SPATE IN GASH BARKA

Findings from the Field

Overall Briefing

Ian McAllister Anderson for SOS Faimianmcanderson@aol.com

Ministry of Agriculture and SOS Faim

What is the role of Spate irrigation in Gash Barka?

Two types of system (i) takes water from local catchment (4-6 km2)(ii) takes water from the larger catchment (15-80 km2)

Sorghum needs about 450 mm for good production 2010 - regarded as good rainfall year

=> shortage of ~ 100 - 200 mm since storms are very intense => wide spatial variations=> higher runoff & reduced effectiveness of the rain falling => less availability to farmer/ crop

Shows importance of Spate irrigation even in good year

Totalin

growing season

>50mm >70mm >100mm

Tesseney 0 0 28 12 66 83 47 0 236 18 14Haikota 0 1 10 15 39 56 39 0 160 22 14Alebu 0 0 0 0 25 33 18 0 76 11 11Mogollo 0 28 0 19 273 115 16 0 450 19 17 1Forto 0 27 0 2 109 68 41 0 246 17 14 1Kulentebay 0 6 0 0 33 84 0 0 123 8 7Aqurdet 0 22 0 27 272 160 53 0 533 26 21 1 1 1Mensura 0 26 26 11 267 95 23 0 448 21 18Duluk 0 0 0 0 109 28 45 0 182 9 9Mogoribe/Dige 0 37 0 0 65 104 39 0 245 13 12Barentu 0 15 20 11 104 246 45 0 442 23 17 1Goluj 0 0 84 80 105 110 224 0 603 25 19 1Gogne 9 9 2 36 40 77 25 0 199 30 21

Sep Oct

Total monthly rainfall (mm) for Gash Barka, 2010

Total

Rainfall Days

Met. Stations Mar Apr May Jun July Aug

Timing of Floods Spate Systems with the smaller catchments

– most of the SOS FAIM schemes, – floods occur at the same time as the rainfall– No rainfall = generally no floods– Poor/low rainfall => good supplement– Good 1 in 3 years

Difficult for the farmer to – both manage the water over the scheme and – to be able to fully utilise the flows.

Schemes with the larger catchments– flood flows occur sometime after the rainfall – originate from Rainfall events in other parts of the wider

catchment– 12 – 24 hour time lag– Useful as no rain often on scheme– Good 1 in 2 years

What are we trying to do with these irrigation developments?

A. Objective to improve livelihoods of the people living in the area.

B. Ensure Sorghum and Millett receive sufficient water to produce reasonable to good crop yields on a regular basis

C. Develop Spate systems to enable farmers to supplement very variable rainfall with run-off => gives sufficient water to meet crop water requirements.

D. Utilise runoff in the Wadi in the larger catchment, even if there is no direct rainfall in cropped area.

What does this require?

A. Relies upon some rainfall occurring somewhere in the catchment => smaller the catchment the greater chance of failure.

B. Gash Barka has considerable periods with no rainfall which has resulted in crop failure or only stalks for the livestock.

C. Realise that actual production from the smaller spate irrigation schemes as being only one year in three.

D. Ensure that when rain/runoff occurs diverted water use is maximised => best opportunities for production but requires good on-farm water management, system that is ready to take advantage of the flood

when it comes, farmers who can manage the flows that arrive in a

satisfactory manner.

Overview of SOS Funded Spate Schemes

8 out of all 34 spate schemes in Gash Barka

Net cultivated area (2010) ~= 1,136 ha10% of estimated current Net cultivated

area for all schemes15 % of estimated current Net cultivated

area for medium to small schemes Implemented from 2002 to 2005Long term involvement and support to

MOA

Area (km2)

ShapeLength

(km)1 Forto 2002 Wakai 12 6 70 No (Land) Bottom Bund/free Spreading

bunds35 SOS Faim

2 Forto 2004 Senketknab 4 4 120 Limited (water) Middle/Upper Masonry Weir

Spreading bunds

150 SOS Faim

3 Haicota 2002 Bultubyay 4 4 152 Limited (water) Middle Masonry Weir

Spreading bunds

112 SOS Faim

4 Haicota 2003 Alebu 19 8 138 Limited (water) Middle (Steep catchment)

Masonry Weir

Spreading bunds

300 SOS Faim

5 Mogollo 2003 Terkina 32 18 79 Yes (to 150) Bottom Masonry Weir

Spreading bunds

60 SOS Faim

6 Agordat 2005 Rahya Abay 3.5 3 100 No (Water) Middle Masonry Weir

Spreading bunds

50 SOS Faim

7 Mensura 2004 Barnabra 40 20 150 Yes (if land) Middle (Steep catchment)

Masonry Weir

Spreading bunds

75 SOS Faim

8 Tesseney 2005–2007

Wedi Keyar 4.5 4 124 No (Land) Middle Masonry Weir

Spreading bunds (partial)

SOS Faim

Mogollo Berhatera (IFAD)

45 26 630 Yes ( to 1,200) Middle/Lower Masonry Weir

Blocks/ Bunds

IFAD

Number of beneficiary households

FinancierSub ZobaDiversion

Type

Water Distribution Method

Year of Constru

ction

Spate Scheme

CatchmentIrrigated Area (ha)

Scope for expansion (limitation)

Location of Scheme in catchment

Summary Overview of Schemes Smaller catchment areas

– More vulnerable to rainfall variations– Very short time between rainfall and runoff – No rain on scheme = generally no rain in catchment– Full Benefits 1 in 3 years– Difficult for farmers

to manage rainfall and run off together to appreciate fully how they can utilise both at the same time

Larger catchment areas will give more than 1 in 3 year benefits but – structures can be more expensive– More experienced designers needed– Good water users associations formed at start of project

The length and shape of the catchment is important– those close to hillside are more difficult to control

stream is entering its floodplain, changing gradient rapidly high velocities more likely to be subject to frequent damage.

– those in the middle to lower part of the catchment have a better conditions

Water Availability and Intake design

Need Maps to estimate flood peaks and volumes – engineers have too small scale maps

Relate flood flows, occurrence and volumes to intake capacity.

All estimates are empirical and need verification using field measurements => great benefit to future designs

No measure gauge exists on the Weirs and no one tasked with the responsibility for the recording and quantifying the flows

Observations on Gash Barka Spate Schemes Diversion structures

– The masonry diversion weirs seem appropriate types of structure durability of most has been shown to be good within the skills of the local people. Field engineers familiar with design Details need improvement (gates; stilling basin; sediment exclusion)

– Gabions have a limited life when exposed to wadi/spate water flow High content of the sediment in the water flow sand can be very abrasive larger stones hit gabions and snap the wire if located in remote places => tendency for nomads and others to

steal the wire.– Diversion bunds/embankments without an orifice control cause a lot of

problems => effectively diverting the river through the scheme. Embankment and bund control approach should not be excluded

provided that Bund is used as a guide bound and that there is a restraint to prevent all floods entering into the system

Water distribution– More use of proportional dividers– Division boxes needed at the beginning and end of the Canals– Need to keep velocity as constant as possible in canals– Limit use of gates

should be on or off user-friendly (accessed easily; quick to open & close) O & M friendly (easy to grease and repair)

Water management– Need to consider over flow approaches down slope

<2-3% slope; Length and width dependant on soil type; Agree time for flows and duration => good WUA management

– Spreading Bund method of moving water across the irrigated area can be effective but

length should be limited good levelling in areas which are undulating. With inexperienced operators => too much soil moved => areas of soil

infertility => moisture stress in some parts of scheme– System of smaller basins where water is dropped from one to the other

would reduce problems being faced by uneven land– Consider broad water front approach

Land levelling. – limited availability of animals suitable for land levelling – initial construction levelling using dozers and graders– alternative open to farmers is machine levelling or improved disc ploughing +

second harrowing (power) Water Uses Associations

– Generally formed and trying to complete tasks– MOA not clear what communities can do + what government can do – Maybe we assume that they could do too much (age distribution; resources

available; expected returns; years with benefit) Operation and maintenance charges

– Activities to be worked out with WUA considering the level of money collected in good year Fee may only be collected in 1 year in 3 Fee based on average yields (10 to 15 quintal/ha) in good year Level of charges related to crop in good year Nakfa 500 (~US$ 30) reasonable in these circumstances

Assume that system has – been built to a good durable standard – system completed – any flaws in the construction or the design will be repaired by government

rather than the farmers. Costs

– Underestimated as not fully complete and documentation weak– Designs not peer checked and complete => return often to repair the systems

Constraints to be faced when making improvements

A. Designs and Experiencea) Lack of institutionalisation of experiences:

a) no documented evidence on performanceb) how to improve upon the built designs c) Approaches that reduce annual recurrent expenditure

b) Relatively high staff turnover with insufficient knowledge handover at intermediate to senior level.

c) Designs often lacking the benefit of practical experience when adapting hydraulic structures to the field.

d) Limited peer review of the designs and insufficient design manuals to guide the less experienced designers.

e) Designs need to be more tailored to the operational capacity and ability of farmers/WUAs

f) Need to invest more in construction to reduce recurrent expenditure.

B. Constructiona) Lack of timeliness and availability of suitable construction

machinery, materials and labour due to other demands.b) Limited availability of skilled workers (masons and experienced

machinery operators)a) machinery comes from a central pool b) wide variety of work with few having experience of the requirements of

good land movement in levelling.c) Lack of appropriate equipment for improved land preparation d) Failure to undertake full land preparation/formation at construction.

C. Water Users Associations and Farmers Involvementa) Tasks required of farmers not explained to them adequately during

constructionb) Many of the tasks assumed to be undertaken by farmers are beyond

their ability particularly considering finance/age/numbers in WUA.c) No clear direction on how much farmers will be able to contribute

towards O & M charges and how this should be spent.d) Insufficient funds for routine repair of items such as breaching of

bunds and repair of canals and intakes for example. e) Farmers in some cases have tried to repair the works but mostly

ineffective and repairs failed in the following flood season.

D. Impact of Constraints

Failure to – complete all of the required works in time for the first

flood season – hand over to the farmers a system that is sustainable

and within their means to maintain Gives

– Continual high annual expenditure on maintenance and repairs

– Water distribution poor in many cases with crop yields varying considerably over the command area.

– Lack of sufficient quality on some aspects of the work during construction, particularly relating to the on-farm works.

Are systems provided sustainable, if not why not?

High annual recurrent expenditure beyond means of farmers.

Outstanding technical problems + repairs if not addresses in a sustainable way =.

– Rapid deterioration of systems– Unable to continue to deliver water as anticipated.

What is needed?

Need to recognise that the systems will only deliver grain (benefits) probably in 1 in 3 years and thus must:

– Ensure good water management and water distribution available

– Assist farmers to obtain sufficient yields to take them through the two dry years.

Can anticipate that in one of these two dry years, farmers may be able to achieve some fodder for their animals even though rainfall may be small and there could be one or two floods within the Wadi.

What is now required to improve chances of sustainability

A. Are we going to invest in more schemes and on what basis?

B. What is to be done about existing schemes that still require significant investments?

C. How can we consolidate what has been done and make systems durable and sustainable?

Proposals: Consolidate experience of the 34 schemes in Gash Barka to:

– Produce good designs that will require minimum expenditure in the future from the farmers

– Develop standard designs to overcome past efficiencies in the design they have produced relatively high operation and maintenance costs

– Establish design approaches to simplify peer revue– Develop clear & realistic guidleines for WUAs formation, tasks, funding– Develop spate design manual as soon as possible– Review performance and costs of water application & dsitribution

methods Plan in parallel to develop more schemes but ensuring that

– they utilise the experiences so far – more systematic approach to design and implementation is adopted. – Establish early working water uses associations that can take over what

is required and what they can do– A full estimate of outstanding design problems and maintenance needs– Improvement of on-farm works to ensure that water distribution is

improved and that breaching of the bunds is repaired and secured against future problems

– Designs that are tailored to farmer management and also endeavour to reduce Operation and maintenance needs through greater capital investments.

What does this mean to MoA/ SOS Faim - Way forward? Agree on approach and resources Adjustment of programme for 2010 and 2011 Detailed assessment of each scheme, with improved design for overcoming

constraints and costing of improvements Design of repairs prepared considering improved designs in locations and

details where problems have been identified. Assessment of performance of 34 spate irrigation systems in Gash Barka to

identify good practice and why this has taken place in relation to (a) physical conditions, (b) size of catchment, (c) technical suitability of designs, (d) quality of design, (e) quality of construction, (f) appropriateness of the design for farmer operation (g) training and involvement of farmers (h) suitability and costs of water application and management and (i) other pertinent issues.

Development of guidelines for field staff recognising the practical experiences that have been gained over a number of years and anticipated experience.

Ensure that good documentation is kept on all schemes and designs together with drawings to remain available within the institution should staff be transferred/leave.

Ensure peer review of all designs (including repairs) and that methodologies are developed for facilitating cross checking and review.

Carry out regular technical training sessions in Barentu for technical staff Organise regular collection of flood flow data at each spate site to compare

with empirical data and predictions to improve designs Establish rain gauges at each village and give responsibility for recording

actual rainfall to Water User Association + training.

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