Irrigation, productivity and the future

1. Irrigation, productivity and the future • Global irrigation in early 1990’s: • 16% of total cropland • 36% of total harvest • Irrigation’s contribution to increased production • (seeds, water, fertilisers, agrochemicals) • Uses about 65% of total available freshwater, and expected to decline to 60%in Y2K.

2. Irrigation, productivity and the future (contd) • Contributed more than 1/2 of productivity gains since 1970 • Asia:2/3 of food supply from <1/2 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 > 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