International Commission on Irrigation & Drainage Commission Interationale des Irrigation et du Drainage



Quality of Irrigation Water

The chemical, the physical and the biological quality of the water for irrigation impacts the agricultural productivity, the productivity of the soil, the safety of the produce and the health of farm labour as well as consumers. Chemical, characteristics such as salinity/toxicity pose hazards for the soil, the plants and the irrigation system such as it is pipe corrosion and emitter chemical clogging. The physical characteristic such as turbidity impacts emitters’ blockages problems from suspended solid particles and other impurities content. The biological characteristics, such as bacteria and pathogens can have harmful effect for human and animal health as well as for the soil the plants and the irrigation systems.

 

Many different elements are dissolved in the water. Some of these elements are beneficial, while other elements provide no beneficial function to plants and may interfere with beneficial elements. Sometimes, a beneficial element can become toxic at high concentrations.

 

All water sources used in irrigation contain impurities and dissolved salts irrespective of whether they are surface or underground water. In agriculture, water quality is related to its effects on soils, crops and management necessary to compensate problems linked to water quality. Many of the problems of soil degradation like salinity, soil permeability, toxicity etc. can be related to irrigation water quality. The quality of the water can affect both the growth of plants and the functioning of the irrigation system.Salts in soil and/or water can reduce water availability to the crop to such an extent that yield can be affected. Many a times some naturally occurring elements in water, such as Arsenic present health and agricultural challenges. Arsenic can contaminate groundwater both naturally and artificially.

 

Water scarcity and increasing demand of high quality water for drinking purposes in the urban areas requires that the low quality water, including naturally occurring brackish water or agricultural drainage effluent, and treated domestic waste water are used for agricultural purposes.

 

Managing irrigation water high in salinity requires constant attention. To evaluate a salt hazard, a water sample should be analysed for three major factors: Total dissolved salts (TDS), Sodium hazard (SAR) or Toxic ions.There may be a need to analyze levels of trace elements as well, particularly if ground water or sewage effluent is used for irrigation purposes.

 

Electrical conductivity or Total Dissolved Solids tests are two means of measuring salinity. The properties of the soil, the ground water and the landscape interact with the salinity of the irrigation water to either increase or decrease the salinity hazard. Crop yield may be substantially reduced when saline irrigation water is used. Some crops are more sensitive to salinity than others.

 

Practices which aid inremedying salinity problems are:

  • Soil Drainage
  • Leaching
  • Frequency of irrigation
  • Soil and water amelioration
  • Plant selection

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