Clary Lake Gate Flow Calculations
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CFS Outflows for Different Sluice Gate Openings for a Given Water Level
Standard Contracted Rectangular Weir Calculations
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Clary Lake Association
When 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 Openingb3.00Length L:100
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Y21.7P5.00C:3.08736973
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Y17.67H1.00
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Cc0.61Q15.98HQ (cfs)
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g32.170.00.0
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Cd0.5725234040.19.8
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V212.71836999
Elevation of bottom of weir: 142' Â±
H0.227.6
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q59.45837972NHWM:151.170.10.520.350.7
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q+261.45837972
Water Level-1.50.21.480.478.1
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Gate Leakage:2
http://ponce.sdsu.edu/onlinechannel13.php
Weir Depth Y17.670.32.700.5109.2
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Sluice Opening Y2
(water level in ft below hwm)
0.44.140.6143.5
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InchesFeetCFS Outflowwith 2 cfs leak
Discharge coefficient Cd
Reference Velocity V2
0.55.770.7180.8
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000.002.00.6113.550897030.67.550.8220.9
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10.08333.125.10.607989389413.506232150.79.480.9263.6
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20.16666.218.20.605998530113.462006040.811.531.0308.7
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30.24999.2911.30.604027100713.418211550.913.701.1356.2
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40.333212.3414.30.602074787313.37484172115.981.2405.8
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50.416515.3817.40.600141282913.331889721.118.361.3457.6
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60.499818.4020.40.598226287513.289348891.220.841.4511.4
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70.583121.4023.40.596329507513.247212711.323.401.5567.2
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80.666424.3826.40.594450656113.205474811.426.041.6624.8
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90.749727.3429.30.592589452613.164128941.528.751.7684.3
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100.83330.2832.30.5907456224
Approximate
13.123169021.631.541.8745.6
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110.916333.2135.20.5889188969error13.08258907
The Gate in the dam is not circular! The bottom 13.5" is closed!
1.734.401.9808.6
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120.999635.3937.40.58710901330.9813.04238326
At 12" opening, calculated area = 398 sq in., actual area = 392 sq in. (98%) Very close!
1.837.312.0873.2
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131.082938.1140.10.58531571430.97713.00254586CFS results below this line will be increasingly in error because calculations assume a rectangular orifice1.940.29
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141.166240.8342.80.58353874830.97512.9630713243.33
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151.249543.5245.50.58177786870.97312.923954092.146.41
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161.332846.1448.10.58003283440.9712.885188882.249.55
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171.416146.8748.90.5783034090.9312.84677041
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181.499447.3549.30.57658936140.8912.80869355
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191.582748.1550.20.57489046480.8612.77095327
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201.66649.3651.40.57320649750.8412.73354463
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Max Open: 20.51.7149.3851.40.57232295840.8212.71391718Fully open, flow is 82% lower than calculated or about 55 cfs when the lake is full.
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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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