The formula to calculate the bottom width of the channel is:

\[ b = 2d \cdot \tan\left(\frac{\theta}{2}\right) \]

Where:

• \(b\) is the bottom width of the channel in meters (m).
• \(d\) is the depth of water in the canal in meters (m).
• \(\theta\) is the angle between the side slope and the horizontal in degrees.