A canal whose bottom width is 20 m, side slopes 2:1, passing a discharge of 200 m³/s. The normal water depth is 4.0 m. The canal is lined with concrete for which 1/n = 80. Determine:
i. The grade of the canal in cm/km.
ii. If Q 100 m³/s instead of 200 m³/s, find the corresponding water depth.
iii. Calculate the discharge if S, is doubled.
iv. Calculate the discharge if n is doubled.