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Surface and sub-surface irrigation methods

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.

Describe the different methods of surface and sub-surface irrigation and their suitability.

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

MethodSuitable for
Wild floodingPasture, undulating land, very cheap water and labour
Border stripClose-growing crops (wheat, fodder), medium to heavy soils, slope 0.2-2%
Check basinRice, level land, heavy soils of low infiltration
Ring basinFruit trees and orchards
FurrowRow 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.
 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.

✓ Answer checked by Claude Opus 5.5 (high effort)

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