Irrigation and Drainage Flashcards Preview

IPNI Soil and Water Management > Irrigation and Drainage > Flashcards

Flashcards in Irrigation and Drainage Deck (14):


  • irrigation
  • water flows down path between crop rows
    • made by tillage equipment
  • inexpensive
  • not most efficient irrigation system



  • efficient reducing surface runoff erosion
  • expensive
    • but automated, reducing labor costs
  • if evapotranspiration exceeds maximum application rate, crop damage can occur 


Drip / trickle

  • water applied at low volume in specific areas
  • efficient
  • can be automated


Subsurface Irrigation

  • water applied through buried tubes that contain openings
  • installed in rootzone below tillage depth
  • can be automated, but is expensive
  • Water use very efficient, application rates reduced
  • Dist of water uniform where plant roots are active


Subsurface Drain / tile

  • line of tiles, is placed in soil to lower the depth of qter table to the depth of the tiles
  • SPacing of tiles is dependent on the permeability of the soil
    • more permeable the sol, the wider the spacing


Water Balance Equation to Schedule Irrigation

Initial soil moisture deficit 1 inch, and present soil moisture deficit is 6 inches, Irrigation would be needed in how many days if 2 inchs of rain fell and average ET is .6 inches per day.

  • (irrigation deficit - current deficit) + (rainfall) / ET
  • (6 - 1 + 2) / .6 = 11.7 days


Water Use Efficiency Calculation

  • Water productivity (WP) - the ratio of crop production or yield to the amount of water trasnpired by the crop 
    • if 10,000 lbs / acre of hay is produced, and 12 inches of water / acre are transpired,
      • WP = 10,000 / 12 = 883 lb / inch
  • WUE = the amount of water transpired by the crop to water applied to the crop
    • expressed as a percentage
    • 15 inches/acre applied and 12 inches/ acre transpired
      • 12/15 = 80% WUE


Soil Texture and Tile Drains

  • Tile drains function in saturated soils and are designed to lower water tables near soil surface
    • must be cost effective
  • Tile line spacing increases as the rate of saturated water movement in the soil increases 
    • tile line spacing is larger for sandy soil than clay soil
  • Depth of Tile drain is a function of depth of water table, depth lowered to
    • The depth to which a water table can be lowered increases as the rate of saturated movement in the soil increases 
      • (soils are sandier)


Eutrophication, hypoxia, anoxia

  • refers to the enrichment of a surface water with particular emphasis on increased concentrations of 
    • Phophorus, Nitrogen, organic C
    • Eutropic bodies of water tend to have low levels of dissolved oxygen, algal blooms, and excessive aquatic plant growth
  • hypoxia refers to bodies of water that have low Oxygen levels detrimental to aerobic life
  • Anoxia is the complete lack of oxygen


ppm vs mg/L

  • ppm = mg/L


Nitrate  analysis as nitrate (NO3-)


Nitrate analysis 

  • Nitrate Analysis = mg of NO3 in a liter of water
    • molecular weight of Nitrate 62


  • Nitrate N = mg of nitrogen in the nitrate form in a liter of water
    • molecular weight of Nitrogen 14


Health Risks of Nitrate Nitrogen or coliform bacteria

Nitrates in drinking water

  • methemoglobinemia  (blue baby syndrome)
    • very poor oxygen transport in blood


  • microorganisms found in the intestines of man and other warm blooded animals



  • subsurface trenches that are filled with wood chips
    • water held within the drainage control structure is passed through the bioreactor where nitrate is denitrified and released to the atmosphere as nitrogen gas
      • wood chips serve as energy source for the anaerobic process
    • removes nitrate from water leaving the field


Salinity water quality

  • salinity in drinking / irrigation waters increases potential to damage humans, plants, animals
    • salinity tolerance greater in animals than humans 
    • plants vary in salinity tolerance
  • sodicity 
    • high levels of sodium has same health problems as ingesting too much sodium with food