Assessment of canal conveyance and cross-drainage structures: (A) Culverts are standard closed conduit structures installed under roads when the road embankment fill is sufficiently elevated above the canal invert; (B) Inverted siphons convey flow under hydrostatic pressure across wide depressions or shallow road cuts where minimal headroom precludes culverts; and (C) Elevated open flumes (aqueducts) span across natural drainages, ravines, and streams. Statements (D) and (E) are incorrect because cross-drainage structures are vital in irrigation layout, and a siphon is a pressure conduit, never termed a flume. Option analysis: (A) (A), (B) and (C) only is correct. (B) Includes false statement (D). (C) Includes false statements (D) and (E). (D) Includes false statement (D).

Water distribution efficiency ($\eta_d$) measures how uniformly water infiltrates and distributes throughout the crop root zone during an irrigation application, computed as $\eta_d = 100 \times (1 - \bar{y}/\bar{d})$, where $\bar{d}$ is the average depth of water stored and $\bar{y}$ is the average numerical deviation from the mean depth. This definition and mathematical formulation are identical to Christiansen's Uniformity Coefficient ($CU$), commonly used to evaluate sprinkler and trickle irrigation uniformity. Option analysis: (A) Friction coefficient relates to pipe head loss. (B) Runoff coefficient is the ratio of runoff to rainfall. (C) Uniformity coefficient is identical in definition and formulation. (D) Drainage coefficient is the depth of water drained from an area in $24\text{ hours}$.