Trapezoidal:

\[ WP = b + 2d \sqrt{z^2 + 1} \]

Triangular:

\[ WP = 2d \sqrt{z^2 + 1} \]

Parabolic:

\[ WP = t + \frac{8d^2}{3t} \]

Where:

• \(WP\) is the wetted perimeter in meters (m).
• \(b\) is the base width of the channel in meters (m).
• \(d\) is the depth of water in meters (m).
• \(z\) is the canal slope (h/d), in decimal form.
• \(t\) is the top width in meters (m).