final wss and new tank project report
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PROPOSAL OF WATER SUPPLY SCHEME AND NEW TANK FOR DHUMMAVAD VILLAGE
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1. INTRODUCTION
The area surveyed for the water supply project is Dhummavad village, which is located at
a distance of 20Km in South-West direction from the centre of the Dharwad city on the
longitude 75’0’54”and latitude15’41’. There exist 250 houses with an average population of
7 persons per house. This village lags behind in supply of potable water. The available water
is inadequate due to rapid urbanization, increasing population etc. The bore wells and open
wells are the main source of drinking water in that area.
The available raw water must be treated and purified before they can be supplied to the
general public for their domestic use. In general the public water supplies are mainly
designed from the view point to the quality requirement of drinking water. The available
water must therefore be made safe and good for domestic use.
The proposed design includes construction of water tank and modeling the pipelines
running through the area. The scheme will be designed for a working period of 30 years. The
aim is to provide these houses safe and potable water and meet their demand efficiently.
1.1 NECESSITY OF THE PROJECT
To provide safe and potable water to the village.
Insufficient water supply. The existing system is supplying the water at a rate of 40 –
50 lpcd, which is insufficient for the people.
Supply of treated water.
1.2 OBJECTIVES OF THE PROJECT
Providing water supply standards to about 100 lpcd.
Treating the water before supply to public use.
To make design and maintenance costs more economical.
To maintain key hygienic issues regarding the water supply system
Design Period is Twenty Years.
S.D.M. COLLEGE OF ENGINEERING AND TECHNOLOGY, DHARWAD
PROPOSAL OF WATER SUPPLY SCHEME AND NEW TANK FOR DHUMMAVAD VILLAGE
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1.3 KEY MAP OF DHUMMAVAD VILLAGE
S.D.M. COLLEGE OF ENGINEERING AND TECHNOLOGY, DHARWAD
PROPOSAL OF WATER SUPPLY SCHEME AND NEW TANK FOR DHUMMAVAD VILLAGE
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1.4 TOPO SHEET
TOPO SHEET : 48M/3
The highlighted area shows the location of Dhummavad village.
S.D.M. COLLEGE OF ENGINEERING AND TECHNOLOGY, DHARWAD
PROPOSAL OF WATER SUPPLY SCHEME AND NEW TANK FOR DHUMMAVAD VILLAGE
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1.5 PLAN OF DHUMMAVAD VILLAGE
S.D.M. COLLEGE OF ENGINEERING AND TECHNOLOGY, DHARWAD
PROPOSAL OF WATER SUPPLY SCHEME AND NEW TANK FOR DHUMMAVAD VILLAGE
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1.6 CONTOUR MAP OF DHUMMAVAD VILLAGE
S.D.M. COLLEGE OF ENGINEERING AND TECHNOLOGY, DHARWAD
PROPOSAL OF WATER SUPPLY SCHEME AND NEW TANK FOR DHUMMAVAD VILLAGE
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2. POPULATION FORECASTING
A] Arithmetic Increase Method
Year Population Increase
1981 2398 ---------------------
1991 3077 679
2001 3411 334
Cumulative Increase 1013
Average Increase in population = cumulative increase/2 = 1013/2 = 506.5Forecasted Population:
Year Calculation Expected Population
2011 3411+(1*506.5) 3918
2021 3411+(2*506.5) 4424
2031 3411+(3*506.5) 4931
B] Geometric Mean Method
Year Population Increase %Increase1981 2398
1991 3077 679 (679/2398)*100=28.32%2001 3411 334 (334/3077)*100=10.85%
Total = 39.17%
Average percentage increase in population = 39.17/3 = 19.59%
Forecasted Population:
Year Calculation Forecasted Population
2011 3411+(19.59/100*3411) 4079
2021 4079+(19.59/100*4079) 4878
2031 4878+(19.59/100*4878) 5834
select the higher value of population for the design of treatment plant.
S.D.M. COLLEGE OF ENGINEERING AND TECHNOLOGY, DHARWAD
PROPOSAL OF WATER SUPPLY SCHEME AND NEW TANK FOR DHUMMAVAD VILLAGE
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Population by geometric mean method: 5834
Population by arithmetic mean method: 4931
Consider population = 5834 say 6000
2.1 WATER DEMAND
S.D.M. COLLEGE OF ENGINEERING AND TECHNOLOGY, DHARWAD
PROPOSAL OF WATER SUPPLY SCHEME AND NEW TANK FOR DHUMMAVAD VILLAGE
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Rate of water demand: 100 lpcd
The Department Of Rural Development And Panchayati Raj has laid down the
minimum per capita domestic consumption for rural communities with population up to
20,000 should not be less than 70 lpcd.
Peak factor = 1.5
Total quantity of water required
Q = lpcd x population x 1.5
= 100 x 6000 x 1.5
= 900000 lit/day
= 900 m3/day
2.2 GENERAL DETAILS OF THE VILLAGE
Name of the area surveyed : Dhumavad
Number of house existed : 641
Number of vacant plots : 132
Number of members per house : 7 (avg)
No of bore well : 2
Population as per 2001 census : 3411
3. DESIGN OF OVER HEAD TANK
Capacity of OHT = (100 X 6000x1.5) / 1000 = 900m3
S.D.M. COLLEGE OF ENGINEERING AND TECHNOLOGY, DHARWAD
PROPOSAL OF WATER SUPPLY SCHEME AND NEW TANK FOR DHUMMAVAD VILLAGE
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OHT is to be designed for 40% of the capacity of the tank.
Hence volume of tank: 0.4x900= 360m3
Assume Depth of tank = 3m
Free board = 0.5m
Overall depth = 3.5m
Area of the tank = 360/3.5=102.857m2
Diameter of the tank = d = 11.44m say 12m
Therefore the dimensions of the over head tank are –
Height from ground level = 12m
Diameter = 12m
Overall depth = 3.5m
3.1 DESIGN OF RISING MAIN
From Lake to Water Treatment Plant(WTP)
S.D.M. COLLEGE OF ENGINEERING AND TECHNOLOGY, DHARWAD
PROPOSAL OF WATER SUPPLY SCHEME AND NEW TANK FOR DHUMMAVAD VILLAGE
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Difference in elevation Bottom of lake = 595m
WTP = 606m
Therefore total difference in elevation = 11m
Distance between lake and WTP = 100m
Quantity required/day = 900cum/day
Taking f= 0.075 and pump working for 8hrs.
Quantity of water to be carried by pipe = 900 / (8 X 60 X 60)
=0.03125cum/sec.
Assuming the velocity through the pipe = 1.25m/sec
Cross – sectional area of pipe required A = Q / V
=0.03125 / 1.25
But, A = ∏ d2 / 4 = 0.025, therefore diameter of pipe 20cm.
Provide 25cm diameter CI pipe
Actual area provided = ∏ X (0.25)2 / 4 = 0.0490m2
Actual velocity V = Q / A = 0.03125 / 0.0490 = 0.64 m/sec.
Loss of Head by Hazen William’s Formula
V = 0.85 CH R0.63 S0.54
V = 0.64 , CH = 130 (for new CI pipe) , R = d/4 = 0.25/4 = 0.0625
0.64 = 0.85 X 130 X (0.0625)0.63 X S0.54
S0.54 = 0.64 / (0.85 X 130 X 0.174 )
S = 1.83 X 10-3
Head loss, HL / L = 1.83 X 10-3 = 0.185m
Therefore total head required = 11 + 0.185 = 11.185m.
Assuming efficiency of pump set as 70%
The required HP for pump = w Q H / 75μ
= (1000 X 0.03125 X 11.185) / (75 X 0.70)
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PROPOSAL OF WATER SUPPLY SCHEME AND NEW TANK FOR DHUMMAVAD VILLAGE
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= 6.65HP ≈ 7 HP.
Rising Main from Clear Water Reservoir to Over Head Tank
Difference in elevation = 608 – 606 = 2m.
Height of OH tank = 14m.
Distance = 400 + 500 + 100 =1000m.
Quantity of water required / day = 900cum/day.
Pump works for 8hrs.
Quantity of water to be pumped by pipe, = 900 / (8 X 60 X 60)
= 0.03125cum/sec
Assuming velocity through pipe as 1.25m/sec
C/S area of pipe required, A = Q/V
= 0.03125 / 1.25 = 0.025
But, A = ∏ d2 / 4 = 0.025 , and d = 0.178m = 0.2m = 20cm.
Therefore adopt a PVC pipe of 25cm diameter.
Actual or provided area = ∏ (0.25)2 / 4 = 0.0490m2
Actual velocity, V = Q /A = 0.64m/sec
Loss of Head by Hazen William’s Formula
V = 0.85 CH R0.63 S0.54
V = 0.64, CH = 130 (for new PVC pipe), R = d/4 = 0.25/4 = 0.0625
0.64 = 0.85 X 130 X (0.0625)0.63 X S0.54
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PROPOSAL OF WATER SUPPLY SCHEME AND NEW TANK FOR DHUMMAVAD VILLAGE
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S0.54 = 0.64 / (0.85 X 130 X 0.174)
S = 1.83 X 10-3
Head loss, HL / L = 1.83 X 10-3 X 1000= 1.83m
Therefore total head required = 14 + 1.83 = 15.83m.
Assuming efficiency of pump set as 70%
The required HP for pump,= w Q H / 75μ
= (1000 X 0.03125 X 14.83) / (75 X 0.70)
= 8.827HP ≈ 10HP.
3.2 DESIGN OF GRAVITY MAIN
From OHT to Village
RL of OHT = 608m, RL of end of gravity main = 599.4m
Length of gravity main = 200m
Quantity of water = 0.0104cum/sec and f=0.075
Q = A X V
0.0104 = (∏ d2 / 4) X velocity
0.0104 = 0.785 d2 X velocity, therefore V = 0.0132 / d2
By Darcy – Weisbach Formula,
HL = f l V2 / 2gd
= (0.075 X 300 {0.0132 / d2 }2 ) / (2 X 9.81 X d)
= 1.15 X {0.0132 / d2 }2
Since all the available water head is lost in overcoming the friction
(608 – 599.4) = (0.764 / d) X {0.0132 / d2 }2
S.D.M. COLLEGE OF ENGINEERING AND TECHNOLOGY, DHARWAD
PROPOSAL OF WATER SUPPLY SCHEME AND NEW TANK FOR DHUMMAVAD VILLAGE
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Solving for d, d = 0.118m = 11.8cm
Provide 15cm diameter pipe line.
3.3 DESIGN OF INTAKE STRUCTURE
Detention time in the intake well = 20 min
Volume of intake well = Q X D.T.
= 0.0133 X (20 X 60)
= 15.96 m^3
Min height of water required = 1 m
Height of F.R.L. = 3 m
Diameter of the intake well (D) = sqrt (( 15.96 x 4)/ ((22 x 4 )/ 7)))
= 2 m
Total height of the intake well = 3+1
= 4 m
Provide 2 m diameter and height of 4 m to the intake structure
3.4 TEST REPORT OF THE WATER SAMPLE
S.I Parameters Result Permissible Limits
S.D.M. COLLEGE OF ENGINEERING AND TECHNOLOGY, DHARWAD
PROPOSAL OF WATER SUPPLY SCHEME AND NEW TANK FOR DHUMMAVAD VILLAGE
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NO
(as per 10500-1991)
01 pH 7.7 6.5-8.5
02 TURBIDITY 15.9 NTU 10 NTU
03 Conductivity 60 ms/m -------
04 Total dissolved solids 390 mg/lit 2000 mg/lit
05 Hardness 156.4 mg/lit 600 mg/lit
06 Calcium (Ca) 39.7 mg/lit 200 mg/lit
07 Magnesium (Mg) 13.9 mg/lit 75.00 mg/lit
08 Chlorides 38 mg/lit 1000.00 mg/lit
09 Alkalinity 154.0 mg/lit 600.0 mg/lit
10 Sulphates 14.0 mg/lit 400.0 mg/lit
11 Fluorides 0.3 mg/lit 1.5 mg/lit
12 Iron 0.5 mg/lit 1.0 mg/lit
13COLIFORM DENSITY
(MPN)900/100 ml 10/100 ml
Remark: Except Coliform density, all tested parameters are with in permissible limits as per
IS 10500 – 1991
By observing the above results we can conclude that the treatment plant is designed
mainly for ‘Turbidity’ & ‘Coliform density (MPN)’
3.5 LOCATION OF OHT AND WTP
The map shows the satellite image of the Dhummavad village.
S.D.M. COLLEGE OF ENGINEERING AND TECHNOLOGY, DHARWAD
PROPOSAL OF WATER SUPPLY SCHEME AND NEW TANK FOR DHUMMAVAD VILLAGE
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Source: Google Earth
RL 606 Indicates the location of water treatment plant (WTP) and the RL 608
indicates the location of over head tank (OHT).
4. DESIGN OF WATER TREATEMENT PLANT
Components of treatment plant.
S.D.M. COLLEGE OF ENGINEERING AND TECHNOLOGY, DHARWAD
PROPOSAL OF WATER SUPPLY SCHEME AND NEW TANK FOR DHUMMAVAD VILLAGE
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01) Chemical feeding tank
02) Design of approach channel
03) Design of mixing tank
04) Design of flocculating tank
05) Design of settling tank
06) Design of rapid sand filter including wash water tank
07) Disinfection
08) Design of clear water reservoir.
01) Chemical Feeding:
Using alum as a coagulant the optimum quantity of dosage will be determined by
actual jar test in laboratory
Let the optimum dose be 5 to 8 mg/ltr
The quantity of alum req will range from
= 6 x 10 2 x 5 x 10 3
106
= 3 kg/day to 4.8 kg/day
The max requirement in summer will be 1.5 times more i.e. 4.5 to 7.2 kg/day
This quantity of alum shall be first mixed with the water to form a soln of 5%
strength and then added through soln feed devices
The max capacity of feeding devices = (7.2x100)/5 = 1 lit/day = 0.1lit/min
Minimum dose which will feed during avg demand
( assuming max demand = 1.5 x min demand) = 0.1/1.5 = 0.0667 lit/min
Quantity of water to be fed in one shift of 8hr = 0.1x 60 x 8 = 48 lit
Say = 50 lit
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PROPOSAL OF WATER SUPPLY SCHEME AND NEW TANK FOR DHUMMAVAD VILLAGE
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Providing 1 sedimentation tank of capacity equal to 50 lts i.e 0.05 m3
Providing 30 cm depth of sedimentation tank & 10 cm as free board
Area of the tank req = 0.05/0.3 = 0.166 m2
Dimension of Square tank are (40 x 40 x 40)cm
02) Design of Approach channel:
One clarifier has been proposed with one separate mixing coagulation tank
The maximum flow in each channel = 1.04x10-2 m3/sec
Providing a velocity of 25 cm/s the c/s area of approach channel
= (1.04x10-2)/0.25
Area = 0.0416 m2
Say = 0.042 m2
= 420 cm2
= 450 cm2
*Provide (30 x 15)cm
03) Design of Mixing tank:
Mechanical flash mixtures will be used for mixing the coagulant solution
with the water assuming the the detention period of = 1 min = 60 sec
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PROPOSAL OF WATER SUPPLY SCHEME AND NEW TANK FOR DHUMMAVAD VILLAGE
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Capacity of flash mixer = 1.04 x 10-2 x 60 = 0.624
Providing depth of 1 m the side of the square plan mixing tank
= 0.624/1 = 0.624 m2
Size = 0.79 x 0.79 x 1 m of mixing tank
04) Design of flocculating tank:
Providing a floculating tank assuming floculating time of = 30 min
The capacity of floculating tank = 1.04 x 10-2 x 10 x 30 x 60
= 18.72 m3
Provide 2 channels laid in parallel to one another capacity of each channel
= 18.72/9.36 = 9.36 m3
Providing 1 m depth of water and 10 m length of channel, its width
= (9.36)/(1x10)
= 0.936 ~ 1m
... Provide channel of side :- (10 x 1x 1)m with water depth 90 cm and 10 cm freeboard
05) Design of settling tank:
Providing rectangular tank with period of 1hr
Capacity of tank = (6x105x1.5)/(24 x 103 )x(1hr) = 37.5 m3
S.D.M. COLLEGE OF ENGINEERING AND TECHNOLOGY, DHARWAD
PROPOSAL OF WATER SUPPLY SCHEME AND NEW TANK FOR DHUMMAVAD VILLAGE
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Assume velocity = 22 cm/min = 0.22m/min
Detention period = 1hr = 60 min
Length of tank = v x d.p = 0.22 x 60 = 13.2 m say 14m
c/s area = capacity/L = 37.5/14 = 2.7 m2
Assuming depth as 2m width of tank = A/Depth = 2.7/2 = 1.35 say 1.5 m
Size of tank 14 x 1.5 x 2.5m with depth of 2.5m including 50 cm freeboard
06) Design of rapid gravity filter:
Quantity of water to be treated = 1.5 x 6 x 105 = 9 x 105
Assuming rate of rapid gravity filter as = 4500 lit/hr/sq.m
and 30 min shall be utilized daily in back washing of filter
Total filter area = (9x105 )/(23.5x4.5x103)
Providing 2 units one as stand with one as stand by
L/B= 1.5
L = 1.5B
Size of tank = LxB = 1.5BxB = 8.5
B = 2.4 m
L = 3.6 m
Let the size of tank be 4X3m
Wash water tank: overhead tank will be provided for back washing of filter.
Assuming quantity of wash water as 4% of total water filtered.
Quantity of wash water = (4/100)x(3x4)x4500 x 23.5
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PROPOSAL OF WATER SUPPLY SCHEME AND NEW TANK FOR DHUMMAVAD VILLAGE
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= 5.08x 104 ltr
= 50.8 m3 ~ 51 m3
Assuming depth of water asa 2m in tank and providing circular tank
Dia of tank = {(51)/(2 x π/4)}1/2
= 5.7 m say 6m
Provide wash water tank of 6m dia and 2.3 m deep with 30 cm freeboard
07) Disinfection:
The disinfection of water will be done by post chlorination using vaccum
vaccum type of chlorinator through which liquid chlorine will be fed in
the water at the end when all other treatment have been completed the
dose of chlorine to be added will be in 1ppm depending on the quality of
of water and chlorine depends on test.
Quantity of chlorine required = (0.9MLD x 1 ppm x 1000)/(24 x 1000)
= 0.0375 kg/hr
= 38 gm/hr
A liquid chlorinator having capacity to feed chlorine at the rate of
38 gm/hr will be installed.
08) Design of Clear water reservoir:
Underground clear water reservoir having a capacity of about 8hr
Quantity of water to be stored =( 0.9x106x8)/(24 x 103)
= 300 m3
Providing a depth of 3 m the area of tank required = 300/3
S.D.M. COLLEGE OF ENGINEERING AND TECHNOLOGY, DHARWAD
PROPOSAL OF WATER SUPPLY SCHEME AND NEW TANK FOR DHUMMAVAD VILLAGE
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= 100 m2
The plan will mainly depend on the area available at the site therefore, reservoir of plan area 100 m2 and depth of 3m shall be provided with additional free board of 50 cm.
4.1 Layout of water treatment plant
4.2 Layout of pipe line
S.D.M. COLLEGE OF ENGINEERING AND TECHNOLOGY, DHARWAD
PROPOSAL OF WATER SUPPLY SCHEME AND NEW TANK FOR DHUMMAVAD VILLAGE
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CONCLUSION:
The project may provide potable water to the Dhummavad village in
accordance with their demands and requirements.
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PROPOSAL OF WATER SUPPLY SCHEME AND NEW TANK FOR DHUMMAVAD VILLAGE
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The provision of such a scheme shall not help only in supplying safe
wholesome water to the people for domestic use. But also keep the diseases
away and there by promoting better health and ensuing better living standards.
S.D.M. COLLEGE OF ENGINEERING AND TECHNOLOGY, DHARWAD
PROPOSAL OF WATER SUPPLY SCHEME AND NEW TANK FOR DHUMMAVAD VILLAGE
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PROPOSAL OF NEW TANK
1. INTRODUCTION
S.D.M. COLLEGE OF ENGINEERING AND TECHNOLOGY, DHARWAD
PROPOSAL OF WATER SUPPLY SCHEME AND NEW TANK FOR DHUMMAVAD VILLAGE
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The arid region of Dharwad district has majority of black cotton soil and farmers
adopt cropping pattern which suits this soil such as cotton, groundnut, wheat, onion, maize,
etc. All these crops require large quantities of water. The New Tank in the village
Dhummavad has been proposed with an emphasis on agriculture.
Bund is a hydraulic structure constructed across a river or stream to store water on its
upstream side. This water is utilized as and when it is needed. As the upstream side is
increased, a large area may be submerged depending upon the water spread of the reservoir
so formed.
1.1 NECESSITY
Basically India is an agricultural country and all resources depend on the agricultural
output, water is the most vital element in the plant life.
To overcome the growing demand of the water for irrigation.
Preservation cultivating of useful aquatic life.
1.2 OBJECTIVES
To construct a tank for the purpose of irrigation in the village.
Providing adequate and quality water for irrigation.
1.3 LOCATION OF THE VILLAGE
S.D.M. COLLEGE OF ENGINEERING AND TECHNOLOGY, DHARWAD
PROPOSAL OF WATER SUPPLY SCHEME AND NEW TANK FOR DHUMMAVAD VILLAGE
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Source: Google Maps
• The village Dhummavad is located on the State Highway 1 (SH1) in between
Dharwad and Kalghatgi. The village is 15km South-west of Dharwad city. The
village has the Latitude of 15W 19’ 0.16’’N and Longitude of 75W 00’ 36.11”E.
2. SALIENT FEATURES
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PROPOSAL OF WATER SUPPLY SCHEME AND NEW TANK FOR DHUMMAVAD VILLAGE
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1 NAME OF PROJECT New Tank Project At Dhummavad
2 LOCATION Village: Dhummavad; Taluk: Kalghatgi;
District: Dharwad
3 LONGITUDE 75 00’ 54’’
4 LATTITUDE 15 19’ 7’’
5 TOPOSHEET 48 M/3
6 WATER SHED DETAILS
5 Arabian Sea
5B Sharavati Basin
5B1 Sharavati To Savitri Basin
5B1A Savitri To Kali River (Sub-Catchment)
5B1A4 Bedti Halla (Water Shed)
7 Catchment Area 4937477.3 m2 = 1220.1 Acres = 4.9 km2
8 Nature Of Catchment AVERAGE
9 Average Rainfall 677.66mm
10 50% Dependable Rainfall 370.75 mm
3. BASIS FOR FORMATION OF TANK
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PROPOSAL OF WATER SUPPLY SCHEME AND NEW TANK FOR DHUMMAVAD VILLAGE
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3.1 AREA OF CATCHMENT BASIN:
Catchment area is the area of the closed traverse obtained by projecting catchment
boundary on to a horizontal plane. It is expressed in Square kilometers.
The catchment area is 4.84 km2, using Toposheet 48-M/3.
3.2 NATURE OF CATCHMENT
The examination of the nature of the catchment is done for computing the run-off
parameters. Generally, catchments with vegetation give good yield and those with porous soil
give more yield. The nature of the catchment is Average since there is no vegetation found
and the soil is loamy clay.
Further the catchment of the proposed tank is examined for the possibility of existing
tanks with ayacuts, their storage capacity, and the ayacuts irrigated by the tank.
3.3 RAINFALL DATA
Rainfall data from the nearest Meteorological Station, i.e. The University of
Agricultural Sciences, Dharwad has been collected for the past 23 years. From the rainfall
data so obtained, the Dependable Rainfall and the Yield of the Catchment has been computed
by using Dependable Percentage value to be 50% of the annual mean rainfall.
The procedure to compute the dependable rainfall is as below
i. The available rainfall for past 23 years is arranged in Descending order by
magnitude.
ii. The order M is given by the equation, M=23*(p/100). The rainfall value
corresponding to this order in the tabulated data represents the required dependable
value.
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PROPOSAL OF WATER SUPPLY SCHEME AND NEW TANK FOR DHUMMAVAD VILLAGE
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RAINFALL DATA
SL NO YEAR RAIN FALL1 1991 1104.82 2005 1011.13 2007 10004 2006 8495 1992 824.26 1993 806.37 2004 7718 1997 760.39 1998 753.810 1988 74911 1994 741.512 1995 731.913 1990 730.514 1996 686.615 1987 62616 1986 594.717 1985 551.318 1989 54519 2000 528.720 1999 435.721 2002 362.322 2001 24723 2003 175.5
3.4 CONVERTING DEPENDABLE RUNOFF TO DEPENDABLE YIELD
Average Rain Fall = 15586.2/23 =677.66mm
M= 23*(50/100) =11.5
M= 11 and Dependable rain fall is 741.5mm
50% Dependable rain fall
=(50/100)x741.5 = 370.75mm
3.5 YIELD OF THE CATCHMENT
From Strange’s table
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PROPOSAL OF WATER SUPPLY SCHEME AND NEW TANK FOR DHUMMAVAD VILLAGE
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Yield of catchment for 370.75mm rain fall
By interpolation, for 370.75mm
= ((15.15x4.735x10-3)/25.4)+0.022129= 0.02495= 24950
Yield of the catchment = 24950 x4.9 = 122255m3
3.6 DESIGN OF NEW TANK
Assumptions:
Number of filling per year = 2
Utilization of the yield per filling = 50%
Capacity of the tank = 50% of yield = 0.5 x 122255 = 61127.5 m3
Utilization of the yield per year = 2 x 61127.5 = 122255 m3
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PROPOSAL OF WATER SUPPLY SCHEME AND NEW TANK FOR DHUMMAVAD VILLAGE
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3.7 CONTOUR MAP
S.D.M. COLLEGE OF ENGINEERING AND TECHNOLOGY, DHARWAD
PROPOSAL OF WATER SUPPLY SCHEME AND NEW TANK FOR DHUMMAVAD VILLAGE
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3.7 CAPACITY TABLE
Sl no
R.L Area (m2) √(A1xA2)Contour interval
Capacity by Prismoidal formula
=[h/3(A1+A2+√(A1xA2))]
Accmulation
(m3)
1 590 57500 1
2 591 34200 44345.24 1 45348.41 45348.41
3 592 58200 44614.35 1 45671.45 91019.86
4 593 71900 64688.33 1 64929.44 155949.30
5 594 67200 69510.29 1 69536.76 225486.06
6 595 75500 71229.21 1 71309.74 295795.81
7 596 12650 30904.29 1 39684.76 335480.57
8 597 11440 12029.80 1 12039.93 347520.5
9 598 101700 34109.35 1 49083.12 396603.62
3.8 AREA ELEVATION CURVE
The areas enclosed by the successive contours were calculated using Auto Cad. A close observation shows that as the value of elevation increases the area also increases a curve is plotted between area and elevation as shown above.
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PROPOSAL OF WATER SUPPLY SCHEME AND NEW TANK FOR DHUMMAVAD VILLAGE
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3.9 STORAGE AREA CURVE
The bund capacity or the volume of storage corresponding to a given area in reservoir may be calculated either by trapezoidal or prismoidal formula. If ‘V’ is the volume of storage and ‘h’ is the contour interval, then by trapezoidal formula.
V = h[(A1+An)/2+A2+A3+A4+……..An-1]
A curve is plotted between area and volume as shown below.
4.0 FEATURES OF THE BUND
An earthen bund must be safe and stable during phases of construction and operation.
The following recommendations are generally used for selecting the suitable values of top
width, free board, upstream and downstream slopes, drainage arrangement etc.
4.1 TOP WIDTH
The top width of the earthen bund depends upon the following criteria
Width of the road on top of the bund
Practicability of the construction
Protection against earthquake forces
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PROPOSAL OF WATER SUPPLY SCHEME AND NEW TANK FOR DHUMMAVAD VILLAGE
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Following are some of the empirical expressions for top width ‘b’ of the earthen bund in
terms of the height ‘H’ of the bund.
b=H/5+3 (this is applicable when the height of the bund is low)
b=1.65(H+1.5) ^1/3 (this is given by USBR)
Top width is assumed to be 2.0m (according to TABLE NO. 2)
4.2 FREE BOARD
Free board is the vertical distance between the horizontal crest of the embankment
and the water level. Sufficient free board must be provided so that there is no possibility what
so ever of the embankment being over topped.
USBR suggests the following free boards:
Nature of spillway Height of dam Free board
Free AnyMin 2m and max of 3m over
the flood level
Controlled Less than 60m 2.5m above top of the gates
Therefore free board of 2.5m is provided
4.3 PITCHING
The upstream slope of the bund is protected from the wave wash by a layer of stones called as stone pitching. A thin layer of spauls is laid on the upstream slope and on this a layer of big size, hand packed and roughly hammered dressed stones is laid. The voids between these big size stones are filled with small stones which are hammered in.
4.4 UPSTREAM AND DOWNSTREAM SLOPES
Using Terzaghi’s table no. 10.2 (c) page no. 409 (Irrigation engineering B.C.Punmia)
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Sl No.
Type of material Upstream Downstream
1 Homogenous W.G material 2:1 2:1
2 Homogenous coarse silt 3:1 2.5:1
3 Homogenous silty clay
a) Height <15m 2.5:1 2:1
b) Height >15m 3:1 2.5:1
4 Silt or sand and gravel with clay core
3:1 2.5:1
5 Sand or gravel with RCC core wall 2.5:1 2:1
4.5 DRAINAGE OF EARTHEN BUND
The water percolates through every earthen bund however it stagnates in the downstream portion of the bund and over-saturates it. This may result in slip of material and also results in the failure of the embankment. The draining of the water from the downstream portion so as to avoid slip is called Artificial Drainage of the earthen bund. This is necessary when the material in the downstream portion of the bund does not have proper natural drainage.
In case of drains, a few longitudinal stone drains are provided parallel to the bund length and its bottom. The cross drains takes the water percolating in longitudinal drain to a downstream longitudinal drain at some distance away from the toe of the bund. Water from the downstream drain is collected by clear drains and is taken away from the bund.
The materials provided in the drains for drainage purpose being more permeable than the material of the dam. As long as the drainage system works properly and efficiently, the ground on the vicinity of the toe of the dam should be in dry condition.
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PROPOSAL OF WATER SUPPLY SCHEME AND NEW TANK FOR DHUMMAVAD VILLAGE
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S.D.M. COLLEGE OF ENGINEERING AND TECHNOLOGY, DHARWAD
PROPOSAL OF WATER SUPPLY SCHEME AND NEW TANK FOR DHUMMAVAD VILLAGE
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5. DESIGN OF WASTE WEIR
Catchment Area, M = 1.89m2
Ryves constant, C =650
Q=C*M(2/3)
= 650x(1.89) 2/3
=27.648m3
Height of the weir , H=3 feet.
Q=2/3X(Cd*L*√2g*h3/2)
27.648=2/3X(0.62XLX√2X9.81X(0.9144) 3/2
L=17.03
Provide length of weir =20m
Crest / Top width of the Waste Weir
Crest width,a,=√d*√(H/1.8)+1
Or a minimum of 3d/2f
d= Depth of water over weir = 1m
f=Specific Gravity of body Wall = 2.40
a=√1 x √(3/1.8)+1 =1.63m
Or ( 3x1)/(2x2.40) = 0.625m
Crest Width ,a=0.625m
Provide Crest width of 0.625m for Stability
Bottom Width =(H+D)/√f
=(3+1)/√2.40 = 2.58m
Provide Bottom width of 5.0m for Stability
Depth of Water Cushion = ((1/2)xd)/(H-d)
=((1/2)x1)/(3-1) =0.25m
Provide Water Cushion of 0.3m
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Proposed Basin floor level =594.00
Discharge per meter=28/20 =1.4 m3/sec
Vth=√2g((H+h)/2) h=3m,H=4m
= √2x9.81x((4+3)/2) = 8.28 m/sec≈8.3m/sec
Vact=0.98x Vth = 0.98x8.3 = 8.134m/sec
Froudes number = Vact/gd1
D1=1.56/8.134 = 0.1917
= 8.134/(9.81X0.1917) = 4.325
5.1 Stability of Weir
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Sl no. Force(kN) Distance from Toe(m) Moment(kNm)
1 W1=(0.625x2x1)x25= 31.250
4.375+(0.625/2)=4.687
146.468
2 W2=((1/2)x4.374x2x1)25= 109.375
(2/3)x4.375 =2.916
318.937
3 Pw=γH2/2=9.81x32/2 =44.145
(1/3)x3 =1m 44.145
∑V=31.25+109.375 =140.625
∑M = (146.468+318.937)-44.145 = 421.272
Step 1:
140.625*X- =421.272
X= 421.272/140.625 = 2.995
Step 2:- Stability against Overturning
=Stability moment/Overturning moment
= (146.468+318.937)/44.145
=10.542 >2 …safe
Step 3:- Stability against Sliding
= Resisting Force/Sliding Force =μ(w+w2)/44.145 =0.6(31.250+109.375)/44.145
= 1.911>1.5. Therefore, Safe.
Step 4:
Pmax = ∑V/B (1+6e/B) = (140.625/5)x(1+(6x0.495)/5) = 44.831
Pmin = ∑V/B (1-6e/B) =(140.625/5)x(1-(6x0.495)/5) = 11.418
S.D.M. COLLEGE OF ENGINEERING AND TECHNOLOGY, DHARWAD
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