Water resources engineering notes

1. Water Resource Engg.
Jitesh Kumar
Water Resource Engg.-1
Jitesh Kumar

2. drology
deals with the study of occurrence, distribution, movemen
e properties of water on the earth.
e properties of water on the earth.
of occurrence, distribution, movemen
earth.
earth.

3. e main applications of engineering hydrology are
ovides guidance for proper planning and management of water resources.
ulates rainfall, surface runoff, and precipitation.
etermines the water balance for a particular region.
etermines the water balance for a particular region.
itigates and predicts flood, landslide and drought risk in the region.
timates the water resource potential of the river basins
bles real-time flood forecasting and flood warning
e main applications of engineering hydrology are:
planning and management of water resources.
ulates rainfall, surface runoff, and precipitation.
etermines the water balance for a particular region.
etermines the water balance for a particular region.
itigates and predicts flood, landslide and drought risk in the region.
timates the water resource potential of the river basins
time flood forecasting and flood warning.

4. rology analyses the variations observed in the catchments by bringing a
tionship between the surface water and groundwater resources of the catc
tionship between the surface water and groundwater resources of the catc
rology studies the required reservoir capacity that is necessary for irrigation
nicipal water supply purpose during drought conditions.
used in the design and operation of hydraulic structures
used for hydropower generation.
gests way to control erosion and sediments.
rology analyses the variations observed in the catchments by bringing a
tionship between the surface water and groundwater resources of the catc
tionship between the surface water and groundwater resources of the catc
rology studies the required reservoir capacity that is necessary for irrigation
nicipal water supply purpose during drought conditions.
used in the design and operation of hydraulic structures
gests way to control erosion and sediments.

6. rological cycle
hydrological cycle is commonly referred to as the Water Cycle.
defined as the process in which water from all the freshwater
defined as the process in which water from all the freshwater
rs etc), oceans, and land move to the atmosphere and back in the form of
cipitation.
important for the balance in the ecosystem and biological system of the ea
necessary for the cycling and processing of solar energy, sediments, and ot
ments that are necessary for sustaining life on Earth.
hydrological cycle consists of a series of processes such as evaporation,
hydrological cycle consists of a series of processes such as evaporation,
cipitation, percolation, runoff, etc.
a continuous cycle.
hydrological cycle is commonly referred to as the Water Cycle.
defined as the process in which water from all the freshwater sources (lake
defined as the process in which water from all the freshwater sources (lake
oceans, and land move to the atmosphere and back in the form of
for the balance in the ecosystem and biological system of the ea
for the cycling and processing of solar energy, sediments, and ot
ments that are necessary for sustaining life on Earth.
hydrological cycle consists of a series of processes such as evaporation,
hydrological cycle consists of a series of processes such as evaporation,

7. e water from the sources like lakes, rivers, ocean etc. converts to
or by evaporation due to solar heat.
e vapor goes on accumulating continuously in the atmosphere.
s vapor is again condensed due to the sudden fall of temperatur
ssure. Thus clouds are formed.
ese clouds again causes the precipitation (rainfall).
me of the vapor is converted to ice at the peak of the mountains
again melts is summer & flows as rivers to meet the sea or ocea
again melts is summer & flows as rivers to meet the sea or ocea
ese process of evaporation, precipitation & melting of ice go on
tinuously like an endless chain & thus a balance is maintained in
mosphere.
e water from the sources like lakes, rivers, ocean etc. converts to
or by evaporation due to solar heat.
e vapor goes on accumulating continuously in the atmosphere.
s vapor is again condensed due to the sudden fall of temperatur
ese clouds again causes the precipitation (rainfall).
me of the vapor is converted to ice at the peak of the mountains
again melts is summer & flows as rivers to meet the sea or ocea
again melts is summer & flows as rivers to meet the sea or ocea
ese process of evaporation, precipitation & melting of ice go on
tinuously like an endless chain & thus a balance is maintained in

8. in Fall :-
e amount of water falling in rain.
s the main form of precipitation in India, rainfall is defined
s the main form of precipitation in India, rainfall is defined
ecipitation in the form of water.
e of drops are larger than 0.5 mm & maximum size of drop
out 6mm.
nfall is expressed as depth of water (in mm or cm) that wo
nfall is expressed as depth of water (in mm or cm) that wo
nd on earth surface.
e amount of water falling in rain.
s the main form of precipitation in India, rainfall is defined
s the main form of precipitation in India, rainfall is defined
ecipitation in the form of water.
e of drops are larger than 0.5 mm & maximum size of drop
nfall is expressed as depth of water (in mm or cm) that wo
nfall is expressed as depth of water (in mm or cm) that wo

9. Rain Gauge
It is an instrument which measures the rainfall at a p
Rain gauges are also known as udometer, pluviomet
Rain gauges are also known as udometer, pluviomet
ombrometer.
Rain Gauge Station
The place at which rain gauges are installed for
The place at which rain gauges are installed for
measurement of rain fall is called as Rain Gauge Stat
It is an instrument which measures the rainfall at a p
Rain gauges are also known as udometer, pluviomet
Rain gauges are also known as udometer, pluviomet
The place at which rain gauges are installed for
The place at which rain gauges are installed for
measurement of rain fall is called as Rain Gauge Stat

10. Site Selection for Rain gauge station
During site selection for rain gauge station, following points sho
kept in mind :-
kept in mind :-
The ground must be leveled & in open space
The instrument should have a horizontal catch surface
The gauge should be near the ground to reduce the wind affect,
must be sufficiently high to prevent splashing, flooding of water
The instrument must be surrounded by an open fence to protec
The instrument must be surrounded by an open fence to protec
from cattle, dogs etc.
The selected site must be protected from strong wind.
Site Selection for Rain gauge station :-
During site selection for rain gauge station, following points sho
The ground must be leveled & in open space
The instrument should have a horizontal catch surface
The gauge should be near the ground to reduce the wind affect,
must be sufficiently high to prevent splashing, flooding of water
The instrument must be surrounded by an open fence to protec
The instrument must be surrounded by an open fence to protec
The selected site must be protected from strong wind.

11. pes of Rain gauge –
n-recording rain gauge. E.g. :-
cording type rain gauge :- Automatic Rain gauge
cording type rain gauge :- Automatic Rain gauge
- Tipping bucket Rain gauge
Weighing bucket rain gauge
Float type rain gauge
symon’s Rain gauge
Automatic Rain gauge
Automatic Rain gauge

12. Non-Recording type rain gauge :
It is commonly used in India by meteorological departmen
This rain gauge does not record rainfall but it only collects
This rain gauge does not record rainfall but it only collects
rain.
Symon’s rain gauge mainly consists of a funnel & receiver.
Receiver :-
The receiver is made up of zinc metal in the shape of a cyli
This collected rain is measured by this cylinder.
This collected rain is measured by this cylinder.
The diameter of the bottle & the top diameter of funnel is
127mm.
Recording type rain gauge :-
It is commonly used in India by meteorological departmen
This rain gauge does not record rainfall but it only collects
This rain gauge does not record rainfall but it only collects
Symon’s rain gauge mainly consists of a funnel & receiver.
The receiver is made up of zinc metal in the shape of a cyli
This collected rain is measured by this cylinder.
This collected rain is measured by this cylinder.
The diameter of the bottle & the top diameter of funnel is

13. Funnel :-
The funnel is fitted in the neck of the bottle
Both receiver & funnel are then placed in a metal casing w
Both receiver & funnel are then placed in a metal casing w
suitable packing
The base of the metal casing is 210 mm.
The funnel is fitted in the neck of the bottle
Both receiver & funnel are then placed in a metal casing w
Both receiver & funnel are then placed in a metal casing w
metal casing is 210 mm.

14. ome Important Terms in Hydrology
ain fall intensity :- It is maximum rainfall during a short per
is the ratio of the total amount of rainfall (rainfall depth) fa
is the ratio of the total amount of rainfall (rainfall depth) fa
uring a given period.
is represented in mm/hr.
nnual Rainfall :-
is the total rainfall during the period of one year.
is the total rainfall during the period of one year.
ome Important Terms in Hydrology
It is maximum rainfall during a short per
is the ratio of the total amount of rainfall (rainfall depth) fa
is the ratio of the total amount of rainfall (rainfall depth) fa
is the total rainfall during the period of one year.
is the total rainfall during the period of one year.

15. erage Rainfall :-
s arithmetic time average of rain fall.
s total rainfall divided by time period.
s total rainfall divided by time period.
erage annual rainfall :-
s the average value of rainfall over a period of 35 years.
s calculated by adding up the annual rain fall for 35 years &
iding the sum by no. of years.
iding the sum by no. of years.
s denoted by ‘P’.
s arithmetic time average of rain fall.
s total rainfall divided by time period.
s total rainfall divided by time period.
s the average value of rainfall over a period of 35 years.
s calculated by adding up the annual rain fall for 35 years &
iding the sum by no. of years.
iding the sum by no. of years.

16. Average , good & bad year :
A year in which annual rain fall is more than 120% of
verage annual rain fall, it is called good year.
verage annual rain fall, it is called good year.
A year in which annual rainfall is less than 80% of aver
nnual fall, it is called as bad year.
A year in which annual rainfall is within _+ 20 % of ave
f average annual rainfall, it is called as a normal or
f average annual rainfall, it is called as a normal or
verage year.
:-
A year in which annual rain fall is more than 120% of
verage annual rain fall, it is called good year.
verage annual rain fall, it is called good year.
A year in which annual rainfall is less than 80% of aver
nnual fall, it is called as bad year.
A year in which annual rainfall is within _+ 20 % of ave
f average annual rainfall, it is called as a normal or
f average annual rainfall, it is called as a normal or

17. Methods for finding out average annual rainfall of a catchm
Arithmetic average method
Isohyetal Method
Thiessen’s polygon method or representative area method
Methods for finding out average annual rainfall of a catchm
Thiessen’s polygon method or representative area method

18. rithmetic average Method :-
is also known as constant weightage method
his method is used in following conditions :
his method is used in following conditions :
atchment should be flat & plain
When rain gauges are uniformly distributed over a catchmen
ainfall values recorded at various rain gauge stations, so litt
ariations.
is also known as constant weightage method
his method is used in following conditions :-
his method is used in following conditions :-
atchment should be flat & plain
When rain gauges are uniformly distributed over a catchmen
ainfall values recorded at various rain gauge stations, so litt

19. hyetal method :-
isohyet is a line joining points of equal rainfall or contour o
ual rainfall.
his method, rainfall magnitudes recorded at various rain
tions are collected & Isohyetal map is prepared.
e area between successive isohyet is measured using
nimeter.
ultiply each of these areas by the average rainfall between t
ultiply each of these areas by the average rainfall between t
hyets & average rain fall is calculated from the expression :
isohyet is a line joining points of equal rainfall or contour o
his method, rainfall magnitudes recorded at various rain-g
tions are collected & Isohyetal map is prepared.
e area between successive isohyet is measured using
ultiply each of these areas by the average rainfall between t
ultiply each of these areas by the average rainfall between t
hyets & average rain fall is calculated from the expression :

20. Thiessen's Polygon Method/Represented area method :
t is also called weighted average or weighted area method.
n this method, the rain recorded by each station is weighed accor
to the area it serves.
n this method, the rain recorded by each station is weighed accor
to the area it serves.
n this method, adjacent stations are joint by straight lines & thus
divided the whole area into number of triangles.
Then perpendicular bisectors are drawn on each of these lines & f
a series of polygons. Each of theses polygons contain one rain gau
station.
station.
Find the area of each polygon & multiply the area of each
polygon by the respective rain gauge value & calculate aver
rainfall.
Thiessen's Polygon Method/Represented area method :-
t is also called weighted average or weighted area method.
n this method, the rain recorded by each station is weighed accor
n this method, the rain recorded by each station is weighed accor
n this method, adjacent stations are joint by straight lines & thus
divided the whole area into number of triangles.
Then perpendicular bisectors are drawn on each of these lines & f
a series of polygons. Each of theses polygons contain one rain gau
Find the area of each polygon & multiply the area of each
polygon by the respective rain gauge value & calculate aver

21. Runoff :-
It can be described as the part of water cycle that flows o
the land as surface water without being absorbed into the
the land as surface water without being absorbed into the
ground or evaporation.
The amount of water which flows over the earth surface a
all losses is called run-off.
Run-off = rainfall-losses
Run-off = rainfall-losses
It is available for storage in dams and other water bodies.
It can be described as the part of water cycle that flows o
the land as surface water without being absorbed into the
the land as surface water without being absorbed into the
The amount of water which flows over the earth surface a
losses
losses
It is available for storage in dams and other water bodies.

22. tors affecting run-off :-
lowing factors affect the run-off :
ological features :- Run-off depends on nature of soil. If soil
ological features :- Run-off depends on nature of soil. If soil
rvious, run-off is less & if soil is impervious, run
pographical features :- Run-off depends on whether surface
ooth or rough. It also depends on degree of inclination of a
teorological :- if temperature is less & ground is saturated,
ount of run-off will be high.
ount of run-off will be high.
emperature is high & ground is dry then run
s.
off :-
off depends on nature of soil. If soil
off depends on nature of soil. If soil
off is less & if soil is impervious, run-off is more
off depends on whether surface
ooth or rough. It also depends on degree of inclination of a
if temperature is less & ground is saturated,
emperature is high & ground is dry then run-off amount wi

23. nfall characteristics :-
ain-fall is more, run-off will be more.
ain-fall duration os small, run-
ain-fall is over an entire area, run
ape of catchment :-
atchment is of fan shaped then run
atchment is of fern shaped then run
atchment is of fern shaped then run
off will be more.
-off will be less.
fall is over an entire area, run-off will be more.
atchment is of fan shaped then run-off will be more.
atchment is of fern shaped then run-off will be less.
atchment is of fern shaped then run-off will be less.

25. alculation of run-off :-
ollowing methods are used for calculation of run
Inglish method
Inglish method
Run-off coeffient method
Strange curve
Binnie’s method
ollowing methods are used for calculation of run-off :-

26. Strange’s Percentage Table & Curves
Mr. W.L.Strange calculated percentage for converting rainf
nto run-off.
nto run-off.
He carried out his investigations on catchments in Mumbai
He also calculated percentage for converting daily rainfall in
daily run-off.
Different run-off percentages were given for different types
catchment for different values of rainfall.
catchment for different values of rainfall.
He classified the catchments into good, average & bad
catchment depending upon the amount of runoff obtained
rainfall.
Strange’s Percentage Table & Curves
Mr. W.L.Strange calculated percentage for converting rainf
He carried out his investigations on catchments in Mumbai
He also calculated percentage for converting daily rainfall in
off percentages were given for different types
catchment for different values of rainfall.
catchment for different values of rainfall.
He classified the catchments into good, average & bad
catchment depending upon the amount of runoff obtained

29. Binnie’s Percentage Tables & Curve :
Sir Alexander Binnie made observation on two rivers in the
entral India.
entral India.
He worked out certain percentage to connect the monthly
ainfall with the monthly yield for the entire monsoon perio
June to October).
The total monsoon rainfall Vs % of rainfall that becomes run
s shown in the curve.
s shown in the curve.
Binnie’s Percentage Tables & Curve :-
Sir Alexander Binnie made observation on two rivers in the
He worked out certain percentage to connect the monthly
ainfall with the monthly yield for the entire monsoon perio
The total monsoon rainfall Vs % of rainfall that becomes run

32. Maximum Flood Discharge (MFD) :
It is the maximum discharge of river during flood .
It is maximum amount of flow from a catchment area at t
It is maximum amount of flow from a catchment area at t
outlet in a small period.
It is expressed as volume per unit time i.e. m3/s.
It is important to estimate it accurately as it is used for de
of spillway.
of spillway.
The safety of reservoir depends on its correct design.
Maximum Flood Discharge (MFD) :-
It is the maximum discharge of river during flood .
It is maximum amount of flow from a catchment area at t
It is maximum amount of flow from a catchment area at t
It is expressed as volume per unit time i.e. m3/s.
It is important to estimate it accurately as it is used for de
The safety of reservoir depends on its correct design.

33. Factors affecting maximum value of MFD :
ollowing factors affect the maximum value of MFD
intensity of rainfall
intensity of rainfall
Shape of CA
Distribution of rainfall over the CA
Slope of CA
Direction of Wind
Direction of Wind
Nature of Soil
Factors affecting maximum value of MFD :-
ollowing factors affect the maximum value of MFD
Distribution of rainfall over the CA

34. Methods of calculation of MFD :
he various methods used for estimation of MFD are as follows :
Inglis formula
Inglis formula
Dicken's Formula
Ryve’s Formula
Khosla’s Formula
Nawab Jang Formula
Methods of calculation of MFD :-
he various methods used for estimation of MFD are as follows :-