1.3 Economic Costs and Benefits
Spate irrigated areas are often among the poorest areas
in a country and therefore require special attention
There are several ways to support spate
irrigation development


Provide earthmoving equipment
Investments:


Improvement of traditional systems
Modern civil engineering
All these approaches have
different costs, benefits, risks
and side-effects
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
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
If possible, promote local rental market in earthmoving equipment
Sana’a, Yemen
Investment:
improvement in traditional systems
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
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
Case: Mochiwal Flow Division
Darabam Zam
North channel:
-500 ha
-low lying area
Mochiwal Division Point
West Canal:
- 3000 ha
Investment:
modernizing spate systems
Typically:
Combined diversion structure, single off-take, extended channel,
sedimentation excluder, syphons and sometimes ‘breaching bund’
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
Typical investment costs
Type
Soil bunds with
gabion structures
Flood water
spreading
Cost range
(USD/ha)
5-125
200
Examples
Eritrea, Pakistan
Iran
Small systems,
permanent
headworks
180-450
Eritrea, Yemen,
Pakistan, Ethiopia
Large systems,
permanent
headworks
650-3500
Yemen, Eritrea,
Pakistan, Tunisia
Rehabilitation
90-300
Yemen, Tunisia
They can be increased though
through better agronomy,
soil moisture management and
farmer organization – yet even
then
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
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
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
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
 Important to balance initial investment costs
as well as subsequent O&M costs
Example: Use of Gabions
-Especially if inferior quality gabions are used,
maintenance may become difficult and expensive
Balancing investment and subsequent maintenance costs
In Wadi Beihan farmers preferred to go back
to the traditional ‘algama’ structures
instead of using gabions
Balancing investment and subsequent maintenance costs
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)
Shorter time horizons:
Case of Sonwah Dam
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
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
The Final Most Important
Consideration
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
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