EFFICIENCIES OF IRRIGATION

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EFFICIENCIES OF IRRIGATION

  • There, it had been stated that existing water resources
  • The country are adequate to irrigate only 50 percent of the cultivable area.
  • This aspect makes it imperative for Indian Engineers to devise ways and means, to conserve water and make its judicious and economical use in irrigation.
  • Studies conducted on canal irrigation projects located in northern India reveal that 15 – 20% of the water supplied
  • from diversion headworks is lost in main and branch canals only 6–8% losses occur in major and minor distributaries.
  • Out of remaining about 50% water supplied to fields,
  • About 22% is further lost due to surface evaporation, deep percolation, and irregular distribution.
  • The effective percentage of water that is utilized by the crops
  • The form of evapotranspiration or consumptive use, is only 28–29% of the total water released in the main canal from diversion headworks.
  • From this study, it is clear that only 28–29% of the water supplied
  • The diversion headworks is used by the crops, and the remaining 71 to 72% water is lost in one way or the other.
  • Due to permeability of soils, topography, and climatic conditions,
  • it is impossible to achieve 100% utilization of water for the growth of crops.
  • But there is ample scope to improve the efficiency of irrigation.
  • With correct management, and by adopting such measures that would cause least losses, reasonably highefficiency can definitely be achieved.
  • Some important terms applicable to the efficiency of irrigation water are given as follows.
  • 1. Project Efficiency

\[_{Ei = \frac{^{We}}{_{Wr}}}\]

where

  • Ei =  Project efficiency
  •  = Amount of irrigation water used in form of evapo-transpiration by the crop
  • _{Wr}= Amount of irrigation water supplied at the diversion point.

 

  • Conveyance losses occur right from the diversion headworks of the main canal to the entry points to the fields.
  • These losses are caused by evaporation and seepage.
  • If somehow these losses are reduced to minimum project efficiency can be considerably increased.
  • These losses can be minimised by the lining of canals and water courses, by designing deep
  • Narrow canals and adopting so many other measures.

2. Conveyance Efficiency.

  • This term indicates the ratio of irrigation water that is available at the outlets, to irrigation water supplied
  • from the diversion point into the main canal.
  • If can be expressed mathematically as follows

3. Application Efficiency.

  • It is the ratio of irrigation water used by the crops as consumptive use, to irrigation water supplied
  • The outlet points of the fields.
  • It can be written as follows:
  • In our country water application efficiency is very low and it requires
  • some serious thinking on the part of Engineers to improve it, by devising suitable measures.

 

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