--- title: "Surface and sub-surface irrigation methods" subject: "Irrigation and Drainage Engineering" chapter: 1 key: "semester_6/irrigation_and_drainage_engineering:surface-subsurface-methods-suitability" source: https://www.bctengineer.com/q/semester_6/irrigation_and_drainage_engineering/surface-subsurface-methods-suitability site: BCT Engineering --- # Surface and sub-surface irrigation methods Irrigation and Drainage Engineering · Chapter 1: Introduction - Asked in: 2073 Magh, 5 marks; 2078 Baisakh, 3 marks; 2064 Jestha (old course), 10 marks; 2065 Shrawan (old course), 8 marks; 2075 Baisakh, 4 marks; 2070 Chaitra (old course), 4 marks; 2063 Asoj (old course), 4 marks; 2062 Kartik (old course), 4 marks; 2068 Chaitra (old course), 5 marks; 2064 Kartik (old course), 4 marks (asked 10 times) - Video: [Types of Irrigation Surface and Subsurface Irrigation - Water Resource Engineering 1](https://www.youtube.com/watch?v=ImF4RK1vGHE) — Ekeeda - 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/surface-subsurface-methods-suitability - Whole chapter: https://www.bctengineer.com/md/semester_6/irrigation_and_drainage_engineering/chapter-1 ## Question Describe the different methods of surface and sub-surface irrigation and their suitability. ## Short answer Surface methods include border strip for close-growing crops, check basin for rice, furrow for row crops, and wild flooding for pasture. Sub-surface irrigation uses natural capillary rise or buried pipes to moisten root zone, suited to permeable soils with an impervious layer and flat land. ## Answer Irrigation methods are grouped as **surface** (water flows over the soil), **sub-surface** (water reaches roots from below) and pressurised methods (sprinkler, drip). #### Surface irrigation - **Wild (free) flooding:** water is let loose over an unprepared, roughly level field and spreads under gravity. Cheap, but uneven and wasteful. - **Border strip:** the field is divided into long, narrow, levelled strips separated by low bunds; water enters at the upper end and advances as a sheet. - **Check basin:** the field is divided into small level plots enclosed by bunds; each plot is flooded to a required depth and left to infiltrate. Used for rice. - **Basin (ring basin):** a circular basin around each tree, fed by a small channel. Used in orchards. - **Furrow:** small parallel channels between crop rows carry water; the soil is wetted by seepage from the sides and bottom. **Suitability** | Method | Suitable for | |---|---| | Wild flooding | Pasture, undulating land, very cheap water and labour | | Border strip | Close-growing crops (wheat, fodder), medium to heavy soils, slope 0.2-2% | | Check basin | Rice, level land, heavy soils of low infiltration | | Ring basin | Fruit trees and orchards | | Furrow | Row crops (maize, potato, sugarcane, vegetables), slopes up to about 3-5% | Surface methods suit large flat areas (Terai), plentiful water and low-cost labour. They need land levelling; efficiency is 40-60%. #### Sub-surface irrigation - **Natural sub-irrigation:** the water table is kept high by seepage from canals or by controlled drainage, so that moisture reaches the root zone by capillary rise (low-lying fertile land, valley bottoms). - **Artificial sub-irrigation:** water is supplied through open ditches or buried perforated/porous pipes (tile drains) laid below the root zone; the water table is raised to the required level. ```text ground ~~~~~~~~~~~~~~~~~~~~~~~~~~~ root zone ^ ^ ^ capillary rise raised w.t. ------------------------ perforated pipe o==o==o==o==o ``` **Suitability:** permeable soil with an impervious layer below, flat land, a good natural drainage outlet, non-saline water. It saves water (no surface evaporation) and does not hinder farm operations, but it is costly and can cause salinity if drainage is poor. #### Pressurised methods (for comparison) Sprinkler suits sandy or undulating land and scarce water. Drip suits orchards and high-value vegetables on steep or sandy land where water is very scarce. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Which surface method floods small level bunded plots to a required depth and is typical for rice? A. Check basin B. Border strip C. Furrow D. Wild flooding Answer: A. Check basins are small level plots enclosed by bunds, flooded and left to infiltrate, which suits rice on heavy, low-infiltration soil. (Key point: Check basin) 2. Furrow irrigation is best suited to which crops? A. Pasture on undulating land B. Row crops such as maize, potato and sugarcane C. Close-growing wheat and fodder only D. Fruit trees only, in ring basins Answer: B. Furrows run between crop rows and wet the soil by seepage from the sides and bottom, so they suit row crops. (Key point: Furrow suitability) 3. How does natural sub-irrigation supply water to roots? A. Spraying water from nozzles above the crop B. Dripping water from emitters near the root C. Capillary rise from a high water table kept up by canal seepage or controlled drainage D. Flooding the surface and letting it infiltrate Answer: C. In natural sub-irrigation the water table is high and moisture reaches the root zone by capillary action. (Key point: Natural sub-irrigation) 4. Which set of conditions suits artificial sub-surface irrigation? A. Heavy clay soil, steep slopes and saline water B. Sandy soil with no impervious layer and no drainage outlet C. Undulating land with very cheap labour and water D. Permeable soil over an impervious layer, flat land, a good drainage outlet and non-saline water Answer: D. The method needs permeable soil with an impervious layer below, flat land, good drainage and non-saline water, otherwise salinity builds up. (Key point: Conditions for sub-surface irrigation) ## Close variants set in other exams - [Surface methods and furrow irrigation](https://www.bctengineer.com/question.md?key=semester_6%2Firrigation_and_drainage_engineering%3Afurrow-irrigation-methods) — Irrigation and Drainage Engineering, chapter 1, asked 11× ## Related in Irrigation and Drainage Engineering - [Short note: Sub-surface irrigation](https://www.bctengineer.com/question.md?key=semester_6%2Firrigation_and_drainage_engineering%3Asubsurface-irrigation-note) — Irrigation and Drainage Engineering, chapter 1 - [Advantages of surface and sub-surface irrigation](https://www.bctengineer.com/question.md?key=semester_6%2Firrigation_and_drainage_engineering%3Asurface-subsurface-pros-cons) — Irrigation and Drainage Engineering, chapter 1 - [Surface methods; drip and sprinkler suitability](https://www.bctengineer.com/question.md?key=semester_6%2Firrigation_and_drainage_engineering%3Asurface-methods-drip-sprinkler-suitability) — Irrigation and Drainage Engineering, chapter 1 ## Related in other subjects - [Control of sub-surface water and seepage](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Asubsurface-drainage-measures) — Transportation Engineering I, chapter 4, asked 15× - [Direct methods of sub-surface investigation](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Adirect-subsurface-methods) — Engineering Geology II, chapter 4, asked 3× - [Surface versus sub-surface investigation](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Asurface-vs-subsurface-investigation) — Engineering Geology II, chapter 4, asked 3× - [Surface versus sub-surface drainage](https://www.bctengineer.com/question.md?key=semester_6%2Ftransportation_engineering_i%3Asurface-vs-subsurface) — Transportation Engineering I, chapter 4, asked 2×