Environmental impact of irrigation
Encyclopedia
Environmental impacts of irrigation are the changes in quantity and quality of soil
and water
as a result of irrigation
and the ensuing effects on natural and social conditions at the tail-end and downstream of the irrigation scheme.
The impacts stem from the changed hydrological conditions
owing to the installation and operation of the scheme.
An irrigation scheme often draws water from the river and distributes it over the irrigated area. As a hydrological result it is found that:
These may be called direct effects.
The effects thereof on soil and water quality
are indirect and complex, waterlogging
and soil salination
are part of these, whereas the subsequent impacts on natural, ecological
and socio-enonomic conditions is very intricate.
Irrigation can also be done extracting groundwater by (tube)wells
. As a hydrological result it is found that the level of the water descends. The effects may be water mining, land/soil subsidence
, and, along the coast, saltwater intrusion
.
Irrigation projects can have large benefits, but the negative side effects are often overlooked
, or by precision land levelling for surface irrigation
, in practice the losses are commonly in the order of 40 to 60%. This may cause:
Case studies:
s, the quality of the river water below the project area can deteriorate, which makes it less fit for industrial, municipal and household use. It may lead to reduced public health.
Polluted river water entering the sea may adversely affect the ecology along the sea shore (see Aswan dam
).
Downstream water users often have no legal water rights and may fall victim of the development of irrigation.
Pastoralists and nomadic tribes may find their land and water resources blocked by new irrigation developments without having a legal recourse.
Flood-recession cropping may be seriously affected by the upstream interception of river water for irrigation purposes.
pressure on the remaining lands may increase considerably, because the ousted traditional pastoralist
tribes will have to find their subsistence
and existence elsewhere, overgrazing
may increase, followed by serious soil erosion and the loss of natural resources
.
The Manatali reservoir
formed by the Manantali dam
in Mali
intersects the migration routes of nomadic pastoralists and destroyed 43000 ha of savannah
, probably leading to overgrazing and erosion elsewhere. Further, the reservoir destroyed 120 km² of forest
. The depletion of groundwater aquifers, which is caused by the suppression of the seasonal flood cycle, is damaging the forests downstream of the dam.
is being mined. Irrigation from groundwater is no longer sustainable then. The result can be abandoning of irrigated agriculture.
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
In Baluchistan
, Pakistan
, the development of tubewell irrigation projects was at the expense of the traditional qanat
or karez
users
Groundwater-related subsidence
of the land due to mining of groundwater occurred in the USA at a rate of 1m for each 13m that the watertable was lowered
Homes at Greens Bayou near Houston, Texas
, where 5 to 7 feet of subsidence has occurred, were flooded during a storm in June 1989 as shown in the picture
can be simulated and predicted using agro-hydro-salinity models like SaltMod
and SahysMod
Soil
Soil is a natural body consisting of layers of mineral constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical characteristics...
and water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
as a result of irrigation
Irrigation
Irrigation may be defined as the science of artificial application of water to the land or soil. It is used to assist in the growing of agricultural crops, maintenance of landscapes, and revegetation of disturbed soils in dry areas and during periods of inadequate rainfall...
and the ensuing effects on natural and social conditions at the tail-end and downstream of the irrigation scheme.
The impacts stem from the changed hydrological conditions
Hydrology
Hydrology is the study of the movement, distribution, and quality of water on Earth and other planets, including the hydrologic cycle, water resources and environmental watershed sustainability...
owing to the installation and operation of the scheme.
An irrigation scheme often draws water from the river and distributes it over the irrigated area. As a hydrological result it is found that:
- the downstream riverRiverA river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...
dischargeDischargeDischarge in the context to expel or to "let go" may refer to:* A military discharge, issued when a member of the armed forces is released from service* Termination of employment, the end of an employee's duration with an employer...
is reduced - the evaporationEvaporationEvaporation is a type of vaporization of a liquid that occurs only on the surface of a liquid. The other type of vaporization is boiling, which, instead, occurs on the entire mass of the liquid....
in the scheme is increased - the groundwaterGroundwaterGroundwater is water located beneath the ground surface in soil pore spaces and in the fractures of rock formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock...
rechargeRechargeGroundwater recharge or deep drainage or deep percolation is a hydrologic process where water moves downward from surface water to groundwater. This process usually occurs in the vadose zone below plant roots and is often expressed as a flux to the water table surface...
in the scheme is increased - the level of the water table rises
- the drainageDrainageDrainage is the natural or artificial removal of surface and sub-surface water from an area. Many agricultural soils need drainage to improve production or to manage water supplies.-Early history:...
flow is increased
These may be called direct effects.
The effects thereof on soil and water quality
Water quality
Water quality is the physical, chemical and biological characteristics of water. It is a measure of the condition of water relative to the requirements of one or more biotic species and or to any human need or purpose. It is most frequently used by reference to a set of standards against which...
are indirect and complex, waterlogging
Waterlogging
Waterlogging or water logging may refer to:* Waterlogging , saturation of the soil by groundwater sufficient to prevent or hinder agriculture...
and soil salination
Soil salination
Soil salinity is the salt content in the soil.- Causes of soil salinity :Salt-affected soils are caused by excess accumulation of salts, typically most pronounced at the soil surface. Salts can be transported to the soil surface by capillary transport from a salt laden water table and then...
are part of these, whereas the subsequent impacts on natural, ecological
Ecology
Ecology is the scientific study of the relations that living organisms have with respect to each other and their natural environment. Variables of interest to ecologists include the composition, distribution, amount , number, and changing states of organisms within and among ecosystems...
and socio-enonomic conditions is very intricate.
Irrigation can also be done extracting groundwater by (tube)wells
Water well
A water well is an excavation or structure created in the ground by digging, driving, boring or drilling to access groundwater in underground aquifers. The well water is drawn by an electric submersible pump, a trash pump, a vertical turbine pump, a handpump or a mechanical pump...
. As a hydrological result it is found that the level of the water descends. The effects may be water mining, land/soil subsidence
Groundwater-related subsidence
Groundwater-related subsidence is the subsidence of land resulting from groundwater extraction, and a major problem in the developing world as major metropolises swell without adequate regulation and enforcement, as well as a being a common problem in the developed world...
, and, along the coast, saltwater intrusion
Saltwater intrusion
Saltwater intrusion is the movement of saline water into freshwater aquifers. Most often, it is caused by ground-water pumping from coastal wells, or from construction of navigation channels or oil field canals. The channels and canals provide conduits for salt water to be brought into fresh...
.
Irrigation projects can have large benefits, but the negative side effects are often overlooked
Reduced downstream river discharge
The reduced downstream river discharge may cause:- reduced downstream flooding
- disappearance of ecologically and economically important wetlands or flood forests
- reduced availability of industrial, municipal, household, and drinking water
- reduced shipping routes. Water withdrawal poses a serious threat to the Ganges. In IndiaIndiaIndia , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
, barrages control all of the tributaries to the Ganges and divert roughly 60 percent of river flow to irrigation - reduced fishing opportunities. The Indus River in PakistanPakistanPakistan , officially the Islamic Republic of Pakistan is a sovereign state in South Asia. It has a coastline along the Arabian Sea and the Gulf of Oman in the south and is bordered by Afghanistan and Iran in the west, India in the east and China in the far northeast. In the north, Tajikistan...
faces scarcity due to 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 dolphinIndus River dolphinThe Indus River dolphin is a sub-species of freshwater or river dolphin found in the Indus River of Pakistan...
, 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 - reduced discharge into the sea, which may have various consequences like coastal erosion (e.g. in GhanaGhanaGhana , officially the Republic of Ghana, is a country located in West Africa. It is bordered by Côte d'Ivoire to the west, Burkina Faso to the north, Togo to the east, and the Gulf of Guinea to the south...
) and salt water intrusion in delta's and estuaries (e.g. in EgyptEgyptEgypt , officially the Arab Republic of Egypt, Arabic: , is a country mainly in North Africa, with the Sinai Peninsula forming a land bridge in Southwest Asia. Egypt is thus a transcontinental country, and a major power in Africa, the Mediterranean Basin, the Middle East and the Muslim world...
, see Aswan damAswan DamThe Aswan Dam is an embankment dam situated across the Nile River in Aswan, Egypt. Since the 1950s, the name commonly refers to the High Dam, which is larger and newer than the Aswan Low Dam, which was first completed in 1902...
). Current water withdrawal from the river NileNileThe Nile is a major north-flowing river in North Africa, generally regarded as the longest river in the world. It is long. It runs through the ten countries of Sudan, South Sudan, Burundi, Rwanda, Democratic Republic of the Congo, Tanzania, Kenya, Ethiopia, Uganda and Egypt.The Nile has two major...
for irrigation is so high that, despite its size, in dry periods the river does not reach the sea. The Aral seaAral SeaThe Aral Sea was a lake that lay between Kazakhstan in the north and Karakalpakstan, an autonomous region of Uzbekistan, in the south...
has suffered an "environmental catastrophe" due to the interception of river water for irrigation purposes.
Increased groundwater recharge, waterlogging, soil salinity
The increased groundwater recharge stems from the unavoidable deep percolation losses occurring in the irrigation scheme. The lower the irrigation efficiency, the higher the losses. Although fairly high irrigation efficiencies of 70% or more (i.e. losses of 30% or less) can be obtained with sophisticated techniques like sprinkler irrigation and drip irrigationDrip irrigation
Drip irrigation, also known as trickle irrigation or microirrigation or localized irrigation , is an irrigation method which saves water and fertilizer by allowing water to drip slowly to the roots of plants, either onto the soil surface or directly onto the root zone, through a network of valves,...
, or by precision land levelling for surface irrigation
Surface irrigation
Surface irrigation is defined as the group of application techniques where water is applied and distributed over the soil surface by gravity. It is by far the most common form of irrigation throughout the world and has been practiced in many areas virtually unchanged for thousands of years.Surface...
, in practice the losses are commonly in the order of 40 to 60%. This may cause:
- rising water tables,
- increased storage of groundwater that may be used for irrigation, municipal, household and drinking water by pumping from wellWater wellA water well is an excavation or structure created in the ground by digging, driving, boring or drilling to access groundwater in underground aquifers. The well water is drawn by an electric submersible pump, a trash pump, a vertical turbine pump, a handpump or a mechanical pump...
s, - waterloggingWaterloggingWaterlogging or water logging may refer to:* Waterlogging , saturation of the soil by groundwater sufficient to prevent or hinder agriculture...
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 are 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 malariaMalariaMalaria is a mosquito-borne infectious disease of humans and other animals caused by eukaryotic protists of the genus Plasmodium. The disease results from the multiplication of Plasmodium parasites within red blood cells, causing symptoms that typically include fever and headache, in severe cases...
, filariasisFilariasisFilariasis is a parasitic disease and is considered an infectious tropical disease, that is caused by thread-like nematodes belonging to the superfamily Filarioidea, also known as "filariae"....
, yellow feverYellow feverYellow fever is an acute viral hemorrhagic disease. The virus is a 40 to 50 nm enveloped RNA virus with positive sense of the Flaviviridae family....
, dengue, and schistosomiasisSchistosomiasisSchistosomiasis is a parasitic disease caused by several species of trematodes , a parasitic worm of the genus Schistosoma. Snails often act as an intermediary agent for the infectious diseases until a new human host is found...
(Bilharzia) in many areas. Health costs, appraisals of health impacts and mitigation measures are rarely part of irrigation projects, if at all. - to mitigate the adverse effects of shallow water tables and soil salinization, some form of watertable controlWatertable controlWatertable control is the practice of controlling the water table in agricultural land by subsurface drainage with proper criteria to improve the crop production.- Description and definitions :...
, soil salinity control, drainageDrainageDrainage is the natural or artificial removal of surface and sub-surface water from an area. Many agricultural soils need drainage to improve production or to manage water supplies.-Early history:...
and drainage systemDrainage system (Agriculture)An agricultural drainage system is a system by which the water level on or in the soil is controlled to enhance agricultural crop production.-Classification:Figure 1 classifies the various types of drainage systems...
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 built up of those nutrients in the ground water aquifer. High nitrate levels in drinking water can be harmful to humans particularly for infants under 6 months where it is linked to 'blue-baby syndrome' (see MethemoglobinemiaMethemoglobinemiaMethemoglobinemia is a disorder characterized by the presence of a higher than normal level of methemoglobin in the blood. Methemoglobin is an oxidized form of hemoglobin that has an increased affinity for oxygen, resulting in a reduced ability to release oxygen to tissues. The oxygen–hemoglobin...
).
Case studies:
- In IndiaIndiaIndia , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
2.189.400 have been reported to suffer from waterlogging in irrigation canal commands. Also 3.469.100 ha were reported to be seriously salt affected here, - In the Indus Plains in PakistanPakistanPakistan , officially the Islamic Republic of Pakistan is a sovereign state in South Asia. It has a coastline along the Arabian Sea and the Gulf of Oman in the south and is bordered by Afghanistan and Iran in the west, India in the east and China in the far northeast. In the north, Tajikistan...
, more than 2 million hectares of land is waterlogged. The soil of 13.6 million hectares within the Gross Command Area was surveyed, which revealed that 3.1 million hectares (23%) was saline. 23% of this was in SindhSindhSindh historically referred to as Ba'ab-ul-Islam , is one of the four provinces of Pakistan and historically is home to the Sindhi people. It is also locally known as the "Mehran". Though Muslims form the largest religious group in Sindh, a good number of Christians, Zoroastrians and Hindus can...
and 13% in the PunjabPunjab (Pakistan)Punjab is the most populous province of Pakistan, with approximately 45% of the country's total population. Forming most of the Punjab region, the province is bordered by Kashmir to the north-east, the Indian states of Punjab and Rajasthan to the east, the Pakistani province of Sindh to the...
. 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. 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 - In the Nile deltaNile DeltaThe Nile Delta is the delta formed in Northern Egypt where the Nile River spreads out and drains into the Mediterranean Sea. It is one of the world's largest river deltas—from Alexandria in the west to Port Said in the east, it covers some 240 km of Mediterranean coastline—and is a rich...
of EgyptEgyptEgypt , officially the Arab Republic of Egypt, Arabic: , is a country mainly in North Africa, with the Sinai Peninsula forming a land bridge in Southwest Asia. Egypt is thus a transcontinental country, and a major power in Africa, the Mediterranean Basin, the Middle East and the Muslim world...
, drainage is being installed in millions of hectares to combat the water-logging resulting from the introduction of massive perennial irrigation after completion of the High Dam at AssuanAswan DamThe Aswan Dam is an embankment dam situated across the Nile River in Aswan, Egypt. Since the 1950s, the name commonly refers to the High Dam, which is larger and newer than the Aswan Low Dam, which was first completed in 1902... - In MexicoMexicoThe United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
, 15% of the 3.000.000 ha if irrigable land is salinized and 10% is waterlogged - In PeruPeruPeru , officially the Republic of Peru , is a country in western South America. It is bordered on the north by Ecuador and Colombia, on the east by Brazil, on the southeast by Bolivia, on the south by Chile, and on the west by the Pacific Ocean....
some 300.000 ha of the 1.050.000 ha of irrigable land suffers from this problem (see Irrigation in PeruIrrigation in PeruWater resources and irrigation infrastructure in Peru vary throughout the country. The coastal region, an arid but fertile land, has about two-thirds of Peru’s irrigation infrastructure due to private and public investment aimed at increasing agricultural exports...
). - 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 IsraelIsraelThe State of Israel is a parliamentary republic located in the Middle East, along the eastern shore of the Mediterranean Sea...
are 13% of the irrigated land,, AustraliaAustraliaAustralia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
20%, ChinaChinaChinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
15%, Irak 50%, EgyptEgyptEgypt , officially the Arab Republic of Egypt, Arabic: , is a country mainly in North Africa, with the Sinai Peninsula forming a land bridge in Southwest Asia. Egypt is thus a transcontinental country, and a major power in Africa, the Mediterranean Basin, the Middle East and the Muslim world...
30%. Irrigation-induced salinity occurs in large and small irrigation systems alike - FAO has estimated that by 1990 about 52 x 106 ha of irrigated land will need to have improved drainage systems installed, much of it subsurface drainage to control salinity
Reduced downstream drainage and groundwater quality
- The downstream drainage water quality may deteriorate owing to leachingLeaching (agriculture)In agriculture, leaching refers to the loss of water-soluble plant nutrients from the soil, due to rain and irrigation. Soil structure, crop planting, type and application rates of fertilizers, and other factors are taken into account to avoid excessive nutrient loss.Leaching may also refer to ...
of salts, nutrients, herbicides and pesticides. This may negatively affect the health of the population at the tail-end and downstream of the irrigation scheme, as well as the ecological balance. The Aral seaAral SeaThe Aral Sea was a lake that lay between Kazakhstan in the north and Karakalpakstan, an autonomous region of Uzbekistan, in the south...
, for example, is seriously pollutedWater pollutionWater pollution is the contamination of water bodies . Water pollution occurs when pollutants are discharged directly or indirectly into water bodies without adequate treatment to remove harmful compounds....
by drainage water. - The downstream quality of the groundwater may deteriorate in a similar way as the downstream drainage water and have similar consequences.
Reduced downstream river water quality
Owing to drainage of surface and groundwater in the project area, which waters may be salinized and polluted by agricultural chemicals like biocides and fertilizerFertilizer
Fertilizer is any organic or inorganic material of natural or synthetic origin that is added to a soil to supply one or more plant nutrients essential to the growth of plants. A recent assessment found that about 40 to 60% of crop yields are attributable to commercial fertilizer use...
s, the quality of the river water below the project area can deteriorate, which makes it less fit for industrial, municipal and household use. It may lead to reduced public health.
Polluted river water entering the sea may adversely affect the ecology along the sea shore (see Aswan dam
Aswan Dam
The Aswan Dam is an embankment dam situated across the Nile River in Aswan, Egypt. Since the 1950s, the name commonly refers to the High Dam, which is larger and newer than the Aswan Low Dam, which was first completed in 1902...
).
Affected downstream water users
Pastoralists and nomadic tribes may find their land and water resources blocked by new irrigation developments without having a legal recourse.
Flood-recession cropping may be seriously affected by the upstream interception of river water for irrigation purposes.
- In BaluchistanBalochistan (Pakistan)Balochistan is one of the four provinces or federating units of Pakistan. With an area of 134,051 mi2 or , it is the largest province of Pakistan, constituting approximately 44% of the total land mass of Pakistan. According to the 1998 population census, Balochistan had a population of...
, PakistanPakistanPakistan , officially the Islamic Republic of Pakistan is a sovereign state in South Asia. It has a coastline along the Arabian Sea and the Gulf of Oman in the south and is bordered by Afghanistan and Iran in the west, India in the east and China in the far northeast. In the north, Tajikistan...
, the development of new small-scale irrigation projects depleted the water resources of nomadic tribes traveling annually between Baluchistan and Gujarat or Rajastan, IndiaIndiaIndia , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world... - After the closure of the KainjiKainjiKainji may refer to several locations in Nigeria:*Kainji Lake*Kainji Dam*Kainji National ParkIt is also used to refer to a group of languages spoken around and to the east of the lake*Kainji languages...
dam, NigeriaNigeriaNigeria , officially the Federal Republic of Nigeria, is a federal constitutional republic comprising 36 states and its Federal Capital Territory, Abuja. The country is located in West Africa and shares land borders with the Republic of Benin in the west, Chad and Cameroon in the east, and Niger in...
, 50 to 70 per cent of the downstream area of flood-recession cropping was lost
Lost land use opportunities
Irrigation projects may reduce the fishing opportunities of the original population and the grazing opportunities for cattle. The livestockLivestock
Livestock refers to one or more domesticated animals raised in an agricultural setting to produce commodities such as food, fiber and labor. The term "livestock" as used in this article does not include poultry or farmed fish; however the inclusion of these, especially poultry, within the meaning...
pressure on the remaining lands may increase considerably, because the ousted traditional pastoralist
Pastoralism
Pastoralism or pastoral farming is the branch of agriculture concerned with the raising of livestock. It is animal husbandry: the care, tending and use of animals such as camels, goats, cattle, yaks, llamas, and sheep. It may have a mobile aspect, moving the herds in search of fresh pasture and...
tribes will have to find their subsistence
Subsistence agriculture
Subsistence agriculture is self-sufficiency farming in which the farmers focus on growing enough food to feed their families. The typical subsistence farm has a range of crops and animals needed by the family to eat and clothe themselves during the year. Planting decisions are made with an eye...
and existence elsewhere, overgrazing
Overgrazing
Overgrazing occurs when plants are exposed to intensive grazing for extended periods of time, or without sufficient recovery periods. It can be caused by either livestock in poorly managed agricultural applications, or by overpopulations of native or non-native wild animals.Overgrazing reduces the...
may increase, followed by serious soil erosion and the loss of natural resources
Natural Resources
Natural Resources is a soul album released by Motown girl group Martha Reeves and the Vandellas in 1970 on the Gordy label. The album is significant for the Vietnam War ballad "I Should Be Proud" and the slow jam, "Love Guess Who"...
.
The Manatali reservoir
Lake Manantali
Lake Manantali is a large artificial lake, formed by the 1989 construction of the Manantali Dam, on the Bafing River in Mali. Its northern point is located 90 km to the south-east of the city of Bafoulabé.-Size:...
formed by the Manantali dam
Manantali Dam
The Manantali Dam is a multi-purpose dam on the Bafing river in the Senegal River basin, 90 km to the south-east of Bafoulabé, in Mali's Kayes Region.-History:...
in Mali
Mali
Mali , officially the Republic of Mali , is a landlocked country in Western Africa. Mali borders Algeria on the north, Niger on the east, Burkina Faso and the Côte d'Ivoire on the south, Guinea on the south-west, and Senegal and Mauritania on the west. Its size is just over 1,240,000 km² with...
intersects the migration routes of nomadic pastoralists and destroyed 43000 ha of savannah
Savannah
Savannah or savanna is a type of grassland.It can also mean:-People:* Savannah King, a Canadian freestyle swimmer* Savannah Outen, a singer who gained popularity on You Tube...
, probably leading to overgrazing and erosion elsewhere. Further, the reservoir destroyed 120 km² of forest
Forest
A forest, also referred to as a wood or the woods, is an area with a high density of trees. As with cities, depending where you are in the world, what is considered a forest may vary significantly in size and have various classification according to how and what of the forest is composed...
. The depletion of groundwater aquifers, which is caused by the suppression of the seasonal flood cycle, is damaging the forests downstream of the dam.
Groundwater mining with wells, land subsidence
When more groundwater is pumped from wells than replenished, storage of water in the aquiferAquifer
An aquifer is a wet underground layer of water-bearing permeable rock or unconsolidated materials from which groundwater can be usefully extracted using a water well. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology...
is being mined. Irrigation from groundwater is no longer sustainable then. The result can be abandoning of irrigated agriculture.
The hundreds of tubewells installed in the state of Uttar Pradesh
Uttar Pradesh
Uttar Pradesh abbreviation U.P. , is a state located in the northern part of India. With a population of over 200 million people, it is India's most populous state, as well as the world's most populous sub-national entity...
, India
India
India , officially the Republic of India , is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country with over 1.2 billion people, and the most populous democracy in the world...
, with World Bank funding have operating periods of 1.4 to 4.7 hours/day, whereas they were designed to operate 16 hours/day
In Baluchistan
Balochistan (Pakistan)
Balochistan is one of the four provinces or federating units of Pakistan. With an area of 134,051 mi2 or , it is the largest province of Pakistan, constituting approximately 44% of the total land mass of Pakistan. According to the 1998 population census, Balochistan had a population of...
, Pakistan
Pakistan
Pakistan , officially the Islamic Republic of Pakistan is a sovereign state in South Asia. It has a coastline along the Arabian Sea and the Gulf of Oman in the south and is bordered by Afghanistan and Iran in the west, India in the east and China in the far northeast. In the north, Tajikistan...
, the development of tubewell irrigation projects was at the expense of the traditional qanat
Qanat
A qanāt is a water management system used to provide a reliable supply of water for human settlements and irrigation in hot, arid and semi-arid climates...
or karez
Kařez
Kařez is a village and municipality in Rokycany District in the Plzeň Region of the Czech Republic.The municipality covers an area of , and has a population of 570 ....
users
Groundwater-related subsidence
Groundwater-related subsidence
Groundwater-related subsidence is the subsidence of land resulting from groundwater extraction, and a major problem in the developing world as major metropolises swell without adequate regulation and enforcement, as well as a being a common problem in the developed world...
of the land due to mining of groundwater occurred in the USA at a rate of 1m for each 13m that the watertable was lowered
Homes at Greens Bayou near Houston, Texas
Texas
Texas is the second largest U.S. state by both area and population, and the largest state by area in the contiguous United States.The name, based on the Caddo word "Tejas" meaning "friends" or "allies", was applied by the Spanish to the Caddo themselves and to the region of their settlement in...
, where 5 to 7 feet of subsidence has occurred, were flooded during a storm in June 1989 as shown in the picture
Simulation and prediction
The effects of irrigation on watertable, soil salinity and salinity of drainage and groundwater, and the effects of mitigative measuresEnvironmental mitigation
Environmental mitigation, compensatory mitigation, or mitigation banking, are terms used primarily by the United States government and the related environmental industry to describe projects or programs intended to offset known impacts to an existing historic or natural resource such as a stream,...
can be simulated and predicted using agro-hydro-salinity models like SaltMod
SaltMod
SaltMod is computer program for the prediction of the salinity of soil moisture, groundwater and drainage water, the depth of the watertable, and the drain discharge in irrigated agricultural lands, using different hydrologic conditions, varying water management options, including the use of...
and SahysMod
SahysMod
SahysMod is a computer program for the prediction of the salinity of soil moisture, groundwater and drainage water, the depth of the watertable, and the drain discharge in irrigated agricultural lands, using different hydrogeologic and aquifer conditions, varying water management options, including...
See also
- Environmental issues with agricultureEnvironmental issues with agricultureThe environmental impact of agriculture varies based on the wide variety of agricultural practices employed around the world.-Climate change:Climate change and agriculture are interrelated processes, both of which take place on a global scale...
- Environmental impacts of reservoirs
- Irrigation in viticultureIrrigation in viticultureThe role of irrigation in viticulture is considered both controversial and essential to wine production. In the physiology of the grapevine, water is a vital component to function of the vine with its presence or lack impacting photosynthesis, new plant shoot growth, as well as the development of...
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: http://www.waterlog.info/saltmod.htm
- Download of simulation and prediction model SahysMod from: http://www.waterlog.info/sahysmod.htm
- "SaltMod: A tool for interweaving of irrigation and drainage for salinity control": http://www.waterlog.info/pdf/toolsalt.pdf
- "Modern interferences with traditional irrigation in Baluchistan": http://www.waterlog.info/pdf/baluchistan.pdf