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Irrigation water quality

The water quality used for irrigation is essential for the yield and quantity of crops, maintenance of soil productivity, and protection of the environment. For example, the physical and mechanical properties of the soil, ex. soil structure (stability of aggregates) and permeability, are very sensitive to the type of exchangeable ions present in irrigation waters.

Irrigation water quality can best be determined by chemical laboratory analysis. The most important factors to determine the suitability of water use in agriculture are the following:

- PH

- Salinity Hazard

- Sodium Hazard (Sodium Adsorption Ration or SAR)

- Carbonate and bicarbonates in relation with the Ca & Mg content

- Other trace elements

- Toxic anions

- Nutrients

- Free chlorine

Parameters of reuse water with agronomic significance

Parameter Significance for irrigation with recycled water Range in secondary and tertiary effluents Treatment goal in recycled water
Total Suspended Solids


Measures of particles can be related to microbial pollution; it can interfere with disinfection; clogging of irrigation systems; deposition 5-50 mg/L <5-35TSS/L
1-30 NTU <0.2-35NTU


Organic substrate for microbial growth; can bring bacterial re-growth in distribution systems and microbial fouling. 10-30mg/L <5-45mgBOD/L
50-150mg/L <20-200mgCOD/L
Total coliforms Measure of risk of infection due to potential presence of pathogens; can bring bio-fouling of sprinklers and nozzles in irrigation systems <10-107cfu/100mL <1-200cfu/10mL
Heavy metals Some dissolved minerals salts are identified as nutrients and are beneficial for the plant growth, while others may be phytotoxic or may become so at high concentrations. Specific elements (Cd, Ni, Hg, Zn, etc) are toxic to plants, and maximum concentration limits exist for irrigation < 0.001mgHg/L



Inorganic High salinity and boron are harmful for irrigation of some sensitive crops <450-4000mgTDS/L


Chlorine residual Recommended to prevent bacterial re-growth; excessive amount of free Chlorine (>0.05mg/L) can damage some sensitive crops 0.5->5mgCl/L
Nitrogen Fertilizer for irrigation; can contribute to algal growth and eutrophication in storage reservoirs, corrosion (N-NH4), or scale formation (P) 10-30mgN/L <10-15mgN/L
Phosphorus 0.1-30mgP/L <0.1-2mgP/L

Source of information: Valentina Lazarova Akiçca Bahri; Water Reuse for irrigation: agriculture, landscapes, and turf grass; CRC Press.

Menu of Options for Improving Irrigation Water productivity

Category Option or Measure
Technical - Land leveling to apply water more uniformly

- Surge irrigation to improve water distribution

- Efficient sprinklers to apply water more uniformly

- Low energy precision application sprinklers to cut evaporation and wind drift losses

- Furrow diking to promote soil infiltration and reduce runoff

- Drip irrigation to cut evaporation and other water losses and to increase crop yields (see table below)

Managerial - Better irrigation scheduling

- Improving canal operation for timely deliveries

- Applying water when most crucial to a crop's yield

- Water-conserving tillage and field preparation methods

- Better maintenance of canals and equipment

- Recycling drainage and tail water

Institutional - Establishing water user organizations for better involvement of farmers and collection of fees

- Reducing irrigation subsidies and /or introducing conservation -oriented pricing

- Establishing legal framework for efficient and equitable water markets

- Fostering rural infrastructure for private-sector dissemination of efficient technologies

- Better training and extension efforts

Agronomic - Selecting crop varieties with high yields per Liter of transpired water

- Intercropping to maximize use of soil moisture

- Better matching crops to climate conditions and the quality of water available

- Sequencing crops to maximize output under conditions of soil and water salinity

- Selecting drought-tolerant crops where water is scarce or unreliable

- Breeding water-efficient crop varieties


Sources: Amy L. Vickers, Handbook of Water Use and Conservation (Boca Raton, FL: Lewis Publishers, in press); J.S. Wallace and C.H. Batchelor, "Managing Water Resources for Crop Production", "Philosophical Transactions of the Royal Society of London: Biological Science, vol. 352, pp.937-47 (1997)

Related pages:

Bicarbonate hazard of irrigation water

Irrigation water lab analysis

Nutrients in irrigation water

Salinity hazard irrigation

SAR hazard of irrigation water

Toxic ions hazard of irrigation water

For more information check the following pages: groundwater contamination, source of groundwater pollution, contaminants (seawater intrusions, nitrates, arsenic, iron), reducing groundwater contamination.

Click here for definitions concerning groundwater, or to learn more about its properties, its origin and quantities, its sources in Europe.

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