Environmental effects of irrigation
The environmental effects of irrigation relate to the changes in quantity and quality of
Amongst some of these problems is depletion of underground
Direct effects
An
Indirect Effects
Indirect effects are those that have consequences that take longer to develop and may also be longer-lasting. The indirect effects of irrigation include the following:
- Waterlogging
- Soil salination
- Ecological damage
- Socioeconomicimpacts
The indirect effects of
Some
Irrigated land area worldwide occupies about 16% of the total agricultural area and the crop yield of irrigated land is roughly 40% of the total yield.[5] In other words, irrigated land produces 2.5 times more product than non-irrigated land.
Adverse impacts
Reduced river flow
The reduced downstream river flow may cause:
- reduced downstream flooding
- disappearance of ecologically and economically important wetlands or flood forests[6]
- reduced availability of industrial, municipal, household, and drinking water
- reduced shipping routes. Water withdrawal poses a serious threat to the Ganges. In India, barrages control all of the tributaries to the Ganges and divert roughly 60 percent of river flow to irrigation[6]
- reduced fishing opportunities. The Indus River in Pakistan faces scarcity due to the over-extraction of water for agriculture. The Indus is inhabited by 25 amphibian species and 147 fish species of which 22 are found nowhere else in the world. It harbors the endangered Indus river dolphin, one of the world's rarest mammals. Fish populations, the main source of protein and overall life support systems for many communities, are also being threatened[6]
- reduced discharge into the sea, which may have various consequences like has suffered an "environmental catastrophe" due to the interception of river water for irrigation purposes.
Increased groundwater recharge, waterlogging, soil salinity
Increased groundwater recharge stems from the unavoidable
- rising water tables
- increased storage of groundwater that may be used for irrigation, municipal, household, and drinking water by pumping from wells
- waterlogging and drainage problems in villages, agricultural lands, and along roads - with mostly negative consequences. The increased level of the water table can lead to reduced agricultural production.
- shallow water tables - a sign that the aquifer is unable to cope with the groundwater recharge stemming from the deep percolation losses
- where water tables are shallow, the irrigation applications are reduced. As a result, the soil is no longer leached and soil salinity problems develop
- stagnant water tables at the soil surface are known to increase the incidence of water-borne diseases like dengue, and schistosomiasis (Bilharzia) in many areas.[9] Health costs, appraisals of health impacts and mitigation measures are rarely part of irrigation projects, if at all.[10]
- to mitigate the adverse effects of shallow water tables and soil salinization, some form of watertable control, soil salinity control, drainage and drainage system is needed
- as drainage water moves through the soil profile it may dissolve nutrients (either fertilizer-based or naturally occurring) such as nitrates, leading to a buildup of those nutrients in the ground-water aquifer. High nitrate levels in drinking water can be harmful to humans, particularly infants under 6 months, where it is linked to "blue-baby syndrome" (see Methemoglobinemia).
Reduced downstream river water quality
Owing to drainage of surface and groundwater in the project area, which waters may be salinized and polluted by
Polluted river water entering the sea may adversely affect the ecology along the seashore (see
The natural contribution of sediments can be eliminated by the detention of sediments behind the dams critical to surface water irrigation diversions. Sedimentation is an essential part of the ecosystem that requires the natural flux of the river flow. This natural cycle of sediment dispersion replenishes the nutrients in the soil, which will, in turn, determine the livelihood of the plants and animals that rely on the sediments carried downstream. The benefits of heavy deposits of sedimentation can be seen in large rivers like the Nile River. The sediment from the delta has built up to form a giant aquifer during flood season and retains water in the wetlands. The wetlands that are created and sustained due to built-up sediment at the basin of the river are a habitat for numerous species of birds.[11] However, heavy sedimentation can reduce downstream river water quality and can exacerbate floods upstream. This has been known to happen in the Sanmenxia reservoir in China. The Sanmenxia reservoir is part of a larger man-made project of hydroelectric dams called the Three Gorge Project [12] In 1998, uncertain calculations and heavy sediment greatly affected the reservoir’s ability to properly fulfill its flood-control function [13] This also reduces the downstream river water quality. Shifting more towards mass irrigation installments in order to meet more socioeconomic demands is going against the natural balance of nature, and use water pragmatically- use it where it is found[14]
Affected downstream water users
Downstream water users often have no legal water rights and may fall victim to the development of irrigation.
Flood-recession cropping may be seriously affected by the upstream interception of river water for irrigation purposes.
- In
- After the closure of the Kainji dam, Nigeria, 50 to 70 per cent of the downstream area of flood-recession cropping was lost[16]
Lost land use opportunities
Irrigation projects may reduce the fishing opportunities of the original population and the grazing opportunities for cattle. The
The
Groundwater mining with wells, land subsidence
When more groundwater is pumped from wells than replenished, storage of water in the
Some notable examples include:
- The hundreds of tubewells installed in the state of Uttar Pradesh, India, with World Bank funding have operating periods of 1.4 to 4.7 hours/day, whereas they were designed to operate 16 hours/day[20]
- In karez users[15]
- groundwater-related subsidence[21] of the land due to mining of groundwater occurred in the United States at a rate of 1m for every 13m that the water table was lowered[22]
- Homes at Greens Bayou near Houston, Texas, where 5 to 7 feet of subsidence has occurred, was flooded during a storm in June 1989 as shown in the picture[23]
Simulation and prediction
The effects of irrigation on the water table, soil salinity and salinity of drainage and groundwater, and the effects of mitigative measures can be simulated and predicted using agro-hydro-salinity models like SaltMod and SahysMod[24]
Case studies
- In India 2.19 million ha of land has been reported to suffer from waterlogging in irrigation canal commands. Also, 3.47 million ha were reported to be seriously salt-affected,[25][26]
- In the Punjab.[27] More than 3 million ha of water-logged lands have been provided with tube-wells and drains at the cost of billions of rupees, but the reclamation objectives were only partially achieved.[28] The Asian Development Bank (ADB) states that 38% of the irrigated area is now waterlogged and 14% of the surface is too saline for use[29]
- In the Assuan[30]
- In Mexico, 15% of the 3 million ha of irrigable land is salinized and 10% is waterlogged[31]
- In Peru some 0.3 million ha of the 1.05 million ha of irrigable land suffers from degradation (see Irrigation in Peru).
- Estimates indicate that roughly one-third of the irrigated land in the major irrigation countries is already badly affected by salinity or is expected to become so in the near future. Present estimates for Israel are 13% of the irrigated land, Australia 20%, China 15%, Iraq 50%, Egypt 30%. Irrigation-induced salinity occurs in large and small irrigation systems alike[32]
- FAO has estimated that by 1990 about 52 million ha of irrigated land will need to have improved drainage systems installed, much of it subsurface drainage to control salinity[33]
Reduced downstream drainage and groundwater quality
- The downstream drainage water quality may deteriorate owing to by drainage water.
- The downstream quality of the groundwater may deteriorate in a similar way as the downstream drainage water and have similar consequences
Mitigation of adverse effects
Irrigation can have a variety of negative impacts on
Delayed environmental impacts
It often takes time to accurately predict the impact that new irrigation schemes will have on the
Case study in Malawi
Frequently
Due to this careful planning, this project was successful both in improving the socioeconomic conditions in the region and ensuring that land and water are sustainable into the future.
See also
- Environmental issues with agriculture
- Environmental impacts of reservoirs
- Alkali soils
- Irrigation in viticulture
- Routing (hydrology)
- Indian Council of Forestry Research and Education
Further reading
- T.C. Dougherty and A.W. Hall, 1995. Environmental impact assessment of irrigation and drainage projects. FAO Irrigation and Drainage Paper 53. ISBN 92-5-103731-0. On line: http://www.fao.org/docrep/v8350e/v8350e00.htm
- R.E. Tillman, 1981. Environmental guidelines for irrigation. New York Botanical Garden Cary Arboretum.
- A comparative survey of dam-induced resettlement in 50 cases by Thayer Scudder and John Gray
External links
- Download of simulation and prediction model SaltMod from: [9]
- Download of simulation and prediction model SahysMod from: [10]
- "SaltMod: A tool for the interweaving of irrigation and drainage for salinity control": [11]
- "Modern interferences with traditional irrigation in Baluchistan": [12]
References
- hdl:1993/33953.
- ^ M. H. Lo and J. S. Famiglietti, Irrigation in California's Central Valley strengthens the southwestern U.S. water cycle, Geophysical Research Letters, Volume 40, Issue 2, pages 301–306, 28 January 20132 [1]
- ^ O. A. Tuinenburg et al., The fate of evaporated water from the Ganges basin, Journal of Geophysical Research: Atmospheres, Volume 117, Issue D1, 16 January 2012 [2]
- ^ P. W. Keys et al., Analyzing precipitation sheds to understand the vulnerability of rainfall dependent regions, Biogeosciences, 9, 733–746, 2012 PDF
- ^ Bruce Sundquist, 2007. Chapter 1- Irrigation overview. In: The earth's carrying capacity, Some related reviews, and analysis. On line: "Chapter 1 -- Irrigation Overview". Archived from the original on 2012-02-17. Retrieved 2012-02-17.
- ^ a b c d World Wildlife Fund, WWF Names World's Top 10 Rivers at Greatest Risk, online: http://www.ens-newswire.com/ens/mar2007/2007-03-21-01.asp
- ^ Timberlake, L. 1985. Africa in Crisis - The Causes, Cures of Environmental Bankruptcy. Earthscan Paperback, IIED, London
- of chart itself)
- ^ World health organization (WHO), 1983. Environmental health impact assessment of irrigated Agriculture. Geneva, Switzerland.
- ^ Himanshu Thakkar. Assessment of Irrigation in India. World Commission on Dams. On line: http://www.dams.org/docs/kbase/contrib/opt161.pdf Archived 2009-08-24 at the Wayback Machine
- ^ <r/r Ellen Wohl, “The Nile: Lifeline in the Desert”, A World of Rivers p. 98f>
- ^ </Allen Wohl, “The Chang Jiang: Bridling a Dragon”, A World of Rivers p 275, p.283. By calculating the amount of sediment that will be carried downstream to the Sanmenxia reservoir is difficult to estimate.
- ^ <Ellen Wohl, “The Chang Jiang: Bridling a Dragon”, A World of Rivers p284
- ^ </Donald Worster, “ Thinking Like a River,” in The Wealth of Nature: Environmental History and the Ecological Imagination (New York: Oxford University Press, (1993), p133ef>
- ^ a b Modern interferences in traditional water resources in Baluchistan. In: Annual Report 1982, pp. 23-34. ILRI, Wageningen, The Netherlands. Reprinted in Water International 9 (1984), pp. 106- 111. Elsevier Sequoia, Amsterdam. Also reprinted in Water Research Journal (1983) 139, pp. 53-60. Download from : [3], under nr. 10, or directly as PDF : [4]
- ^ C.A. Drijver and M. Marchand, 1985. Taming the floods. Environmental aspects of the floodplain developments of Africa. Centre of Environmental Studies, University of Leiden, The Netherlands.
- ^ Ecosystems Ltd., 1983. Tana delta ecological impact study. Nairobi, Kenya.
- ^ A. deGeorges and B.K. Reilly, 2006. Dams and large scale irrigation on the Senegal river: impacts on man and the environment. UNDP Human Development Report. On line: http://hdr.undp.org/en/reports/global/hdr2006/papers/DeGeorges%20Andre.pdf
- Erklärung von Bern/internationalrivers: [5]
- ^ Center for development studies (CDS), 1988. A study of water distribution and management in new design public tubewells in eastern Uttar Pradesh. Lucknow, UP, India
- ^ Anthropogenic subsidence
- ^ D.K. Todd, 1980. Groundwater hydrology. 2nd edition. John Wiley and Sons, New York
- ^ US Geological Survey, Land Subsidence in the United States. on line: http://water.usgs.gov/ogw/pubs/fs00165/
- ^ SaltMod: A tool for the interweaving of irrigation and drainage for salinity control. In: W.B. Snellen (ed.), Towards integration of irrigation, and drainage management. ILRI Special report, pp. 41-43. Free download from : [6], under nr. 8: Salted application, or directly as PDF : [7]
- ^ N.K. Tyagi, 1996. Salinity management: the CSSRI experience and future research agenda. In: W.B. Snellen (Ed.), Towards integration of irrigation and drainage management. ILRI, Wageningen, The Netherlands, 1997, pp. 17-27.
- ISBN 978-0-934223-78-2, 404 p.
- ^ a b Green Living Association Pakistan, Environmental Issues.
- ^ A.K. Bhatti, 1987. A review of planning strategies of salinity control and reclamation projects in Pakistan. In: J. Vos (Ed.) Proceedings, Symposium 25th International Course on Land Drainage. ILRI publ. 42. International Institute for Land Reclamation and Improvement, Wageningen, The Netherlands
- ^ Asian Development Bank (ADB), Water in the 21st Century: Imperatives for Wise Water Management, From Public Good to Priced Commodity.
- ^ M.S. Abdel-Dayem, 1987. Development of land drainage in Egypt. In: J. Vos (Ed.) Proceedings, Symposium 25th International Course on Land Drainage. ILRI publ. 42. International Institute for Land Reclamation and Improvement, Wageningen, The Netherlands.
- ^ L. Pulido Madrigal, 1994. (in Spanish) Anexo Tecnico: Estudio general de salinidad analizada. CNA-IMTA, Cuernavaca, Mexico. The data can be seen online in the article: "Land drainage and soil salinity: some Mexican experiences". In: Annual Report 1995, International Institute for Land Reclamation and Improvement (ILRI), Wageningen, The Netherlands, pp. 44-52, [8]
- ^ Claudio O. Stockle. Environmental impact of irrigation: a review. State of Washington Water Research Center, Washington State University. On line: "Archived copy" (PDF). Archived from the original (PDF) on 2007-08-13. Retrieved 2008-04-04.
{{cite web}}
: CS1 maint: archived copy as title (link) - ^ United Nations, 1977. Water for Agriculture. In: Water Development and Management, Proceedings of the United Nations Water Conference, Part 3. Mar del Plata, Argentina.
- ^ a b c d e f "Irrigation potential in Africa: A basin approach". Natural Resources Management and Environment Department. Retrieved 13 March 2014.
- ^ Dougherty, T.C. "FAO Irrigation and Drainage Paper 53" (PDF). Environmental Impact Assessment of Irrigation and Drainage Projects. Food and Agriculture Organization of the United Nations. Archived from the original (PDF) on 2017-05-18. Retrieved 13 March 2014.
- ^ "Smallholder Irrigation and Value Addition Project (SIVAP)" (PDF). Retrieved 13 March 2014.