Uploaded by Ernie Rivera

Hydraulics Notes

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FLOOD FREQUENCY ANALYSIS
1. Arrange the annual peak discharge highest to lowest (rank 1-n)
Normal Distribution Method ((xĢ„, σ, ∑)
Rank
Observed
Return Period, T
Discharge
1/p
p
p>
0.5
1-p
w
KT
X2
xT
xĢ„ + KTσx
2. Plotting position, p
(n = total , m = rank)
šŸ šŸ/šŸ
š° = [š„š§ ( šŸ )]
When p > 0.5, use (šŸ − š©) to solve for š°
š©
3.
4.
KT = w − [
5.
X2
2.515517 + 0.802853w + 0.010328w2
1 + 1.432788w + 0.189269w2 + 0.001308w3
]
Log-Normal Distribution Method (xĢ„, σx, CS, CV ; yĢ…, σy, CS, CV)
Rank
Rank
x, Observed
y
Discharge
log(x)
Observed
Return
Period, T
1/p
p
Return Period, T
p>
0.5
1-p
w
KT
KT
yT
xT
yĢ… + KTσy
10 yT
xT
X2
X2
Discharge
Gumbel distribution Method (xĢ„, σx, CS, CV)
xĢ„ + KTσx
1/p
Chi-squared
Log Pearson Type III (Gamma) Distribution (xĢ„, √σšŸ”x, CS, CV ; yĢ…, σy, CS,
š“ CV)
Rank
x,
Observed
Discharge
š‘§=w−[
y
log (x)
šŠš“ = −
{šŸŽ. šŸ“šŸ•šŸ•šŸ + š„š§ [š„š§ (
)]}
š›‘
š“−šŸ
p
p>
w
z
k
KT
0.5
1-p
CSy/6
Return
Period, T
1/p
yT
xT
yĢ… + KTσy
10 yT
X2
2.515517 + 0.802853w + 0.010328w 2
]
1 + 1.432788w + 0.189269w 2 + 0.001308w 3
When CSy = 0, šŠš“ = z
When CSy ≠ 0;
šŠš“ = š³ + (š³šŸ − šŸ)š¤ +
šŸ
šŸ‘
šŸ
(š³šŸ‘ − šŸ”š³)š¤šŸ − (š³šŸ − šŸ)š¤šŸ‘ + š³š¤šŸ’ + š¤šŸ“
šŸ‘
WATER DEMAND
Level II Water Service
No. of Faucets
Nf =
Total Domestic Consumption
Population
faucets
×
Person per HH
HH
= n faucets
Tdc = SL−II × Nf =
Unit Consumption (50 -60 lpcd, 4-6 HH)
Uc =
š‘›
š‘™š‘–š‘”š‘’š‘Ÿ
š‘š‘Žš‘š‘–š‘”š‘Ž
š‘‘š‘Žš‘¦
(lpcd) ×
persons
HH
=
Water Demand (Wd / ADD)
š‘› š‘™š‘–š‘”š‘’š‘Ÿ
š‘‘š‘Žš‘¦−š»š»
Wd=ADD= Tdc + NRW(%Wd)= Tdc / 1-%NRW
Supply per faucet
SL−II = š‘ˆš¶ ×
HH
faucets
š‘› š‘™š‘–š‘”š‘’š‘Ÿ
š‘‘š‘Žš‘¦
Source Capacity
=
š‘›
š‘™š‘–š‘”š‘’š‘Ÿ
š‘‘š‘Žš‘¦
SC = š‘Šš‘‘ ×
š‘“š‘Žš‘¢š‘š‘’š‘”
š‘‘š‘Žš‘¦
1 ā„Žš‘Ÿ
× 36000 š‘ 
operating hrs
=
š‘› š‘™š‘–š‘”š‘’š‘Ÿ
š‘ š‘’š‘š‘œš‘›š‘‘
Level III Water Service
š‘š
3
š‘š
3
No. of Connections [lnstitutional (1.0 day), commercial(0.8 day), etc. ]
HH
Nc = (Population × Person ) + Other Connections = n connections
Unit Consumption (80-100 lcpd)
Uc =
š‘›
š‘™š‘–š‘”š‘’š‘Ÿ
š‘š‘Žš‘š‘–š‘”š‘Ž
š‘‘š‘Žš‘¦
(lpcd) ×
persons
HH
=
Total Domestic Consumption
Tš‘‘š‘ = š‘ˆš¶ × š‘›š‘œ. š‘œš‘“ š»š» =
š‘› š‘™š‘–š‘”š‘’š‘Ÿ
š‘‘š‘Žš‘¦
Water Demand (Wd / ADD)
š‘› š‘™š‘–š‘”š‘’š‘Ÿ
š‘‘š‘Žš‘¦−š»š»
Wd = ADD = Tdc + NRW ; Tdc = ADD/ 1-NRW
Source Capacity
SC = š‘Šš‘‘ ×
š‘‘š‘Žš‘¦
1 ā„Žš‘Ÿ
× 36000 š‘ 
operating hrs
=
š‘› š‘™š‘–š‘”š‘’š‘Ÿ
š‘ š‘’š‘š‘œš‘›š‘‘
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