Global irrigation in early 1990s:

1
Irrigation, productivity and the future

• Global irrigation in early 1990s
• 16 of total cropland
• 36 of total harvest
• Irrigations contribution to increased production
  
• (seeds, water, fertilisers, agrochemicals)
• Uses about 65 of total available freshwater, and
  expected to decline to 60in Y2K.

2
Irrigation, productivity and the future (contd)

• Contributed more than 1/2 of productivity gains
  since 1970
• Asia2/3 of food supply from lt1/2 of cultivated
  area.
• 40 of all agricultural production from 20 of
  arable land in developing countries
  (Seregeldin 1996)
• 46 grain, 57 total value of wheat and rice in
  developing countries produced under irrigation in
  1990.
• See overhead of production and arable area

3
The future of irrigation?

• 1960- 1980 buoyant investment in irrigation
  projects
• (high yielding varieties, and good grain prices)
• between 1961 and 1982- 500 bn (95 prices)
• However, there has been a decline in investment
  due to
• fall in grain prices
• real costs of irrigation increased
• thus low rates of return
• low efficiencies of projects
• growing competition for freshwater (65)
• environmental concerns
• However, the need for irrigation projects remains

4
The future of irrigation?

• The future of large-scale funding seems to be
  giving priority funding the improvement of
  existing irrigation systems
• However, the future of irrigation and water
  provision both seem to be intricately linked to
  the ability of agriculture to feed the human
  population
• See overhead of human population and
• overhead of water provision scenarios

5
Choice of irrigation systems (Is it worthwhile
irrigating?)

• climate and soils
• topography
• water supply
• crop types
• labour
• legal aspects
• Other issues
• farmer training available, pests, machinery
  spares and mechanics?,

6
Choice of irrigation systems

• climate and soils
• topography
• will affect choice of irrigation method, height
  of fields compared to water supply, use of pumps,
  levelling costs,
• water supply
• elevation, distance, quality, cost, quantity of
  water required is frequently underestimated, need
  to consider seasonal availability and maximum
  demand
• crops
• may have to introduce new crops- will they sell?
• Is the price of crop gt irrigation costs?

7
Choice of irrigation systems

• labour
• more intensive than rain-fed cultivation, small
  farms-little added labour, more tied to land
• legal aspects
• many countries have legislation governing the use
  of limited water resources, common rights,
  upstream uses
• Other issues
• farmer training available, pests, machinery
  spares and mechanics?,

8
Soil and Water Conservation

• Runoff agriculture provides moisture by
  collecting surface/subsurface runoff where other
  sources are likely to too costly, unsustainable
  or damaging.
• Concentration of surface runoff for cultivation
• Effectively uses moisture that would otherwise go
  to waste (unavailable to agriculture)
• Characteristics and advantages of runoff farming
• cheap to establish
• uses local materials (remote areas)
• a sustainable practice
• improved harvest security
• improved yields, more crops per year
• improve quantity and quality of streamwater and
  groundwater recharge

9
Soil and Water Conservation

• Agronomic techniques
• Mulching
• plastic sheets underground
• soil amendments
• Fallowing
• Conservation tillage
• Mechanical techniques (devices that act as
  cross-slope barriers
• trash lines
• stone lines
• wattling/staking
• contour bunds, hillside ditches, soil pits,
  terraces

10
Soil and Water Conservation

• Vegetative techniques
• plant cover
• agroforestry
• Fog and mist harvesting
• 150-750 litres per day from 48m2 mesh trap
• Further reading
• Barrow 1987
• Hillel 1997
• Stern 1979