Água em África - africanos
TRANSCRIPT
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Água em África: Hidropessimismo ou Hidrooptimismo
Water in Africa: HydroPessimism or HydroOptimism?
Centro de Estudos Afr icanos da Universidade do Por to Porto, Portugal, 23 October 2008
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Rainwater Management for
Increased Agricultural production
Centre of Afr ican Studies – Por to Por tugal 2 – 3 October 2008
CONFERENCE ON WATER IN AFRICA SESSION ON WATER AND AGRICULTURE
Nico van Leeuwen
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Outline
• Food for all ?
• Key role of water
• Smallholder adapted technologies
• Where does the rainwater go ?
• Options for management of rainwater
• Conclusions
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< 2.5 2.5–4 5–19 20–34 ≥35
No data
% undernourished
UNDERNOURISHMENT
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UNDERNOURISHMENT IN THE WORLD
• 776 million people in developing countries remain undernourished
• World Food Summit goal (1996) to reduce undernourishment to 410 million but present expectations are 610 million
• Seven out of ten of the world's poor live in rural areas and depend on agriculture
• Arid zones cover 45% of the world area
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< 2.5 2.5–4 5–19 20–34 ≥35
No data
% undernourished
UNDERNOURISHMENT SUB SAHARA AFRICA
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UNDERNOURISHMENT IN SUBSAHARAN AFRICA
• SSA undernourishment rose from 200 m people in 1995 to 450 m today.
• SSA population 62% in rural areas
• SSA rural poverty accounts for 90% of total poverty
• SSA 80% of the poor depend on agriculture
• 38 % of SSA is arid land
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< 2.5 2.5–4 5–19 20–34 ≥35
No data
% undernourished
Undernour ishment and water scarcity Sub Sahara Afr ica
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Dry land areas and rain fed agr iculture
Definition and distr ibution of dry land areas
Classifica tion
Length of growing per iod for annual crops in days*
% of Wor ld
Land area
% of land area SubSaharan
Afr ica Hyper ar id 0 19 24 ar id 1 – 59 7 6 semiar id 60 – 119 20 13 drysub humid
120 179 18 19
Arid land: 45% of wor ld area, 38% of SubSaharan Afr ica
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Strong relationship between water availability and cereal production
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In order to reach the Wor ld Food Summit and Millennium goals
• to reduce the number of undernour ished
• and feed the world population expected to increase by 30% over the next 30 years
wor ld food production should
be increased by 50 % in 2030
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Some realities:
•The green revolution is slowing down
•Ser ious environmental problems are appear ing
•Investment in agr iculture and ir r igation has been reduced
•Groundwater resources are dangerously low in many countr ies
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Yield increase
66 % Arable land expansion
22 % Cropping intensity
12 %
How to grow 50 % more food in 2030
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Yield Increase: •Adequate water supply to crops through Ir r igation, water harvesting/runoff farming. •Improved seed •Fertiliser •Agricultural practices
Arable land expansion •Ir r igate dry areas •Expand use of wetlands •Water harvesting on arid lands
Cropping intensity •Expand and improve ir r igation •Reclamation and intensive use of wetlands
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Large ir r igation projects for small number of farmers ? or Smallscale water development for a large number of farmers?
In developing countr ies
• 80% of the farmers are smallholder farmers
• practicing mainly subsistence farming
• located largely in arid and semiarid zones or zones with erratic rainfall
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Improvement of water supply to crops • accessible and affordable • to poor, • smallholder • subsistence farmers
Most appropr iate technologies for smallholder farmers:
• Verysmallscale irrigation (with groundwater, surface water or collected/stored rainwater
• Water management in wetlands and valley bottoms
• Management of water from rainfall.
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17 (Rockström, Fox, Persson et Falkenmark(SIWI)
RAINWATER MOVEMENTS
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Rainwater distr ibution in ar id areas
(Rockström, Fox, Persson et Falkenmark(SIWI)
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Improved use of r ainwater
• Prevent runoff • Reduce evaporation from soil sur face • Keep water in the root zone en prevent deep percolation
Options:
• Conservation agr iculture • Rainwater harvesting – runoff farming
“Rainwater that falls on my land remains on my land”
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CONSERVATION AGRICULTURE
• No tillage
• Maintain coverage on soil sur face
• Stimulate biological functioning of the soil
• Reduces evaporation and runoff
Conservation agr iculture only works when rainfall is sufficient
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21 Smallscale conservation agr iculture
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Permanent soil coverage
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Mechanized conservation agr iculture
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Runon area = storage in the soil profile or in a reservoir
Runoff area = catchment
The collection of runoff for its productive use
• Water applied to the crop and stored in the soil
profile: runoff farming
• Water stored in a reservoir for future use : ir r igation,
Domestic use, livestock, aquaculture, etc
Rainwater Harvesting
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Potential areas for runoff farming
> 800 mm
400 < x < 800 mm
200 < x < 400 mm
100 < x < 200 mm
< 100 mm
Annual r ainfall
> 179 days
Too wet for runoff farming
> 0.65 Humid
120 – 179 days
Suitable for runoff storage
0.5 – 0.65 Dry sub humid
60 – 119 days
Suitable for runoff farming
0.21 – 0.5 Semi ar id
1 – 59 days
Suitable for runoff farming
0.05 – 0.2 Ar id
0 day Too dry for runoff farming
< 0.05 Hyper arid
Length Growing Per iod
Suitability P/ETP Zone
Source: GAEZ (FAO – IIASA, 2003)
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Microcatchment Macrocatchment
Floodwater harvesting
Types of runoff farming water harvesting
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Smallscale rainwater harvesting (zai)
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28 Tree planting for reforestation or land rehabilitation
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29 Inter row water harvesting in orchard in ar id area
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ADVANTAGE :
• coverage of 1015 ha / day
width 0.40 m
length 4 5 m
depth 0.40 m
DIMENSIONS :
DISADVANTAGE :
• high investment costs
Microcatchments made by the “Dolphinplough”
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32 Mechanized runoff farming
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Rainwater harvesting or conservation •Very small scale •Large scale
Keita project in Niger FAO/Italy and WFP 1984 – 1999 13 000 km² 300,000 people living in 400 villages • 50 ar tificial lakes • 42 dams • 65 village wells • 10,000 ha water conservation • 16 million trees • Infrastructure: schools, maternity centres, veter inary facilities, storehouses, microcredit, literacy courses, etc.
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Keita project Niger
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Keita project Niger
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1
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Example:
Keita (Niger) 2
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Character istics of runoff farming techniques
• Or iented towards increased agr icultural production
• Reduces r isks of crop failure and encourages other investments (seed, fer tilizer , etc)
• Relatively LowCost and high return of investment
• Immediate benefits to farmers
• Reduces downstream flooding and consequent damages
more……
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• Contr ibutes to increased recharge of groundwater
• Protects and rehabilitate the environment
• Combat deser tification
• Alleviates the negative impact of climate change on water resources
Character istics of runoff farming techniques
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Rainwater management:
a new green revolution ?
Thanks for your attention
Merci pour votre attention
Obrigado