# Water Flow Measurement Calculator

$$
Q = 3.247 \cdot L \cdot H^{1.48} - \frac{0.566 \cdot L^{1.9}}{1 + 2 \cdot L^{1.8}} \cdot 0.609 \cdot H^{2.5}
$$
$$
\text{where }
$$
$$
Q = \text{Flow Rate in cfs}
$$
$$
L = \text{Bottom width of the weir}
$$
$$
H = \text{Height of the upstream water above the weir crest}
$$

$$
Q = 2.49 \cdot H^{2.48}
$$
$$
\text{where }
$$
$$
Q = \text{Flow Rate in cfs}
$$
$$
H = \text{Height of the upstream water above the weir crest}
$$

Throat Width: 3 inch
$$
Q = 0.992 \cdot H^{1.547}
$$

Throat Width: 6 inch
$$
Q = 2.06 \cdot H^{1.58}
$$

Throat Width: 9 inch
$$
Q = 3.07 \cdot H^{1.53}
$$

Throat Width: 12 inch (1 foot)
$$
Q = 3.95 \cdot H^{1.55}
$$

Throat Width: 2ft through 8ft
$$
Q = 4 \cdot W \cdot H^{1.522} \cdot W^{0.026}
$$

Throat Width: 10ft through 25ft
$$
Q = (3.6875 \cdot W + 2.5 ) \cdot H^{1.6}
$$

$$
Q = 3.247 \cdot L \cdot H^{1.48} - \frac{0.566 \cdot L^{1.9}}{1 + 2 \cdot L^{1.87}} \cdot H^{1.9}
$$
$$
\text{where }
$$
$$
Q = \text{Flow Rate in cfs}
$$
$$
L = \text{Bottom width of the weir}
$$
$$
H = \text{Height of the upstream water above the weir crest}
$$

$$
Q = 0.61 \cdot A \cdot \sqrt{64.1 \cdot H}
$$
$$
\text{where }
$$
$$
Q = \text{Flow Rate in cfs}
$$
$$
A = \text{The cross sectional area of the open rectangular orifice in square feet (height x width)}
$$
$$
H = \text{Height (elevation) difference between the upstream and downstream still water surfaces}
$$

For bottom width of 1 foot (b in diagram):
$$
Q = 1.36 \cdot H^{2.5} + 10.37 \cdot H +0.05
$$
For bottom width of 2 foot (b in diagram):
$$
Q = 1.32 \cdot H^{2.5} + 0.82 \cdot pow(H,1.5) + 0.19
$$
$$
\text{where }
$$
$$
Q = \text{Flow Rate in cfs}
$$
$$
H = \text{Height of the upstream water above the bottom of the flume in feet}
$$

For H less than 0.37d:
$$
Q = 6.17 \cdot d^{1.25} \cdot H^{1.35}
$$
For H greater than 1.4d:
$$
Q = 5.01 \cdot d^{1.99} \cdot H^{0.53}
$$
Flow Rate is taken as the lesser cacluated value of the two equation (least reliable estimates)
$$
\text{where }
$$
$$
Q = \text{Flow Rate in gpm}
$$
$$
d = \text{Inside diameter of the pipe (inches)}
$$
$$
H = \text{Height of free water surface above the end of the pipe (inches)}
$$

cfs:

Cubic feet per second

gps:

Gallons per second (US Liquid)

lps:

Litre per second

cms:

Cubic meter per second

cfm:

Cubic feet per minute

gpm:

Gallons per minute (US Liquid)

lpm:

Litre per minute

cmm:

Cubic meter per minute

cfh:

Cubic feet per hour

gph:

Gallons per hour (US Liquid)

lph:

Litre per hour

cmh:

Cubic meter per hour

ft:

Feet

in:

Inch

m:

Meter

cm:

Centimeter

mm:

Millimeter

**Cipolletti (Trapezoidal) Weir Calculator:**

This calculator determines the flow rate over a Cipolletti weir, which is a trapezoidal-shaped weir. The unique aspect of this weir is its sloping sides, typically at a 1:4 horizontal to vertical ratio. This calculator helps in estimating the amount of water flowing over the weir by considering the weir dimensions and the head of water.

**90° Triangular Notch Weir Calculator:**

This tool is used for calculating the flow rate through a 90° triangular notch weir. The triangular notch, forming a perfect right angle, is crucial for measuring small to medium flow rates in open channels. The calculator evaluates the flow based on the height of water above the apex of the triangle.

**Parshall Flume Calculator:**

The Parshall Flume calculator is designed to compute the flow rate in a Parshall Flume, which is recognized by its contracting sides and a drop in the bottom elevation. This flume is commonly used in irrigation and wastewater treatment. The calculator assesses the flow by measuring the depth of the water at a specific point in the flume.

**Rectangular Contracted Weir Calculator**

This calculator measures the flow rate over a rectangular contracted weir. The weir has a rectangular opening with vertical sides, and it's used to measure water flow in open channels. The calculator takes into account the height of water above the weir crest to estimate the flow rate.

**Rectangular Submerged Orifices Calculator:**

This tool calculates the flow rate through a rectangular submerged orifice, which is an underwater rectangular opening. It's often used in dams, reservoirs, and other hydraulic structures. The flow rate is calculated by considering the dimensions of the orifice and the water head on both sides.

**Trapezoidal Flume Calculator:**

This calculator is used to determine the flow rate in a trapezoidal flume. Characterized by its trapezoidal cross-section with sloping sides, this flume is a common structure in water measurement and management. The calculator provides flow rate estimates based on the water depth in the flume.

**Vertical Pipes Calculator:**

This calculator is designed to compute the flow rate of water in vertical pipes. It is particularly useful in plumbing and civil engineering, where understanding the flow dynamics in vertical pipe systems is crucial. The calculator typically considers factors such as the internal diameter of the pipe, water velocity, and pressure differences.

Based on Prosser IAREC (Washington State University)