--- title: "Dry river intake with sketch" subject: "Water Supply Engineering" chapter: 5 key: "semester_5/water_supply_engineering:dry-river-intake" source: https://www.bctengineer.com/q/semester_5/water_supply_engineering/dry-river-intake site: BCT Engineering --- # Dry river intake with sketch Water Supply Engineering · Chapter 5: Intakes - Asked in: 2074 Asoj, 8 marks; 2068 Chaitra, 8 marks (asked 2 times) - Video: [Types of Intake Structure - Water Supply and Distribution of Water - Environmental Engineering 1](https://www.youtube.com/watch?v=RrtbXAqmyIo) — Ekeeda - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_5/water_supply_engineering/dry-river-intake - Whole chapter: https://www.bctengineer.com/md/semester_5/water_supply_engineering/chapter-5 ## Question Why is an intake structure necessary for a water supply scheme? Describe a dry type river intake with a neat sketch showing all major components and operation. ## Short answer An intake ensures controlled, safe water withdrawal. A dry intake tower on the riverbank has a dry chamber with valves; water enters through screened ports, passes through valves to a separate sump. Operator selects best port level; maintenance is easy but structure needs watertight walls and deep foundation, increasing cost. ## Answer #### Need for an intake structure Water cannot be taken directly from a river, lake or reservoir in a safe, controlled way. The intake is needed to: - draw the design quantity in all seasons and draw it from the best level; - keep out floating matter, silt, fish and debris with screens; - protect the supply from floods, scour and erosion; - allow valves to control and isolate the flow; - provide a stable base for pipes and pumps. #### Dry type river intake A **dry intake** is a tower built on the river bank (or just inside it) whose interior is kept dry. Water enters through ports in the wall, flows into a **separate sump** by a connecting pipe, and only the valves and pipes are in the dry chamber. The operator can work inside it at any time. ```text Foot bridge ===+ | operating floor HFL ~~~~~~~~~ || gate valves ||[=]---+ NWL ~~~~~~~~ ||[=]---+--> pipe to ||[=]---+ sump/pump well LWL ~~~~~~~ || dry chamber ///////// ||____________ screens at ports river bed | (water-tight walls) ``` **Operation** - Water flows from the river through the screened ports, then through the valves in the dry chamber, to the sump or directly to the pump. - The operator selects the port at the best level and closes the others. - Valves and screens can be inspected, cleaned or repaired from inside, in dry conditions. **Merits and demerits**: Operation and maintenance are easy, but it needs stronger water-tight walls and a heavier, deeper foundation (to resist floatation when it is empty), so it costs more than a wet intake. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Why is an intake needed? A. Draw design flow safely, exclude debris, resist floods and allow control B. Only to store water C. Only to add chlorine D. Only to measure flow Answer: A. It gives controlled, protected withdrawal at the best level. (Key point: Need for intake) 2. What is distinctive about a dry intake? A. It has no ports B. Interior is dry, water goes to a separate sump, valves in dry chamber C. Tower is full of water D. It is built in the reservoir only Answer: B. Water goes via pipe to a separate sump; the operator works in a dry chamber. (Key point: Dry intake) 3. What does the operator do in a dry intake? A. Fill the chamber B. Select the port at best level and close the others C. Dive to open valves D. Rake screens from the sump Answer: B. Valves and screens are accessed from inside without getting wet. (Key point: Operation) 4. What is the drawback of a dry intake? A. Draws too much silt B. Costlier, needs stronger water-tight walls and deeper foundation C. Cannot use valves D. Hard to operate Answer: B. It is easy to maintain but expensive compared with a wet intake. (Key point: Merits) ## Related in Water Supply Engineering - [Wet and dry river intake](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Awet-dry-river-intake) — Water Supply Engineering, chapter 5 - [Intake definition, components, river intake](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Aintake-components-river) — Water Supply Engineering, chapter 5, asked 2× - [Necessity and impacts of water supply scheme](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Anecessity-impacts-ws) — Water Supply Engineering, chapter 1, asked 3× - [Typical water supply system and components](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Atypical-ws-system-components) — Water Supply Engineering, chapter 1, asked 4× - [Objectives of water supply and components](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Aobjectives-ws-rural-diagram) — Water Supply Engineering, chapter 1, asked 3× - [Dry and wet river intakes; unstable bank](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Awet-dry-intake-unstable-bank) — Water Supply Engineering, chapter 5 ## Related in other subjects - [Is treatment necessary? Industry near river](https://www.bctengineer.com/question.md?key=semester_6%2Fsanitary_engineering%3Atreatment-industry-river-1p72) — Sanitary Engineering, chapter 6 - [Layout of hydropower scheme components](https://www.bctengineer.com/question.md?key=semester_6%2Fhydro_power%3Ahydropower-scheme-layout) — Hydro Power, chapter 5 - [Micro hydro scheme components and classification](https://www.bctengineer.com/question.md?key=semester_6%2Fenergy_resources%3Amicro-hydro-scheme-components-classification) — Energy Resources, chapter 5 - [Daily pondage run-of-river components](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Adaily-pondage-ror-components) — Power Plant Design, chapter 3