20620130101005

Journal of Civil Engineering and Technology (JCIET), ISSN 2347 –4203 (Print),
ISSN 2347 –4211 (Online), Volume 1, Issue 1, July-December (2013), © IAEME
46
VALIDATION OF DESIGN NORMS OF MULTI-VILLAGE WATER
SUPPLY SCHEMES
A.Raja Jeyachandra Bose1
, Dr.T.R.Neelakantan2
, Dr.P.Mariappan3
1
DGM/Water&Infra, Fichtner Consulting Engineers (India) Pvt. Ltd, Chennai and Research
Scholar, SASTRA University, Thanjavur, TN.
2
Professor, School of Civil Engg., SASTRA University, Thanjavur, TN.
3
TWAD Board, 6A, Balasubramanian Nagar, Rajakkapatty, Dindigul-4, TN.
ABSTRACT
Trend in the method of providing community water supply scheme is changing with
time due to various reasons. Depending upon the availability of safe source, schemes from
hand pump to multi-village schemes are chosen. Most preferred option among the consumers
is to have a multi-village water supply scheme from a perennial river source. Lot of such
schemes are in operation and maintenance in the state of TamilNadu, which is generally a
water-starved state. Reliability, cost, and sustainability of such schemes mainly depend on the
design norms being adopted during project planning. Due to recent origin of the concept, no
standard guidelines are available. A critical evaluation of the design guidelines has been done
and suggestions made.
Key Word: Multi-village water supply scheme, design guidelines, reliability, cost.
INTRODUCTION
In general, various schemes are being followed for providing drinking water supply to
communities. Open well with manual drawal method was the oldest system. Hand pumps
fitted in bore wells were introduced during seventies followed by individual power pump
(IPP) scheme. Groundwater is the only source for all the above schemes. Due to increase in
demand & drawal and reduction in ground water recharge activities, ground water table is
fast depleting, coupled with deterioration in quality, making the ground water sources as non-
reliable. To overcome the same, reliable surface water sources are being tapped and a new
JOURNAL OF CIVIL ENGINEERING AND TECHNOLOGY
(JCIET)
ISSN 2347 –4203 (Print)
ISSN 2347 –4211 (Online)
Volume 1, Issue 1, July-December (2013), pp. 46-56
© IAEME: www.iaeme.com/jciet.asp
JCIET
© IAEME

47
concept of combined water supply scheme (CWSS) was formulated two decades back, to
supply water to multi villages from a common source. Number of such schemes have been
installed and brought into beneficial use in various parts of Tamilnadu, drawing water from
river sources such as Cauvery, Vaigai, Tamirabarani etc., To name a few, CWSS to 674
habitations in Trichy district, 829 habitations in Thiruvarur and Nagapattinam districts, 3163
habitations in Ramanathapuram district are based on the above concept. Hogenakkal Water
Supply and Fluorosis Mitigation Project, being implemented now, plans to cater to the
drinking water requirement of 6755 rural habitations in Dharmapuri and Krishnagiri districts.
Design norms adopted in the planning of such CWSS are mainly governed by the following
factors:
Configuration
Per capita supply
Velocity of flow
Design Population
Pipe material
Capacity of Storage (Sump and Service Reservoir)
System of Operation and Maintenance &
Cost
Performance reports on the functioning of CWSS always indicate a handful of un-
served habitations, at any point of time, due to various reasons. Even though the planning and
design is made to ensure simultaneous supply to all beneficiaries, it is observed that the
planned objective could seldom be achieved during the operation and maintenance of the
scheme and the system do not behave as expected. In most of the schemes, principle of
operator based operation is being followed during O&M period to ensure supply to all
beneficiaries, which solicit attention for all the factors listed above for validation. This paper
critically reviews the above factors.
Configuration
Configuration of the scheme shall be decided with special reference to the O&M
needs of the scheme. While finalizing the configuration, capacities and location of water
treatment plant, booster stations, balancing reservoirs etc shall be fixed considering the O&M
needs also. In practical, cost factors namely capital cost and maintenance cost (ie., per capita
cost and cost per kilo litre) are given priority during project planning with least importance
for the above factors. Sustainability and reliability are also to be considered in addition to the
above aspects during the planning stage.
Locating the water treatment plant (WTP) at the highest contour in the project area
and gravitating water to all the villages from the Master Service Reservoir (MSR) is a
common practice of configuration. A typical arrangement of a CWSS with Balancing
Reservoir (MBR) near WTP is shown in Figure 1 below:

48
Figure 1 - Model configuration of a CWSS
Instead of gravitating water from single MSR to elevated service reservoirs (ESRs)
located at the beneficiaries, it is preferable to locate zonal balancing reservoirs (ZBRs) at
suitable locations i.e at the center of the group of villages. ZBRs may be fed by separate
pumping mains from the clear water sump at WTP, if topography warrants or water may be
conveyed from the MBR by gravity to the ZBRs (Figure 2). The WTP shall preferably be
located close to a habitation so that the operation and maintenance staff will not hesitate to
reside with their families in the quarters.
Figure 2 - Configuration with ZBRs
W
T
P
MSR
ESR
180
160
140
200
ZBR
W
T
P
MSR
ESR
180
160
140
200

49
Pipelines from MBR/WTP to ZBRs should be more reliable and accordingly the pipe
material and joints should be chosen. Diameter of the pipe shall be fixed based on economical
analysis. In the first configuration (Figure 1) many habitations will suffer without supply if
breakdown occurs at any location whereas in the second configuration, only 2 to 3 ESRs
would be left sans supply. The reliability of supply to all villages from MBR/WTP is quite
equal as reliable pipe material is proposed upto ZBRs. In this case, the pipe sizes will be
relatively less ensuring easy maintenance. It is preferable to have different outlets for the
villages located in different directions (Domkondwar, 2000). Each ZBR should be located in
such a way that the single outlet shall cover not more than four ESRs in the region where the
gradient is higher. In plain areas, this shall be preferably less than 10.
The topography of Tamil Nadu very rarely permits gravity system and most of the
CWSS incorporate rising/pumping mains with or without boosters as shown in figure 3.
Booster locations are decided based on the static head and length.
Figure 3 - Configuration with booster station
Each booster station may cover around 10 to 15 kms of length and about 100 meters
of head. Number of villages (ESRs) included along the main and booster stations may vary
according to the level difference. Residual head difference between the ESRs located in
lowest and highest elevations should be less than 5 meters. Height of ESRs shall also be
suitably fixed satisfying the residual pressure requirements. Booster stations in treated water
pumping mains may be limited to two stages. Third stage pumping can be resorted to when a
few tail end villages are to be covered.
Mother tank concept has recently attracted the practitioners in this field due to its
inherent merits. Mother tank is nothing but a storage tank which acts as buffer storage to
absorb flow from the MBR during low consumption period and feeds the ZBRs during peak
hours or any break down in the mains. Water coming from MBR will be collected in mother
Source
Sump cum
Pump House
Booster
Booster
Booster
100
180
220
300

50
tank when the ZBRs are getting filled up one by one. It is an additional storage to ensure
reliability. This concept is preferable for 24X 7 distribution plan. Schematic representation
of the Mother tank is shown in figure 4.
Figure 4 - Model configuration with mother tank
LWL (Lowest water level) of MBR is to be fixed higher than the MWL (Maximum
water level) of mother tank. MWL of all ZBRs is to be lower than the LWL of mother tank.
Site selection / staging of mother tank is to be chosen / fixed accordingly. All the ZBRs
should be provided with automatic flow control valve synchronized with the MWL. ESRs
can also be suitably integrated with mother tank instead of ZBRs if situation demands.
Per Capita Supply
CPHEEO manual on water supply and treatment recommends per capita water supply
levels for designing schemes. It varies from 40 lpcd to 150 lpcd depends on the classification
of towns / habitation. CWSS are proposed to benefit both urban and rural communities,
predominant one being the rural areas. During planning of such schemes, existing local
sources are also taken into account and the final suggested demand from the proposed scheme
is in the order of 15 lpcd or so. Pipe sizes are reckoned for the corresponding flow based on
the optimization calculation and minimum pipe size consideration. In such a scenario, the
carrying capacity of the proposed pipes is grossly under utilized. The impact of per capita
supply on cost of installation is analyzed by considering a model scheme with ten habitations,
which is listed in Table 1 below:
MBR
ZBR
ZBR
ZBR
ZBR
ZBR
ZBR
Mother
tank

51
Table 1 Requirement at various per capita supply levels
Requirement (lpm) for various supply levels
Habitation
Per Capita Supply (lpcd)
15 25 40
Int Ult Int Ult Int Ult
1 7 9 12 15 19 24
2 4 5 7 8 11 13
3 12 13 20 22 32 35
4 17 19 28 32 45 51
5 8 9 13 15 21 24
6 8 9 13 15 21 24
7 10 13 17 22 27 35
8 13 17 22 28 35 45
9 7 9 12 15 19 24
10 11 14 18 23 29 37
Total 97 117 162 195 259 312
The requirement in lpm for each habitation is tabulated for various supply levels
(lpcd). Total length of pipeline considered is 10 kms. Based on the pipe sizing arrived at, the
installation cost works out to Rs.10.02, 12.82 and 14.48 lakhs for the supply levels of 15, 25,
40 lpcd respectively.
Cost versus per capita is presented in figure 5 below and it is observed that the
increase in cost is 25 % for the rise in supply level from 15 lpcd to 25 lpcd and 13% for 25
lpcd to 40 lpcd. Further it is also observed that only a marginal increase in pump capacity is
required with no change in pipe size.
Figure 5 - Per Capita Supply Vs Cost
9
10
11
12
13
14
15
10 15 20 25 30 35 40 45
Per Capita Supply
Installation Cost, Rs. in lakh

52
Velocity of flow
Velocity of flow is an important factor which decides the pipe size and the carrying capacity.
Regarding the maximum and minimum allowable velocities in conveying mains, it is generally
suggested that the minimum shall be above the silting velocity and maximum shall be below the
scouring velocity, and no specific value is suggested by any manual/guidelines. As the continuity
equation mainly governs the flow, carrying capacity increases with the increase in velocity of flow for
given diameter of pipe. In the optimization of rising mains, a compromise between velocity and
frictional loss is generally considered. Velocity of the corresponding pipeline which yields the most
economical cost considering all factors is considered and hence the optimum velocity varies with
schemes.
Figure 6 - Optimum Velocity
A study of optimum velocity for 16 different water supply schemes, which is arrived at based
on economical analysis is depicted in Figure 6 above. It is observed that the optimum velocity is in the
range of 0.65 to 1.20 m/s. It is in agreement with the value of 1 m/s, as reported by Domkondwar. By
selecting appropriate velocity of flow, the following advantages can be reaped:
Reduction in pipe size and corresponding capital cost
Ease in commissioning of the scheme and easy O & M
Reduction in aging of water & maintaining residual chlorine & D.O
For a particular CWSS, installation cost was studied by varying the velocity and the same is
depicted in Figure 7 below:
Figure 7 - Cost of scheme with velocity range
A
B
C
S1
0
10
20
ALTERNATE
COST
Rs IN
CRORE
A- Velocity - 0.20- 0.57 m/s
B- Velocity - 0.40- 0.71 m/s
C- Velocity - 0.65 - 1.20 m/s
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
SCHEME NUMBER
V
E
L
O
C
I
T
Y
m /s

53
Lesser velocity will consume more time for water to reach the tail end beneficiary.
Quantum of water leaking will also be more during non-supply hours in the large diameter
pipes. Velocity ranges obtained in the optimum size analysis (A, B, and C), indicate that the
least cost combination results in the velocity range of 0.65 to 1.20 m/s.
Estimation of optimum velocity and the computation of corresponding frictional
losses in the conveying system are very important. Among the practicing engineers, Hazen
Williams and Darcy Weisbach formulae are being used for the estimation of frictional loss in
pipeline. The formulae and its merits and limitations are discussed below:
Hazen William’s formula: V = 3.83 C d0.6575
* ( gs )0.5525
/ ν 0.105
Where V- Velocity in mps, C- pipe roughness coefficient, d - Pipe diameter,
g - acceleration due to gravity, s - slope, ν - viscosity of liquid
Limitations of Hazen William’s formula:
Widely followed Hazen William’s formula has its own inherent limitations.
Numerical constant in the formula (0.849 in SI units) is arrived at based on the hydraulic
radius of 1 foot and friction slope of 1/1000. Hence it is appropriate to use the same for the
diameter and slope in that range. If the same is used for other ranges, it may result in an error
of up to ±45% in estimation of frictional head loss.
The formula is dimensionally inconsistent, since the Hazen-Williams C has the
dimension of L-0.37
T-1
and therefore, is dependent on units employed. Further it is
independent of pipe diameter, velocity of flow and viscosity. However to be dimensionally
consistent and to be representative of friction conditions, relative roughness of pipe and
Reynolds’s number or viscosity need to be accounted for.
Darcy Weisbach’s formula: S = H/L = f V2
/2 g d
where H- head loss due to friction over length L, f- Dimensionless friction factor
Merits of Darcy Weisbach’s formula:
The formula is dimensionally consistent. Applicable parameters i.e. velocity and
diameter are included. The formula used in combination with Colebrook-White equation for
‘f’ value takes into account relative roughness and Reynolds’s number, which in turn includes
viscosity.
So, it is important to adopt appropriate equation to estimate velocity and
corresponding friction loss.
Design Population
Population forecast is usually done to arrive at the design population for the project.
Various methods are recommended by CPHEEO for this purpose. Average of forecasted
population by arithmetical increase method, geometrical increase method and incremental
increase method is generally adopted as design population. Sometimes, large variation in
design population, ie., 5 to 6 times the base year population, is observed. But, these are to be
restricted judiciously to 2 to 3 times of base value. Population density map may be used for
the distribution of expected population in the project area. Anticipated growth of population
shall be distributed to developed plots as well as vacant plots.

54
Table 2 Population forecast statement
Sl.
No.
Name
Projected Population & Year
As per
census
Year Base
Year
Year Int.
Year
Year Ult.
year
2001 2009 2012 2021 2027 2036 2042
1 Gajanur 1474 1476 1477 1486 1495 1514 1530
2
Gajanur
Agrahar
2172 3240 3783 6167 8738 15273 22665
3
Halle
Honapura
794 877 936 1196 1441 1931 2358
4
Hosa
Honapura
5 Hosahalli
2190 2435 2536 2871 3120 3537 3844
6
Lakshmi
pura
Total 6630 8028 8732 11720 14794 22255 30397
A case study for the population projection method and its observation is presented
above in Table 2 wherein population forecast of six villages are listed. Actual survey was
done during 2009. Various methods were used for the projection. The results obtained shows
that the ultimate population for the village Gajanur Agrahar is about 10 times the 2001
census. In this case, a judicious decision, i.e 5 times the base year population may be
considered for planning.
Pipe Material
Reliability of any piped water supply system mainly rests with the pipe material used.
Major classifications of the pipe material are metallic and non-metallic. Choice of the pipe
material is mainly influenced by the cost of the project. Materials such as asbestos cement,
which are predominantly used earlier, are totally abandoned now. On the other hand, cost of
certain pipe materials is becoming relatively cheaper due to improvement in manufacturing
process and other influencing factors. Among the two options, metallic pipes are considered
to be more reliable. Type of pipe joints is also playing an important role in the performance
of the piping system. There are cases where the system failed due to improper selection of
type of joint. For example, selection of socket and spigot joint with rubber rings for pipes laid
underground in black cotton soil. Hence suitable pipe material and pipe joints are to be
chosen considering reliability and cost.
Capacity of Storage Component (Sump and Service Reservoir)
Capacity of the storage structures such as sump is generally arrived at based on the
CPHEEO norms and hours of pumping proposed. Capacity of the service reservoir is fixed
based on mass curve analysis or design norms according to population. Cost of sump and SRs
for five schemes and the total cost are tabulated in Table 3 below:

55
Table 3 - Cost of Storage Component (Sump/SR) Vs Total cost
Name of
Scheme
Cost of Sumps/SRs Rs
Crore
Total Cost
Rs Crore
Percentage
1 7.64 53.00 14 %
2 4.22 110.43 4 %
3 2.88 39.02 7 %
4 0.15 0.81 18 %
5 0.14 0.81 17 %
It is observed that the share of above components in a project is in the range 4 to 17
percent, which is less than 1/5th
of the project cost. Reliability of the system can be vastly
improved if higher capacities of storage are considered. Another practical constraint observed
is the lack of space for capacity addition of storage tanks in future for up-gradation of the
distribution and conveying system, particularly in dense urban areas. Hence it is preferable to
consider a higher capacity accordingly. Donkondwar suggested 12 hours capacity for service
reservoirs and 4 hours capacity for ZBRs. In case of gravity system, higher capacity sump/SR
results in containment of non-revenue water due to wastages during non-supply hours.
System of Operation and Maintenance
Simultaneous supply to all service reservoirs is the major design parameter invariably
adopted in the design of all CWSS. But this is seldom achieved, particularly in major CWSS
covering hundreds of habitations, due to various reasons. In such cases, water supply is
ensured by the following ways:
Operator based operation &
Provision of head dissipating / boosting devices
In operator based operation, the operator starts closing the control valves, one by one,
controlling the flow to end reservoirs. Mostly, the valve is closed when SR starts
overflowing. In such a scenario, the actual hydraulics of the system totally differs with that of
the design stage, which is based on simultaneous flow to all SRs. But such typical cases are
not analyzed while finalizing the design. Hence, it is always necessary to check the flow
conditions for the operator based operation situation, which are designed otherwise.
Cost
Overall cost of the project includes cost of the source, conveying system, storage
system and distribution system. Percentage cost of the conveying system versus the total cost
for some projects are depicted in Figure 8 below:

56
Figure 8 - Percentage of Cost of pipeline
It is observed that the conveying system absorbs 43 to 89 percent of total cost of the
project. Hence more emphasis is to be paid while planning. A minimum of three alternatives
shall be worked for choosing techno-economical option.
CONCLUSION
Proper planning and design is a pre-requisite to implement sustainable and reliable
CWSS projects. Suitable configuration with judicious population forecast forms the base for
proper planning. To ensure high reliability, proper material and joint is to be chosen. Velocity
around 1.0 m/s will generally yield an economic combination of conveying mains. Higher
capacity of storage structures will greatly influence the reliability of the system, which
accounts for less than 20 % of cost of scheme. System of operation and maintenance of the
project needs to be taken into consideration during project formulation stage itself.
Monitoring and evaluation of performance of the schemes in operation shall be a continuous
process and the feed shall necessarily be transferred to the planning table for proper review of
the design guidelines adopted.
REFERENCES
1. “Manual on Water Supply and Treatment”, Central Public Health and Environmental
Engineering Organization, Ministry of Urban Development, Government of India, New
Delhi, 1991.
2. Domkondwar, M.V., “Configuration of Regional Rural Water Supply Scheme for
effective operation and maintenance”, Journal of IWWA, Vol. XXXIV, No: 4, PP: 261-
271, 2000.
3. Mariappan, P., “Rejuvenation of Rural Water Supply schemes – An experience”,
Journal of IWWA, Vol. XXXIV, No: 1, PP: 1-3, 2002.
4. Pramod R. Bhave and Rajesh Gupta, “Design, Performance and Operation of Regional
Rural Water Supply Systems”, Journal of IWWA, Vol. XXXIV, No: 4, PP: 273- 278,
2002.
1 2 3 4 5 6 7 8
0
10
20
30
40
50
60
70
80
90
SCHEME NUMBER
PERCENTAGE COST OF
PIPELINE TO TOTAL COST

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