Water use for irrigation Agriculture is by far the largest water use at global level. Irrigation of agricultural lands accounted for 70% of the water used worldwide. In several developing countries, irrigation represents up to 95% of all water uses, and plays a major role in food production and food security. Future agricultural development strategies of most of these countries depend on the possibility to maintain, improve and expand irrigated agriculture. On the other hand, the increasing pressure on water resources by agriculture faces competition from other water use sectors and represents a threat to the environment. Water is a resource that may create tensions among countries down and upstream. Irrigated agriculture is driving much of the competition since it accounts for 70-90% of water use in may of these regions. | Country | Share of Total Flow with origin outside of border (%) | Turkmenistan
Egypt
Hungary
Mauritania
Bostwana
Bulgaria
Uzbekistan
Netherlands
Gambia
Cambodia
Syria
Sudan
Niger
Iraq
Bangladesh
Thailand
Jordan
Senegal
Israel | 98
97
95
95
94
91
91
89
86
82
79
77
68
66
42
39
36
34
21 |
|  
|
Source: Turkmenistan and Uzbekistan figures from David R. Smith "Climate Change, Water Supply, and Conflict in the Aral Sea Basin", paper presented at the "Pri-Aral Workshop 1994", San Diego State University, March 1994: Others from Peter H. Gleick, Water in Crisis (NY, Oxford University Press, 1993)  Within the European Union (EU) agriculture represents around 30% of total water abstraction. The intensity of irrigation in different countries obviously varies depending on the climate, the crops cultivated and the farming methods. For example, the role of irrigation is completely different in Southern European countries, where irrigation is essential for agricultural production, compared to Central and Western Europe.
In fact the major part of irrigated land in Europe is located in the South with Spain, Italy, France, Greece and Portugal accounting for 85% of the total irrigated area in the EU. For example, in Spain irrigated agriculture accounts for 56% of total agricultural production, occupying only 18% of the total agricultural surface.
Water resources for irrigation  Water used for agriculture comes from natural or other alternative sources.
Natural sources includes rainwater and surface water (lakes and rivers). These resources must be used in a sustainable way.
Rain water resources rely on the atmospheric conditions of the area. Surface water is a limited resource and normally requires the construction of dams and reservoirs with a significant environmental impact.  Alternative sources of irrigation water are the reuse of municipal wastewater and drainage water. However the use of recycled water for irrigation may have some adverse impacts on the public health and the environment. This will depend on the recycled water application, soil characteristics, climate conditions and agronomic practises. Therefore it is important that all these factors are taken into account in the management of recycled water. Lets study this a little bit further. Reuse of water for irrigation
 Water reuse for irrigation is a normal practice worldwide. In Europe, for example there is a large project in Clermont-Ferrand, France since 1997 where more than 10.000m3/day of tertiary treated urban wastewater are reused for irrigation of 700Ha of maize. In Italy more than 4000 Ha of various crops are irrigated with recycled water. Spain also counts with several similar projects.
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 Turbidity | 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 | | BOD5 COD | 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 <0.01mgCd/L <0.02-0.1mgNi/L | | Inorganic | High salinity and boron are harmful for irrigation of some sensitive crops | | <450-4000mgTDS/L <1mgB/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. | 
