3 Diversity of Irrigation by Hydrological Conditions, etc....15 1 Diversity of Irrigation by Hydrological Conditions, etc. Global annual precipitation averages around 1,000 mm. However,

15

1

Diversity of Irrigation by Hydrological

Conditions, etc.

Global annual precipitation averages around 1,000 mm. However, it is characterized by a verywide divergence from desert regions, where it is virtually zero, to other regions where it exceeds4,000 mm.

Irrigation undertaken with the use of agricultural water takes a variety of forms indifferent parts of the world. This results from a combination of differences inrainfall, sunshine, temperature, and other climatic conditions, differences in soil,topography, and other geographical conditions, differences in the waterrequirement of agricultural crops on farmland, and so on. These factors lead to avery rich diversity of irrigation.Meanwhile, there is a close correlation between annual precipitation and regionsthat cultivate the world's big three grains (rice, wheat and maize).If the regions are divided into arid and humid regions for comparison, it becomesthat they differ in the very purpose of irrigation.

Great diversity of precipitation supporting water cycles onthe planet, from deserts to humid regions

Annual precipitation (mm)

0 - 400

400 - 1000

1000 - 2000

＞2000

Distribution of annual precipitation

Source: Climate Data sets, GNV174 - Annual precipitation (UNEP)

3

16

Distribution of “water Balance”(calculated by subtracting potential evapotranspiration from precipitation)

400

350

300

250

200

150

100

50

0

（mm）

400

350

300

250

200

150

100

50

0

（mm）

400

350

300

250

200

150

100

50

0

（mm）

400

350

300

250

200

150

100

50

0

（mm）

400

350

300

250

200

150

100

50

0

（mm）

400

350

300

250

200

150

100

50

0

（mm）

400

350

300

250

200

150

100

50

0

（mm）

Precipitation (mm)Potential Evapotranspiration (mm)

Water Balance (mm/yr)

～－1000

－1000～－500

－500～0

0～＋500

＋500～＋1000

＋1000～＋1500

＋1500～

Lyon (France)

Banghazi (Libya)

San Francisco (USA)

Moscow (Russia)

Colombo (Sri Lanka)

Tokyo (Japan)

Canberra (Australia)

Jan.Mar. May Jul. Sep.

Nov. Jan.Jan.

Mar. May Jul. Sep.Nov. Jan.


Nov. Jan.


Nov. Jan.


Nov. Jan.


Nov. Jan.


Nov. Jan.

Note: Diagram compares annual precipitation with potential annual evapotranspiration. The actual water balance for individual regions maytherefore be different, depending on precipitation patterns and thesituation of water use.

Sources: 1) Climate Data Sets, GNV183 - Tateishi Monthly Potential and Actual Evapotranspiration and Water Balance (UNEP)

2) Fukui, E., et al. "Japan and World Climate Charts", 1985 (Tokyodo Shuppan) (original chart by J.R. Mather)

The "water balance" is calculated by subtracting potential evapotranspiration from precipitation.This balance is negative in most parts of Africa (except Central Africa), the Middle East,Central Asia, central and western North America, western South America, Australia, andelsewhere.

Regions having annual precipitation of less than 500 mm are called "arid regions". In theseregions, soil is often desertified, and agricultural products are difficult to cultivate without irrigation.By contrastingly, arid-subhumid regions with annual precipitation of 500 - 1,000 mm are generallyused as grasslands for grazing livestock, as well as rain-fed cultivation of beans, wheat and othercrops that have a smaller water requirement. In this pamphlet, regions with annual precipitation of less than 1,000 mm (including arid-subhumidregions) shall be referred to as "arid regions", and those with annual precipitation above this as"humid regions" for the purpose of our discussion.

17

2

In East and Southeast Asia, there are regions that have annual precipitation of more than 1000mm, under the influence of monsoons. These regions belong to temperate, subtropical or tropicalzones, and include zones in which orogenic movement is lively due to plate tectonics (shift zones).They are generally assumed to include Japan, the Korean peninsula, China (except the westerninterior, the Yellow River basin, and surrounding areas), all of Southeast Asia (the Indochinapeninsula and the island nations), Nepal, Bhutan, Bangladesh, Sri Lanka, and areas east of theDeccan Plateau plus southwestern coastal regions of India. In this pamphlet, these regions shallbe referred to collectively as the "Asia monsoon region".The Asia monsoon region generally has extreme seasonal or short-term fluctuations in river flowrate, under the influence of monsoons. It also has a relatively conspicuous tendency for flashflooding, and it contains numerous fast-flowing rivers.This is why, at first glance, the countries in this region appear to have large absolute quantities ofwater resources. But in fact, they suffer from severe water shortages and water pollution, resultingfrom an imbalance against increasing demand for water due to population growth and otherfactors. Thus, these countries could be said to suffer from severe hydrological conditions,demanding immense efforts to improve the utilization efficiency of water resources.

The Asia monsoon region: A warm, high-precipitationclimate with severe hydrological conditions

Diversity of Irrigation byHydrological Conditions,etc.3

18

3

North and Central America

96 （12.9％）

South America35

（4.7％）

Europe133

（17.8％）

Russia48

（6.5％）

West Asia52

（7.0％） East Asia98

（13.0％）

Southeast Asia49

（6.6％） South Asia128

（17.1％） Oceania16

（2.2％）

Africa92

（13.0％）

OtherRice

Wheat

Maize

Distribution of major cereal harvested areas

Note: Upper - Cereal harvested area (million ha) Lower - The ratio to world cereal harvested area

Source: Statistical Databases (FAO)

Rice, wheat and maize are the three grains with the highest individual production volumes in theworld. A survey of the cultivation of these "big three grains" in various regions of the world showsthat the cultivation of rice (paddy rice) predominates in East Asia, Southeast Asia and South Asia.Southeast Asia, in particular, accounts for the majority of production. The cultivation of wheat,meanwhile, predominates in Europe, Russia, West Asia, and Australia. Maize is the dominant cropin South America, while wheat and maize account for the majority of grain cultivation in North andCentral America.Paddy rice has a large physiological water requirement, on the one hand, but is also most resistantto inundation. Moreover, although it has a higher ratio of production for food, it also has anextremely low ratio of use in international trade. Of the big three grain crops, therefore, it offers thegreatest potential for self-sufficiency. By contrast, maize has a lower ratio of use for food, and ismore important as a fodder grain.

The world's agricultural production: Regional characteristicsin cultivation of the "big three grains" (rice, wheat and maize)

19

154 214 138

　　　Name

Rice PaddyWheatMaize

Harvested area(2000) 1）

(mil. ha)

600 585 593

Annual production(2000) 1）

① (mil. tons)

682 557 349

Water required to produce 1g of

dried plant body2）

(g)

○ × ×

Ability to withstand immersion

521 419 115

　　　Name

Rice PaddyWheatMaize

Consumption of ① as food 1）

②

(mil. tons)

87 73 19

②／① (%)

③／① (%)

36 138 85

Amount of ① exported 1）

③

(mil. tons)

6 24 14

Comparison of the 3 major grains

Notes: 1) Rice production is based on unhulled rice.2) The amount of water required to produce 1g of dried prant body has a degree of latitude depending on the reference.

Source: 1) Statistical Databases (FAO)2) Black, C. C., T. M. Chen and R. H. Brown, Biochemical basis for plant competition. Weed Soc.17,10-20, 1969


20

Ratio of wheat production by region (2000)

4

11.3％

3.9％

3.5％

15.9％

22.0％ 2.5％

40.9％


Asia

South America

Africa

Oceania

Europe

Former Soviet Union countries


Top 10 wheat production countries (2000)

12345678910

ChinaIndiaUSAFranceRussian FederationCanadaAustraliaGermanyPakistanTurkey　　Sub-totalOther　　Total

CountryRank

17 13 11 7 6 5 4 4 4 4 75 25 100

Ratio to world production

(%)

100 76 61 37 35 27 22 22 21 21 422 152 585

Production

(mil. tons)

27 27 22 5 20 11 12 3 8 9

144 70 214

Harvested area

(mil. ha)


The world's wheat production in 2000 was about 590 million tons. Of this total, 40.9% wasproduced in Asia, 22% in Europe, and 15.9% in North and Central America. In terms of productionvolume by country, the majority of the world's wheat is produced in regions with annualprecipitation of less than 1,000 mm, including the 10 countries with the largest production volumes.

Asia and the West each produce 40% of the world's wheat

21

Relationship between precipitation and wheat planting ratio


Ratio

of w

heat

har

vest

ed a

rea

to c

erea

l har

vest

ed a

rea

(%)

0

25

50

75

100

0 500 1,000 1,500 2,000

UzbekistanUzbekistan

Saudi ArSaudi Arabiaabia

IrIranan

GreeceGreece

SyrSyriaia

EgyptEgypt

SwSwedeneden

PPolandoland

SpainSpain

HungarHungaryyEthiopiaEthiopia

ArgentineArgentine

BelgiumLuxBelgiumLuxembourgembourgEnglandEngland

ItalyItaly

RumaniaRumania

DenmarDenmarkk

UkrUkraineaineBulgarBulgariaia

ChileChile

Uzbekistan

Saudi Arabia

Iran

Greece

Syria

Egypt

Sweden

Poland

Spain

HungaryEthiopia

Argentine

BelgiumLuxembourgEngland

Italy

Rumania

Denmark

UkraineBulgaria

Chile

Mainly Middle Eastern countries

Australia

Pakistan

Russian Federation

Canada

Turkey

Germany USA

France

India (northern)

China (central and western)

Mainly European countries

Notes: 1) Annual precipitation in China and India is the figure for main cities in provinces that cultivate wheat (China: Beijing, India: New Delhi). In other countries, it is the figure for the national capital or cities near the capital.

2) Countries with wheat cultivation of less than 100,000ha or a wheat cultivation ratio of less than 10% are not included. The diagram was drawn up to show the top 30 wheat producing countries.

3) The top 10 wheat producing countries are boxed.

Source: 1) Statistical Databases (FAO)2) Japan Meteorological Agency, 1994


22

5

2.9％

0.4％ 1.8％ 3.4％ 0.2％

0.2％

91.1％


Asia

South America

Africa

Oceania

Europe

Former Soviet Union countries

Ratio of rice production by region (2000)


Top 10 rice production countries (2000)

12345678910

ChinaIndiaIndonesiaBangladeshVietnamThailandMyanmarPhilippinesJapanBrazil　　Sub-totalOther　　Total

CountryRank

32 22 9 6 5 4 4 2 2 2 87 13 100

Ratio to world production

(%)

190 129 52 38 33 26 21 12 12 11 524 76 600

Production(unhulled)(mil. tons)

30 45 12 11 8 10 6 4 2 4

132 22 154

Harvested area

(mil. ha)


The world's rice production in 2000 was about 600 million tons (unhulled), of which 91.1% wasproduced in Asia. The top 10 rice-producing countries all have annual precipitation in excess of1,500 mm. About 87% of the world's rice is produced in these 10 countries, of which 9 are in Asia.Similarly, countries whose proportion of rice cultivation to the total grain cultivation area exceeds50% generally have annual precipitation of more than 1,500 mm.

Asia, with annual precipitation of more than 1,500 mm,produces 90% of the world's rice

23


Ratio

of r

ice

harv

este

d ar

ea to

cer

eal h

arve

sted

are

a (%

)

0

25

50

75

100

0 1,000 2,000 3,000 4,000

China (southern)

Brazil

Vietnam

India (eastern)

Philippines

Myanmar

Bangladesh

Indonesia

Thailand

Japan

Mainly Asian countries

Mainly South Americanand African countries

IvIvorory Coasty CoastUrUruguauguayy

ColombiaColombia

PPereruu

GuianaGuiana

EgyptEgypt

CubaCuba

MadagascarMadagascar

KKoreaoreaLaosLaos

MalaMalaysiaysiaGuyGuyanaana

SrSri Lankai LankaLiberLiberiaia

SierrSierra Leonea Leone

BoliviaBolivia

MozambiqueMozambiqueNigerNigeriaia

MaliMali

TTanzaniaanzania

PPakistanakistanVVenezuelaenezuela

EcuadorEcuador

Ivory CoastUruguay

Colombia

Peru

Guiana

Egypt

Cuba

Madagascar

KoreaLaos

MalaysiaGuyana

Sri LankaLiberia

Sierra Leone

Bolivia

MozambiqueNigeria

Mali

Tanzania

PakistanVenezuela

Ecuador

Notes: 1) Annual rainfall is the value for the major cities in the region (China: Hong Kong, India: Calcutta) where rice is growth primarily in the case of China and India2). It is the national average in the case of Japan3).In other countries, it is the value in the capital or in a city near the capital2).

2) Countries with less than 100,000 ha in rice cultivation or countries with less than 10% are not indicated in the diagram above.

3) The name of the ten top ranking rice producing countries are displayed in boxes.

Source: 1) Statistical Databases (FAO)2) Japan Meteorological Agency, 19943) Land & Water Resources Bureau, Ministry of Land, Infrastructure and Transport, 2002


24

Main purpose of irrigation by region

6

＞1,000mm

500～1,000mm

250～500mm

＜250mm

Humidregions

Arid regionsIncluding arid-subhumid regions

Annual precipitationRegion Main purpose ofirrigation

(Reference) Main purpose of drainage

・Supplement the non-uniform temporal and spatial distribution of rainfall・Prevent frost damage・Hinder the growth of weeds・Insurance for short-term drought・Increase crop revenues that require a

water supply that is more uniform than rainfall・Produce high value crops that would be

impossible if they depended on rainfall・Supplement rainfall shortages during

the crop production season・An essential condition for cultivation

・Remove excess rainfall

・Prevent salinization

・An essential condition for the prevention of salinization

Inundation during the rainy season(Bangladesh)

Irrigation zone in northern Israel

Source: Ie-no-hikari Association, 1995

In arid regions, where precipitation is small, the absolute volume of moisture needed for the growthof crops tends to be in short supply. Therefore, supplying the moisture needed for crop growth isthe single main purpose of irrigation in these regions. The same may also be true in high-precipitation humid regions when prolonged dry weathercauses unforeseen abnormal droughts. Normally, however, the purpose of irrigation in humidregions is not only to supply the moisture needed for crops to grow. Paddy field irrigation,particularly predominant in the Asia monsoon region of all humid regions, supplies agriculturalwater in excess of the moisture supply volume of crops in the rainy season, and at other timeswhen potential water resources are abundant. By so doing, it achieves a multiplicity of purposes,including simplifying the work of plowing the land (turning the soil in paddy fields), reducing theproliferation of weeds, making use of the nutrients present in irrigation water, preventing soilerosion, preventing replant failure, and removing salinity. It also makes it possible, for example, toavoid typhoon damage immediately before the harvest by irrigating during the dry season, therebyadvancing the planting phase. Irrigation, therefore, also broadens the range of options for cropsand planting times.

Irrigation has a single purpose in arid regions but amultiple one in humid regions

Source: Prepared with reference to Hitoshi Fukuda, 1974


Source: Ie-no-hikari Association, 1995

25

1

Primary arable areaSeasonally

arable area

Ground surfaceVillage

Vertical shaft

Spring water

Increase in salt

concentration

Aquiclude

Village

Open channel zone

Transferzone

Mother wellTunnelzone

Impermeable layer

Drinking water

Groundwater level

Aquifer

Mother wellMother well

4

Source: Toshisuke Maruyama, Ryota Nakamura et al., 1998 (Asakura Shoten)

Irrigation in Arid Regions

A traditional form of irrigation in arid regions is the "khanat", which uses groundwater. This methodof extracting groundwater have been passed down in arid regions since prehistoric times. Thoughgoing under different names in different countries, they involve driving vertical shafts into theground, digging horizontal underground tunnels that stretch laterally from hundreds of meters totens of kilometers, from which groundwater is gathered.

In arid regions, wisdom on securing water for agricultural production and daily lifehas been passed down since ancient times. These traditional forms of irrigationare characterized as being sustainable, even though relatively small in scale.Meanwhile, in Israel, central and western USA, Australia and other aridregions,modern large-scale irrigation systems have been developed. Here, large-scale, low-cost farming has evolved making use of the climatic conditions of aridregions, i.e. warmth and plenty of sunshine, as well as expansive land conditions. The side effects of this, however, are concerns over the accumulation of salinityin soil, the loss of groundwater resources, the impact on ecosystems, and othernegative aspects. A famous case of this is the example of the Aral Sea. Suchcases can cause situations that threaten human habitation itself. The occurrenceof these side-effects could also be seen as another example in which thecharacteristics of rain-starved arid regions are conspicuously manifest.

Groundwater used since ancient times due to lack of precipitation

Plane and cross-sectional views of a qanat(example on the Arabian Peninsula)

26

Conceptualization of irrigation using floodwater (example in Pakistan)

2

Simple water diversion Water harvesting system from the main water channel

Bank

Bank

Irrigated area

Irrigated area

Earth dam

Source: Toshisuke Maruyama, Ryota Nakamura et al., 1998 (Asakura Shoten)

Conceptualization of water harvesting (example in Tunisia)

160

22

EL （m）

Water harvesting area

Closs sectional view

100（m）

Arable area

Arable areaWater harvesting area

Source: Toshisuke Maruyama, Mashahiko Tomita et al., 1996 (Asakura Shoten)

In arid regions, dams are sometimes built on dried-up rivers in which water does not normally flow.From these, water is extracted in flood seasons and used for irrigation. Elsewhere, the "water harvesting method" is sometimes used. Here, rainwater is collected on landof a certain size, and crops are sown in hollows and low-lying areas on a smaller part of that land.This is classified as rain-fed agriculture, but it could also be characterized as self-contained,sustainable small-scale irrigation.

Effective use of rainwater and other precious watersources

27

Golan Heights

Syria

Lebanon

Haifa

West Bank of the Jordan

Tel Aviv

Sedom

Gaza

Negev Desert

Jordan

CanalReservoirPump station

Egypt

Eilat

Jerusalem

Dead Sea

Sea of Galilee

Map of Israel

Mediterranean Sea

0

5

10

15

20

25

30

35

Tem

pera

ture

( ℃)

Prec

ipita

tion

(mm

)

0

20

40

60

80

100

120

140

160

180Har-Kenaan

Precipitation (mm) Temperature (℃)


0

5

10

15

20

25

30

35

Tem

pera

ture

( ℃)

Prec

ipita

tion

(mm

)

0

20

40

60

80

100

120

140

160

180Eilat

Jordan River

Janu

ary

March

May July

Septe

mber

Novem

ber

Janu

ary

March

May July

Septe

mber

Novem

ber

Kinneret Negev National Canal (Israel)

Source: 1) Ie-no-hikari Association, 19952) Israel Central Bureau of Statistics website

3

In Israel, water is lifted from the Sea of Galilee in the north of the country, where there is relativelyabundant rainfall in the winter. From here, 300 million cubic meters of water a year are conveyedto Tel Aviv in the center and to the southern Negev desert (where rainwater is virtually nil) throughwater channels that traverse the country for about 200 km. However, since even then it is still notpossible to maintain a supply commensurate with the demand for water, the reuse of processedsewage and other initiatives are now being promoted.

Desert zones irrigated with water from highlands as far as200 km away

Irrigation in Arid Regions4

28

4

San Francisco

San Francisco

Los Angeles

More than 2000mm

1500―2000

1000―1500

500―1000

250― 500

125― 250

Less than 125mm

0

5

10

15

20

25

30

0

20

40

60

80

100

120

Tem

pera

ture

( ℃)

Prec

ipita

tion

(mm

)

Janu

aryFe

bruary

March

April

MayJu

ne July

Augu

stSe

ptembe

rOcto

ber

Novem

ber

Decem

ber


125125125

125125125250250250

250250250

500500500

500500500

500500500

500500500

500500500

500500500

500500500

100010001000

100010001000150015001500

150015001500

150015001500200020002000

1500

1500

1500

Source: 1) Tatsuro Katsuyama, 1993 (Chikyusha)2) Japan Meteorological Agency, 1994

Annual precipitation in California

Annual average precipitation in California, USA, is 580 mm. Near the northern Sierra Nevadamountains it exceeds 2,000 mm, while the central and southern parts are mostly arid regions withless than 250 mm. The northern rainwater and snowmelt water are stored in a group of hugedams, before being carried through the 710 km California Water Canal (flow rate 370 m3 persecond) and others to irrigate more than 3 million ha of arable land. Making maximum use of thisplentiful water and a warm climate, California's production of agricultural produce is now thehighest in the entire USA, in monetary terms. However, the salinity contained in low concentrationsin irrigation water has gradually accumulated in irrigated arable land. Due to this and other factors,about 900,000 ha of irrigated arable land is already affected by salinity accumulation.

Wasteland revived by irrigation

29

Oregon

Sacramento River

Hoover Dam

San Joaquin River

Sacramento plains

（1960）

（1961）

San Luis Dam

（1967）

California Canal

（1967）

Delta Mendota Canal

（1951）

All American Canal

（1938）

Oroville dam

（1968）

Las Vegas

San Francisco

Mexico

Sacramento

（　　）

Major agricultural area

Rice production areaCanal

Dam

year of completion

Clair Engle DamClair Engle Dam

Colorado RiverColorado River

Shasta DamShasta Dam

（（19451945））

Corning CanalCorning Canal

Tehama Colusa canalTehama Colusa canal

Friant-Kern CanalFriant-Kern Canal

（（19441944））

Central plains

Central plains

FresnoFresno

Los AngelesLos Angeles

San DiegoSan Diego

Imperial plainsImperial plains

Monterrey plains

Monterrey plains

Sierra Nevada M

ountains

Sierra Nevada M

ountains

Clair Engle Dam

Colorado River

Shasta Dam

（1945）

Corning Canal

Tehama Colusa canal

Friant-Kern Canal

（1944）

Central plains

Fresno

Los Angeles

San Diego

Imperial plains

Monterrey plains

Sierra Nevada M

ountains

Pacific Ocean

Nevada

Arizona

Major water use facilities in California

Farmland subject to reduced productivity dueto salinity accumulation

Source: U. S. Soil Conservation Service, 1983

Source: 1) Tatsuro Katsuyama, Turning Point for, 1993(Chikyusha)

2) California State Water Resources Bureau


30

Paddy field zone and annual precipitation in Australia

5

800mm

800mm

500mm

500mm

800mm 500mmSydney

Paddy fieldPaddy field

Source: Toshio Tabuchi, 1999 (Yamazaki Agriculture Research Institute)

Region Paddy field

MIA

CIA

MV

total

40,000 ha

24,000 ha

56,000 ha

120,000 ha

Murray River

Murrumbidgee River

DamWeir Urban areaIrrigated area

100km

10.0 million m3/day

4.90 million m3/day

Dam

Dam

Dam

1.6 1.6 million mmillion m331.6 billion m3

3.0 billion m3

1.0 billion m3

CIA regionMV region

MIA region (190,000 ha)


Summary of paddy field zone

The Murray River basin in southeastern Australia is an arid region with annual precipitation ofabout 400 mm. Here, a paddy field zone of about 120,000 ha has been developed, using anirrigation system that channels water from a group of massive dams some distance away. Usingsuperior cultivation technology and favorable sunshine conditions, a high single yield of 8 tons/ha(unhulled) has been achieved. Due to progressive underground percolation of water from paddyfields over such a wide area, however, water-logging and salt damage (accumulation of soilsalinity near the ground surface) have occurred in nearby upland fields and perennial croplands.To address this, shallow groundwater is being forcibly drained, but effluents containing largeamounts of salinity cannot be released into rivers downstream. Therefore, the water is channeledinto a massive evaporation reservoir constructed from 2,100 ha of purchased farmland, where it isdisposed of through evaporation.

Paddy field irrigation in arid regions

31

evaporation pond

well and pipeline

Ｎ 0 5km

Evaporation pond and drainage facilities


Vast evaporation pond



32

Scene of central-pivot irrigation

6

Source: Chiba Prefectural Information Education Center (provided by KiyoshiAndo)

Distribution of annual precipitation in the U.S. and the location of the Ogallala aquifer

30～40

0～10 40～6010～20 60～10020～30 ＞100

Annual precipitataion (inches)

Annual precipitaion 20-inch (510mm) line↑

West East

：Ogallala aquifer

Source: Hattori, 1992 (Fumin Kyokai)

ColoradoKansas

Oklahoma

Nebraska

Texas (panhandle)

In the central USA, meanwhile, large-scale agriculture has been developed using a system called"center pivot irrigation". This taps groundwater from a vast groundwater source known as theOgallala Aquifer, which stretches from northern Texas to Oklahoma, Kansas, Colorado, andNebraska.The irrigated arable land that uses this aquifer accounts for about a fifth of all irrigated arable landin the USA. But since 22.2 billion cubic meters of groundwater - or three times the volume ofgroundwater accumulated from rainwater (6-8 billion cubic meters annually) - are brought up everyyear, falling groundwater levels are becoming a problem. Meanwhile, due to rising costs for waterpumping accompanying this, many of the farmers who depend on this aquifer are abandoningirrigation agriculture.

Formation of a granary zone by tapping groundwater

Ogallala aquifer


Documents

3 Diversity of Irrigation by Hydrological Conditions, etc....15 1 Diversity of Irrigation by Hydrological Conditions, etc. Global annual precipitation averages around 1,000 mm. However,