| Depth
(inches) |
Dishcharge per Foot of Weir Width |
Depth
(inches) |
Dishcharge per Foot of Weir Width |
|||
|---|---|---|---|---|---|---|
| cfs | gpm | cfs | gpm | |||
| 1/2 | .03 | 13 | 7 | 1.48 | 665 | |
| 3/4 | .05 | 24 | 7 1/4 | 1.56 | 702 | |
| 1 | .08 | 36 | 7 1/2 | 1.65 | 738 | |
| 1 1/4 | .11 | 50 | 7 3/4 | 1.73 | 776 | |
| 1 1/2 | .15 | 66 | 8 | 1.81 | 814 | |
| 1 3/4 | .19 | 83 | 8 1/4 | 1.90 | 853 | |
| 2 | .23 | 102 | 8 1/2 | 1.98 | 890 | |
| 2 1/4 | .27 | 122 | 8 3/4 | 2.07 | 930 | |
| 2 1/2 | .32 | 142 | 9 | 2.16 | 971 | |
| 2 3/4 | .36 | 164 | 9 1/4 | 2.25 | 1012 | |
| 3 | .42 | 187 | 9 1/2 | 2.35 | 1053 | |
| 3 1/4 | .47 | 211 | 9 3/4 | 2.44 | 1096 | |
| 3 1/2 | .53 | 236 | 10 | 2.53 | 1136 | |
| 3 3/4 | .58 | 262 | 10 1/4 | 2.63 | 1179 | |
| 4 | .64 | 287 | 10 1/2 | 2.73 | 1223 | |
| 4 1/4 | .70 | 315 | 10 3/4 | 2.82 | 1268 | |
| 4 1/2 | .77 | 343 | 11 | 2.92 | 1312 | |
| 4 3/4 | .83 | 372 | 11 1/4 | 3.03 | 1358 | |
| 5 | .90 | 402 | 11 1/2 | 3.12 | 1401 | |
| 5 1/4 | .97 | 433 | 11 3/4 | 3.23 | 1448 | |
| 5 1/2 | 1.03 | 463 | 12 | 3.33 | 1495 | |
| 5 3/4 | 1.10 | 495 | ||||
| 6 | 1.18 | 528 | ||||
| 6 1/4 | 1.25 | 562 | ||||
| 6 1/2 | 1.33 | 596 | ||||
| 6 3/4 | 1.41 | 631 | ||||
*cfs = cubic feet per second
*gpm = gallons per minute
Use the above table to estimate the water flow over damboards or similar devices. In a stream without such a device, a wooden board (1 inch x 6 inches or 1 inch x 8 inches) can be placed on edge in the stream from bank to bank so that the water flows over the board. Once the average depth and the width of the water over the weir is measured with a ruler (Figure 1), use the table to estimate the flow.
For example:
water depth = 1.5 inches
weir width = 3 feet
flow estimate = 3 x 66 or 198 gallons per minute
from: King’s “Handbook of Hydraulics”, Fourth Edition, Table
36.
