--- title: "Non-modular outlet working, merits, demerits" subject: "Irrigation and Drainage Engineering" chapter: 7 key: "semester_6/irrigation_and_drainage_engineering:non-modular-outlet-working-pros-cons" source: https://www.bctengineer.com/q/semester_6/irrigation_and_drainage_engineering/non-modular-outlet-working-pros-cons site: BCT Engineering --- # Non-modular outlet working, merits, demerits Irrigation and Drainage Engineering · Chapter 7: Regulating Structures - Asked in: 2068 Baisakh (old course), 3+3 marks - Video: [Types of canal outlet with Live video Example || Irrigation canal module types](https://www.youtube.com/watch?v=sw5seo8N21M) — Gyan Tokri - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_6/irrigation_and_drainage_engineering/non-modular-outlet-working-pros-cons - Whole chapter: https://www.bctengineer.com/md/semester_6/irrigation_and_drainage_engineering/chapter-7 ## Question Explain the working of a non-modular outlet. What are the advantages and disadvantages of this type of outlet? ## Short answer A non-modular outlet’s discharge depends on both distributary and water course levels (q proportional to sqrt(Hd-Hw)). Advantages: simple, cheap, low head. Disadvantages: discharge varies with water course level, farmer can tamper, not equitable. ## Answer #### Working of a non-modular outlet (3 marks) A **non-modular outlet** is one whose discharge depends on the water levels in **both** the distributary and the water course. The flow through the outlet is orifice or sluice flow: $q = C_d\,a\,\sqrt{2g\,(H_d - H_w)}$ when submerged, where $H_d$ and $H_w$ are the water levels in the distributary and in the water course. If the level in the distributary rises, the discharge rises; if the water course silts up or its level rises, the discharge falls. Examples: open sluice, submerged pipe outlet. ```text Distributary Water course ~~~~~ H_d ~~~~~|======pipe=====|~~~~~ H_w ~~~~ ______ bed ____| |______ bed ____ ``` #### Advantages (about 1.5 marks) 1. Simple, cheap and easy to construct. 2. No moving parts, so little maintenance is needed. 3. Needs only a small working head, so it can command a large area. 4. The discharge can be adjusted by changing the opening size or setting. #### Disadvantages (about 1.5 marks) 1. The discharge varies with the water levels in both channels, so distribution is not equitable. 2. The farmer can alter the discharge by changing the water course level (tampering). 3. Silting or weeds in the water course reduce the discharge. 4. It cannot give a fixed discharge. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. On what does the discharge of a non-modular outlet depend? A. Only the water level in the distributary B. Only the opening size C. Water levels in both the distributary and the water course D. Only the water level in the water course Answer: C. Its flow is q = Cd a sqrt(2g(Hd - Hw)), so it depends on both levels. (Key point: Definition of non-modular outlet) 2. What happens to the discharge if the water course silts up and its level rises? A. Discharge increases B. Discharge falls because the head difference reduces C. Discharge stays the same D. The outlet becomes proportional Answer: B. A higher Hw reduces (Hd - Hw), so the discharge falls. (Key point: Effect of silted water course) 3. Which is an advantage of the non-modular outlet? A. It gives a fixed discharge B. It is immune to water course level changes C. It needs a large working head D. It has no moving parts and needs a small working head, so it commands a large area Answer: D. It is simple, cheap and works with little head, which maintains command over a large area. (Key point: Advantage) 4. Why is distribution through non-modular outlets not equitable? A. Discharge varies with levels in both channels and farmers can tamper by changing the water course level B. They always draw too much silt C. They have moving parts that jam D. They need very high working head Answer: A. Because discharge depends on the water course level, it cannot be fixed and can be altered by farmers. (Key point: Disadvantage) ## Related in Irrigation and Drainage Engineering - [Non-modular, semi-modular outlet; module requirements](https://www.bctengineer.com/question.md?key=semester_6%2Firrigation_and_drainage_engineering%3Anonmodular-semimodular-working-module-requirements) — Irrigation and Drainage Engineering, chapter 7 - [Outlet, requirements, modular vs semi-modular](https://www.bctengineer.com/question.md?key=semester_6%2Firrigation_and_drainage_engineering%3Aoutlet-requirements-modular-distinction) — Irrigation and Drainage Engineering, chapter 7 - [Semi-modular pipe outlet design, flexibility 0.9](https://www.bctengineer.com/question.md?key=semester_6%2Firrigation_and_drainage_engineering%3Asemimodular-pipe-outlet-flexibility-09) — Irrigation and Drainage Engineering, chapter 7 - [Modular, semi-modular, non-modular outlets](https://www.bctengineer.com/question.md?key=semester_6%2Firrigation_and_drainage_engineering%3Aoutlets-modular-semimodular-nonmodular) — Irrigation and Drainage Engineering, chapter 7, asked 3× ## Related in other subjects - [Cofferdam types, uses, merits and demerits](https://www.bctengineer.com/question.md?key=semester_5%2Ffoundation_engineering%3Acofferdam-types-merits) — Foundation Engineering, chapter 5, asked 7× - [Incineration: merits and demerits](https://www.bctengineer.com/question.md?key=semester_6%2Fsanitary_engineering%3Asolid-waste-incineration) — Sanitary Engineering, chapter 10, asked 7× - [Merits and demerits of river and ridge routes](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Ariver-ridge) — Transportation Engineering I, chapter 5, asked 7× - [Distribution layouts, merits and demerits](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Adistribution-layouts-merits-demerits) — Water Supply Engineering, chapter 7, asked 6×