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CFS Outflows for Different Sluice Gate Openings for a Given Water Level
Standard Contracted Rectangular Weir Calculations
Broad Crested Weir Calculations
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Clary Lake Association
100.00When the lake level reaches the high water mark, the top of the dam becomes a uncontrolled spillway over it's entire length which is about 100' long, more or less. This calculates flows over the top of the dam in increments of 1/10th of a foot.
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Prepared by George Fergusson January 6, 2019
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Length L5.00
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Any Openingb5.00Length L:96
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Y20.1P5.00C:3.08736973
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Y17.77H0.34
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Cc0.61Q3.26HQ (cfs)
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g32.170.00.0
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Cd0.6076195412L:5.000.19.4
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V213.58572346
Elevation of bottom of weir: 142' ±
H0.226.5
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q3.763245398NHWM:151.170.10.520.348.7
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q+24.263245398
See this site for more information:
Water Level-0.40.21.480.475.0
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Gate Leakage:0.5
http://ponce.sdsu.edu/onlinechannel13.php
Weir Depth Y17.770.32.700.5104.8
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Sluice Opening Y2
(water level in ft below hwm)
0.44.140.6137.7
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InchesFeetCFS Outflowwith 2 cfs leak
Discharge coefficient Cd
Reference Velocity V2
0.55.770.7173.6
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000.000.50.6113.638947970.67.550.8212.1
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10.08333.143.60.608015139813.594568620.79.480.9253.1
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20.16666.256.80.606049529813.550619680.811.531.0296.4
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30.24999.359.80.604102860913.507094240.913.701.1341.9
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40.333212.4312.90.602174830713.46398555115.981.2389.6
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50.416515.4816.00.600265143713.421286991.118.361.3439.3
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60.499818.5219.00.598373510813.37899211.220.841.4491.0
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70.583121.5422.00.596499649513.337094571.323.401.5544.5
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80.666424.5425.00.594643283213.29558821.426.041.6599.8
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90.749727.5328.00.592804141213.254466951.528.751.7657.0
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100.83330.4931.00.5909819589
Approximate
13.21372491.631.541.8715.8
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110.916333.4433.90.5891764773error13.17335626
The Gate in the dam is not circular! The bottom 13.5" is closed!
1.734.401.9776.2
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120.999635.6436.10.58738744270.9813.13335536
At 12" opening, calculated area = 398 sq in., actual area = 392 sq in. (98%) Very close!
1.837.312.0838.3
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131.082938.3738.90.5856146070.97713.09371665CFS results below this line will be increasingly in error because calculations assume a rectangular orifice. They've been adjusted by the amounts in column F1.940.29
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141.166241.1241.60.58385772710.97513.05443469243.330.82220.1
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151.249543.8344.30.58211656530.97313.015504182.146.41
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161.332846.4747.00.58039088830.9712.976919882.249.55
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171.416147.2047.70.57868046820.9312.93867672
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181.499448.2248.70.57698508140.912.900769682.249.55
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191.582748.5049.00.5753045090.8612.86319388
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201.66649.7250.20.57363853650.8412.82594451
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Max Open: 20.51.7149.7450.20.57276437190.8212.80639913Fully open, flow is 82% lower than calculated or about 55 cfs when the lake is full.
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Gate Openings to release Minimum Flows
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Assumptions: Water Level -2 below HWM
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Date
Minimum Flow
Gate Opening
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1-1 to 3-1511.30.320.28
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3-16 to 5-1535.91.04
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5-16 to 6-308.30.24
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7-1 to 9-151.90.06
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9-16 to 11-153.50.1
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11-16 to 12-3115.50.45
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This picture shows the obstruction across the bottom of the 34" diameter outlet pipe that represents a reduction in area of about 37%
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150.890.01
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150.900.01
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150.910.01
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150.920.01
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150.930.04
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150.940.08
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150.950.13
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150.960.19
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150.970.28
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150.980.41
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150.990.56
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151.000.74
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151.010.97
86
151.021.23
87
151.031.53
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151.041.85
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151.052.21
90
151.062.60
91
151.073.03
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151.083.51
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151.094.03
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151.104.60
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151.115.24
96
151.125.93
97
151.136.68
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151.147.49
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151.158.37
100
151.169.30