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1.3Economic Costs and Benefits. Spate irrigated areas are often among the poorest areas in a country and therefore require special attention.

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Presentation on theme: "1.3Economic Costs and Benefits. Spate irrigated areas are often among the poorest areas in a country and therefore require special attention."— Presentation transcript:

1 1.3Economic Costs and Benefits

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 Risks: -distortion of water distribution -creates dependency of farmers -bulldozer bunds less compact, breaks easily 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

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

8 Investment: improvement in traditional systems 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 Fixating diversion of traditional flood channel Example

9 Investment: improvement in traditional systems 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 Risks: -Maintenance (of gabions) can be problematic -Not many engineers easily ‘know’ what to do – requires good understanding and interaction

10 Case: Mochiwal Flow Division Darabam Zam Mochiwal Division Point North channel: -500 ha -low lying area West Canal: - 3000 ha

11 Example: Wadi Laba, Eritrea Typically: Combined diversion structure, single off-take, extended channel, sedimentation excluder, syphons and sometimes ‘breaching bund’ Investment: modernizing spate systems 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

12 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

13 Typical investment costs TypeCost range (USD/ha) Examples Soil bunds with gabion structures 5-125Eritrea, Pakistan Flood water spreading 200Iran Small systems, permanent headworks 180-450Eritrea, Yemen, Pakistan, Ethiopia Large systems, permanent headworks 650-3500Yemen, Eritrea, Pakistan, Tunisia Rehabilitation90-300Yemen, Tunisia

14 Investment strategy  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 They can be increased though through better agronomy, soil moisture management and farmer organization – yet even then

15 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

16 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

17 Additional ‘economic’ considerations 1. Balance investments costs and O&M costs 2. Advantage of small systems over large systems 3. Use different time horizons in assessing costs and benefits 4. Other considerations: livelihood and environment

18  Important to balance initial investment costs as well as subsequent O&M costs

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

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

21 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) Investment in large spate systems often higher per ha than investments in small systems

22 Shorter time horizons: Case of Sonwah Dam

23 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

24 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

25 The Final Most Important Consideration

26 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

27 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

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