economic cost and benefits l.
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  2. Spate irrigated areas are often among the poorest areas in a country and therefore require special attention

  3. There are several ways to support spate irrigation development • Provide earthmoving equipment • Investments: • Improvement of traditional systems • Modern civil engineering

  4. All these approaches have different costs, benefits, risks and side-effects

  5. Earth moving equipment programs Making bulldozers available on subsidy/ for free allows construction of bunds and gully plugs has made it possible to control flood water where previously this was not possible Often combined with gabion structures

  6. Earth moving equipment programs • Costs/ benefits: • Low cost (5-125 USD/ ha) • Very large impact • High flexibility • In many areas the ‘only option’ • Construction can be ‘farmer-driven’ Recommendation: In bulldozer programs the allocation of bulldozer services should be fair and preferably to communities rather than individuals • Risks: • distortion of water distribution • creates dependency of farmers • bulldozer bunds less compact, breaks easily

  7. If possible, promote local rental market in earthmoving equipment Sana’a, Yemen

  8. Investment:improvement in traditional systems Example Fixating diversion of traditional flood channel No change to system of intakes and flood channels Improve traditional structures with gabions and small civil works Range of improvements such as bed level fixation, reinforcing diversions, flow regulation, improved water distribution, improved overflow structures

  9. Investment:improvement in traditional systems • Risks: • Maintenance (of gabions) can be problematic • -Not many engineers easily ‘know’ what to do – requires good understanding and interaction • Costs/ benefits: • Medium cost (USD 200-400/ha) • Medium impact • No disruption of water rules • O&M burden of farmers drastically reduced • Farmers remain in charge

  10. Investment:modernizing spate systems Typically: Combined diversion structure, single off-take, extended channel, sedimentation excluder, syphons and sometimes ‘breaching bund’ Example: Wadi Laba, Eritrea In Pakistan the equivalent civil engineering approach has used designs that in almost all cases were inappropriate to spate irrigation – leading to spectacular failures such as Mithawan Dam silting up in first year

  11. Investment:modernizing spate systems • Costs/ benefits/risks: • High cost (USD 600-3000/ha) • Difficult to control sedimentation • Operation problematic (gates, cleaning of sedimentation ponds etc..) • Disturbance of water rules – upstream ‘takes charge’ • Farmers expect government to maintain

  12. Typical investment costs

  13. Investment strategy They can be increased though through better agronomy, soil moisture management and farmer organization – yet even then • Investments per ha in spate irrigation should be modest, because economic benefits in spate irrigation are limited: • Fluctuations in cropped area and production over the years • Risk of total crop failure • Predominance of traditional crops • Diversion and conveyance efficiency in traditional systems already high

  14. There are other important advantages of low cost approaches: • Simple technology • Technically often most suitable: • Control of sedimentation • In tune with existing water rules • Independence from external input • Construction by farmers • Low-cost repairs • No ‘total’ failures • Civil engineering approaches only possible in limited number of areas

  15. General lessons: • High investment returns for: • Improvement of traditional systems • Investments in soil bunds • Subsidized bulldozer programmes • Permanent head works on small systems Besides, these programmes: • Improve local groundwater water storage • Support improving soil moisture conservation

  16. Additional ‘economic’ considerations • Balance investments costs and O&M costs • Advantage of small systems over large systems • Use different time horizons in assessing costs and benefits • Other considerations: livelihood and environment

  17. Important to balance initial investment costs as well as subsequent O&M costs

  18. Example: Use of Gabions • Especially if inferior quality gabions are used, • maintenance may become difficult and expensive Balancing investment and subsequent maintenance costs

  19. In Wadi Beihan farmers preferred to go back to the traditional ‘algama’ structures instead of using gabions Balancing investment and subsequent maintenance costs

  20. Investment in large spate systems often higher per ha than investments in small systems Because of their complexity (long weirs withstanding peak floods, sediment excluders, long conveyance channels) investments in large sized spate systems are often higher than improvements in small system)

  21. Shorter time horizons:Case of Sonwah Dam

  22. Shorter time horizons:Case of Sonwah Dam • At the request of farmers a huge earthen bund was built across the tail of the large Nari River in Balochistan. • Inevitably this would cause the river to silt up and force the river to divert itself to a different course. Farmers were aware of this and estimated it would take seven years for this to happen. • They were not worried and argued that: • before the new bund they could not control the flood water from the deep river • if the river would take a new course, for instance one of the flood channels, they would start making diversion bunds in this new course

  23. Shorter time horizons:Case of Sonwah Dam • Lessons: • Take a dynamic approach – the river may change its course • This is not a disaster – one can ‘play’ with this and follow the river • But conventional economic analyses based on permanent solutions with twenty year horizons of costs and benefits are not suitable

  24. The Final Most Important Consideration

  25. Important consideration • Farmers and livestock keepers in spate irrigated area often have no other viable alternative means of support • Often there is no other comparable source of drinking water or fuel wood in the area • Once an area looses it spate system, it is depopulated and the resources and social organization are lost

  26. Important consideration • Investment in spate irrigated areas is very much justified from economic and social benefit viewpoint • Best to look at spate irrigation as form of macro catchment water harvesting and not compare it with conventional irrigation • Need to build up the national capacity to support spate irrigation areas in appropriate manner