--- title: "Intake site factors; spring intake" subject: "Water Supply Engineering" chapter: 5 key: "semester_5/water_supply_engineering:spring-intake-site-factors" source: https://www.bctengineer.com/q/semester_5/water_supply_engineering/spring-intake-site-factors site: BCT Engineering --- # Intake site factors; spring intake Water Supply Engineering · Chapter 5: Intakes - Asked in: 2069 Chaitra, 8 marks - Video: [What is intake structure? Purpose of Intake in Water Supply Scheme, Factors Affecting Site Selection](https://www.youtube.com/watch?v=l3aEZnqaFro) — Nepal Engineers Loksewa Solutions - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_5/water_supply_engineering/spring-intake-site-factors - Whole chapter: https://www.bctengineer.com/md/semester_5/water_supply_engineering/chapter-5 ## Question What are the factors that should be considered during selection of an intake site? With neat sketches, describe the construction of a spring intake. ## Short answer Selection depends on adequate dry-season yield, clean water upstream of pollution, a stable outer-bend reach with sufficient depth, flood safety, good foundation, no navigation obstruction, nearness to treatment, accessibility, and future expansion. A spring intake is a chamber at the spring eye with gravel filter, outlet, overflow, washout, vent, diversion drain, and fence. ## Answer #### Factors for selecting an intake site 1. **Water quantity**: the source must give the design flow even in the driest season; the minimum flow must exceed the demand. 2. **Water quality**: the site should be upstream of towns, sewage and industrial discharges, and away from tributaries that bring silt or pollution. 3. **Stable bank and bed**: choose a stable, non-eroding reach, preferably on the concave (outer) side of a bend where the water is deep and the current scours silt away. 4. **Depth of water**: enough depth at all stages so the intake port stays submerged at low water. 5. **Flood level**: the structure must stand above the highest flood level (HFL) or be safe against it, and the site should be free from flood and drift damage. 6. **Foundation**: sound strata for the foundation of the intake tower and pipes. 7. **Navigation**: the site must not obstruct navigation and should not be in a navigation channel. 8. **Distance and elevation**: close to the treatment plant and consumers (shorter pipeline, lower cost); for gravity schemes, enough head. 9. **Accessibility**: access for construction, inspection and maintenance in all seasons, and nearness to power for pumping. 10. **Future expansion** and **ownership of land/legal rights** at the site. 11. **Ice and silt**: the site should not be affected by ice formation or heavy sedimentation. #### Construction of a spring intake A **spring intake** (spring box or spring capture) is a small chamber built at the spring eye to collect all the flow from the spring, protect it from pollution, and send it to the pipeline by gravity. It is the most common intake for rural hilly areas of Nepal because springs give clean water at a high level. **Parts of a spring intake** - **Collection chamber** (spring box) of stone masonry or concrete, with a pre-cast cover and manhole. - **Gravel filter / perforated pipes** at the back wall to collect water uniformly from the spring eye. - **Outlet pipe** with a gate valve (and a strainer) to the pipeline. - **Overflow pipe** to take excess water; **washout (drain) pipe** with a valve for cleaning; **vent pipe** with a screen. - **Protection works**: clay/impervious cap over the spring, a **diversion drain** (catch drain) uphill to divert surface water, a **fence**, and a vegetation or plantation cover. **Plan** ```text Diversion drain (uphill) ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | fence | | +---------------------+ | | | gravel filter :::: | | | | (spring eye) |-->| overflow | | collection chamber | | | | [manhole] outlet |==>| pipe to tank | +----------+----------+ | | washout pipe | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ``` **Section / elevation** ```text Vent Manhole cover | ____|_____ ground | | | clay cap (0.5 m) =======+--+ +============= | | air | Spring->|::| water lvl|--> overflow gravel |::|~~~~~~~~~~| filter |::| |==> outlet+valve |__|__________| washout pipe ``` ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. For a river intake, why is the concave (outer) side of a bend preferred? A. Water is deep there and the current scours silt away B. Water is shallow and calm so silt settles C. It is the shortest route to the treatment plant D. It is always above the highest flood level Answer: A. On the outer side of a bend the water is deep and the current keeps silt from depositing, so the intake port stays submerged and clear. (Key point: Site on bend) 2. What must the source give at the intake site? A. The average annual flow equal to demand B. The design flow even in the driest season C. Only the flood flow D. Any flow, as storage can be added later Answer: B. Minimum (dry season) flow must exceed demand, otherwise the supply fails when it is most needed. (Key point: Water quantity) 3. Where should the intake be located relative to sewage and industrial discharges? A. Downstream so they dilute the water B. Directly at the outfall C. Upstream of towns and discharges, away from silty tributaries D. Position is unimportant if chlorine is used Answer: C. An upstream site avoids pollution and silt carried by tributaries and outfalls. (Key point: Water quality) 4. What is the purpose of the diversion (catch) drain and clay cap of a spring intake? A. To increase the spring yield B. To store water for the dry season C. To provide head for the pipeline D. To keep surface water and pollution out of the spring box Answer: D. The impervious cap and uphill diversion drain protect the spring eye from surface runoff and contamination. (Key point: Spring intake parts) ## Related in Water Supply Engineering - [Reservoir intake and site selection factors](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Areservoir-intake-site-factors) — Water Supply Engineering, chapter 5, asked 2× - [Factors in constructing a spring intake](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Aspring-intake-factors-constructing) — Water Supply Engineering, chapter 5 - [General river intake and site selection](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Ageneral-river-intake) — Water Supply Engineering, chapter 5, asked 3× - [Intake, its functions and site factors](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Aintake-functions-site-factors) — Water Supply Engineering, chapter 5 - [Intake components and site factors](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Aintake-components-site-factors) — Water Supply Engineering, chapter 5 - [Spring intake with neat sketch](https://www.bctengineer.com/question.md?key=semester_5%2Fwater_supply_engineering%3Aspring-intake-sketch) — Water Supply Engineering, chapter 5, asked 8× ## Related in other subjects - [Bridge site factors and components with sketches](https://www.bctengineer.com/question.md?key=semester_7%2Ftransportation_engineering_ii%3Abridge-site-factors-components-sketches) — Transportation Engineering II, chapter 5 - [Hydropower site selection factors](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Asite-selection-discharge-factors) — Power Plant Design, chapter 3 - [Intake site selection for RoR plant](https://www.bctengineer.com/question.md?key=semester_6%2Fhydro_power%3Aintake-site-selection-ror) — Hydro Power, chapter 5 - [Distribution substation site selection factors](https://www.bctengineer.com/question.md?key=semester_6%2Findustrial_power_distribution_and_illumination%3Asubstation-site-location-factors) — Industrial Power Distribution and Illumination, chapter 4