groundwater. Most
groundwater eventually returns to the ocean. Other
precipitation runs directly into streams or rivers. Water that
collects in rivers, streams, and oceans is called runoff.
RUNOFF

INTRODUCTION
Groundwater is water that exists in the pore spaces and
fractures in rocks and sediments beneath the Earth’s
surface.
It originates as rainfall or snow, and then moves through the
soil and rock into the ground water system, where it
eventually makes its way back to the surface streams,
lakes, or oceans.
It is regulated by the quantum and speed of rains, extent of
vaporization at the time of rain, temperature, slope of land,
dryness of air, porosity and permeability of rocks, vegetative
cover and water absorbing capacity of the soil.

Groundwater mainly comes from three sources.
They are, first: ‘Meteoric Water’, which is the main source of
groundwater and is received in the form of rain and snow. This
water infiltrates from the surface through fissures, pores and joints
of rocks till it is stored on non-permeable rocks in the form of
groundwater; Second: ‘Connate Water’, which exists in pores and
cavities of sedimentary rocks of seas and lakes. It is also called
sedimentary water. Thirdly: ‘Magmatic Water’ which converts into
water after condensation of vapour as a result of volcanic action at
the time of entering hot rocks.
Sources of Groundwater:

GROUNDWATER MOVEMENT
The path of groundwater through an aquifer affects the
hydraulic conductivity.
•Clay content and
adsorptive properties
• Packing density
• Surface tension
• Preferred orientation
of grains
• Shape (angularity or
roundness) of grains
• Grain size

The geological factors that control the occurrence and
distribution of ground water in any region may be
summarized under the following heads:
• Topography of the area
• Stratigraphy
• Morphology
• Soil conditions
• Lithology of the area
Factors
Topography

Lithology
Soil conditions
Stratigraphy
Morphology

VERTICAL DISTRIBUTION OF
GROUND WATER
The vertical distribution of ground
water mainly divided into two
zones:
Zone of Aeration
Zone of Saturation

ZONE OF AERATION
• The zone of Aeration
consists of interstices
occupied partially by
water and partially by
air.
• The zone of Aeration is
subdivided in to three
types
• Soil water zone
• Intermediate zone or
vadose zone
• Capillary zone

CONT
• Water in the soil-water zone exits at less
than saturation except when excessive
water reaches the ground surface as from
rainfall or irrigation “its thickness varies
with soil type”
• The amount of water present in the soil
water zone depends primarily on the recent
exposure of the soil to moisture .
• Under hot arid conditions a water vapour
equilibrium tends to become established
between the ambient air and the surface of
fine grained soil particles . As a result, only
thin films of moisture knows as
“hygroscopic water” remain adsorbed on
the surfaces.
• For coarse grained materials and where
additional moisture is available.

CONTD..
• Soil water zone was classified by ‘Briggs’ into three subzones
depending on the concentration of moisture content they are:
1.Hygroscopic water.
2.Capillary water .
3.Gravitational water.

CONTD..
1.Hygroscopic water: Absorbed
from the which forms thin layer of
moisture on soil particles surface. The
force are large so that this water is
unavailable to plants.
2. Capillary water:
Exists as continues films around the soil
particles and it is yield by surface
tension and is moved by capillary action
and is available to plants.
3. Gravitational water : Is
excess soil water which drains through
the soil under the influence of gravity.
Capillary water

2.INTERMEDIATE VADOSE ZONE
• The intermediate vadose zone extends
from the lower edge of the soil water zone
to the upper limit of the capillary zone.
• The thickness may vary from zero, where
the bounding zones merge with a high
water table approaching ground surface to
more than 100m under deep water table
conditions.
• Non moving vadose water is held in place
by hygroscopic and capillary forces
temporary excesses of water migrate
downward as gravitational water.

3.CAPILLARY ZONE
• The capillary zone extends from the water table up to
the limit of capillary rise of water or capillary fringe is
one which lies immediately above the zone of saturation
. The water available in the zone is termed as capillary
water.
• Water is drawn up from the zone of saturation through
capillary action and suspended by capillary force .
• Thickness of this zone is dependent upon the texture of
soil formation, above the zone of saturation .if the size of
pores is fine the upward movement of water through the

CONTD..
The important features of capillary fringe are
1. Its lower part, which is immediately adjacent to the water table,
contained water in all pores.
2. Moisture content is being equal to the porosity of soil formation .
3. Water pressure is less than the atmospheric pressure.
4. Thickness of capillary fringe tends to get increased or decreased,
depending upon water table fluctuation.

WATER TABLE
The subsoil horizon below the surface is called as the zone of aeration
or vadose zone. Below this zone there is a water saturated media is
called as the ground water.
The upper most surface of the zone of saturation is termed as the water
table. Water table forms the boundary between the zone of aeration and
zone of saturation.

ZONE OF SATURATION
• In Zone of saturation all interstices are filled with water
under hydrostatic pressure.
• In the zone of saturation, groundwater fills all of the
interstices; hence the porosity provides a direct measure of
the water contained per unit volume.
• A portion of the water can be removed from subsurface
strata by drainage or by pumping of a well. However,
molecular and surface tension forces hold remainder of the
water in place.

CONCLUSION
• Vertical Distribution gives the distribution of water in
varies stages.
• To access the movement of water either horizontally or
vertically based on geological condition.
• Most of the well which gives high yield it means to gives
the surface to subsurface runoff easily through vertical
distribution of ground water.
• It helps the quantity of water availability in the system.

HYDROLOGICAL PROPERTIES OF
ROCKS

CONTENTS
Hydrological properties of rocks
a. Porosity
b. Permeability
c. Specific yield
d. Specific retention
e. Hydraulic conductivity
f. Transmissibility
g. Transmissivity
h. Storativity
Conclusion

POROSITY (n)
Most of the rocks contain pores or pore spaces or voids within.
Porosity is nothing but the ratio between the total voids or pores
of a particular rock to the total volume of the same rock.
Vpor
i.e. Porosity (n) = ------- where, Vpor = Volume of the Pores
Vtot Vtot = Total Volume of the Rock

Porosity is an index of the amount of the groundwater that can be
stored in a saturated formation.
It is usually expressed as percentage of the bulk volume of the rock,
for instance, if one cubic meter sand contains 0.40 cubic meter of
pores, then, the porosity is said to be 40%.

• The Porosity of a formation is mainly
controlled by the shape, sorting, packing
and degree of cementation of the grains
with which it is made up of.
• When the grains are shaped like flakes
and compressed together, the porosity will
be low. If the grains that make up the
rocks are mostly spherical in shape, the
rock will have higher porosity.

They are 2 types of porosity:-
Primary Porosity:
It is the Porosity that developed during the final stages of
Sedimentation or that was present within the Sedimentary
particles at the time of Deposition..
Secondary Porosity:
It is the Porosity developed in a rock after its deposition
or emplacement through processes such as the action of
Solution, Fracturing, etc.

PRIMARY AND SECONDARY POROSITY

It is the capacity of a porous
medium to transmit water or
fluid i.e. a relative ease to flow
of a fluid under unequal
pressure.
It is a factor how a rock will act
as a source of water for a well.
We call a rock permeable when
the rock has got many
connected pore spaces of which
a large part are sizeable so that
water can move freely through
them.
PERMEABILITY (p)

PERMEABILITY OF DIFFERENT SEDIMENTS

FACTORS AFFECTING PERMEABILITY
• Groundwater temperature and pressure
• Size of the pore openings in the rock
• Number of the pore openings in the rock
• The connectivity of the pores
• Grain Size, sorting, solution openings.
Hence, some rocks may be porous but not
permeable.
E.g. Shales can have substantial porosity,
but it has low permeability because its pores
are too small for water to pass through it.

SPECIFIC YIELD (SY)
Specific yield is the percentage (%) of total
volume of the saturated aquifer which can be
drained from unit volume of saturated
aquifer material under gravity.
It can be expressed as follows;
Volume of water drained
Specific Yield = ----------------------------------------------
Total Volume of Rock or Aquifer

SPECIFIC RETENTION (SR)
Specific retention is the percentage (%) of total volume of the
saturated aquifer which will be held/retained in a unit
volume of saturated
aquifer by molecular
and surface tension
forces against the
force of gravity after
full gravity drainage.
It can be expressed as follows;
Volume of Retained Water
Specific Retention =
Total Volume of Rock or Aquifer

HYDRAULIC CONDUCTIVITY
It is the ability of a porous material to transmit a fluid or
Liquid. It is usually expressed in units of length per time, i.e.
feet per day or centimeter per second, etc.

HYDRAULIC CONDUCTO-METER
The hydraulic conductivity is a measure of a soil's ability to
transmit water. Water movement, whether under saturated or
unsaturated conditions, is highly dependent on the hydraulic
conductivity.

FACTORS AFFECTING HYDRAULIC CONDUCTIVITY
• Groundwater temperature.
• Size of the pore openings in the rock.
• Number of the pore openings in the rock.
• The connectivity of the pores.
• Grain size, sorting, solution openings, etc.

TRANSMISSIBILITY
Transmissibility is the rate of flow of
water, at prevailing temperatures,
through a vertical strip of the aquifer,
one unit width and extending the full
saturated thickness of the aquifer
under a gradient of 100 per cent.

Co-efficient of Transmissibility
can expressed as follows;
Q = Pmi
where,
Q = rate of flow through the cross section of an aquifer
P = average co-efficient of permeability of the material from
top to bottom of the aquifer
m = thickness of the aquifer
i = hydraulic gradient

TRANSMISSIVITY (T)
Transmissivity , the aquifer that is transmissive while the water
itself is transmissible. Transmissivity of confined or
unconfined aquifers usually is evaluated from pumping tests
on wells. The dimension of T is length2/time.

the unit of T is U.S gallons per day per foot or gpd/ft
(1m2/day=80.5 gpd/ft). Using water table slope i and
transmissivity T, the flow rate in an aquifer can thus be
calculated with simple equation.
Q=WTi
Where W is the width of the aquifer normal to the direction of
the flow.

STORATIVITY
Storativity is the volume of water that an
aquifer takes into storage per unit
surface area of the aquifer. For an
unconfined aquifer, the
Storativity is equal to the specific yield.
For a confined aquifer, the strata is not
dewatered. Thus, the amount of water
gained is much less than the specific
yield.

STORAGE CO-EFFICIENCY
Storage co-efficient can be expressed as follows;
n γw b α
S = ----------- (β + ------)
104 n
Where,
S = Co-efficient of storage
n = Porosity of an aquifer
b = Saturated thickness of the aquifer
γw = Unit of water
β,α = Reciprocals of the bulk modulus of
elasticity of aquifer

CONCLUSION
• Porosity=Specific yield + Specific Retention
• Transmissibility is the rate of flow of water through a Vertical
strip of the Aquifer.
• Thus, the recharge of Meteoric Water and other Surface Water to
Underground, discharge of water and its movement through
Rocks, wholly depend on the above Hydrological Properties of
Rocks.
• Different Rock types and Sediments have their own specific
Hydrological Properties based mainly on their Texture.

Water bearing geologic formations
INTRODUCTION
• Aquifer is a saturated, permeable, geologic unit
that can transmit a significant amount of
groundwater under an ordinary gradient.
• The place where water enters an aquifer, through
precipitation or stream input, is called the
recharge area.
• Springs or gaining streams, where groundwater
comes out of the aquifer, are termed discharge
areas.

• Simply Aquifers are geologic units that can store and
transmit significant quantities of water.
• Good aquifers include sandstone, conglomerate, sand
and gravel ,well-joined limestone, and some
fragmental or fractured volcanic rocks such as
columnar basalt

• Aquifuge
• A geological unit is neither porous nor permeable
• That neither transmits nor stores water
• Aquiclude
• A geologic unit that can only store water but does not transmit
enough water
• Aquicludes are made up of low porosity and low permeability
rock/sediment such as shale or clay.
• Aquitard
• Partly permeable geologic formation.
• A unit that stores and transmits water fast enough to be
hydrologically significant but insufficient for well production
• For example, sand lenses in a clay formation will form an aquitard
Important Terminologies

CLASSIFICATION OF AQUIFERS
• Aquifers are classified in terms of their structure,
hydraulic performance, texture, lithology, and the
mobility of the water.
• According to the mobility of the water an aquifer can be
classified into aquifuge ,aquitard and aquicludes.
• Aquifers can be classified as unconfined and confined,
depending on the presence or absence of a water table.
• According to the lithology they are classified in detritus
and carbonated.
• According to the texture may be classified into porous
and fissure aquifers.

1. Unconfined aquifers
• They are covered by permeable geologic formations and
the upper surface where the rock formations are fully
saturated is called the water table.
• Also called a phreatic or water table aquifer
• They receive recharge directly from the infiltration of
rainfall and surface water.
• The hydraulic conductivity of unconsolidated aquifers is
variable, depending on the sorting of aquifer materials
and the amount of silt and clay present, but generally it is
high.
• Unconsolidated sand and gravel aquifers are susceptible
to contamination because of their high hydraulic
conductivity.
TYPES OF AQUIFERS

2. Confined aquifers
• Confined aquifers are those covered (confined) by an
impermeable or semi-permeable layer of rock.
• The water level in a well; that is open in such an
aquifer is higher than the impermeable surface that
bounds the aquifer from above.
• They are not directly recharged by vertical infiltration.
• Need to be connected to an unconfined area through
which recharge can occur.
• There is generally some transfer or flow of groundwater
between the confined aquifer and the confining layers.

3. Perched Aquifer
• Perched aquifers occur where groundwater is perched above unsaturated
rock formations as a result of a discontinuous impermeable layer.
• Perched aquifers are fairly common in glacial sediments.
• They occurs above the main water table.
• They also occur in other sedimentary formations where weathered layers,
ancient soils or caliches have created impermeable zones.

4. Artesian Aquifer
• An artesian aquifer is confined by rock layers that restrict water flow, resulting in
an aquifer that is "pressurized."
• Water is virtually squeezed to the pressure level above the ground surface.
• Water in an artesian aquifer could rise to the same height as the water table in the
recharge area.
• The well installed in an artesian aquifer is called an artesian well or flowing well.
• A freely flowing spring supplied by an artesian aquifer is an artesian spring.

5. Leaky aquifer
• A leaky aquifer is a phreatic aquifer that is bounded from below by
an aquitard.
• This is a layer less permiable than the aquifer overlying it and often
much thin. Thus it behaves as a "semi-permeable membrane" through
which leakage out 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 aquitards.

6. Bounded aquifer
• An aquifer is limited to its extent due to the
presence of an impermeable layer or barrier, if it
checks a source of recharge such as a stream or any
canals the aquifer is said to be bounded aquifer.

7. Coastal aquifers
• The available fresh water is limited in coastal areas, over
pumping may cause the sea water intrusion and this
ultimately result in the deterioration of ground water quality.
• This is a major problem faced by the public in several parts of
the world. Coastal hydrological condition can be represented
by a confined aquifer

CONCLUSION
• An aquifer is a body of saturated rock through which water
can easily move.
• Aquifers must be both permeable and porous and include
such rock types as sandstone, conglomerate, fractured
limestone and unconsolidated sand and gravel.
• Fractured volcanic rocks such as columnar basalts also
make good aquifers.
• Provide two important functions: They transmit ground
water from areas of recharge to areas of discharge, and they
provide a storage medium for useable quantities of ground
water.
• Aquifers are classified in terms of their structure, hydraulic
performance, texture, lithology, and the mobility of water.

CONTENT
• Introduction
• Physical properties of
water
• Temperature
• Transparency
• Colour
• Odour
• Taste
• Water density
• Compressibility
• Viscosity
H

WATER STATISTICS
• Covers 75% of Earth’s surface
• 97% oceans
• 3% freshwater
• 2% (of Total) in ice caps and glaciers
• 1% in lakes, underground, or in
atmosphere (usable by humans)
• Makes up 70% of the human body
• 92% of blood plasma
• 80% of muscle tissues
• 60% of red blood cells

INTRODUCTION
water is a transparent fluid which forms the
World streams lakes oceans and rain and is the
major constituent of the fluid of living things. As a
chemical compound a water molecules contains one
oxygen and two hydrogen atoms. That are
connected by covalent bonds. Water is a liquid at
standard ambient temperature and pressure, but it
often co-exists on earth with its solid state ice and
gaseous state, steam (water vapour ).it also exist as
snow, fog, dew and cloud.

PHYSICAL PROPERTIES
Water:
• Is clear, colorless, odorless, and tasteless
* Colors, tastes and odors are caused by substances dissolved in the water.
• Boils at 100°C
• Freezes at 0°C
• Density = 1.0 g/mL (at 4°C)
• Water is a Polar Molecule

TEMPERATURE
The temperature of groundwater varies greatly with geologic
structure and geologic evolution of structural units, as well as
with physiographic conditions and the regime of recharge. In
the permafrost regions, saline waters locally have subzero
temperatures of about-5degree and lower. In middle
latitudes, of shallow underground water vary with local
climatic and hydrologic.

TRANSPARENCY
Transparency of underground water of controlled by the
concentrations of dissolved mineral matter, mechanical impurities,
organic matter and colloids, in terms of transparency, the following four
classes of underground water are specified: (1) transparent;(2)slightly
muddy;(3)muddy; and (4)very muddy.

COLOUR
Colour is a common
constituent of many natural waters
and it is caused by metallic
substances such as iron and
manganese compounds, humus
materials, algae, weeds and
protozoa. Colour of groundwater is
dictated by its chemistry and the
presence of impurities. Most
underground waters are colourless.
Hard waters are bluish, ferrous
salts and hydrogen sulfide colour
the waters in Greenish blue,
organic humic compounds make it
yellowish, while suspended
mineral particles make it grayish.

ODOUR
No water can be quite satisfactory for
domestic and industrial purposes if it possess any
odour. Underground waters usually have no odour,
but sometimes it is detectable for example, the
hydrogen sulfide imparts the smell of rotten
eggs to the water; stagnant water in some wood
cased wells often has an objectionable musty
odour; shallow underground waters
communicating with swamp waters have a special
marsh odour . It has been found that the water
odour is often related to the bacterial decay of
organic matter.

TASTE
Water may have a taste brought about by dissolved mineral
matter, gases and impurities. Water containing calcium and
magnesium bicarbonates or carbonic acid gives it a nice taste. Taste is
always accompanied by odour. Abundant organic compound ,presence
of magnesium and sodium sulphates gives it a sweet taste while Iron
ions bring about the special rusty taste.

WATER DENSITY
Water density is the ratio of its mass
to its volume at a certain temperature. Unit
density is that of the distilled water at 4
degree . The density of water depends upon its
temperature and an amount of dissolved salts,
gases and suspended and particles.
Underground water densities range from 1to
1.4g/cm2 and it is measured by an aerometer
or picknometer. If the water contain
perdominantly sodium chloride , the water
density is determined from its salinity in
baume degree.

COMPRESSIBILITY
Compressibility of water shows the magnitude of
changes in water volume induced by pressure changes . Water
compressibility depends mainly on an amount of dissolved gas,
temperature, and water chemistry .in deep portion of the earths
crust, water is subject not only to the action of pressure, but also
to that of temperature and gases dissolved therein . Pressure
causes a decrease in water volume, whereas temperature and
gases dissolved therein. Pressure causes a decrease in water
volume, whereas temperature and dissolved gases in increase.

VISCOSITY
Viscosity characterizes the
internal resistance offered by water
particles to a water flow . Dynamic
viscosity and kinematic viscosity are
distinguished viscosity of underground
water depends mainly upon the
temperature and amount of dissolved
salts (salinity). Water viscosity
decreases with rising temperature and
increases with growing salinity.

TURBIDITY
Turbidity is an important parameter
for characterizing water quality. It is an
expression of optical property of water
containing insoluble substances which cause
light to be scattered rather than transmitted in
straight lines. The amount and angular
distribution of this scattered light of governed
not only by the insoluble substances but also
by their size shape and refractive index . In
most of the water turbidity is due colloidal and
extremely fine dispersions .suspended matter
such as clay , silt, finely divided organic and
inorganic matter, plankton and other
microscopic organisms also contribute to
turbidity .

Biological Properties of Water

BIOLOGICAL CHARACTERISTIC OF WATER
-It refers to a variety of living organisms that can
be found in water. These include microscopic
viruses, bacteria, protozoan as well as
phytoplankton, zooplankton, insects, etc.
Bacteria Zooplankton Protozoa

BIOCHEMICAL OXYGEN DEMAND(BOD):-
Biochemical oxygen demand the amount of dissolved oxygen required
by aerobic biological organisms to degrade the organic material
present in a water body at certain temperature over a specific time
period. It widely used as an indication of the organic quality of water
and thus representing the pollution load.
It is most commonly expressed in milligrams of oxygen consumed per
liter of sample during 5 days (BOD) of incubation at 20°C. When
organic matter decomposes, microorganisms (such as bacteria and
fungi) feed upon this decaying material and eventually the matter
becomes oxidized. The harder the microorganisms work, the more
oxygen will be used up giving a high measure of BOD, leaving less
oxygen for other life in the water.

Microbial contamination is one of the major concerns of water quality.
Many types of microorganisms are naturally present in the water such as
Protozoans -Amoeba, cryptosporidium.
Bacteria – typhus, cholera,
Viruses –Polio, hepatitis A, etc.,
Helminths – hookworm, roundworm, Etc.,
E. coli is a bacterial species found in the fecal matter of warm-blooded
animals (humans, other mammals, and birds). There are certain forms of
coliform bacteria that do not live in fecal matter but instead live in soils.
Most of the fecal coliform cells found in fecal matter are E. coli.
Untreated sewage, poorly maintained septic systems, un-scooped pet
waste, and farm animals with access to water bodies can cause high
levels of fecal coliform bacteria to appear in and make the water
unhealthy.
Microbial Contamination

BIOLOGICAL CONTAMINANT:-
A description of the factor, along with information
on where it comes from and its potential human
health impacts is given in the table below:-
Potential
contamination
Contamination source Human effects
Blue Green
algae
Naturally occurring but generally
compete well in low light condition;
warm temperature and high nutrient
concentrations.
Presence of gas vacuoles.
Diarrhea,
Vomiting
Nausea.
Cryptosporid
ium
Cryptosporidium is a microscopic
water born parasite, it can be spread
by person to person contact, handling
of fecal materials
Watery diarrhea ,
abdominal
cramps, nausea,
weight loss, low
grade fever.

Fecal coliform
bacteria
Human sewage
Animal waste
Septic systems
Coliform bacteria may
include diarrhea, cramps,
nausea
Other
bacteria
Human sewage
Animal waste
Septic systems
In house hold cause
staining unpleasant and
taste. Pathogenic
bacteria may cause
gastrointestinal illness .
viruses Septic tanks
human sewage
Animal waste
Hepatitis, Fever, nausea

ALGAE CONTROL:-
The maintenance and
prevention of algal growth is
important. There are two
groups of algae:
1.Free floating types i.e. green
and mustard varieties.
Fig: Free Floating Algae
2. Black algae i.e. dark blue
green algae.
The growth of both types can prevented by using Algaecides.

CHEMICAL PROPERTIES OF WATER
The health concerns associated with chemical
constituents of drinking-water arise mainly from
the ability of chemical constituents to cause adverse
health effects after extended exposure time. There
are few chemical constituents of water that can lead
to health problems resulting from even a single
exposure. Number of serious health concerns may
occur as a result of the chemical contamination of
drinking-water.

pH:
pH is a measure of how acidic or basic (alkaline) the water is. It is
defined as the negative log of the hydrogen ion concentration. The
pH scale is logarithmic and ranges from 0 (very acidic) to 14 (very
alkaline). For each whole number increase (i.e. 1 to 2) the hydrogen
ion concentration decreases tenfold and the water becomes less
acidic. The range of natural pH in fresh waters extends from around
4.5, for acid, peaty upland waters, to over 10.0 in waters where there
is intense photosynthetic activity by algae. However, the most
frequently encountered range is 6.5-8.0. The range of pH for fisheries
is considered to be 5.0-9.0, though 6.5-8.5 is preferable. At the
extreme ends of the pH scale, (2 or 13) physical damage to gills,
exoskeleton and fins occurs. Changes in pH may alter the
concentrations of other substances in water to a more toxic form.
Ammonia toxicity, chlorine disinfection efficiency, and metal
solubility are all subjective to changes in pH value.

THE PH SCALE
The pH scale in any aqueous solution : [ H+ ] [OH-] = 10-14

Electrical Conductivity:
The conductivity of water is an expression of its ability to conduct an
electric current as a result of breakdown of dissolved solids into
positively and negatively charged ions. The major positively charged
ions are sodium (Na+), calcium (Ca+2), potassium (K+) and
magnesium (Mg+2). The major negatively charged ions in water
include chloride (Cl-), sulfate (SO4-2), carbonate (CO3-2), and
bicarbonate (HCO3-). Nitrates (NO3-2) and phosphates (PO4-3) are
minor contributors to conductivity, although they are very important
biologically. Conductivity in itself is a property of little interest but it
is an invaluable indicator of the range of hardness, alkalinity and the
dissolved solids content of the water. Conductivity will vary with
water source: ground water, water drained from agricultural fields,
municipal waste water, rainfall. Therefore, conductivity can indicate
groundwater seepage or a sewage leak.

Salinity
Salinity is a measure of the amount of salts in the water.
Because dissolved ions increase salinity as well as
conductivity, the two measures are related. The salts in sea
water are primarily sodium chloride (NaCl). High salinity
due to a combination of dissolved ions including sodium,
chloride, carbonate and sulfate. Salts and other substances
affect the quality of water used for irrigation or drinking.
They also have a critical influence on aquatic biota, and
every kind of organism has a typical salinity range that it
can tolerate. The presence of a high salt content may make
water unsuitable for domestic, agricultural or industrial use.

Alkalinity
The alkalinity of natural water is generally due to the presence of
bicarbonates. It is a measure of the capacity of the water to neutralize
acids. It is due to presence of carbonates and hydroxides. Alkalinity is
important for fish and aquatic life because it protects against rapid pH
changes. Living organisms, especially aquatic life, function best in a
pH range of 6.0 to 9.0. Higher alkalinity levels in surface waters can
buffer the acid rain and other acid wastes. This inhibits harmful pH
changes for the protection of aquatic life. Alkalinity in streams is
influenced by rocks and soils, salts, plant activities, and certain
industrial wastewater discharges. Low nutrient (oligotrophic) lakes
tend to have lower alkalinity while high nutrient (eutrophic) lakes have
a tendency of higher alkalinity.

Hardness
Hardness is a natural characteristic of water which determines the
consumer acceptability for drinking purposes. The hardness of water is
due to the presence of calcium and magnesium minerals that are
naturally present in the water. The common signs of a hard water
supply are poor lathering of soaps and scum. The hardness is made up
of two parts: temporary (carbonate) and permanent (non-carbonate)
hardness. The temporary hardness of water can easily be removed by
boiling the water.
The following is a measure of hardness (expressed in mg/l as CaCO3):
Soft: 0 - 100 mg/l as CaCO3
Moderate: 100 - 200 mg/l as CaCO3
Hard: 200 - 300 mg/l as CaCO3
Very hard: 300 - 500 mg/l as CaCO3
Extremely hard: 500 - 1,000 mg/l as CaCO3

There are various kinds of trace ions in water supply that influence chemical
nature and account for the bulk of natural water mineral content. Most of the
dissolved, inorganic chemicals in freshwater occur as ions. These ions come
in water body from atmospheric deposition, rock weathering, runoff etc.
Cations:
Sodium may be of health significance to individuals. Sodium salts are
generally highly soluble in water and are leached from the terrestrial
environment to groundwater and surface water
Potassium is an essential nutritional element in drinking water supplies but
in its excessive quantities, it acts as a laxative.
Calcium is essential to human nutrition and a key element in the formation
of teeth and bones. It is also known as limestone and is a cause of water
hardness.
Magnesium is one of the most common elements in the earth’s crust.
Sulfates of magnesium at very high concentrations may have a laxative
effect on some people. It also give an unpleasant taste at high concentration
Major ions in Water:

Anions:
Chloride in drinking water is generally not harmful to human
health except when present in high concentrations. The high
concentration may be injurious to heart and kidney patients. The
restriction on chloride concentrations in potable water are
determined by taste requirements.
Water with objectionable Sulfate content may have a bitter taste. It
also contributes to odor problems.
Excessive bicarbonate adds to the salinity and total solid content of
water while Carbonate content of water can also be considered as
the temporary water hardness as it can easily be removed by
boiling.
Nitrates even at low concentrations can cause health problem to
infants of six months of age or less and pregnant women by
affecting the oxygen carrying capacity of the blood.

Heavy Metals
Heavy metal refers to any metallic chemical element that has a
relatively high density and toxic at low concentration. Some major
examples of heavy metals are mercury (Hg), cadmium (Cd), arsenic
(As), chromium (Cr), nickel (Ni), copper (Cu), cobalt (Co) and lead
(Pb) etc. These are the natural components of geological environment.
They enter the human body via food, drinking water and air to small
extent. Some heavy metals (e.g. copper, selenium, zinc) are necessary
to keep up the metabolism of the human body as trace elements.
However, they can be poisonous at higher concentrations leading to
various serious diseases.

Dissolved Oxygen
Dissolved oxygen is the amount of gaseous oxygen (O2) dissolved in
an aqueous solution. It gets into water by diffusion from the
surrounding air, by aeration (rapid movement), and as a waste product
of photosynthesis. The oxygen in dissolved form is needed by most
aquatic organisms to survive and grow. Organisms such as trout and
stoneflies require high amount of DO while some others like catfish,
worms and dragonflies can survive in somewhat lower amount. The
absence of enough amount of oxygen in water can lead to death of
adults and juveniles, reduction in growth, failure of eggs/larvae to
survive, change of species present in a given water body. The hypoxic
condition in water body (DO< 3mg/L) causes reduced cell
functioning and disrupts circulatory fluid balance in aquatic system,
eventually leading to death.

It is an indicative measure of the amount of oxygen that can be
consumed by reactions in a measured solution. It is commonly
expressed in mass of oxygen consumed over volume of solution
which in SI units is milligrams per liter (mg/L). A COD test can be
used to easily quantify the amount of organics in water. The most
common application of COD is in quantifying the amount of
oxidizable pollutants found in surface water (e.g. lakes and rivers)
or wastewater. COD is useful in terms of water quality by providing
a metric to determine the effect an effluent will have on the
receiving body
Chemical oxygen demand (COD)

Hydrogeology

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