~ CHAPTER 5 ~
DEGRADATION OF IRRIGATED LAND
Edition 5 of July, 2007 (
Updated October 2010)

~ TABLE OF CONTENTS ~

(5-A) ~ Global Overview ~ [A1]~Irrigation System Degradation. [A2]~Irrigation system Abandonment, [A3]~Irrigation System Restoration, ~
(5-B) ~
Regional Degradation ~ Asia ~ [B1]~Asian Sub-Continent, [B2]~Central Asia, [B3]~Eastern Asia, [B4]~Mid-East, [B5]~Southeast Asia, ~
(5-C) ~
Regional Degradation ~ Africa and Australia ~ [C1]~Africa, [C2]~Australia, ~
(5-D) ~
Regional Degradation ~ North and South America ~ [D1]~US, [D2]~US -Western, [D3]~US- Great Plains, [D4]~South America, [D5]~Central America, ~
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ir5

NOTE: The notation (su4) means that the adjacent data was used in the document analyzing the sustainability of the productivity of the world's systems for producing food, fiber and water.

SECTION (5-A) ~ Global Overview ~ [A1]~Irrigation System Degradation, [A2]~Irrigation system Abandonment, [A3]~Irrigation System Restoration, ~

See a listing of large databases in Chapter 8 Section (8-E) for sources of tabulations of:
- Total population estimates and projections (1980, 2005, 2030) by country

Part [A1] ~ Global Overview ~ Irrigation System Degradation ~

Buringh (1977) estimated that due to salinization, the world loses at least 1.6 million hectares (16,000 km2) of fertile, arable land every year. (Buringh, P. (1977): "Food production potential of the world. In R. Sinha (Editor), The World Food Problem: Consensus and Conflict," Pergamon Press, Oxford, pp. 477-485.)

Ghassemi et al. (1995) estimated that about 20% - or about 45.4 million hectares (454,000 km2) of irrigated land are salt-affected. (Ghassemi, F., A. J. Jakeman, and H. A. Nix (1995): "Salinization of Land and Water Resources: Human Causes, Management and Case studies." Center for Resources and Environmental Studies, Canberra, Australia.)

The 1977 United Nations Conference on Desertification estimated that 22 million hectares (220,000 km2) of the world's irrigated lands are waterlogged. (Holdgate, M. W., M. Kassas and G. F. White (Editors.) (1982): The World Environment. Tycooly International, Dublin.)

Globally, more than 770,000 km2 of land is salt-affected by secondary salinization. About 20% of this is irrigated land, and about 2% of this is dryland agricultural land (FAO, AGL, 2000 data) (05S1).

Worldwide, 40% of agricultural land is moderately degraded and 9% is highly degraded (reducing global crop yield by as much as 13% (00W3)). In rain-fed agriculture, land productivity is declining on an estimated 40% of cultivated area (04H1).

Nearly 1.6 million ha./ year (16,000 km2/ year) are lost globally due to salinization ("How to Feed the World", Christian Science Monitor (2/20/03)).

Poor drainage and irrigation practices have led to waterlogging and salinization of approximately 10% of the world's irrigated lands (Reference lost - about 2000).

Half of the world's irrigation capacity (area) has been developed since 1950 (78B2).

Soil salinization is spreading at a rate of up to 20,000 km2/ year (globally), offsetting a significant portion of the increased productivity achieved by expanding irrigation. (Dina L. Umali, "Irrigation-Induced Salinity", World Bank, Washington DC, 1993) (Ref. 12 of (96P1)). Comments: These statements are also in the Soil Degradation Review.

Yields on 50% of the world's irrigated land - 1.2 million km2 - have fallen in recent years (98H1). (su4) Comments: Ref. (98H1) does not list its information sources.)

(Salinization) In some semi-arid countries, 10-50% of the irrigated area is affected (by salinization) to a greater or lesser degree (93U1) (97F1), with average yield decreases of 10-25% for many crops (93F1) (93U1). Estimates of the rates of change in area affected by salinization are in the range of 1-1.5 million ha/ year and increasing (93U1) (03N1).

(Salinization) Oldeman, Hakkeling and Sombroek (91O1) estimate the total global area affected by salinization to be over 760,000 km2, but they do not differentiate between irrigated and rain-fed areas. It seems possible that 20% of the total irrigated area is affected, and 120,000 km2 of irrigated land may have gone out of production (01N1) (03N1). (la)

(Salinization) A World Bank study of the performance of Bank-funded irrigation projects concluded that the Bank should not insist that its client countries construct drainage systems before they are needed, but that it should at least fund pilot schemes to identify the best solutions (to the salinization problem) before large-scale schemes get under way. (Wm. I. Jones, "The World Bank and Irrigation", World Bank, Washington DC, 1995) Comments: Drainage systems are what prevent salinization and waterlogging. After an irrigation system has been built and paid for and in operation for some years and salinization problems appear, the World Bank would appear to have little leverage to force installation of drainage systems.

(Salinization) As many as half of all existing irrigation systems in the world are influenced by secondary salinization, alkalization and waterlogging (88S1) (FAO and UNESCO data).

(Salinization and waterlogging) The FAO estimates that salt build-up in soil has severely damaged 300,000 km2 of the world's 2.4 million km2 of irrigated land. Another 800,000 km2 are affected by a combination of salinization and waterlogging (98H1). (la)

(Salinity and waterlogging) 26% of the world's irrigated area suffers from some degree of waterlogging and salinity (91B3). Comments: 0.26 * 2.4 million = 624,000 km2 (la)

(Waterlogging) Over 100,000 km2 (globally?) (of irrigated lands?) are estimated to be affected by waterlogging (91O1) (03N1). (la)

(Salinization) 250,000 km2 of the world's irrigated lands appear to suffer from salt buildup enough to lower crop yields (Ref. 12 of (96P1)). (la)

(Salinization) A 1995 study, drawing on the global data of the 1980s, estimated that 20% of the world's irrigated area suffers from salinization (Ref. 52 of (96G2)). (la)

(Salinization) 20% of the world's irrigated land is losing productivity because of spreading salinization. (99P1) Comments: Because such a large fraction (60%??) of the world's irrigation systems is younger than 50 years, and because the growth of irrigation has slowed so dramatically, and because it takes some decades for salinization (and waterlogging) to begin degrading productivity, the fraction of irrigated lands losing productivity is sure to climb dramatically in coming decades.

More than 50% of the world's irrigated soils are affected by secondary salinization and/or alkalization (Refs. 355, 356, p. 207 of (88S1)). (la)

The area of irrigated land damaged by salt in 1995-97 is charted for 8 regions of the world on p. 58 of Ref. (00W1).

(Salinization) The UNEP estimates that, globally, irrigated area damaged by salinization at 400,000 km2 (Ref. 15 of (89P3)). (la)

(Salinization) Salinity seriously affects productivity on 200,000 km2 of the world's irrigated lands (Ref. 14 of (85E1)). (la)

(Salinization) 200,000-300,000 km2 of the world's irrigated area suffer serious salinization (94P2). (la)

(Salinization) 600,000-800,000 km2 (globally) are moderately affected by salinization (Ref. 5 of (94P2)).

(Salinization) Productivity on at least 1/3 of the world's irrigated land is being undermined by salinity problems (76E1).

(Salinization) A third of the world's irrigated lands have serious salinization problems (79S1).

A 1977 UN report indicated that, globally, 210,000 km2 of irrigated land (10% of the total) were waterlogged, and productivity has dropped 20% (78B3) (81B2) (Ref. 23 of (78B2)). 200,000 km2 were affected mainly by salinization, and productivity has been reduced by a similar amount (Ref. 14 of (78B3)) (81B2). These data imply an overall reduction in productivity in the world's irrigated lands of 4% (cumulative) (78B2), (78B3). (50% of global irrigation capacity has been developed since 1950 (81B2)).

Waterlogging and salinization are reducing irrigation yields to varying degrees in virtually all of the 30 or so countries with over 5000 km2 of land under irrigation (76E1).

About 150,000 km2 in developing countries are experiencing serious reductions in crop yields because of salt buildup in irrigated soil (Ref. 9 of (92P1)). (la)

About 250,000 km2 (about 10% of the world's irrigated area) are suffering from salt buildup sufficient to reduce yields (Ref. 10 of (92P1)). (la)

About 10% of the world's irrigated area appears to be suffering from salinization serious enough to reduce yields. Another 30% may be moderately affected (Ref. 20, Chapter 8 of (94B1)). Additional amounts suffer from waterlogging (Ref. 9, Chapter 11 of (94B1)).

About 20% of the world's irrigated area suffers from salinization (97G1). Comments: This would be about 500,000 km2.

About 60% of the world's irrigated area needs upgrading to remain in good working order (90P1).

Large irrigated regions with serious salinity problems include (85D1):

Irrigated Land Damaged by Salinization ((89P1), Table 2) (90P1)
(Areas (Col. 2) are in units of 1000 km2.)

Region -|Area| % of irrigated land
India ~ |200 | 36%
China ~ | 70 | 15%
US~ ~ ~ | 52 | 27%
Pakistan| 32 | 20%
USSR~ ~ | 25 | 12%
Total ~ |379 | 24%
World ~ |602 |*24%

* (by extrapolation)

Irrigated Land Damaged by Salinization in the late 1980s (la)

Region - - -|Area(km2| % of irrigated land
India ~ ~ ~ | 70,000 | 17%
China ~ ~ ~ | 67,000 | 15%
Pakistan~ ~ | 42,000 | 26%
US~ ~ ~ ~ ~ | 42,000 | 23%
Uzbekistan~ | 24,000 | 60%
Iran~ ~ ~ ~ | 17,000 | 30%
Turkmenistan| 10,000 | 80%
Egypt ~ ~ ~ | ~9,000 | 33%
Subtotal~ ~ |281,000 | 21%
World Est.~ |477,000 | 21%

Source: F. Ghassemi, A. J. Jakeman, H. A. Nix, "Salinization of Land and Water Resources", University of New South Wales Press, Sydney (1995).

Part [A2] ~ Global Overview ~ Irrigation System Abandonment ~

Nearly 4 million acres (16,000 km2) of the world's irrigated farmland is lost to excessive salt every year. (Stanley Wood et al, report released by International Food Policy Research Institute (2/9/01) [satellite data]). (la)

The major problems of water resource development and operation are not technical, but relate to the socio-political situation (74F1). (The author (a hydrologist) is reasonable certain that most, if not all, the water projects he designed will meet the same fate as the ancient Middle-Eastern irrigation projects people now find buried in the sands.)

Recent research puts the current loss of world farmland due to salinization at 15,000 km2/ year (Ref. 60 of (94K1)). (la)

Globally, 20-30,000 km2/ year of irrigated lands may be coming out of production due to salinization. (Average irrigated-area expansion in recent years has been about 20,000 km2/ year) (Ref. 12 of (96P1)).

David Seckler, Director General of International Irrigation Mgmt. Institute, believes that global losses in irrigated areas may now exceed gains (97B2).

A Soviet soil scientist estimates that 60-80% of the world's irrigated lands are becoming saline and hence infertile (76E1). By his calculation, 200-250,000 km2 have been laid to waste over the centuries by mismanaged irrigation systems, and 2000-3000 km2/ year out of a total world-wide irrigated area of nearly 2 million km2 pass from cultivation due to waterlogging and salinity (76E1) (1978 Aspen Institute study in Ref. (82S1)).

Globally, salinization severe enough to remove land from production claims 15-25,000 km2/ year. (Ref. 52 of (96G2)). (la)

Soviet agronomist Victor Kovda estimates a global rate of irrigation system abandonment of 10,000-15,000 km2/ year (Ref. 12 of (90B1)). (la)

According to the UN-FAO and UNESCO, irrigated lands (globally) are being abandoned at a rate of 100,000 km2/ year, mainly due to secondary salinization and alkalization (88S1). Comments: This figure is way out of line -10,000 km2/ year is more likely. 100,000 sounds more like the total of degraded cropland abandonment + urbanization + irrigated land abandonment.

Aerial views of abandoned irrigation lands in the world's dry regions reveals vast expanses of glistening white salt-encrustation -useless land (Ref. 21 of (89P1)).

Ref. (87P2) references a study (not named) claiming that, globally, as much irrigated land is being taken out of production due to salinization and waterlogging as is being bought into production by new irrigation schemes.

About 20,000 km2/ year of irrigated land (globally) are lost to salinization (Ref. 29 of (94P1)). (la)

Waterlogging and salinization are sterilizing irrigated lands in the world at the rate of 10-15,000 km2/ year (85P1).

Salinization (of irrigated lands?) is spreading at a rate of 10-15,000 km2/ year on a global basis. This rate is about half the rate at which new land is being bought under irrigation (Ref. 10 of (92P1)).

Salinization (of irrigated lands?) may be spreading (globally) by as much as 10-15,000 km2/ year (Ref. 7 of (94P2)).

Ref. 18 of Ref. (79S1) estimates that 34 million km2 of arid lands in the world have been converted to desert by Man's destruction of vegetation and altering the water budget unfavorably. Ref. (79S1) estimates 9 million km2. Comments: The 34 million figure seems suspect - It is doubtful that there is that much desert today.

Part [A3] ~ Irrigation System Restoration ~

Rejuvenating salt-covered fields costs $100,000-200,000/ km2, and the efforts often fail. But salinization can be prevented with underground pipes to draw excess water off the field (95W1). Comments: In addition to underground drainage tiles, his also requires settling ponds for the salt, and the salt must ultimately be disposed of.

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SECTION (5-B) ~ Regional Degradation ~ Asia ~ [B1]~Asian Sub-Continent, [B2]~Central Asia, [B3]~Eastern Asia, [B4]~Mid-East, [B5]~Southeast Asia, ~

Part [B1] ~ Regional Degradation ~ Asian Sub-Continent ~

[B1a] ~ Irrigation System Degradation ~ Asian Sub-Continent ~ Bangladesh ~

Bangladesh irrigation systems do not suffer from salinization because the heavy monsoon rains wash away accumulated salt (81G1).

[B1b] ~ Irrigation System Degradation ~ Asian Sub-Continent ~ India ~

India has lost a total of about 70,000 km2 of once-irrigated area (93U1) (94F1) (99F2). (la)

In Haryana (an important breadbasket for India) 4000 km2 now have a water table up to within 3 meters of the surface - dangerously high. The high water table threatens to spread to 20,000 km2 (99P1).

In India, 20% of irrigated land suffers from salinization (99P1) (00W2).

Nonexistent or inadequate drainage seriously limits irrigated agriculture in India. A total of 85,000 km2 are damaged by salinity in India (70T1).

Over 60,000 km2 of irrigated lands have been severely damaged by waterlogging and salinity in India, out of a total Indian irrigated area of 400,000 km2 (76E1).

In India and Pakistan, an estimated 120,000 km2 (of irrigated lands?) have been degraded (85P1).

In Rajasthan in N. W. India, 24 km2 of irrigated land has been lost to salinization, and another 40.3 km2 are threatened (Ref. 27 of (78B2)).

Extent of degraded land in India, circa 1980 (88B1): 70,000 km2 are saline or alkaline, as compared to 130,000 km2 that are wind-eroded, 740,000 km2 that are water-eroded, and 350,000 km2 that are degraded forest land (out of India's total land base of 3,290,000 km2). Some 60,000 to 70,000 km2 of India's irrigated lands are affected by waterlogging, salinity and alkalinity (Ref. 45, 54 of (81G1)).

Salinity reduces crop yields on 200,000 km2 in India (90P1).

About 70,000 km2 have been abandoned as salty wasteland in India (90P1). (la)
Over 20,000 km2 of India's land undergoing salinization, have been abandoned (96G2). Comments: Note the disparity between the two estimates. (la)

[B1c] ~ Irrigation System Degradation ~ Asian Sub-Continent ~ Pakistan ~

In 1947, 400 km2/ year of Pakistan's irrigated land were going out of production due to waterlogging and salt buildup. Underlying water tables were rising steadily. Aerial photos (1952-1958) showed nearly 50,000 km2 of irrigated land were highly salty (99P1).

Salinity has cut yields on 21% of Pakistan's irrigated land (98H1).

About 25% of the 121,000 km2 of irrigated land in the Indus River Basin are encountering serious drainage- and salinity problems (74F1).

Waterlogging and salinity have reduced yields of major crops in Pakistan by 30% (92P1).

Because of the limited water in much of Pakistan, and the lack of adequate drainage systems, salinity has become a major constraint on crop production (70T1).

Pakistan's Mona Reclamation Area began irrigation in 1901. Close to 90% of the soils were waterlogged by the early 1960s. The problem is now being corrected by foreign-aid-supported reclamation (81B2).

In some districts in Pakistan, virtually all irrigated land is plagued with waterlogging and salinity (Ref. 28 of (78B2)) (76E1).

By 1960, waterlogging and salinity were severely affecting more than 20,000 km2 of the Indus Plain. As many as 400 km2/ year of new areas were being affected (76E1).

Of the 138,000 km2 of irrigated land in Pakistan, 21,000 are salt affected after a few years of irrigation (Ref. 387 of (88S1)).

Some 25,000-35,000 km2 in Pakistan have severe salinity problems. Another 25,000-45,000 km2 are moderately affected by salinity. Provinces of Sind and Punjab are areas most damaged (Ref. 62 of (81G1)). Yields on tens of thousands of km2 of Pakistan's irrigated cropland have been substantially reduced. Water tables are within 3 meters of the surface in more than 50% of Pakistan's irrigated area, and within 1.5 meters in some regions (Ref. 62 of 81G1).

Pakistan has 32,000 km2 of saline and alkaline agricultural land (90P1). (la)

Over 16% of Pakistan's agricultural land suffers from salinization (96G2).

Part [B2] ~ Irrigation System Degradation ~ Central Asia ~

[B2a] ~ Central Asia ~ Central Asian Republics (Also see USSR (former))

In the Central Asian Republics, salinization has caused cotton yields to fall from 280 tons/ km2 to 230, even with increased fertilizer (97G1).

In the Central Asian Republics, salinization reduced cotton yields from 280 to 230 tonnes/ km2 between the late 1970s and late 1980s, despite increasing use of fertilizer during this period (Ref. 52 of (96G2)).

The share of irrigated land that has been moderately to heavily affected by salinization is 35% in Tajikistan and 80% in Turkmenistan (all in the Aral Sea Basin) and 60% for the entire basin (Ref. 25, Ch. 8 of (94B1)) (91B2).

Land productivity in the Area Sea basin (in terms of cotton yields) has fallen 15% since its peak year in 1979 (Ref. 26, Ch. 8 of (94B1)).

Some 21% of Kazakhstan's irrigated area has undergone salinization (93M3). About 13% of Kazakhstan's irrigated area is waterlogged (93M3). (Kazakhstan's total area of irrigated cropland is 18,560 km2)

In Uzbekistan, 15,000 km2 of land have been abandoned during the past 30 years (500 km2/ year) due to high salinity (81F1). (To grow 1.0 kg. of cotton requires 660 gal. of water in Uzbekistan (81F1).) (This is in Chapter 8 - Conversions.)

Yield losses due to salinity: 30% in Uzbekistan, 40% in Turkmenistan, 30-33% in Kazakhstan, 18% in Tadjikistan, and 20% in Kirghizia (89K1).

Mainguet quotes Khakimov in her book as saying that the percent of moderate-to-severe salinization of irrigated areas in Central Asia are: Uzbekistan-60%, Turkmenistan-80%, Tadjikistan-35%, Kirghizia-40%, Kazakhstan-60-70% (89K1).

Turkmenistan expanded its irrigated area by 31% during 1990-94. Newly irrigated lands were not equipped with drainage, so the salt problem may worsen (99P1).

[B2b] ~ Irrigation System Degradation ~ Central Asia ~ USSR (former) (Also see Central Asia Republics) ~

About 25,000 km2 of the former USSR are salt-affected, most of them in irrigated deserts of Central Asia (Ref. 10 of (92P1)) (90P1).

Egorov et al found that in the USSR cotton belt, weakly- and medium-saline soils increased from 49.6% to 85% during 1945-1961 (71R1).

Some 12% of irrigated farmland (25,000 km2) (in Central Asia) is contaminated with salt or salt compounds due to poor drainage systems (89P1) (91F1).

Between 1975-1985 (in Central Asia), land area that has been affected by salinization nearly doubled (89P1) (Ref. 31 of (91F1)).

Irrigation ceased on 29,000 km2 (in Central Asia) during 1971-1985 (2100 km2/ year) (Ref. 14 of (89P1)). This was 25% of the new area bought under irrigation in that period (Ref. 11 of (90P1)).

Winds pick up 90-140 million tons/ year of salt from the dry Aral Sea bed and deposit it as far away as Byelorussia (91B2).

Winds pick up dried salt from the Aral Sea basin and deposit 43 million tons/ year of it on 150,000 km2 of cropland and pasture (Ref. 16 of (89P3)).

Nearly all of Karakalpakia's agricultural land is either salinized or waterlogged. (Karakalpahia is the republic around the southern portion of the Aral Sea (Pop.: 1.2 million)). The process began around 1958, therefore no more than 37 years were required to salinize (95H1).

In 1994, 28% of the Aral Sea Basin had salt buildup severe enough to lower crop yields by 20-50%, compared to 23% 4 years earlier (99P1).

Part [B3] ~ Irrigation System Degradation ~ Eastern Asia ~

[B3a] ~ Irrigation System Degradation ~ Eastern Asia ~ China ~

Salinity has cut yields on nearly 25% of China's irrigated land (98H1).

In China, 20% of irrigated land suffers from salinization (99P1) (00W2).

Waterlogging and salinity have reduced productivity on 15% of China's irrigated land (p. 71 of (95B3)).

China: About 20% of cropland suffers from salinization in northwest (Baotou and Tarim basin) and along the China coast (89H1).

Yields on at least 20% of the irrigated area of some major regions of China are reduced by salinity, and hundreds of thousands of km2 throughout the country are barren because of salt - some of it natural, and some of it left by farmers in the past (76E1).

During the 1950s and 1960s, salt-affected soil occurred in over 40,000 km2 of the North China Plain (85X1).

Over 9300 km2 of irrigated farmland have come out of production in China since 1980 (1160 km2/ year) (Ref. 14 of (89P1)) (90P1). Comments: 46% of China's 970,000 of croplands are irrigated (90W1).

Waterlogging and salinization are reducing productivity on 15% of China's irrigated land (94B2).

China has 70,000 km2 of saline and alkaline agricultural land (90P1). (la)

Part [B4] ~ Irrigation System Degradation ~ Middle-East ~ [B4a]~Iraq, [B4b]~Arab States, [B4c]~Iran, [B4d]~Israel, [B4e]~Jordan, [B4f]~Syria, [B4g]~Turkey, [B4h]~Saudi Arabia, ~

Rhoades (1998) estimated that, in the Near East Region, 83.4 million hectares (834,000 km2) of land (not necessarily arable land) are salt-affected. (Rhoades J. D. (1998): Sustainability of Irrigation: An Overview of Salinity Problems and Control Strategies. Proceeding of the 1988 Advanced Short Course on Sustainable Use on Non-Conventional Water Resources in the Mediterranean Region, International Center for Agricultural Research in the Dry Areas (ICARDA), Aleppo, Syria.)

Grain yields declined in most Middle East countries in the first half of the 1960s due to (70T1):

[B4a] ~ Irrigation System Degradation ~ Middle East ~ Iraq ~

Roughly 75% of Iraq's irrigated land suffers from salinity caused by inappropriate water management practices (03I1).

Barley, more salt-resistant than wheat, is increasingly the predominant cereal in southern Iraq, even though farmers would prefer to plant wheat. This pattern holds true also for ancient- and Islamic Mesopotamia (74G1).

Mesopotamia agricultural systems had the capacity to feed 17 million people when Babylon flourished. In the many centuries since that time, the lower valleys of the Tigris and Euphrates Rivers have not sustained more than 3 million people (70W1).

Some 20-30% of Iraq's potentially irrigable land is unusable (76E1), i.e. has been converted to desert by salinization of irrigation projects (79S1). Comments: Turkey's GAP project is decreasing the water supply to Iraq.

Viewed from the air, vast areas of southern Iraq glisten with salt like new-fallen snow (85S1) (76E1).

[B4b] ~ Irrigation System Degradation ~ Middle East ~ Arab States ~

Over 10,000 km2 of irrigated land in the Arab states region suffer from salinization (96M2). (la)

[B4c] ~ Irrigation System Degradation ~ Middle East ~ Iran ~

Officials say that the majority of irrigated lands in Iran are saline, and crop yields are depressed by the toxicity of salt (Ref. 13 of (76E1)).

More than 50% of irrigated soils in Iraq and Iran are affected by secondary salinization (Ref. 388 of (88S1)).

Salinization affects 160,000 km2 of Iran's agricultural land, and has forced over 80,000 km2 out of production (96G2). (la)

[B4d] ~ Irrigation System Degradation ~ Middle East ~ Israel ~

Israel faces serious nitrate-pollution and salinity in its coastal aquifer. Continued water shortages and rising fuel prices may make the Negev's agricultural system uneconomical (78E1). Comments: Nitrate pollution is often a result of excess dosage of organic and/or chemical fertilizer.

[B4e] ~ Irrigation System Degradation ~ Middle East ~ Jordan ~

In 1970, less than 10 years after Jordan initiated irrigation agriculture in the Jordan River Valley, salt and sogginess (water logging) were affecting 12% of the project area. The extent of the damage was increasing every year (76E1).

[B4f] ~ Irrigation System Degradation ~ Middle East ~ Syria ~

The FAO reports of salinity in the Euphrates Valley of (Ref. 20 of (88S1)):

[B4g] ~ Irrigation System Degradation ~ Middle East ~ Turkey ~

More than 25% of Turkey's alluvial soils are affected by salinity (88S1).

[B4h] ~ Irrigation System Degradation ~ Middle East ~ Saudi Arabia ~

During the late 1980s, Saudi Arabia launched a plan to become self-sufficient in wheat. By tapping a deep underground aquifer, the Saudi's raised grain output from 0.3 million tons in 1980 to 5 million tons in 1994. The aquifer could not sustain large-scale pumping and, by 2003, the wheat harvest had fallen to 2.2 million tons (04B1).

Part [B5] ~ Irrigation System Degradation ~ Southeast Asia ~

[B5a] ~ Irrigation System Degradation ~ Southeast Asia ~ Vietnam ~

The area in Vietnam used for rice paddies has doubled over the past 20 years, but one third of the area has deteriorated, reducing rice yields (01U1). Comments: This could reflect the usual degradation of tropical soils, or it could reflect salinization.

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SECTION (5-C) ~ Regional Degradation ~ Africa and Australia ~ [C1]~
Africa, [C2]~Australia, ~

Part [C1] ~ Irrigation System Degradation ~ Africa ~

[C1a] ~ Irrigation System Degradation ~ Africa ~ North Africa ~

Irrigated agriculture is rather non-productive in the 2000 km2 of irrigated croplands of the arid- and desert zones of North Africa. Lack of drainage causes excessive salt deposits or hydromorphology (waterlogging?) or both (70L1).

[C1b] ~ Irrigation System Degradation ~ Africa ~ Egypt ~

In Egypt, half of irrigated croplands suffer from salinization (Stephen Leahy, "Environment: Millions Flee Floods, Desertification", I.P.S., Brooklin, Canada (10/12/05)). (su4)

Over 10,000 km2 of Egypt's irrigated land suffer from salinization (96M2).

Half of all irrigated land in Egypt is experiencing salinization enough to show reduced yields (90P1).

Over the past 22 years, Egypt has reclaimed 3,600 km2 south of the Nile Delta, but 65 km2 have relapsed into barren wastes. The remainder can be operated only through massive subsidies (77A1).

Egypt's Aswan Dam made possible the cultivation of over 3,600 km2 of former desert, but 810 km2 of this are once again barren (due to salinity?), and the rest are cultivated at a loss (77U1).

Before Aswan Dam, annual flooding washed salt away. After Aswan Dam, irrigation replaced annual flooding, so Egypt's Nile Delta salt levels are rising rapidly. Before dams, seasonal floods were effective in carrying salts to the rivers. Today the salt is being stored within river basins, and salt levels in irrigated soils are rising (87P1).

Ref. (76E1) describes salinization problems of Egyptian irrigation systems outside the Nile flood plain. Waterlogging and salinity are becoming major problems. The Aswan Dam has contributed to the salinization problem (76E1).

Waterlogging and salinity in Egypt's Nile Delta have reduced yields of major crops by 30% (92P1). Cultivated land in the Nile Delta (100% irrigated) grows increasingly saline, since annual flooding no longer flushes out evaporitic salt (Ref. 40 of (93S1)).

Nearly 50% of Egypt's Delta is affected by salinity, alkalinity, and waterlogging. Rising water tables in Egypt's Western Desert are causing salinization (89E1).

Some 75% of Egypt's Delta topsoil is non-saline, 15% moderately-to-highly saline; 10% is very highly saline (89E1).

Part [C2] ~ Irrigation System Degradation ~ Australia ~

In irrigation systems in the Ord River basin of Western Australia, the water table has risen 15 meters and is rising by 0.5 meters/ year (01P1). Comments: When the water table rises to the root zone of plants, salinization becomes a serious problem. The system apparently lacks a system of underground drainage tiles to carry off the water.

The majority of Australia is hot desert (01F1). Total Australian land stock is 7.7 million km2. Less than 300,000 km2 (less than 4%) of Australia's land are of good, or very good, quality in terms of broad scale cropping potential (02C1).

Problems with dry-land salinity in Australia affect 25,000 km2, with 170,000 km2 of the 300,000 km2 likely to be destroyed by salinity by 2050 based on current trends (01F1) (02C1).

Salinity ravages key waterways and agricultural zones in Australia, according to the new Australian State of the Environment report by over 100 scientists, government agencies and private sector groups. Committee chairman Bruce Thom said, "Although there has been some improvement since 1996, as a nation we are not sustainable in environmental concerns." Salinity is increasing in the Murray-Darling basin, which provides 40% of Australia's agricultural value. Salinity poses a risk to 57,000 km2 of land in 2001, and is expected to impact 170,000 km2 by 2050 ("Salt Ravages Australia's Environment", Canberra Times, 3/20/02).

In Southwestern Australia, 4400 km2, once used as cropland or pasture, are now salt-affected - a +500% increase in salinated area since 1955. Virtually all secondary soil salinity is found in the rain-fed wheat belt of Western Australia where 130,000 km2 of indigenous woodlands were cleared in the 20th Century (90C1).

About 800 km2 in the valley of Australia's River Murray and in northern Victoria are affected by secondary salinity and alkalinity (Ref. 389 of (88S1)).

Over 45,000 km2 of Australia's dry-lands -10% of all croplands and more than 8% of irrigated area - are affected by salinization. Area affected by dryland salting doubled in size during 1975-89 (96G2).

SECTION (5-D) ~ Regional Degradation ~ North and South America ~ [D1]~US, [D2]~US -Western, [D3]~US- Great Plains, [D4]~South America, [D5]~Central America, ~

Part [D1] ~ Irrigation System Degradation ~ United States ~

In the US, 20% of irrigated land suffers from salinization (99P1) (00W2).

About 21% of irrigated US cropland is fed by drawing down water tables (USDA data) (91B3). (la)

About 25% of US irrigated land suffers from some degree of salinization or waterlogging (78D1) (82S1).

Salt accumulation is lowering crop yields on 25-30% (50,000 km2) of US irrigated land (92P1).

Bower and Foreman estimated that 25% of irrigated soils in the US were salty or alkaline to the point where productivity was lowered (71R1).

Dry cropland areas in the western US where production has ceased or is significantly reduced due to increased salinity: 600-800 km2. This area is growing at 10%/ year (80C1).

Some 20-25% of all US irrigated land (40,000 km2) suffers from salt-caused yield reductions (Ref. 2 of (85E1)). (la)

Maps showing US irrigation problem areas (salinity and/or waterlogging) in 17 western US states are shown in Ref. (82S1) and in Ref. (85E1).

Some 25-35% of irrigated western US croplands have excessive salinity (83B1). Salt buildup lowers crop yields on 25-30% of irrigated lands (90P1).

Part [D2] ~ Irrigation System Degradation ~ US- Western ~

[D2a] ~ Irrigation System Degradation ~ US ~ Western ~ California ~

Some 25% of California's irrigated land has undergone moderate- to heavy salinization (91B2).

Of California's 34,800 km2 of irrigated land, 18,200 km2 are affected by salinity or sodicity (85G1). Croplands damaged by salinity are expected to increase from 18,200 to 21,000 km2 by 2000 (Ref. 8 of (85G1)).

The amount of water-storage capacity lost through aquifer compaction in California's Central Valley is over 40% of the combined storage capacity of all human-made reservoirs in California (00S1).

Some 1620 km2 of irrigated farmlands in San Joaquin Valley California are affected by high, brackish water tables (81S3), (81S1), (83B1) resulting in a 10% reduction in productivity since 1970. (Ave. rainfall = 14" in the north, and 5" in the south.) By 2080, 4,500 km2 of San Joaquin farmlands will become unproductive unless sub-surface drainage systems are installed (81S1).

Trends in salinity in irrigated lands in California's San Joaquin Valley indicate that in two decades, 3,000 km2 will be affected (82S1). San Joaquin Valley crop yields have declined 10% ($31.2 million) since 1970 because of high saline water tables. Losses are expected to increase to $321 million/ year if action is not taken (Ref. 19 of (85E1)).

Not far below the surface of California's San Joaquin Valley and Imperial Valley (like the Tigris-Euphrates Valley) is a tight layer of material that blocks water passage. Hence saltwater builds up. When it meets the roots of plants, salt is drawn up to the surface, destroying the irrigation system (81S1).

Imperial Valley (Southern California) experienced about 90% of the agricultural damage from salinity in the US portion of the Colorado River Basin. Imperial Valley is under pressure to give some of its water to nearby cities (87P1). The Imperial Dam on the Lower Colorado River sends about 95% of the water flowing into it to California and to Wellton-Mohawk (AZ) for irrigation. When Wellton Mohawk opened in 1961, the average salinity of the water delivered by the Colorado to Mexico doubled to 1500 ppm., causing Mexican crop failures and protests (87P1).

A recent study in California's Grand Valley (which puts 0.5 million tons of salt into the Colorado River yearly) found that 85% of the water reaching rivers was irrigation water, carrying salt from marine shales that lie under local farms (87P1).

Some irrigation problems (water-table rises, salt-buildup) and solutions (improved drainage) in Southern California's Imperial Valley are described in Ref. (56T1).

[D2b] ~ Irrigation System Degradation ~ US ~ Western ~ New Mexico ~
In New Mexico's Pecos River, salinity increases from 760 to 2020 mg./liter over 30 miles (85E1).

Part [D3] ~ Irrigation System Degradation ~ US ~ Great Plains ~

[D3a] ~ Irrigation System Degradation ~ US Great Plains ~ Colorado ~

In Crowley County Colorado, salt crusts are visible on a number of irrigated fields. Urban areas (Colorado Springs, Pueblo) are buying water rights, so irrigation systems are being abandoned (Ref. 331 of (81S1)).

Arkansas River salinity in Colorado increases from a trace to 2200 mg./ liter over 120 miles (85E1). (This is usually due to seepage and return-flow from irrigated land.)

[D3b] ~ Irrigation System Degradation ~ US Great Plains ~ Texas ~

Rio Grande River salinity increases from 870 to 4000 mg./ liter over 75 miles (Ref. 5 of (85E1)). (This is usually due to seepage and return flow from irrigated land.)

Part [D4] ~ Irrigation System Degradation ~ South America ~

[D4a] ~ Irrigation System Degradation ~ South America ~ Argentina ~

A United Nations survey found that 20,000 km2 of irrigated land in Argentina have declined in productivity due to salinization and alkalinization (78B2).

About 20-30% of the agricultural lands in Argentina's Patagonia region have been damaged by salt accumulation (76E1).

Some 50% of the 400 km2 irrigated in the 19th century in Argentina have undergone salinization (88S1).

[D4b] ~ Irrigation System Degradation ~ South America ~ Brazil ~

In Northeast Brazil, at least 50% of irrigated land is affected by waterlogging and salinity. Yields on some irrigated fields are lower than before irrigation (76E1).

Brazil, Sertao (nearly 3/4 of area of the Northeast Brazil): Irrigation leads rapidly to salinization of soils. Water supplies have average salinity of 500 mg./liter+ (85L1).

[D4c] ~ Irrigation System Degradation ~ South America ~ Peru ~

The lack of complete studies for irrigation projects in Peru has caused increased drainage and salinity problems on the coast. This is the main problem facing irrigation agriculture on Peru's coast, and affects 2500 km2. In all irrigation projects on the coast, drainage- and salinity problems have developed within a few years after the beginning of irrigation. Documentation supporting this is presented for the Santa Rosa- and several other irrigation projects (70C2).

A UN survey found that, of 8000 km2 of irrigated land in the coastal desert of Peru, 3000 km2 are affected by poor drainage and salinization (Ref. 27 of (78B2)).

Over 2000 km2 along Peru's coast (almost a third of the cultivated area) suffers from salinity and rising water tables (76E1).

Nearly all of Peru's irrigated alluvial soils show salinity/ alkalinity (Ref. 64 of (88S1)).

Part [D5] ~ Irrigation System Degradation ~ Central America ~

[D5a] ~ Irrigation System Degradation ~ Central America ~ Mexico ~

Constraints on irrigation water supplies in the Rio Grande river basin are causing food production to fall. In 1996 the Mexican government was forced to import almost $2 billion worth of grain to alleviate growing hunger, with much of the grain going to northern Mexico (Ref. 24 of (02K2)).

Salinization reduces Mexico's crop output by one million tons of grain/ year (90P1).

Some 10% of Mexico's irrigated (cropland?) area have undergone salinization (03K1).

[D5b] ~ Irrigation System Degradation ~ Central America ~ Haiti ~

FAO researchers identified salinity as the reason why Northwest Haitian farmers have had to change from peanuts and beans to cotton to cactus and thorn brush (76E1).

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