Water education ppt

Hydrology
The flow of water
across and through
near surface
environments

Precipitation
• Single strongest variable driving hydrologic
processes
• Formed by water vapor in the atmosphere
• As air cools its ability to ‘hold’ water
decreases and some turns to liquid or ice
(snow)

• Weather (day to day) vs. climate (years-decades
and patterns)
• What are hydrologists most concerned with?
• Climate and geography result in biome
classification
Weather vs. Climate Patterns

Fig. 4.1
Evaporation & Transpiration

Plant Transpiration
Most water absorption occurs in upper half of root zone

Evaporating playa lake with salts around margin,
eastern Washington

WaterFlow
Hillslope Hydrology
Runoff Processes:
Horton overland flow
Subsurface stormflow,
Return flow
Groundwater flow

Factors Affecting
Water Movement
in Soils

As we discuss mechanisms, remember…
– Many processes occur simultaneously
– Shifts can occur between processes in space
and time
– Antecedent wetness conditions are important
– Watershed characteristic play a central role
Runoff Generation

Horton overland flow occurs when the rainfall
intensity exceeds the infiltration capacity
Horton Overland Flow

Once thought to be the ONLY mechanism of runoff
generation
Became coded into hydrologic models still in use today
Subsequent work showed role of partial source area where
Saturation overland flow is produced

If rainfall exceeds soil infiltration capacity:
– Water fills surface depression then
– Water spills over downslope as overland
flow and
– Eventually to the stream

Subsurface Stormflow
Lateral flow through soil above conductivity
contrast.
Consists of both slower matrix flow and faster
macropore flow

Macropore flow,
Tennessee Valley,
California

Saturation Overland Flow
Direct rainfall onto saturated areas.
Return flow from saturated soils in
topographic lows and along valley bottoms
where water table rises to intersect the
surface.

Overland flow, Tennessee Valley, California

Generally a minor
contribution to runoff, why?
Direct Precipitation on Channels

Groundwater Flow
Driven by hydraulic
gradients
Q = K I A
K is hydraulic conductivity
A is cross sectional area
I is hydraulic gradient

Hydrographs
by Runoff
Mechanism
Lag to peak
Throughflow
SOF
HOF
Peak Runoff
HOF
SOF
Throughflow

Water balance of drainage basins
Net difference between precipitation and evaporation yields
streamflow or groundwater recharge

Dams
Dam is a solid barrier constructed at a suitable location across
a river valley to store flowing water.
Storage of water is utilized for following objectives:
 Hydropower
 Irrigation
 Water for domestic consumption
 For drought and flood control
 Other additional utilization is to develop fisheries.

Arch Dam
 This type of dams are concrete
dams which are curved or convex
upstream in plan
 This shape helps to transmits the
major part of the worlds loads to the
abutments
 Arch dams are built across narrow
deep river gorges But now in recent
years they have been considered even
for little wider valleys.

 Earth dams are trapezoidal in shape
 Earth dams are constructed where
the foundation rocks are weak to
support
 Earth dams are relatively smaller in
height and broad at the base
 They are mainly built with clay ,
sand and gravel. hence they are also
known as Earth Fill dam or Rock Fill
dam
Earth dam

o Buttress Dam - Is a
gravity dam reinforced by
structural supports
o Buttress Dam –A support
that transmits a force
from a roof or wall to
another supporting
structure
Buttress Dam
This type of structure can be considered even if the foundation rocks are little weaker

Gravity Dam
These dams are heavy and massive wall-like structure of concrete
in which the whole weight acts vertically downwards

Bhakra Dam
 Bhakra dam is the highest concrete
gravity dam in asia and 2nd highest in the
world
 This dam is present across the river
Sutlej in himachal Pradesh
 About construction it was started in the
year 1948,completed in 1963
Details: About measurements 740 ft high from the deepest foundation as
straight concrete dam being more than 3 times the height of Qutub Minar.

Leakages Below dams takes place generally due to the weak planes or zones
occurring at the dam sites
The reservoirs,which lies in the
upstream side(when full),contain an
enormous plenty of water due to
great extent, on downward side of
the dam,the water level wil be very
low.due to this difference in
levels,the reservoir water attempts to
leak through the rocks of dam with
considerable pressure and emerge
in the downstream side

Dams are very costly projects,so
their construction in seismic areas
needs careful study to ensure their
safety.when earth quakes occurs,a dam
is subjected to two forces are due to
the dam and due to reservoir water.
conclusion

Water never leaves the Earth. It is constantly being
cycled through the atmosphere, ocean, and land.
This process, known as the water cycle, is driven by
energy from the sun. The water cycle is crucial to the
existence of life on our planet.

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.

The process of evaporation from plants is called
transpiration. (In other words, it’s like plants
sweating.)

As water (in the form of gas) rises higher in the atmosphere, it
starts to cool and become a liquid again. This process is called
condensation. When a large amount of water vapor
condenses, it results in the formation of clouds.

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

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.

The Hydrological
Cycle
Higher Geography
The Hydrosphere

The Hydrological Cycle
What you need to know:
Be able to draw a diagram of the hydrological
cycle.
Describe its main elements.
Explain how balance is maintained within the
system.

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.

Describing the Cycle:
• Evaporation
Solar energy powers
the cycle. Heat energy
from the sun causes
evaporation from
water surfaces (rivers,
lakes and oceans)
and….

• … transpiration from
plants. Transpiration is
essentially evaporation
of water from plant
leaves.
• Evapotranspiration –
water loss to the
atmosphere from plants
and water surfaces.

Condensation
 The warm, moist air
(containing water
vapour) rises and, as it
cools, condensation
takes place to form
clouds.

Advection
• Wind energy may
move clouds over land
surfaces where …

Precipitation
• …precipitation occurs,
either as rain or snow
depending on altitude.

• Stemflow (red
arrows) – Precipitation
flows down stems and
branches to ground
• Throughflow (yellow)
Rate at which
precipitation flows
through branches

Run off / Overland flow
• The rainwater flows,
either over the ground
(run off) into rivers
and back to the
ocean, or…

Groundwater flow
• … infiltrates
downwards through the
soil and rocks where it
is returned to the
oceans through
groundwater flow.

Hydrological Cycle Bingo
Also called the hydrological cycle
Split your page into 8 squares and write one word from the list
below in the each square
Condensation Ground Water Infiltration
Evaporation Precipitation Percolation
Run off Evapotranspiration Interception
Saturation The Hydrological Cycle The water table

The water cycle balance
 Usually the water cycle is in balance, and the amount
of precipitation falling will slowly soak into the
ground and eventually reach the rivers.
 However, if rain falls for a long period of time or if
the ground is already soaked or saturated with water
then the chance of flooding is increased.

A closed system
 The hydrological cycle is a good example of a closed
system: the total amount of water is the same, with
virtually no water added to or lost from the cycle.
 Water just moves from one storage type to another.
 Water evaporating from the oceans is balanced by
water being returned through precipitation and
surface run off.

Your Turn
Write down the meaning of the following words:
• Infiltrate
• Groundwater flow
• Surface runoff
• Evapotranspiration
• Closed system
Use the New Higher Geography Textbook p.10 to help you.
Then complete Activity 1 (a) – (c)

Human Inputs to the Cycle
 Although this is a closed system there is a natural
balance maintained between the exchange of water
within the system
 Human activities have the potential to lead to
changes in this balance which will have knock on
impacts.
 For example as the earth warms due to global
warming the rate of exchange in the cycle (between
land and sea and atmosphere) is expected to
increase.

Human Inputs
 Some aspects of the hydrologic cycle can be utilized
by humans for a direct economic benefit
 Example: generation of electricity (hydroelectric
power stations and reservoirs)
 These are effectively huge artificial lakes and this will
disrupt river hydrology (amount of water in a river)

Other Human Activities
• Paving, compacting soils, and altering the nature of
the vegetation (including deforestation)
• The mining of ground water for use in agriculture
and industry
• Large amounts of water vapour released into the
atmosphere from industrial activity
• Large changes in vegetation by wildfire, logging,
clearance for agriculture

Impacts
• These human activities can lead to increase
chances of flooding
• Increases in soil erosion
• A cooling effect on the north west of Europe
(climate change)
• Possible higher precipitation levels in the
Arctic but less in the Tropics

Watershed development
Watershed area mainly has three types of land
use
1.Forest area
Nonarable land
2.Pasture land
3.Arable land

In arable land soil and water conservation
structures:
1.Bunding
2.Water ways
3.Farm pond
4.Loose boulders
5.Waste weir

Soil and water conservation structures between
nonarable land:
1. Diversion drain
2. Nallah bund
3. Check dam

Peak run off rate estimation by
Rational formula
Q= CIA/360
Q =Peak runoff (Cu.m/sec)
C=Runoff Coefficient (Weighted mean)
I = Design Intensity of rainfall (mm/hr) for the
design frequency and for duration equal to the time
of concentration.
A = Catchment area (Hectares)

Table of Runoff coefficient value(C)

Runoff Coefficient (C):
weighted value of “C”
=(A1C1 + A2 C2 + A3C3+ ……+AnCn) / (A1+A2+A3+….+An)
To calculate I (design rainfall intensity)
I = 2xIo / 1+Tc
where, Tc = time of concentration
Kirpitch formula , Tc = 0.01947x( k): · ⁷⁷
where, k = √(Lᶟ/H)
L= length of nallah
H= level difference
Iᶟ = rainfall intensity in mm/hr

Type of structure Recurrence
interval
1. Earthen structure like bunds, terraces ,
waterways, diversion drains, and dry
stone works
10 years
2. Semi permanent masonary structures like
small check dams , waste weir etc.
25 years
3. Permanent structures made of cement
concrete and RCC and other large structures
50 years

PROBLEM: calculate the discharge of a watershed having area 120ha
out of that 20ha is forest area having 11% slope and sandy loam soil
condition ,10ha pasture land with 7% slope having silty loam soil and
the remaining 90ha is under cultivated land with only 3%slope under
clay soil the major nala length is 800m &level diff. from farthest point
to end point is 50m the watershed is located an 16 ° latitude &76 °
longitude type of structure is a small check dam.
Solution:
Runoff coefficient(C) from table :
c for forest area =0.30
c for pasture area =0.36
c for argil. Area =0.60
weighted value of C=0.3x20+0.36x10+0.6x90/120
=0.53

Design intensity(I) = 2Iᶟ/1+Tc
Where Tc = 0.01947×{√(Lᶟ/H)} : · ⁷⁷
= 0.01947 × {√(800ᶟ/50)} : · ⁷⁷
= 9.73min = 0.162hrs
Iᶟ = 60 mm/hr from rainfall intensity map for16°
latitude &76 ° longitude for 25 years R.I.
So, I= 2 ×60/(1+0.162) = 103.44 mm/hr
From Rational formula , Q = CIA/360
=0.53×103.44×120/360
=18.27 cum/s

Check dam
Check dams mainly classified as:
1. Temporary check dams, Ex.:- loose boulders
2. Permanent check dams, Ex.:- drop spillway
Check dams are used for controlling the soil
erosion and runoff in small and medium sized
gullies.
Components of check dam:-
Head wall, head wall extension, side wall, apron,
wing wall, weir, end sill, cut off wall, toe wall

Check dam in netranahalli watershed
Length of weir

Dam height and weir height in check
dam
Dam height
Weir height
Head wall
extension

Head wall extension of check dam
Head wall extension

Length of apron of check dam
Length of apron
Side wall

End wall of check dam
End wall

Design of check dam
1. Peak rate of runoff, Q= CIA/360
2. Q for rectangular weir = 1.71LH³′²
where, L= length of weir = width of nala, m
H= height of weir , m
From this we can find H because L and Q is
known.
total height of weir = H+ free board
Free board is 0.15 to 0.30m

3. Height of dam,D = nala height-weir height
4. Head wall extension = 2H+0.3
5. Length of apron = 2D
6. Height of wing wall and side wall = 2H
7. Wall thickness, head wall = 0.45m
side wall= 0.3m
wing wall=0.3m

Problem(cont.) : design a rectangular weir from the
data given in previous problem and following data:
Catchment area = 120 hac, Nallah width = 15m .
Calculate head wall extension, length of apron, dam
height for 3.5 m nala depth.
Solution: from above problem Q= 18027 cumec
Q for rectangular weir = 1.71LH³′²
18.27 = 1.71 * 15 * H³′²
H = 0.71 m
add free board(.29) , H = .71+.29 = 1.0 m
Head wall extension = 2H+0.3 = 2.3m
Height of dam, D = nala height – weir height = 3.5 – 1
=2.5m
Length of apron = 2D = 2* 2.5 = 5 m

Diversion drain
Diversion drain is excavated to intercept
the runoff from the area situated above
(nonarable land) for protecting arable lands
down below and to conduct it safely to natural
nalas.
Design of diversion drain
1. calculate total area (nonarable) in hectares .
2. Use rational formula, discharge Q=CIA/360
for 10 years frequency .

Diversion drain
Upstream side downstream
bermTop width
Side slope

Diversion drain in Ramsagara
watershed

3. Q =VA
area of cross-section , A= (b+zd)d
where, b=bottom width , m
d=depth of drain, m
z=side slope
top width of drain , T = b+2dz
velocity of flow , V by manning’s formula
= C R2/3 S1/2
where, C= 1/n , n= manning’s roughness
coefficient
R= hydraulic radius = A/P ,m

P= wetted perimeter , m
= b+ 2d {√(z²+1)}
S= grade of diversion drain (0.2 to 0.3 %)
V should be in between 2 – 6 m/s
4. Length of drain = perimeter of hillock , m
5. Depth of diversion drain is assumed as
a) d = 0.5 to 1 m in rough terrains .
b) d = 1.5 to 2 m in marginal terrains.
6. Construct stabilizers(local stones) to reduce
velocity when fall of bed slope is >30 cm.
7. Excavated earth is put on D/S with leaving a berm
of 0.6m and vegetative barriers on U/S side

• Problem :- Calculate the peak discharge and design the diversion
drain in forest land having catchment area 30 ha and sandy soil . I
=90mm/hr ,slope of land 20% using modified ‘C’ value.
Solution:
Q=CIA/360
Q=0.2x90x30/360 1 1.5 1
1
Q= 1.5 cumec
assume V = 0.6m/sec non erosive velocity
Q =VA 1:1
1.5=0.6A
A=2.5 sqm
A=(b+zd)d
where, b=bottom width
d=depth 1.5
2.5=(b+zd)d (assume d=1)
2.5=(b+1)1
2.5-1=b
b=1.5m
T = b+2dz = 1.5+2*1*1 = 3.5m

Problem : calculate the discharge and Design diversion drain from
above problem data by using ‘C’ value from the table.
Solution:
C = 0.3 from table
Q=CIA/360
Q=0.3x90x30/360 = 2.25 cumec
assume V = 0.6 m/sec non erosive velocity
Q = AV
A = Q/V = 2.25/0.6 = 3.75 m²
Now , A = (b+zd)d assume d = 1m
3.75 = (b+1)1
b = 2.75 m
T = 2.75 + 2*1*1 = 4.75m

Farm pond
it is a water harvesting/storage structure in arable
land.
Types:-
1. Embankment type.
2. Dug out type.
Embankment type pond is built across the stream
in areas of gentle to moderately slope.
Dug out type pond are constructed by excavating
the soil , relatively in level areas.

Outlet of farm pond
OUTLET
Stop dam

Design of dug out type farm pond
1. Calculate the runoff volume(V1) from
catchment area(A).
V1=A × d
where, d= runoff depth i.e. some % of rainfall.
2. Calculate design runoff volume(V) i.e. some %
of total runoff volume(V1).
3. Side slope(z:1) of farm pond:-
(A) for red soil= 1.5:1
(B) for black soil= 2:1

4. Depth(d) of farm pond can be assumed according to farm
pond capacity, it should not more than 3m.
5. Bottom width(b)= b= √(3V - d3Z2) - dz
√ 3d
6. Top width (T) = b+2dz
7. Capacity of farm pond can be determined by trapezoidal rule
V = (A₁+A₂)×H/2
where , A₁ and A₂ are areas b/w 2 successive contours
H = vertical interval of contours
8. Volume of excavation for construction of pond by prismodial
formula
V = (A+4B+C)*D/6
9. Design of inlet and outlet such as mechanical and emergency
spillway.

Problem : design a farm pond in red soil region from the
following information :
catchment area = 5ha, mean annual rainfall = 450mm
runoff = 10% of total mean annual rainfall, assume 50% of
runoff collection for design , side slope can be assured 1.5:1
solution:
10% of annual rainfall = 450 x 0.10 = 45 mm
total runoff volume for 45 mm from 5ha = 45/1000 x 5 x10000
=2250 cubic m
design runoff volume (v) = 50% of total runoff volume
= 0.50 x 2250 = 1125 cubic m
then , b= √(3v - d3z2) - dz
√3d

b = Bottom width
V = Volume = 1125 mᶟ
Z = Side slope = 1.5
assume d= Depth = 2.5m
b= √ (3 x1125 – 2.5ᶟx 1.5²) – 2.5x1.5
√ 3 x2.5
= 21.10–3.75 = 17.35m
Top width = T = b +2dz
= 17.35 + 2 x 2.5 x 1.5 = 24.85m

Bunding
 It is a soil conservation measure , used for
retaining the water , creating obstruction and
thus to control erosion.
Bunds are embankment type structures,
constructed across the slope.
By bunding practice entire area is divided into
several small parts, there by effective slope
length, thus reducing soil erosion.

Types of Bund:
1. CONTOUR BUND:
• constructed on contour of area.
• used in relatively low rainfall (<600mm/year)
area for the purpose of controlling soil
erosion and to store rain water.
• Suitable for land having slope of 2 to 6%.
• Black soil is not suitable for contour bund.

Bund with
borrow pits,
waste weir and
revetment

2. GRADED BUND:
• When a grade is provided to bund is called GB.
• Constructed in relatively medium to high
RF(>700mm/year).
• Suitable for black soil.
• Purpose of controlling soil erosion and to
store rain water.
• Suitable for land having slope of 2 to 6%.

Specification of contour bund
Soil Type
Land Slope
(%)
VI (m)
Common
Cross
section
(Sqm)
Side slope Surplussing
arrangement
Deep black Upto 3 0.9 1.61 1.5:1 Waste weir
Shallow
black
Upto 3 1.0 1.0 to 1.5 1.5:1 Waste weir
Red and
Lateritic
Upto 3 0.5 1.0 to 1.5 1.3:1or 1.5:1 Open ends
with
vegetative
checks

Typical spacing of contour bund
Slope % VI (m)
(S/3 + 2 ) 0.3
HI (m)
VI/Slope % X
100
Length of
Bunds (m)
(10,000)/HI
1.0% 0.70 70 145
1.5% 0.75 50 200
2.0% 0.80 40 250
2.5% 0.85 35 205
3.0% 0.90 30 335

Design of contour bund
1. Spacing of bund by formula
a) Ramser’s formula
VI = (S/3+2)0.3
b) USDA formula
VI = (S/4+2)0.3
c) Cox formula
VI = (XS+Y)0.3 where, X= rainfall factors
Y= infiltration and crop
cover factor

Values of X and Y for Cox formula
Rainfall Annual rainfall
(cm)
Value of X Intake Crop cover
during erosive
period of rains
Y values
Scanty 64 0.8 Below average Low coverage 1.0
Moderate 64-90 0.6 Average or
above
Good coverage 2.0
Heavy >90 0.4 One of above
favorable &
Other
unfavourable
Good coverage 1.5
Value of X Y values

2. Horizontal interval (HI) = (VI/slope) x 100
3. Rainfall excess (Re) = Rainfall x % runoff
100
(Rainfall of 24 hrs, 10 yr. recurrence interval)
4. Depth of impounding (h)= (VI x Re)/50
5. Depth of temporary storage = 0.3 m
6. Free board (25% inclusive of settlement
allowance) = 0. 25 (h+0.3)m
7. Total height of the bund = h + 0.25 (h +0. 3)
m.

Select top width and slope of bund
depending on soil type
Type of the
soil
Top width (m) side slope
Sandy 0.5 2:1
Loamy 0.4 1.5:1
Clayey 0.3 1:1 or 1.5:1

9. Computation of the bottom width and cross
section area ‘A’
10. Total length of bund/ha
L = 10,000 x 1. 3
HI
30% extra length of soil bunds.
11. Earthwork in bunding/ ha
V = L X A
V= Volume of bund, cum per ha
L= Length of bund, m per ha
A= C/S area of bund, sqm

Specification of graded bund
Soil
Type
Slope
(%)
VI (m)
Cross
Section
(Sqm)
Side
slope
grade
Black Upto 5 0.75 to
1.0
0.6 to
0.87
1.5:1 0.1 to
0.3
Red Upto 5 0.75 to
1.0
0.6 to
0.87
1.3:1 0.2 to
0.4
Lateritic 5 to 6 0.75 to
1.5
0.34 to
0.56
1.3:1 0.2 to
0.4

• Steps in design of graded bund are similar to
that of contour bund.

Waste weir (WW)
• WW(surplus weirs)or rubble/grass outlets are
normally provided in valley points by using
loose stones properly embedded in soil to
avoid scouring and to drain the excess water
accumulated against bund.
• WW are constructed when catchment area is
<40 hac.
• For larger catchment areas, water diversion is
necessary.
• constructed in series from ridge to valley.

Waste weir
Upstream side
Downstream side
Length

Specification of waste weir
 width is equal to width of waterway.
 crest height
in black soils= 15 to 20 cm
in red soils = 30 to 40 cm
 upstream slope = 1.5:1
 down stream slope =3:1
 whenever open ends are used for draining excess
water; the ends are to be vegetated to prevent cutting
and scouring.
 2m long murram or hard soil packing may be given to
either ends of WW in continuation of bund.

Gabion structure
• gabion is a ‘Italic’ word in which small-small
stones combined with G.I. wire mesh, to form
a large stone and placed across the nala to
control heavy flow there by silt.
• this structure is comparatively strong under
both compression and tensile strength.

Gabion structure in Netranahalli
watershed
Length of gabion
width

Gabion structure with vegetative
barriers to reduce runoff velocity
Vegetative barriersgabion

Technical specification
1. G.I wire 10-14 gauge
2. Foundation = 0.3m
3. Height above ground = 0.70 m
4. Length inside nala = 1 m at both sides
5. Total Length of gabion = width of nala+2m
6. Wire mesh size = 3 inch
so, stones should be >3 inch size
7. Spacing
for 1-3% slope = 50 m
for 3-5% slope = 30 m

• Gabion should be constructed maximum in a
2 m box and join them, filled with stones and
tie them together.
• Bigger stones should be in the bottom and
smaller stones (not < 3inch) at the top.
• Binding should be proper.

Contour trenching
• Contour Trench/’V’ ditches are trenches dug on
contour in non-arable lands of more than 3%
slope to hold run off for conservation and
reducing erosion.
• They are established for development of trees
and grass species and are adoptable in areas with
annual rainfall of up to 950 mm.
• contour trenches have been used on all slopes,
trenching on slopes exceeding 20% is not
advisable either technically or economically.

Trenches are categorized in 3 types
1.Continuous trenches:
Continuous contour trenches are recommended
for storage of water in low rainfall relatively flat
areas receiving storms of mild intensity.
2. Graded trenches
These are drainage type ditches for intercepting
and safe disposal of surface flow in very high
rainfall areas and impermeable black soils.
• The grade is given so that the intercepted runoff
from the above will be carried safely at non-
erosive velocity to the vertical drain without
overflow.

3. Staggered or interrupted trenches
In high rainfall areas with highly dissected
topography staggered trenches are usually
adopted.
Staggered trenches are of shorter lengths in a
row and are arranged along the contour with
inter space between them.

Earthen dam for water harvesting
(NALABUND)
Nala bund is an earthen structure constructed across the
nala/gully in order to store the runoff water flowing
through the nala during rainy season.
Objectives:
• reducing the velocity of flow,
• storing the runoff and thereby allowing it to percolate
into the soil profile which in turn helps to enhance the
water table of the downstream area.
• This structure also prevents the silt flowing down and
causing the siltation of reservoirs in the downstream
side, which can affect the storage capacity of the
reservoir.

Site selection of nala bund
1.First and foremost requirement is that it should have sufficient
catchment to fetch the runoff required for storage.
2. The upstream side of the location there should have enough
area for water storage.
3. The nala site selected for the structure should have a relatively
narrow cross section.
4. Should be located on the straight stretch of nala.
5. There should be provision for locating surplussing weir on one
of the banks.
6. The nala bed should have good hard soil for proper bondage
between the structure and natural soil profile. A hard rock
foundation may have less bondage with the proposed
structure, hence discouraged.

Design of nala bund
1. Top width, W = Z/5 +3
Where: W= width of crest (m), Z=Height of
embankment above the stream bed(m).
2.EMBANKMENT SIDE SLOPES:
The side slope of the nala bund depends
primarily on stability of the material used for
embankment.

Recommended side slopes for earthen
embankment

3.CORE WALL:
The core wall is a centrally provided fairly impervious wall in the
dam.
4. KEY TRENCH:
This is a bondage/foundation component of the structure to ensure
the stability for the embankment almost like foundation of a
structure.
5. Spillway :
This is a vent /channel provided at the full tank level in order to
dispose of the excess runoff coming in.
6.FREE BOARD:
Free board is the additional height of the bund provided to avoid
water overtopping the embankment during unexpected flow of
runoff
7.REVETMENT (wave protection):
Since this an earthen structure and it will be coming in contact with
the water in the upstream side of the dam, in order to with stand
against the wave action of storage .

Forest for conservation of natural
resources
• Forest: An area set aside for the production of
timber and other produce or maintain under
woody vegetation.
Theory and practice and creation
Conservation
Scientific management of forest
Utilization of their resources

Conservation forestry
• Production of forest product
• Restoration & maintenances of resource base

Conservation forestry
Its need & scope
At the global level 15% of the earth’s forest &
woodland disappeared during the last one and
half century as a result of human activities.
Its aim is to prevent erosion from the fertile
agricultural land as well as production as socially
acceptable uses.

The role of forest in functioning of
watershed
Conserves soil moisture
Maintain soil temperature
Infiltration increases
Root binding capacity increases
Prevent soil erosion

Objective of agroforestry
To utilize available farm resource.
Production of fuel, fodder, food, wood etc.
Integration of trees with agricultural land and
animal production.
To maintain ecological balance.
To check erosion hazard.
To improve employment potential and rural
economy.

Pra (participatory rural apprisal
• The PRA technique is an useful technique for use in
analysis of any situation
STEPS
Social Mapping
Resource Mapping
Seasonal analysis
Transect walk
Preference ranking
Historical time line
ITK

In situ soil &moisture conservation
measures
• Tillage a)Conservation tillage
b)Conventional tillage
• Graded furrow
• Vegetative barriers
• Repeated inter culturing
• Graded border strips
• Zing terrace
• Contour cultivation
• Compartmental bunding
• Tied ridges & furrows
• Broad furrow & ridges
• Scooping
• Border planting method

Effect of in situ moisture conservation
on soil physical properties
• Soil temperature
• Bulk density
• Penetration resistance
• Soil compaction
• Soil aggregation & pore space
• Runoff & soil loss
• Nutrient losses
• Crop growth & yield

Definition & concept of Water shed
management
• Watershed is the integration of technologies
with in the natural boundaries of drainage
area for optimum development of land ,
water, & plant resources to meet the basic
needs of people & animal in sustainable
manner.

Components of watershed
management
• Treatment of arable & non arable land for
effective in situ & ex situ moisture
conservation
• Identification of sound crop production
system & its implementation through
development & input agencies
• Developing suitable infra structure facilities &
people organizations to maintain developed
resources

The systematic arrangement of land into
various categories according to its capability
to sustain particular land use without land
degradation.
LAND CAPABILITY CLASSIFICATION

OBJECTIVES OF LCC
• It makes available the technical data
contained in a soil survey map in a simple &
practical language
• Indicates the hazards of soil erosion
• Indicates the most intensive , profitable & safe
use of any piece of land

Land capability groups
• Land suitable for cultivation and other uses
(Class I to IV lands)
• Land not suitable for agriculture but well
suited for forestry, grass land and wild life
(Class V to VIII)

Influence of effective soil depth on
LCC

Influence of soil texture on LCC

Determination of bulk density, particle density and
pore space
Readings taken from soil samples in lab:
Sl no. Weight of soil
taken , W(gm)
Volume of soil
taken, V1 (ml)
Volume of
water added,
V2(ml)
Volume of
soil+water
Volume of
soil+water
at end of
exp V3(ml)
1. 30 23.5 50 72.5 59.5
2. 30 20.5 50 70.5 62.5

calculation
1. Pore space volume(V4) = (V1+V2)-V3
V4 = 23.5+50-59.5= 14ml
% pore space = V4/V1*100 = 14/23.5*100
= 59.57%
bulk density = weight of soil/volume of soil
= 30/23.5 = 1.27 gm/cc
Particle density = weight of soil/(V1-V4)
= 30/(23.5- 14 )
= 3.157 gm/cc

2. Pore space volume(V4) = (V1+V2)-V3
= 20.5+50-62.5
= 8ml
%pore space = = V4/V1*100 = 8/20.5*100
= 39.02%
bulk density = weight of soil/volume of soil
= 30/20.5= 1.46 gm/cc
Particle density = weight of soil/(V1-V4)
= 30/(20.5-8)
= 2.4 gm/cc

Sources of water (RAIN)
Surface Sources Ground Sources
Streams Springs
Lakes Infiltration Galleries
Ponds Infiltration Wells
Rivers Wells and Tube wells
Impounded Reservoirs
Oceans

Springs
•Natural outflow of GW @ earth’s surface.
•Gravity springs : GW table rises high & water overflows though the
sides of a natural valley or depression.
•Surface springs : an impervious obstruction supporting underground
storages becomes inclined causing water table to go up & get exposed
to ground surface.
•Artesian Springs : when water flowing through some confined
aquifer is under pressure.

Non artesian or Unconfined aquifers & well

Wells
•A water well is a hole usually vertical, excavated in the earth to
bring GW to the surface.
•Open Wells / Tube Wells.

Open Wells (Dug Wells)
•Open masonry wells, 2 – 9 m dia, less than 20 m depth. Discharge 5 L/s
•Walls built of brick or stone masonry or precast concrete ring
•To improve yield of well, 10 cm dia hole @ centre of well is made
(Shallow well/Deep Wells)
•Shallow well rests in a pervious strata.
•Deep well rests on an impervious ‘mota’ layer & draws its supply from
the pervious formation lying below ‘mota’ layer.
•A shallow well might be having more depth than a deep well

Infiltration Galleries (Horizontal Wells)
•Horizontal tunnels (with holes on sides) constructed of masonry walls
with roof slabs to tap GW flowing towards rivers/lake.
•Constructed @ shallow depths (3-5m) along the banks of river either
axially along or across GW flow.
•Width (1m), depth (2m) , length (10 – 100m)
•If large GW quantity exists, porous drain pipes are provided and they
are surrounded by gravel and broken stone.
•Yield, 15,000 L/day / Meter length
•A collecting well @ shore end of gallery serves as sump from where
water is pumped.

Section of infiltration gallery

•They are shallow wells constructed under beds of rivers.
•Deposits of sand exist at least 3m deep in river beds. As the water
percolates down, impurities are removed. Quality of water is better
than river water.
•They are sunk in series in the bank of the river.
•They are closed @ top & open & bottom. Manholes are provided @
top for inspection.
•They are constructed of brick basonry with open joints.
•Various infiltration wells are connected by porous pipes to sump
called jack well.
Infiltration Wells

•Structures used to withdraw water from various sources.
•Lake / Reservoir / River /Canal/ Intake.
Intakes

•Submersible intake.
•A pipe laid in the bed of the lake.
•One end is in the middle of the lake & is fitted with bell – mouth
opening covered with a mesh & protected by concrete crib.
•Water enters in the pipe through bell-mouth opening & flows under
gravity to the bank where it is collected in a sump – well & then
pumped to TP.
Lake Intakes

•A circular masonry tower (4-7m dia) constructed along bank of the
river.
•Water enters in the lower portion of the intake (i/e sump – well) from
penstocks.
•Penstocks are fitted with screens to prevent entry of floating solids.
• No. of penstock openings are provided in intake to admit water @
different levels.
•Opening & closing of penstock valves is done with wheels provided @
pump – house floor.
River Intakes

• Constructed inside river @ suitable place.
•A concrete circular shell filled with water upto water level inside the
river.
•Water enters through openings provided on outer circular shell, as
well as on inside shell.
•Water is taken to the bank of the river through the withdrawal
conduit in the sump well from where it is pumped to WTP.
a) Wet Intakes

b)Dry Intake tower
•In wet intake tower, water enters first in the outer shell then it enters
in the inner shell.
•In dry intake, water enters directly withdrawal conduit.

•An intake tower constructed on the slope of the dam.
•Intake pipes are fixed @ different level to withdraw water at all
variations of water level.
•All inlet pipes are connected to one vertical pipe inside the intake
well.
•Screens are provided @ mouth of all intake pipes to prevent entry of
floating matter.
•Water entering the vertical pipes is taken to other side of the dam by
means of an outlet pipe.
Reservoir Intake

•At the top of intake tower, sluice valves are provided to control flow
of water.
•Valve tower is connected to the top of the dam by means of foot-
bridge gang- way.
•For earthen dams, intake towers are separately constructed.
•For RCC masonry dams, intake tower is constructed inside the dam it
self.

Canal Intake
•No need to provide multiple ports, as water level in canal remains
constant.
•A pipe placed in a brick masonry chamber constructed partly in the
canal bank.
•On one side of chamber, opening is provided with coarse screen for
entrance of water.
•A bell mouth fitted with a hemispherical fine screen is provided @ the
mouth of the pipe.
•Outlet pipe carries water to the other side of the canal bank from
where it is taken to TP.
•One sluice valve operated by a wheel from top of masonry chamber
is provided to control flow of water in the pipe.

Dry intake tower standing in the river
or reservoir

Water education ppt

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Viewers also liked

Viewers also liked (10)

Similar to Water education ppt

Similar to Water education ppt (20)

Recently uploaded

Recently uploaded (20)

Water education ppt