By application of SW software different gravity based scheme can be designed and optimized. The software is especially used in Nepal for design of water supply projects in rural hilly areas of Nepal.

1. Gravity Water Supply Design Illustration using SW-CBWSS
-Pratap Bikram Shahi
Table of Contents
1. Introduction.....................................................................................................................................................................2
2. Illustrated Problem .........................................................................................................................................................2
3. Calculations .....................................................................................................................................................................4
4. Drawings:.......................................................................................................................................................................10

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1. Introduction
Water Supply Engineering is the branch of engineering which deals with the transmission, distribution and treatment
of water to be supplied for drinking purpose.
SW-CBWSSP is a Water Supply Design and Analysis project developed by Nepal Based Company called
SOFTWEL(http://softwel.com.np/). The software is used to design and analyses gravity based rural water supply
schemes.
2. Illustrated Problem

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Fig 1: CAD drawing of the problem

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Doti
The above figure 1 represents a water supply system based in Doti with an average household size of 4. The
project is to be designed by ABC Company with DWSSM as the support organization. The Construction
period is taken as 2 years and design period as 20 years. The per capita demand is taken as 60 lpcd with 10%
as non-domestic demand.
3. Calculations
Organization
Scheme Code
Scheme Name
Name of the Community
Name of the Support Organization
Location : Ward No.:
VDC :
District :
ABC Company
5
Risaltar WSSP
Gaire
DWSSM
4
-
Doti
SCHEME TYPE Gravity
SURVEY / DESIGN INFORMATION
District Pop Growth Rate (r)
Construction Period (n1)
Design Period (n)
Peak Factor
Per Capita Domestic Water Demand
Per Capita Water Demand for Students
Present Year ( Survey Year)
Base Year ( Project Completion Year)
Design Year
Minimum Flow Rate per Tap
0.74 % From District Growth Rates
years
years
Factor
l/d
l/d
lps
2
20
3
60
10
2021 AD
2023 AD
2043 AD
0.10
DATA INPUT FORM
Spread Sheets Developed by SOFTWEL (P) Ltd.

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SN PipeLength RL Branch Point(1/0)
Intake to RVT1
IN 0 120.75 1
CC 50 100.5 1
P1 75 98.65 1
JP 100 95.43 1
RVT1 50 92.875 1
JP to RVT2 1
JP 0 95.43 1
RVT2 150 93.69 1
Distribution RVT1 to T2
RVT1 0 92.875 1
P2 45 90 1
P3 50 85 1
J1 80 82.3 1
P4 40 80.5 1
J2 80 78 1
T2 73 66 1
Branch J2 to T1
J2 0 78 1
T1 75 68 1
Branch J1 to T3
J1 0 82.3 1
P5 90 80.4 1
T3 150 68.96 1
Distribution RVT2 to T4
RVT2 0 93.69 1
P6 55 90.49 1
J2 80 85.46 1
J3 110 82.3 1
P7 75 78.9 1
J4 40 75 1
T4 75 68 1
Distribution J4 to T5
J4 0 75 1
T5 70 72 1

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Table C.1 : Water Demand and Tap Flow Calculation Sheet
SCHEME NAME : Risaltar WSSP
SUPPORT ORGANIZATION :
LOCATION : WARD NO : 4 VDC : - DISTRICT : Doti
Name of Community : Gaire
Required Datas: Construction Period (n1) 2
Peak Factor: 3 Design Period (n) 20
Per Capita Demand : 60 lpcd
Per Capita Demand for Students: 10 lpcd Minimum flow rate 0.10 lps
Average Household Size 4
District Pop Growth Rate (r) 0.74
Per Capita Domestic Water Demand 60.00
Description of Tap
Ward
No.
Population forecast
Total
Domestic
Demand
Institutional Water Demand
Live
Stock
Demand
Total
Water
Demand
Tap Flow Calculation
Remarks
Tap
No
Cluster Name
or
Locality
Nos
of
HH
resent Yea
2021
(P)
Base Year
2023
(Po)
Design Year
2043
(Pn)
No. of
Pupil in
School
Other
Institutional
Demand
Total
Institutional
Demand
Average
Tap Flow
Peak
Factor
Peak
Flow
Design
flow
Adjusted
Peak
factor
(Nos) (Nos) P(1+r)^n1 P(l+r)^(n1+n) (lpd) (Nos) (lpd) (lpd) (lpd) (lpd) (lps) (Factor) (lps) (lps) (lps)
[1] [2] [2-1] [3] [4] [5] [6] [8] [9] [10] [11] [11-1] [12] [13] [14] [15] [16] [17] [18]
RVT1
1 J1 4 18 72 73 85 5,081 2,500 508.07 7,581 0.09 3.00 0.26 0.26 3.00
2 J2 4 20 80 81 94 5,645 564.53 5,645 0.07 3.00 0.20 0.20 3.00
3 T1 4 25 100 101 118 7,057 1,500 705.66 8,557 0.10 3.00 0.30 0.30 3.00
4 T2 4 30 120 122 141 8,468 846.79 8,468 0.10 3.00 0.29 0.29 3.00
5 T3 4 45 180 183 212 12,702 1,270.18 12,702 0.15 3.00 0.44 0.44 3.00
sub total 138 552 560 649 38,952 - - 4,000 3,895 42,952 0.50 1.49 1.49
RVT2
1 J2 4 15 60 61 71 4,234 1,500 423.39 5,734 0.07 3.00 0.20 0.20 3.00
2 J3 4 10 40 41 47 2,823 1,500 282.26 4,323 0.05 3.00 0.15 0.15 3.00
3 J4 4 10 40 41 47 2,823 1,500 282.26 4,323 0.05 3.00 0.15 0.15 3.00
4 T4 4 30 120 122 141 8,468 846.79 8,468 0.10 3.00 0.29 0.29 3.00
5 T5 4 35 140 142 165 9,879 987.92 9,879 0.11 3.00 0.34 0.34 3.00
sub total 100 400 406 470 28,226 - - 4,500 2,823 32,726 0.38 1.1363 1.1363
Grand Total 238 952 966.1417 1119.64352 67178.61 0 0 8500 75678.6 0.88 2.63 2.63 0.00
NOTE : 1 Peak factor of 3 has been adopted
2 Design Tap Flow has been adjusted for the Peak flow by rounding off to nearest 0.01lps.
3 If flow is less than 0.1 lps then it has been adjusted to 0.1 lps and if flow is greater than 0.25 lps provide additional tapstand.
Create RVT Sheets

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Sheet No. : 1 of 1
PIPELINE DESIGN
(HYDRAULIC CALCULATIONS)
Pipe Class abbreviation HC Soil Code GMS OS
MC (Ctrl+a for using solver) HR BMS
SCHEME NAME : SOURCE NAME : SAFE YEILD : DI SR MR
LOCATION : WARD NO : VDC : DISTRICT : CI HS SS Pipe Line Design from CW Method
HS Steel
S.
No.
Pipe Line Length Design
Dis.
Q
Direction Reduced Level Level
Diff.
New
Static
Level
Total
Head
Available
Max.
Static
Pressure
PIPE USED Friction
Factor
Head
Loss
Residual
Head
Flow Hydraulic Gradient L Soil
Type
Remarks
(UL/UR
/DL/DR
)
HDPE G.I. Velocity
From To Actual Design From To O.D. Class I.D. N.B. Class From To
(m) (m) (lps) (L/R/U/D (m) (m) (m) (m) (m) (m) (mm) kg/cm² (mm) (mm) (m) (m) (m/s) (m) (m)
[0] [1] [2] [3] 0 [5] (6) (7) (8) (9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (21) (22) (23) (24) (25)
Intake to RVT1
1 IN CC 50 55 1.000 D 120.75 100.50 20.25 120.75 20.25 20.25 63 10.0 52.90 0.0301 0.32 19.93 0.45 120.75 120.43 OS Collection Chamber
2 CC P1 75 82.5 1.000 DR 100.50 98.65 1.85 100.50 1.85 1.85 63 10.0 52.90 0.0301 0.48 1.37 0.45 100.50 100.02 BMS
3 P1 JP 100 110 1.000 D 98.65 95.43 3.22 100.50 4.59 5.07 63 10.0 52.90 0.0301 0.65 3.94 0.45 100.02 99.37 BMS
4 JP RVT1 50 55 0.500 DL 95.43 92.88 2.56 100.50 6.49 7.63 50 10.0 42.00 0.0334 0.29 6.20 0.36 99.37 99.08 BMS
JP to RVT2
1 JP RVT2 150 165 0.380 DR 95.43 93.69 1.74 100.50 5.68 6.81 50 10.0 42.00 0.0353 0.52 5.16 0.27 99.37 98.85 BMS
Distribution RVT1 to T2
1 RVT1 P2 45 49.5 1.290 D 92.88 90.00 2.88 92.88 2.88 2.88 75 6.0 67.40 0.0293 0.14 2.74 0.36 92.88 92.74 BMS
2 P2 P3 50 55 1.290 DL 90.00 85.00 5.00 92.88 7.74 7.88 75 6.0 67.40 0.0293 0.16 7.58 0.36 92.74 92.58 BMS
3 P3 J1 80 88 1.290 D 85.00 82.30 2.70 10.28 -82.30 75 6.0 67.40 0.0293 0.25 10.03 0.36 92.58 92.33 BMS
4 J1 P4 40 44 0.590 DL 82.30 80.50 1.80 0.00 11.83 -80.50 50 10.0 42.00 0.0323 0.32 11.51 0.43 92.33 92.01 GMS
5 P4 J2 80 88 0.590 D 80.50 78.00 2.50 0.00 14.01 -78.00 50 10.0 42.00 0.0323 0.64 13.37 0.43 92.01 91.37 BMS
6 J2 T2 73 80.3 0.290 DR 78.00 66.00 12.00 0.00 25.37 -66.00 40 12.5 32.00 0.0362 0.60 24.77 0.36 91.37 90.77 BMS
Branch J2 to T1
82.5 0.300 DL 78.00 68.00 10.00 0.00 23.37 -68.00 40 12.5 32.00 0.0360 0.65 22.72 0.37 91.37 90.72 GMS
99 0.440 DR 82.30 80.40 1.90 0.00 11.93 -80.40 50 10.0 42.00 0.0341 0.42 11.51 0.32 92.33 91.91 GMS
165 0.440 D 80.40 68.96 11.44 0.00 22.95 -68.96 50 10.0 42.00 0.0341 0.70 22.25 0.32 91.91 91.21 GMS
60.5 1.130 D 93.69 90.49 3.20 93.69 3.20 3.20 75 6.0 67.40 0.0299 0.14 3.06 0.32 93.69 93.55 BMS
88 1.130 DR 90.49 85.46 5.03 93.69 8.09 8.23 75 6.0 67.40 0.0299 0.20 7.89 0.32 93.55 93.35 OS
121 0.930 D 85.46 82.30 3.16 93.69 11.05 11.39 63 10.0 52.90 0.0304 0.63 10.42 0.42 93.35 92.72 OS
82.5 0.78 DR 82.30 78.90 3.40 93.69 13.82 14.79 63 10.0 52.90 0.0314 0.31 13.51 0.35 92.72 92.41 OS
44 0.78 D 78.90 75.00 3.90 93.69 17.41 18.69 63 10.0 52.90 0.0314 0.16 17.25 0.35 92.41 92.25 OS
82.5 0.290 DL 75.00 68.00 7.00 93.69 24.25 25.69 40 12.5 32.00 0.0362 0.62 23.63 0.36 92.25 91.63 BMS
77 0.340 DR 75.00 72.00 3.00 93.69 20.25 21.69 40 12.5 32.00 0.0351 0.76 19.49 0.42 92.25 91.49 BMS
1 J2 T1 75
Branch J1 to T3
1 J1 P5 90
2 P5 T3 150
Distribution RVT2 to T4
1 RVT2 P6 55
2 P6 J2 80
3 J2 J3 110
4 J3 P7 75
5 P7 J4 40
6 J4 T4 75
Distribution J4 to T5
1 J4 T5 70

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Table C.2.1 : Reservoir Tank Sizing (RVT1)
ABC Company
SCHEME NAME : Risaltar WSSP
LOCATION : WARD NO : 4 VDC : - DISTRICT : Doti
a) Scheme Information
a.1 Reservoir Tank No:
a.2 Served Standposts
a.3 Average Design Demand to be Supplied through Reservoir
a.4 Available Minimum flow from the Source (Safe Yield)
l/s = 42952.304 l/day
l/s
a.5 Adjusted/Optimized supply to Reservoir from Source 0.500 l/s = 43200.0 l/day
a.6 Total Design Flows of all Standposts : 1.491 l/s
b) Reservoir sizing assuming Continuous System using Consumption Patterns
Time Period Hours Water
Consumption
(%)
Cummu.
Supply
(lt)
Cummu.
Demand
(lt)
Surplus
(lt)
Deficit
(lt)
From To
5:00 AM 7:00 AM 2 25.0% 3600 10738 7138
7:00 AM 12:00 PM 5 35.0% 12600 25771 13171
12:00 PM 5:00 PM 5 20.0% 21600 34362 12762
5:00 PM 7:00 PM 2 20.0% 25200 42952 17752
7:00 PM 5:00 AM 10 0.0% 43200 42952 248
Maximum Deficit 17752 lt
Minimum required Reservoir capacity 17.75 cum
Provide Reservoir of capacity 18.00 cum 42% of Average Demand
Check if Reservoir gets filled during night (7:00 PM - 5:00 AM)
Volume of water collected during night 18.00 cum
50000
45000
40000
35000
30000
25000
20000
15000
10000
5000
0
Supply Demand
c) Reservoir sizing assuming Intermittent System (Optional)
Maximum Required supply hours based on Supply from Source 8.05 hours
Maximum Required supply hours based on Demand 8.00 hours
Adopted hours of Supply 8.00 hours
Recommended Supply Hours and Period
First Shift 5:00 AM To 9:48 AM
Second Shift 3:48 PM To 7:00 PM
Time Period Hours Cum. Inflow
(lt)
Cum. Con-
sumption (lt)
Surplus
(lt)
Deficit
(lt)
From To In Out
5:00 AM 9:48 AM 4.80 4.8 8640 25771 17131
9:48 AM 3:48 PM 6.00 0.0 19440 25771 6331
3:48 PM 7:00 PM 3.20 3.2 25200 42952 17752
7:00 PM 5:00 AM 10.00 0.0 43200 42952 248
c) Recommended Reservoir Size
Recommended Size for RVT 01 = 18.00 cum Time to Fill the RVT 10.00 Hr
Max Deficit 17752 lt =
Provide Reservoir Capacity of
17.75 cum
18.00 cum
12:00
AM
04:48
AM
09:36
AM
02:24
PM
07:12
PM
12:00
AM
04:48
AM
09:36
AM
1
1 to 8
0.497
2.000

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Table C.2.2 : Reservoir Tank Sizing (RVT2)
ABC Company
SCHEME NAME : Risaltar WSSP
LOCATION : WARD NO : 4 VDC : - DISTRICT : Doti
a) Scheme Information
a.1 Reservoir Tank No:
a.2 Served Standposts
a.3 Average Design Demand to be Supplied through Reservoir
a.4 Available Minimum flow from the Source (Safe Yield)
l/s = 32726.307 l/day
l/s
b) Reservoir sizing assuming Continuous System using Consumption Patterns
Time Period Hours Water
Consumption
(%)
Cummu.
Supply
(lt)
Cummu.
Demand
(lt)
Surplus
(lt)
Deficit
(lt)
From To
5:00 AM 7:00 AM 2 25.0% 2736 8182 5446
7:00 AM 12:00 PM 5 35.0% 9576 19636 10060
12:00 PM 5:00 PM 5 20.0% 16416 26181 9765
5:00 PM 7:00 PM 2 20.0% 19152 32726 13574
7:00 PM 5:00 AM 10 0.0% 32832 32726 106
Maximum Deficit 13574 lt
Minimum required Reservoir capacity 13.57 cum
Provide Reservoir of capacity 14.00 cum 43% of Average Demand
Check if Reservoir gets filled during night (7:00 PM - 5:00 AM)
Volume of water collected during night 13.68 cum
35000
30000
25000
20000
15000
10000
5000
0
Supply Demand
c) Reservoir sizing assuming Intermittent System (Optional)
Maximum Required supply hours based on Supply from Source 6.12 hours
Maximum Required supply hours based on Demand 6.10 hours
Adopted hours of Supply 7.00 hours
Recommended Supply Hours and Period
First Shift 5:00 AM To 9:12 AM
Second Shift 4:12 PM To 7:00 PM
Time Period Hours Cum. Inflow
(lt)
Cum. Con-
sumption (lt)
Surplus
(lt)
Deficit
(lt)
From To In Out
5:00 AM 9:12 AM 4.20 4.2 5746 22550 16804
9:12 AM 4:12 PM 7.00 0.0 15322 22550 7228
4:12 PM 7:00 PM 2.80 2.8 19152 37583 18431
7:00 PM 5:00 AM 10.00 0.0 32832 37583 4751
d) Recommended Reservoir Size
Recommended Size for RVT 02 = 20.00 cum Time to Fill the RVT 14.62 Hr
Max Deficit 18431 lt =
Provide Reservoir Capacity of
18.43 cum
19.00 cum
0.380
1.491
a.5 Adjusted/Optimized supply to Reservoir from Source
a.6 Total Design Flows of all Standposts :
l/s =
l/s
32832.0 l/day
12:00
AM
04:48
AM
09:36
AM
02:24
PM
07:12
PM
12:00
AM
04:48
AM
09:36
AM
2
1 to 8
0.379
2.000

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4. Drawings:

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