Irrigasjon, en produskjonsfaktor og globalt problem
(agrohydrology)
Johannes Deelstra
Bioforsk – Jord og Miljø
1432 Ås
•Wageningen Agricultural University, The Netherlands
•Irrigation and Drainage
•Kenya, FAO, Associate Expert, 79 - 81, irrigation
•Egypt, Dutch bilateral cooperation, DRI, drainage, 82 - 87
•Norway, Bioforsk, 1987
Working areas
Environmental monitoring, nutrient runoff, sediment losses, small
agricultural dominated catchments, winter erosion, agrohydrology,
Where
The Netherlands, Colombia, Kenya, Egypt, Mozambique, Eritrea,
Sudan, Estonia, Latvia, Lithuania, Russia, Guatemala, Tanzania,
Nicaragua, Norway.
Main themes
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•
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Hydrosolidarity
Crop water requirements
Irrigation systems
Efficiencies
Cases studies/examples
Hydrosolidarity
Water is a strategic resource in socio-economic development. Because of its
mobility, water links three different water dependent security dimensions:
• water security,
• food security and
• ecological security.
Hydrosolidarity
To balance water requierement
1) upstream/downstream catchment scale
2) local scale allocation
For the upstream/downstream catchment scale, balancing is needed
between water impacting activities upstream and water dependent
phenomena downstream. One example is between consumptive
(evaporative) use upstream, and flow dependent human needs and
aquatic ecosystems downstream.
Another example is between pollution loads added upstream, and quality
dependent ecosystems downstream.
For the local scale allocation, balancing is needed locally, such as between
water for city supply and water for irrigation.
Hydrosolidarity
Runoff production
The amount of precipitation over an area that ends up supplying the river
system depends on many factors. These include
1.
2.
3.
the permeability of the land, geological setting
land cover and consumptive water needs,
evaporative demand/climate.
Hydrosolidarity
Blue and green water flows in the catchment
context
Water use to support plant growth - the so-called green water flow.
Blue water = precipitation – green water = total runoff in the river system
(surface runoff, subsurface runoff, groundwater contribution)
Hydrosolidarity
Excess precipitation – green water use = runoff returning to open water
systems, can lead to the runoff of plant nutrients/pesticides to open
water systems.
Much of the water diverted to irrigate fields is used in plant
production processes (evaporation/green water). Only part of the
irrigation water applied to crops is involved in crop production. Excess
(drainage/leakage) returns to the river system, containing salt and
plant nutrients
A large part of the blue water diverted to cities and industries returns to
the river system as polluted return flow (treated/non-treated sewage)
Water returning to the river can be used downstream (reuse of
drainage water). Either directly when quality is still good or mixed with
“fresh”, upstream blue water.
Hydrosolidarity
Human activities and ecosystems depend on the same water
– the precipitation over the catchment. Their needs are only
partly compatible. This makes trade-offs necessary.
Integrated Water Resources Management
(IWRM)
Water requirements to grow agricultural crops green water requirement.
How to calculate crop water requirements
transpiration + evaporation
Crop water requirements
• Determined by;
Climatic conditions
Crop type
Crop water requirements, cont’d
• FAO method described in/making use of
Crop evapotranspiration - Guidelines for computing crop water
requirements(1998) - FAO Irrigation and drainage paper 56
Crop water requirements, (rev.) 1977 - FAO Irrigation and drainage
paper 24
CROPWAT - a computer program for irrigation planning and
management, (1992) - FAO Irrigation and drainage paper 46
Crop water requirements
• In the crop coefficient approach the crop
evapotranspiration, ETc, is calculated by multiplying the
reference crop evapotranspiration, ETo, by a crop
coefficient, kc:
ETc = kc ETo.
where
ETc crop evapotranspiration [mm d-1],
kc crop coefficient [dimensionless],
ETo reference crop evapotranspiration [mm d-1].
Crop water requirements
(ETc = kc ETo)
• Reference crop evapotranspiration
The evapotranspiration rate from a reference surface, not
short of water, is called the reference crop
evapotranspiration or reference evapotranspiration and is
denoted as ETo.
The method requires (called FAO Penman-Monteith).
radiation,
air temperature,
air humidity.
wind speed data.
Crop water requirements
(ETc = kc ETo)
• The crop coefficient, kc, is basically the ratio of the crop ETc to
the reference ETo, and represents an integration of the effects
of four primary characteristics that distinguish the crop from
reference grass.
Crop height.
Albedo (reflectance) of the crop-soil surface. The albedo is affected by
the fraction of ground covered by vegetation and by the soil surface
wetness.
Canopy resistance. The resistance of the crop to vapour transfer is
affected by leaf area (number of stomata), leaf age and condition,
and the degree of stomatal control.
Evaporation from soil, especially exposed soil.
Crop water requirements, cont’d
(ETc = kc ETo)
• Example of crop water requirement calculation scheme for
beans
Crop water requirements influenced by management and environmental
conditions
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•
•
•
•
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soil salinity,
poor fertility/limited application of fertilizers,
the presence of hard or impenetrable soil horizons,
the absence of control of diseases and pests and.
poor soil management.
other factors like.
ground cover,
plant density.
the soil water content. The effect of soil water content on ET is
conditioned primarily by the magnitude of the water deficit and
the type of soil. On the other hand, too much water will result in
water logging which might damage the root and limit root water
uptake by inhibiting respiration.
Irrigation scheduling/irrigation rotation
• water is distributed to farmers according to a fixed schedule,
determined by soil type, crop type, climatological conditions,
irrigation system
light soil, shallow rooting crops, high water demand
frequent water delivery
medium textured soils, deep rooting crops
less frequent delivery
Irrigation scheduling,
example
TAM = rooting depth(mm) x (PF(2) – PF(4.2))
RAM = that part which is easy accesible by plant roots, it is said
that this is 50 % of TAM
Irrigation water application
when practising surface irrigation
when designing water delivery system
• How much water is applied to the farmer? How much water can
the farmer handle?
as a rule of thumb one can say that a farmer can handle
approximately 25 l/s
Irrigation water application
when practising surface irrigation (cont’d)
• How does one get a quick impression of water requirements and
irrigation potentials given a water resource?
irrigation water requirement based on ET0 = 8.64 mm.day-1
(10000 x ET0) /(24 x 3600) = 1 l.s-1.ha-1 (24 hrs . day-1)
2 l.s-1.ha-1 with an overall irrigation efficiency of 50%
4 l.s-1.ha-1 when irrigating 12 hr . day-1
supply/requirement = total area
Irrigation efficiencies
1. Evaporation from the water surface
2. Deep percolation to soil layers underneath the canals
3. Seepage through the bunds of the canals
4. Overtopping the bunds
5. Bund breaks
6. Runoff in the drain
7. holes in the irrigation canal bunds/maintenance
econ = 80%
eappl = 80%
eproj = ea x ec = 64%
Furrow irrigation
http://www.fas.usda.gov/pecad/highlights/2001/08/Turkey_Crop_Tour_fi
les/ataturk/furrow.jpg
http://food.orst.edu/images/FRUITVEG/IRRIGATION/furrow(b)
.jpg
http://www.ag2020.net/2001/32-4/32-4_FURROWIRR_6-14-01.JPG
application efficiency;
low to moderate
Furrow irrigation
infiltration, example of application efficiency
http://www.ianr.unl.edu/pubs/irrigation/g1338.htm
Border irrigation
www.fao.org/docrep/S8684E/ s8684e0h.jpg
application efficiency; low to moderate
Basin irrigation
www.fao.org/docrep/T0231E/ t0231e02.jpg
application efficiency;
low to moderate
www.mdbc.gov.au/naturalresources/ about/images/arial.jpg
http://www.panasia.org.sg/dec_fut/nepal/image/am1.gif
Flood irrigation
www.lahontan.org/ difference.htm
http://www.earthwake2001.org/kbphotos/irrig_images/floodirrig.jpg
application efficiency;
low to moderate
sprinkler irrigation methods
www.florence.ars.usda.gov
www.sce.ait.ac.th/.../wem/ 2001/~asadi/Title.html
application efficiency; moderate - good
salinity can be problem
Drip or trickle irrigation
bioag.byu.edu/aghort/aghort100/ irrigati.htm
application efficiency; good
salinity can be problem
Spate irrigation
qi  qi 1
Farmers in the low lying area of
Sheeb(Eritrea) near the Red Sea coast
use the sudden amounts of water to
irrigate their land in a system known
as spate irrigation. After being
diverted, the water sinks into the deep
soil and provides the crops, sorghum
and maize, with moisture for the rest
of the growing season. The problem is
that the water sometimes flows with
such a force that the dams in the wadi
(agim), which are used to divert the
water to the fields, are regularly
washed away.
Supplemental irrigation/
water harvesting
• In the arid and semi-arid belts of the world where rainfall is
limited and very irregular and often leading to immediately to
crop failure.
• Irrigation is often the logic solution but water scarcity and the
high cost of irrigation infrastructure are major handicaps.
• Water harvesting is a proven technology to increase food security
in drought prone areas. Erosion control and recharge of ground
water are additional advantages of water harvesting techniques
• Water harvesting and supplemental irrigation for improved water use efficiency in
dry areas
Published by the International Water Management Institute (IWMI), through
the Systemwide Initiative on Water Management (SWIM), by Theib Oweis,
Ahmed Hachum, and Jacob Kijne (1999).
Irrigation in arid and semi arid areas
Rainfall deficit but still a need for subsurface drainage
systems
Drainage systems in agriculture
(you find them everywhere)
salinity control
surface water control
longer growing season
better established root system
water table control
erosion control
Drainage systems in agriculture
One of the most immediate benefits to subsurface drainage is an increase in crop
yield. (prevent water logging, extend growing season, erosion control)
Subsurface drainage is widely used to drain excess water from fields to reduce
waterlogging/combat salinity.
Waterlogging and high-water tables caused by irrigation are the main reason that
good agricultural land becomes salty wastelands.
Subsurface drainage often the only solution to prevent salinity or to reclaim salt
effected land.
Subsurface drainage leads to loss of plant nutrients from the rootzone
Salinisation process
A soil may be rich in salts because the parent rock from which it was
formed contains salts. Sea water is another source of salts in low-lying
areas along the coast. A very common source of salts in irrigated soils is the
irrigation water itself. Most irrigation waters contain some salts.
After irrigation, the water added to the soil is used by the crop or evaporates
directly from the moist soil. The salt, however, is left behind in the soil. If
not removed, it accumulates in the soil; this process is called salinization
Very salty soils are sometimes recognizable by a white layer of dry salt on
the soil surface.
Drainage installation
Subsurface drainage - eutrophication
• Due to drainage – leakage of plant nutrients (nitrogen, phosphorus)
• Subsurface drainage –salinity control - limit nutrient losses
More info on drainage and agriculture
• Drainage principles and applications, ILRI Publication 16, H.P.
Ritzema
• Environmental Soil Physics, Daniel Hillel, 1998
• Irrigation Water Management, Training manual 1, FAO
• Management of agricultural drainage water quality, Water reports
13, FAO/ICID, 1997
• Environmental impact assessment of irrigation and drainage
projects, FAO Irrigation and drainage paper 53
• The internet
Irrigasjon, produksjonfaktor og globalt problem
Johannes Deelstra
Bioforsk
1432 Ås
The Nile Basin
•Water availability, present and
potential problems
Egypt
irrigation and salt problems
Sudan
limited water resources
Eritrea
water storage, dams and soil and water
conservation
Kenya
Turkana/Turkwell gorge
The Nile Basin
Water use in Egypt
• Agriculture; Delta, Nile valley, desert
• crops; rice, cotton, maize, berseem, wheat
• water supply; year round irrigation,surface, sprinkler, centre
pivot
• closure period February, maintenance
Egypt, Nile Delta
http://worldroom.tamu.edu/mideast/photos/photos_L/sts057-73075.jpg
http://worldroom.tamu.edu/mideast/photos/052-74058.html
Egypt water use
centre pivot irrigation system, western desert, direction
of Suez canal http://spot4.cnes.fr/spot4_gb/obsagric.htm
Irrigation Egypt scenarier
Water resources
River Nile Water
Groundwater
Agricultural drainage
water
Treated municipal water
Saving flow water
management programmes
Deep groundwater
Total
1990
55.5
2.6
4.7
2000
57.5
4.9
7
0.2
1.1
1
0.5
63.5
2.5
74.0
Water demands
Irrigation
Municipal uses
Industrial
Navigation and regulation
Total
1990
49.7
3.1
4.6
1.8
59.2
2000
59.9
3.1
6.1
0.3
69.4
population; 55 million(1994), 63 (2000), 86 (2025)
From: Water resource planning in Egypt, Martin Hvidt, Odense University, Denmark in The
Middle East Environment. (Dr Abu Zeid, “Water Resources Assessment for Egypt”,
Alexandria, Egypt, 11 – 13 April 1992
Irrigation method,
sakia/water wheel
Irrigation water applied to
crops in the Delta, using
both modern technology
and the traditional Egyptian
water wheel, the sakia
Agriculture in Egypt
• Egypt is a gift of the Nile,
• Floods of Nile in July, August > agricultural traditions
• Regulation of water flow > controlled irrigation > increased
cropping intensities(100 > 200)
• No salinity problems before High Dam
• Increased cropping intensities
But then happened the following
• High groundwater levels > salinity problem
• Solving through subsurface drainage systems
system with buried suction pipes/collector drains and open
drains
• Water scarcity > reuse of drainage water, mixing of open
drain water with irrigation water
Egypt and salinity
• Why did Egypt's irrigation system never stop - what made the
Mesopotamian systems collapse?
• In Mesopotamia (Sumer, Akkad, Babylonia, Assyria)erosion in upland area, due to deforestation and overgrazing, lead to
sedimentation downstream, in rivers and canals leading to an
irregular canals system
a rise in ground water table occurred leading to a salt problem,
inadequate drainage
floods came before the hottest time of the year in spring
• Why did this not happen in Egypt?
sedimentation due to upland erosion (Blue Nile, White Nile) was not as
sever as in Mesopotamia
good drainage possibilities, river levels below the land, thin clay cap
giving enough natural drainage
stable river system with water levels below the land after the floods
had receded
floods after the hottest time of the year
Egypt and water use
• Increasing population in Egypt -> increasing demand for water?
• Ethiopia, on average provides 80-85% of the annual discharge
of the Nile, yet to date uses virtually none of it.
• Egypt and Ethiopia; conflicting interests
Egypt plans to divert water from the Nile (New Valley Project) to the
Western Dessert (5 – 10 km3 yr-1)
Ethiopia plans to construct microdams (500 – estimated 4 km3 yr-1)
Egypt/Ethiopia
Toshka project
Nile basin Initiative
Playing Chicken on the Nile? The Implications of Microdam Development in the
Ethiopian Highlands and Egypt’s New Valley Project, by John Waterbury,
American University of Beirut and Dale Whittington, University of North
Carolina – Chapel Hill
Water supply to Egypt, the Aswan High
Dam
others
• over and
year storage
of water (3 yrs, 165 km3) guarantees reliable water
•
•
•
•
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supply, food production (drought period 79 - 88)
increased cropping intensities have lead to salt problems =>drainage
water loss, evaporation
increased water use in Ethiopia. effects on water supply at High Dam
increased water use in Sudan, effects on water supply at High Dam
what about the Junglei canal
www.gtoevolution.ch/convoy/Convo
y-images/ jonglei-canal-m.jp
Sudan,
Um Ja Wasir irrigation scheme
• Pump scheme, utilising water from the Nubian Sand stone
aquifer
• Available; 200 km3 of water
• Water levels 25 m bss, very good quality water
• Estimated age of water; 10000 - 20000 yrs old
• High water requirements
• Crops grown; wheat in winter and sorghum during summer
time
Sudan,
Um Ja Wasir irrigation scheme
implement monitoring
system for water use, crop
production, fuel
consumption, etc
Crop water requirements(cwr),
a comparison
• Sudan; cwr wheat 850 mm appr. Assuming an irrigation
efficiency of 50 %, tcwr = 1700 mm. Assuming a yield of 7
tons/ha, 2.4 m3 of water is needed to produce 1 kg of wheat.
• In Norway, or Baltic countries, Eastern Europe, wheat grown
under rainfed conditions, cwr = ± 300 mm with a yield of 4
tons/ha, which means 0.75 m3 water to produce 1 kg of
wheat.
• Export/import of food = transport of virtual water.
Eritrea
The Foro dam
• In the 1960s, a new dam was built at
Foro on the River Haddas, with a
capacity of 23 million m³ but by
1988 this reservoir was completely
silted up. The total drainage are is
appr. 2100 km2
• Foro = Adulis, a port city on the Red
Sea. Throughout most of ancient
times it stood in the forefront of
trade between Yemen and the cities
of Nubia. Completely covered by
sediments
• Main reason; upland erosion
• The intention was to irrigate 4000 ha
Eritrea
why erosion
agricultural activities on steep
slopes without proper
conservation measures
research, measurements,
monitoring is needed to
implement the right
agricultural systems
Kenya,
Turkana, Turkwell Gorge
FAO Irrigation projects
Turkana, Borana area
Turkana, nomads, livestock
Three irrigation projects
Lodwar, Katilu,
Turkwell
Two rivers; The Wei Wei and
Turkwell
Seasonal rivers, meandering,
irregular discharge
Dam construction in Turkwell
gorge
Turkwell Gorge, Kenya
• RECENT CASES OF CORRUPTION INVOLVING UK COMPANIES AND UK-BACKED INTERNATIONAL
FINANCIAL INSTITUTIONS
TURKWELL, KENYA
• UK Company Involvement: Knight Piesold . UK Government Involvement: Export Credits
Guarantee Department
• Other companies involved in the dam included GE Alsthom, Norconsult and Sogreah. Spie
Batignolles, the French construction company, won the construction contract which did not
go out to competitive tendering. [124]
• In March 1986, an internal memorandum written by Achim Kratz, then European
Commission delegate to Kenya, was leaked to the Financial Times. [125] The memo stated
that the contract price was "more than double the amount Kenya's Government would have
had to pay for the project based on an international competitive tender." The memo
continued, "The Kenyan government officials who are involved in the project are fully
aware of the disadvantages of the French deal . . . but they nevertheless accepted it
because of high personal advantages." [126]
• Kenyan observers say that these "personal advantages" included payments of millions of
dollars to Kenya President Daniel Arap Moi and to the then Energy Minister Nicholas Biwott.
[127] When the dam was completed in February 1991, the Kenyan press described it as
"the whitest of white elephants" and a "stinking scandal".
http://www.parliament.the-stationery-office.co.uk/