Transcript Have we learned the lesson of history

History of Irrigation 1
Ancient irrigation
At least 6 major
irrigation based
civilizations arose
between 2000 and 6000
years ago:
In Mesopotamia:
Sumerians, Babylonians
and Assyrians
The Egyptians formed
the longest lasting
irrigation society
The Indus Valley in
present day Pakistan
The Yellow River Basin in
China
Harappan Civilization
The Indus Valley
Length: 3.200 km
Originating in the
Tibetan Plateau
Civilizations:
Harappan c. 3300–1300 BC
Indo-Aryans c.1700 - 600 BC
The Shaduf
The people of Indus prospered on the foundations of an
agriculture based system of irrigation and fertility, maintained
by silt-bearing floods
Indus valley
 Ancient irrigation history using a network of
inundation canals aligned with natural
drainage canals
 Based on maintaining fertility by silt bearing
floods
 The canals flowed for 4-5 months during
the monsoon – then as drainage canals
 They did not cause water logging
Hohokam - Arizona
 Later irrigation based
cultures arose in the
western hemisphere,
central Mexico, Peru
and the US Southwest
 All reflected a
common threat of
vulnerability and
environmental
deterioration.
 Hohokam A.D. 300900 build the first
large-scale irrigation
in the US
Hohokam - Arizona
 Advanced canal network along the Gila
River dug out over centuries
 The biggest canal 30 feet wide, 7 feet deep
and 8 mile long enough to irrigate 8.000
acres
 Could tap the entire spring run-off,
channeling it to their fields high above the
riverbed
 As in Mesopotamia this resulted in increased
salinity and finally to abandonment of the
area
Irrigation’s modern era
Major irrigation sources
The Indus Valley:
The Nile
China:
United States:
Groundwater:
Indus River
Yellow River
Yangtze River
Colorado River
Columbia River
Ogallala Aquifer
Edwards Aquifer
Colonization - technology
 Colonial powers wanted increase in
production and export to mother country
 Change to European technology allowed
bigger dams and longer and bigger canals
 Technology implemented in a different
environment, causing problems
 In England big and straight canals not a
problem, but in Pakistan and India problems
with siltation and erosion of canals a major
issue
Colonization - technology
 The new irrigation technology disrupted
many local small-scale irrigation systems
which had functioned for centuries:
 Haveli system:
 Rainwater during the wet season was held in
fields by earth embankments 2 to 12 hectares.
 At beginning of dry season they drain the fields
and plant the crop – water enough in soil
profile to grow the crop
 Tank (dugout) system
 Store rainwater and run-off from wet seasons
 2 million tanks in India irrigate 3.5 mil. ha
The Indus - Pakistan
Located on the river Indus 50 miles northwest of Islamabad. Was
completed in 1974. It is the world’s largest earth and rock-filled
dam. Sedimentation has reduced its capacity by 30%
The Indus in Pakistan
 With the Tabela Dam on the Indus and
Mangla Dam on the Jhelum river and
associated canal system the Indus Basin
Irrigation system became the world
largest contiguous irrigation network – 14
million hectares
 Accounts for 6% of worlds irrigated area
The Nile
River Atbara
The White Nile
The Blue Nile
The Nile
 Irrigation’s greatest challenge: Sustain tens of
millions of people in a land that gets virtually
no rain
 A narrow strip of green and life in a sea of
desert
 This strip and the fertile delta has supported
Egypt’s civilization for millennia
 But the type of irrigation that sustain its people
today is markedly different from its past –
driven by population growth
The Nile:
Length 6.700 km
Source:
The White Nile: Lake Victoria, Uganda
The Blue Nile: Lake Tan, Ethiopia
River Atbara
Major Dams:
Roseires Dam
Sennar Dam
Aswan High Dam
Owen Falls Dam
Owens Falls in Uganda
Uganda, as Ethiopia, is predominantly using their dams on
the Nile for hydropower and not irrigation. However the
potential is there – could cause conflict with Egypt
Sennar Dam in
Sudan
Build in 1920,
45 m high and
3 km long
Supply irrigation
water to 60% of
Sudan’s agriculture
The Nile
 Prior to 1800, cultivated area and population peaked
about 100 A.D. at which time Egypt supplied the
Roman empire with vast quantities of grain
 Flood based irrigation only supported crop production
1/3 of the year - one winter crop
 Build large flat-bottomed basins for growing crops
along the river bank
 They sluiced water into these basins when the river
was in flood using simple gate structures
 Water left on fields 40 to 60 days and then drained
back into the river downstream
 Plenty of water so salt never built up in the soil
The Nile
 The flow in the canals was strong enough to prevent
siltation. Siltation in the basins beneficial as fertilizer
 Ditches and canals were short and irrigation systems
very local
 Early 19th century the population exploded and crop
production started to fall short of needs
 In 1861 a series of diversion dams build across the
Nile north of Cairo followed by a number of other
dams. Aswan Dam completed by British engineers in
1902, expanded twice by 1934
 This allowed two to three crops a year and
fundamentally changed irrigation in Egypt
The Nile
 The River did not flood anymore – irrigation
depends on perennial canal irrigation only
 Soil constantly moist all year round
 Even with low salinity content this change has
caused a build up of salt as water evaporates
 In 1928 water scholars warned about the threat of
salinization of the land and that the big dams would
hold bag the silt that had replenished the fertility of
the floodplain for millennia
 Trend in cotton yields already suggested decline in
soil fertility
The Blue Nile flowing down from the
Ethiopian Plateau rainy season April to October
The Aswan High Dam
transformed Egypt’s irrigated agriculture from a
Resolution from the International Space Station
seasonal system to a perennial one
The Nile Delta
The Delta is sinking:
Northeast corner by 5 mm a year
Northwest corner by 3 mm a year
A former delta village is now 2 km out to sea
The Yellow River, China
Yellow River
Animaqing Peak
Bayabkala Mountain
Animaqing Mountain
Bayankala Mountain
Hetao Plain
Dari Yellow River
Hetao Irrigation Area
Heisan Gorge
Mountain Grassland
Hukou fall
The Flood
 In 1949 irrigation was
depressed after the war
 Still 19.5 mil ha under
irrigation, about the same
as India at the time
 Millions of peasants set to
work on repairing and
expanding systems
 Over next 35 years build
more than 83,000
reservoirs, repaired or
constructed 177,000 km
of dikes, sunk 2.3 mil
wells and brought 29 mil
more hectares under
irrigation
 Peoples Victory Irrigation
district was completed in
1952
 The first of more than
100 irrigation districts in
Henan and Shnadong
provinces over next
decade
 By 1990 4.4 mil hectares
irrigated
 Nearly a third as much
as the Yangtze River
Great Man-Made River Project
Started in 1980 - the Great ManMade river project is the largest
engineering scheme currently
being carried out in the world.
The 4 meter diameter pipe is abou
1600 Km long and transfers 6.5
million cubic meters of water/day
Rapid development of coastal
Areas and increased population
Have placed a severe strain on
the coastal water supply.
Some now attributes the drying
of the Ubari Lakes and various
water holes to the side effect of
the project
Colorado River Basin
 Competition for water severe –
constant litigation over water
 Without Colorado River water no
Imperial Valley
 Flowed into gulf of
Mexico, but not anymore
 1922 Colorado River
Compact - 7 states
 1928–36 construction of
Hoover Dam
 First high span dam
major accomplishment
 Followed by many others
 Parker Dam supply LA
and San Diego
 1963 US Supreme court
made explicit allocations
to each state and Indians
 Prompted the Central
Arizona project mountain tunnel and
aqueduct to supply
Phoenix and Tucson
Columbia River
Basin
 Unique hydrology and
gradient
 Second largest run-off in US
 Given much of the wealth to
the N.W. - Minerals and
fertile soils
 Half the hydroelectric energy
in the US
 Irrigate 7.8 mil. acres – arid
part of Washington, Oregon
and Idaho: wheat, corn,
potatoes, peas, alfalfa etc
Columbia River basin
 Columbia Basin Project turned the desert area of
central Washington into another US bread basked
 Irrigates 0.5 mil. acres and can expand to 1.1 mil
 The biggest hydroelectric power capacity in the US
 Individual irrigation authorities regulate timing and
volume of extraction locally
 But the cumulative impact is felt downstream
 Some areas more affected than others – The effect on
Snake River more severe than main stream
 Minidoka project – thousands of miles of canals supply
1.1 mil. acres
Groundwater recharge 1960 - 1990
Only 2.5% of the water available is freshwater. Of that
approximately 68.9% is locked in glaciers and permanent
snow cover, and 30.8% is groundwater – many countries
therefore rely on it. Only 0.3% is in rivers and lakes
Groundwater
An important resource
2 billion people depend on it for drinking
40% of the worlds food is produced by it
But little attention was given to it until recently –
out of sight out of mind
 Pollution and depletion of rivers are obvious and
reported in media, while depletion and pollution
of groundwater can be hidden for years
 Also provide ‘base flow’ for many rivers
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Groundwater Aquifers:
 North America: Ogallala Aquifer
The Edwards Aquifer
The High Plain Aquifer
 South America: Amazon Basin Aquifers
Puelches Aquifer
 Africa:
Nubian Sandstone Aquifer
The Northwest Sahara Aquifer System
Congo Basin
 Asia:
Erdos Basin Aquifer
Huang-Hai-Hai Plain Aquifer
Indo-Gangetic-Brahmaputra
 Arabien Shield: Mukalla Aquifer
Umm-Er-Radhuma Aquifer
 Australia:
Great Artesian Basin Aquifer
Populations in mega-cities
depending on groundwater
Typically groundwater would provide at least 25 % of the
water supply to such a city.
Groundwater for towns
 Even more widespread in smaller towns
and rural communities
 E.g. in the Huang-Huai-Hai aquifer
system in China: 160 mil. people
 1/3 of Asia’s drinking water
 In the US more than 95% of the rural
population
Extent of groundwater used for
drinking water in Asia and Latin
America