Agricultural Engineering Practice Exam

The base measurement of the most efficient trapezoidal channel is determined by the channel geometry that minimizes the overall resistance to flow, thereby maximizing the flow efficiency. In open channel hydraulics, the "most efficient" trapezoidal channel is one that has a specific ratio of width to side slope that optimizes flow characteristics.

For trapezoidal channels, the optimal efficiency often occurs at a width: depth ratio that can be derived from theoretical studies and empirical data. This is typically around 6.14 m for the base width measurement in ideal conditions, which allows for the best flow while minimizing energy losses due to friction and turbulence. This base width contributes significantly to the hydraulic radius, which in turn affects the velocity of flow and the overall efficiency of the channel.

A base measurement of 6.14 m is thus recognized for providing the right balance between flow capacity and hydraulic performance in trapezoidal channels, making it the correct choice in this scenario.