Canal cross-section terminology: Pick the incorrect statement about the positions of banks and the 'dowla' (inspection berm) in a typical irrigation canal cross-section.

Introduction / Context:

In open-channel irrigation engineering, a canal cross-section is described with reference to its two banks (right and left, defined while facing downstream) and ancillary features that aid operation and maintenance. One such feature is the 'dowla'—a narrow inspection berm or service path provided on a specific bank to facilitate patrol, minor maintenance, and emergency interventions. This question checks familiarity with standard layout conventions used in many canal systems.

Given Data / Assumptions:

• Conventional earthen canal in a distributary or minor system.
• Right bank and left bank are referenced facing the direction of flow (downstream).
• The 'dowla' is the inspection berm commonly assigned to one designated bank for uniformity of operations.

Concept / Approach:

Canals have two banks by definition, one on either side of the waterway. The 'dowla' is not a central feature; it is constructed on a selected bank (commonly the right bank in many standard practices) to give staff safe access and a consistent side for patrolling and silt/debris management. Hence, statements that merely acknowledge the existence of left and right banks are correct, while a statement that misplaces the standard position of the 'dowla' is considered incorrect in the conventional context.

Step-by-Step Solution:

Verification / Alternative check:

Standard canal drawings and departmental manuals typically show a single inspection berm on the right bank for consistency of field operations. Local practices can vary, but the conventional answer follows the common standard.

Why Other Options Are Wrong:

• A bank on the right / on the left: Both are inherently true (two banks exist).
• None of these: Incorrect because one statement is indeed wrong.
• A 'dowla' at bed centreline: Not standard practice; 'dowla' is on a bank, not at the channel centre.

Common Pitfalls:

• Confusing local variations with generalized exam conventions.
• Assuming the dowla could be on either side without recognizing the widely adopted “right-bank” convention in many texts.

Final Answer:

A 'dowla' in the cross-section of a canal is provided on the left