Q1: Most economical section of a circular channel for maximum discharge

ANS:E - 3707" all the above.

1. Depth of water = 0.95 times diameter of circular section: This statement suggests that the depth of water in the circular channel is nearly equal to the diameter of the circular section. While this may be a common scenario, it doesn't directly relate to the most economical section for maximum discharge.
2. Hydraulic mean depth = 0.286 times diameter of circular section: The hydraulic mean depth is a measure of the average depth of flow in a channel. While this equation provides a relationship between the hydraulic mean depth and the diameter of the circular section, it doesn't correspond to the most economical section for maximum discharge.
3. Wetted perimeter = 2.6 times diameter of circular section: The wetted perimeter is the length of the perimeter of the cross-section of the channel that is in contact with the fluid. This statement provides a specific value for the wetted perimeter but doesn't indicate the most economical section for maximum discharge.
4. Wetted perimeter = 2.83 times depth of water: This statement provides another relationship between the wetted perimeter and the depth of water. However, it doesn't directly relate to the most economical section for maximum discharge.

None of the options provided directly explain the most economical section of a circular channel for maximum discharge, which occurs when the hydraulic mean depth is approximately 0.81 times the diameter of the circular section. This specific relationship optimizes the flow characteristics of the channel, leading to maximum discharge efficiency.