Canal outlets classification: An outlet that maintains practically constant discharge irrespective of fluctuations in the upstream channel water level and the watercourse level is called a

Introduction / Context:
Canal outlets are devices that draw water from distributaries into watercourses. Their hydraulic behaviour under upstream/downstream level fluctuations defines their type and equity of distribution among farmers.

Given Data / Assumptions:

• Outlet required to deliver nearly constant discharge.
• Both distributary (supplying channel) and watercourse levels may fluctuate.
• Device calibrated to be insensitive to such variations.

Concept / Approach:
A “right modular outlet” (also called a rigid module) is designed so that its discharge is essentially independent of both upstream and downstream heads within a working range. Non-modular outlets are sensitive to both levels; semi-modular depend only on upstream head (insensitive to downstream).

Step-by-Step Solution:
Classify by discharge sensitivity to levels.Need: independence from both → modular (rigid).Therefore, the correct classification is right modular outlet.

Verification / Alternative check:
Handbooks present proportional, semi-modular, and modular types; rigid modules are used where equitable distribution regardless of backwater is essential.

Why Other Options Are Wrong:

• Non-modular: Varies with both levels.
• Semi-modular: Independent of downstream only.
• Flexible modular: Non-standard phrasing; “rigid module” is the accepted term.
• Open flume outlet: Descriptive geometry, not behaviour class.

Common Pitfalls:
Confusing semi-modular with modular; assuming proportional outlets are constant discharge (they are not).

Final Answer:
Right modular outlet (rigid module)