081126 report aideco version
TRANSCRIPT
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ENGINEERS WITHOUT BORDERS
Imi NTizghte
Agricultural project irrigation and boar fences
Stephen Ollier and Clare Wilding
1/1/2008
December 2008
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Contents1.0 Introduction ...................................................................................................................................... 4
2.0 Lifestyle and Agriculture in Anbdour and Imi NTizghte ................................................................... 5
3.0 Soil testing ............................................................................................................................................... 8
3.1 Introduction to soil surveys ................................................................................................................ 8
3.2 Factors affecting Soil Fertility, Erosion and Desertification ................................................................ 8
3.3 Methodology Used ............................................................................................................................ 10
3.4 Results Obtained ............................................................................................................................... 11
3.5 Analysis of Results and Recommendations ...................................................................................... 11
4.0 Irrigation System ................................................................................................................................... 13
4.1 Indroduction ..................................................................................................................................... 13
4.2 Khettara ............................................................................................................................................ 144.2.1 History ........................................................................................................................................ 14
4.2.2 Existing Khettara in Imi NTizghte .............................................................................................. 15
4.2.3 Problems with Khettara 1 .......................................................................................................... 16
4.2.4 Khettara Remediation Options .................................................................................................. 17
4.2.6 Recommendation ....................................................................................................................... 18
4.3 Seguia and Water Tanks .................................................................................................................... 19
4.3.1 Existing Infrastructure ................................................................................................................ 19
4.3.2 Problems with existing Infrastructure ....................................................................................... 20
4.3.3 Remediation Options ................................................................................................................. 21
4.3.4 Costs ........................................................................................................................................... 22
4.3.5 Recommendations ..................................................................................................................... 22
4.4 Clothes washing area ........................................................................................................................ 22
4.4.1 Existing usage and problems ...................................................................................................... 22
4.4.2 Remediation options .................................................................................................................. 23
4.4.3 Costs ........................................................................................................................................... 24
4.4.4 Recommendations ..................................................................................................................... 24
4.5 Earth Channels (Earth Seguia) ........................................................................................................... 24
4.5.1 Existing Infrastructure and the problems .................................................................................. 24
4.5.2 Problems with existing infrastructure........................................................................................ 25
4.5.3 Options for re-lining channels .................................................................................................... 25
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4.5.4 Recommendations ..................................................................................................................... 26
4.6 Field Application ............................................................................................................................... 27
4.6.1 Existing Operation Strategy ....................................................................................................... 27
4.6.2 Crop requirements and Irrigation Efficiency .............................................................................. 27
4.6.3 What is the potential?................................................................................................................ 28
4.6.4 A note on Drip by Drip irrigation ................................................................................................ 28
4.6.5 Summary table, costs and Recommendations........................................................................... 29
5.0 Boar Fence ...................................................................................................................................... 30
5.1 Introduction ...................................................................................................................................... 30
5.2 Initial design considerations and materials ...................................................................................... 31
6.0 Crops ..................................................................................................................................................... 38
Different crop typesa critique with respect to Imi nTizghte .............................................................. 38
6.1 Existing Crops .................................................................................................................................... 38
6.2 New crops ......................................................................................................................................... 38
6.3 Future outlook .................................................................................................................................. 40
7.0 Final Recommendations........................................................................................................................ 41
8.0 Project 2009EWB in Imi nTizghte ..................................................................................................... 42
References .................................................................................................................................................. 43
Appendix A: Leaflet, invitation and poster .....................................................................................................
Appendix B: Crops questionnaire and results .................................................................................................
Appendix C: DPA fiche techniques ..............................................................................................................
Appendix D: Soil test results ...........................................................................................................................
Appendix E: Calculations .................................................................................................................................
E1 Flow calcs ............................................................................................................................................
E2 Flow losses ..........................................................................................................................................
E3 Crop Requirements .............................................................................................................................
Appendix F: Drawings .....................................................................................................................................
Appendix G: Bill of Quantities .........................................................................................................................
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Figure 1.1: View of Imi nTizghte
1.0IntroductionA project has been established by Engineers Without Borders with a local NGO, AIDECO, in the
mountainous Ammeln Valley region of Morocco. EWB provided AIDECO with a source of free
engineering consultancy to progress design work on agricultural infrastructure in the village of IminTizghte. AIDECO is likely to be able to source funding to pay for the post design construction costs but
would have been unable to pay for a comprehensive design to be carried out.
The overall goal of the EWB project was to increase agricultural productivity, and thus economic
stability, in Anbdour and Imi nTizghte. One indicator for success would be for the farmers to be less
affected by price fluctuations and to have a more steady income. What was found in the village was that
the majority of the farming is subsistence and many people rely on money sent from relatives living in
the cities for their income. The goal has therefore been extended to have less reliance on money sent
from cities/abroad and to stem the movement of people to the cities by providing better opportunities
in agriculture in the village.
Another goal is to suggest ways for slowing and preventing mass soil erosion and eventual
desertification in the valley. It is clear to see when travelling through the region that many areas of land
which used to be cultivated are now abandoned, leaving a bare and extremely vulnerable soil behind.
This is generally due to lack of water (drought), and possibly lack of labour or inadequate boar
protection. In these areas, mass erosion and desertification are inevitable in this arid/semi-arid climate.
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2.0 Lifestyle and Agriculture in Anbdour and Imi NTizghteImi nTizghte is a small Berber village in the Ammeln valley with a population of about 320. The local
language is Teshleheet and most people also speak Moroccan Arabic. Some more educated people also
speak French. There is mixed primary school in the village. The secondary school and college are inTafraout 10km away and now that there is school transport provided, the girls are able to get there as
well as the boys who used to cycle or catch a lift. This is only a recent change so there are girls in their
twenties who only had primary school education. Most women over the age of about 35 didnt have any
schooling and are illiterate.
The traditional houses are built with stone and earth based mortar however they require yearly
maintenance and many are now in ruins. Newer construction is normally in concrete blocks which are
often rendered and painted, though some are not. The village has mains electricity and a piped drinking
water supply which comes from the same source as the irrigation water and is occasionally treated.
There is also a water supply from ONEP (Office National dEau Potable) but this is expensive and only acouple of houses are connected to this.
Out of 17 households questioned, two had washing machines. Most people use the communal clothes
washing area though some do it at home particularly if they live a long way from the wash area. An
average family uses the wash area 2 to 3 times a week. Some of the girls find that the position washing
on the concrete floor gives them back ache and would prefer sinks, others are happy with the set up but
say that the surface is too rough and sometimes rips the clothes.
There is no municipal waste collection and so all households are forced to burn their rubbish and the
majority of people use the dry river bed for this. This is a poor environmental solution and is
aesthetically very unpleasing particularly in view of the fact that the association would like to increase
tourism. A future project for the Association in collaboration with a Peace Corps volunteer is to set up a
waste collection service providing communal bins and someone to collect the rubbish. Of those
questioned on this they all thought it was a great idea but it will be interesting to see whether people
will actually be prepared to pay for this service. It is hoped that some materials can be separated for
recycling.
Many of the younger generation move to the big cities to work (generally Casablanca), often in family
run shops, or because of marriage. This means that there are less people to work on the land and some
fields are abandoned. Also for those families receiving money from family in the cities there is less
incentive to invest in the land and use it to its full potential. There are currently two family run shops inthe village. There is at least one person employed at a local hotel and two families with edukan
(traditional shoes) shops in Tafraout. Other than this there is little employment opportunity.
There is a womens Co-operative about 12 strong who produce Argan oil. There is also a group of about
10 girls in their twenties and thirties who use the AIDECO building to make crafts. They also receive
French and English lessons.
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Figure 2.1: Freshly ploughed parcels
Figure 2.2: Local fruit trees
Figure 2.3: Parcels sprouting wheat
Agriculture here is not done on a large scale. Most families own a
few plots of land and these are often shared with extended family.
Up to five households might share land and trees. The plot sizes
are on average 5m x 10m and often a families land is scattered in
many areas. It is mostly the women who work in the fields and all
the work is manual or with donkeys. There is no machinery as even
if it was economically viable it would not suit the small terraced
plots
A lot of the land is covered in trees, the most common being
Argan, Almond, Olive and Date with a few Carob and the
occasional Pomigranite. The majority of the produce is kept for
personal use. Even if a large quantity of Argan oil is produced, any
surplus is usually given as presents to visiting relatives rather than
being sold. Last year the harvest was particularly bad because of
the drought, some trees produced no fruit at all and some evendied. So far in 2008, rainfall has been higher than usual so a better
harvest is hoped for in 2009.
From the information gathered from the questionnaire the only products sold are Carob pods and the
bitter Almonds (edible ones are kept). These can both be sold in Tafraout to someone who then sells on
to factories in Agadir. Carob is sold for 7DH/kg and Almonds for 35DH/kg. Of 17 families asked only two
sell Almonds and, although anyone who has a Carob tree does sell the pods, there were only 4 families
with any trees and a total of only 6 trees amongst these families.
Any crops grown are only for personal consumption. The main one
is wheat and this is something the boars do not eat. This year it
was sown in November after the fields had been ploughed with
donkeys. Some other vegetables are grown but this has diminished
a lot because the boars eat them. The main vegetables that are still
grown are squash, 50% of families questioned continue to grow
them. A very few people also grow onions, tomatoes, potatoes and
other root vegetables. In the past there was a market in the village
where people sold their vegetables. Now most people dont even grow enough for themselves and go to
Tafraout to buy them. The general opinion of people we spoke to was that they would like to be able to
grow their own vegetables again to save money.
On Sunday 23rd October 2008 a presentation was given to the people of Imi NTizghte to present the
work carried out during the EWB project.
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Figure 2.6: Presentation of work
Figure 2.4: EWB and AIDECO meeting
Figure 2.5: The survey team
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3.0 Soil testing
3.1 Introduction to soil surveys
A soil survey was necessary to gain an understanding of the nature of the ground in Imi nTizghte. This
exercise was carried out in order to asses the state of the existing soil and determine its fertility,
suitability to existing/recommended crops and whether desertification and soil erosion are a real
concern. As with most aspects of the project, one of the main aims is to try and establish a baseline
against which future studies can be compared. Since the soil type does not really vary across the site
(apart from the topsoil, which will vary slightly based on crop type, etc) a soil map has not been
produced.
3.2 Factors affecting Soil Fertility, Erosion and Desertification
Soil Fertility
There are many factors which affect soil fertility, and different plant species thrive in different
conditions. The primary factors are listed below with a short text highlighting the indicators;
Aeration - Good free movement of air is essential for a healthy soil (see free drainage).
Moisture content - Should be adequate and balanced. Affects size and texture of soil particles.
Organic content - Relates to moisture content, high organic content gives a fertile soil.
Temperature - Increased temperatures (within threshold
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Soil Erosion
As a general rule, the topsoil is the most fertile part of the soil and simultaneously the most vulnerable.
Simply put, a decrease in vegetation cover, and hence organic content, leads to an increase in soil
erosion. Organic matter fertilizes the soil by binding particles, increasing microbial activity and promotes
permeability and infiltration capacity. The loss of vegetation cover can turn an arid region into desert in
just 10 years! Note an arid region is classified as an area with annual rainfall < 250mm/year. Imi
nTizghte receives 170mm/year and hence is classed as arid. Figure 3.1 shows that Imi nTizghte is right
on the boundary of Hyperacid andDrylands classification (Hyper arid regions receive less than 100mm
of rainfall annually).
Conservation techniques, in principle, are implemented to ensure that the erosion rate equals the rate
of new soil formation. The main aims are to protect the soil from raindrop erosion, increase infiltration
capacity (minimising run-off) and increase ground roughness (retard wind and water erosive forces).
Methods for achieving this include;
Terracing; to reduce effective slope angle and length.Planting crops; provides necessary protection
Contour farming; reduces run-off and promotes soil moisture conservation.
Crop rotation; in 4/5 year cycles. Helps retain moisture by utlising soil retaining crops e.g.
Alfalfa, control pests by eliminating abnormal molds/blights/viruses, control erosion, increase
soil nutrients, and improve soil structure.
Fallow periods; allows the soil to conserve moisture (land must be mulched, tilled and weeded
carefully) and in arid regions can be recommended up to every other year.
Mulching; disturbs capillary action to conserve water and provides soil nutrients to promote
repair after harvest (0.5kg/m2 provides enough cover to protect from wind erosion also). Also
reduces wind and run-off erosion and increases soil surface permeability.Afforestation; increases soil permeability and provides wind and raindrop shelter.
Gullies; to provide run-off with a designated route. Can be grassed, impermeable, etc.
Many of these techniques work by reducing moisture loss from the soil. Another method of doing this is
humid culture where plants are grown in a poly-tunnel. Water is initially provided by irrigation and then
because it is recycled it does not need to be replaced for a few weeks. (1)
Desertification
Defined as the environmental degradation in arid and semi arid
lands causing a critical decrease in the productive capacity of the
soil. Deserts expand and contract naturally over time, the
problem comes when human activity generates unsustainable
demands on already fragile soils ecosystems. The three main
causes are overgrazing, over farming and poor water
management, all of which can lead to desertification of arid and
semi arid lands within 5 10 years!Figure 3.2: Desertification approaches
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Figure 3.5: Cohesion and
plasticity test
Figure 3.4: Basic soil grading
Desertification can be permanent if there is no capital or resources invested. It is without doubt far
cheaper and easier to invest initially in measures to avoid desertification in the first place! Poor
communities may abandon areas once the soil is, in effect, destroyed.
The cause and effects of desertification come hand in hand. Lack
of vegetation, organic matter and moisture leads to soil removalwhich decreases fertility and increases wind erosion. The process
of desertification is difficult to recognise in the field, it is a kind of
creeping disaster. Therefore, effective monitoring is key, this
can be through annual agricultural surveys (production, etc) and
aerial photos.
3.3 Methodology Used
Four sets of tests were undertaken on site, these were soil description, classification, 1-D permeability
and home mineral testing. Samples were also sent to INRA for further testing.
Soil Description
Every soil has its own unique properties and qualities, a soil description is a
qualitative method of explaining the details of a particular soil. The testing
should also include a shear strength test (Standard Cone Penetration Test).
Also useful is the general geography, land use and historical land use if
known. The data is useful in design for estimating bearing pressures, etc. For
this test, the topsoil was removed (top 200mm or so). (2)
Soil ClassificationThis system involves the testing of samples and classifying the soil based on a
list a categories including properties such as particle size and plasticity. For
example, a gravelly silt with little plasticity and a liquid limit of 50%. This data
is useful when using soils as part of a stability design, earth embankments for
example. Again the geography, land use and historical land use is useful and
the topsoil is removed for testing.
Permeability Tests
Permeability coefficient, k, is defined as the as the quantity of unit flow through unit area of soil under a
unit pressure gradient. This is the basis of Darcys L aw. Here, we have only conducted an on site test as
specified by Engineering in Emergencies (3). The macrostructure of soils have a large influence on
permeability, the lack of these features in small laboratory test samples make it difficult to obtain true
values. A field test has its own problems, but in this case it was deemed more appropriate. Simply, a
100mm diameter cylinder (large tin can) was driven into the soil, the top section was filled with water
and the rate at which the water level dropped was recorded over a 60 minute period. Generally the
initial infiltration rate is high and then, as the soil approaches saturation, the rate levels off, it is this rate
that we are most interested in (in m/s).
Figure 3.3: Desertification complete
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Figure 3.6: pH testing
Mineral Testing
A home tester kit was used to measure pH and nutrient levels. The nutrient
levels are interpreted through levels of Potassium, Nitrates and
Phosphorous. The aim is to gather information on the general quality and
fertility of the soil. It is important to note that nutrient levels vary
significantly throughout the year, depending on the type of crops, the
harvest, the season and application of fertilizer.
3.4 Results Obtained
The site owners, Soltana and Hassin Sain, agreed for their plot to be surveyed 24th September, this was
after the summer harvest so mainly only grass was growing. A flat parcel at the base of the valley, the
plot receives lots of sunlight and irrigation water from the khettara via the earth seguia network. Trees
on the northern edge shade a portion of the plot whilst providing wind protection. The plot had
corn/maize, marrow, mint and grass (for feeding their 5 goats) and carrots. They use fertilizer (cow
manure) every February, also if they plant new crops.
Soil Description
The fines area a brown uncompacted silt. The particles are fine to coarse silt with some clay and sand
particles with frequent fine to coarse gravel. The gravel is angular, possibly Gneiss. The Topsoil is
frequent organic matter. Shear strength was estimated as SPT = 10 (ground is difficult to dig due to
gravel).
Soil Classification
Gravelly SILT (approx 40% fines) with low to intermediate plasticity. The sample showed some cohesion
and a little plasticity. Liquid Limit (LL) estimated at approx 40% (category silt with some clay).
Permeability
A rate of 24mm/hour was taken (varying from 24 to 39mm/hour). A typical sandy loam has a rate of
25mm/hr and a silt loam up to 20mm/hr. Considering the fissures and gravel in the soil, this seems like a
reasonable result. According to Cassagrand and Farram (1940) (4) 24mm/hr (6.7x10 -6m/sec) represents
a low permeability soil with good drainage conditions or a fissured clay modified by the effects of
vegetation.
Results of home testing
The pH result was 7.5 (slightly alkaline). Nitrates levels low/medium to low and Phosphorous levels are
low.
3.5 Analysis of Results and Recommendations
This plot is well looked after, receiving plenty of irrigation water and sunlight. The area is sheltered from
wind and the plot is flat which help to minimize soil erosion and facilitate moisture retention. The
permeability is reasonable also, that value will be more useful later on in the earth seguia chapter. The
low nutrients and slightly high pH are most probably due to the recent harvest and lack of fertilizer. This
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plot is exemplorary for others, it also has a functioning boar fence which allows the user to plant root
vegetables, etc which the boar would otherwise eat.
Recommendations
It is recommended that an annual land use survey is undertaken every year to keep check on
deteriorating or abandoned parcels. All abandoned parcels should be planted with dryland crops toreduce the risk of crop failure and soil deterioration. For example prickly pears survive and fruit without
irrigation water and provide a valuable crop. It is also recommended that some food waste and plant
waste is placed back on the land rather than being fed to the animals, thus increasing organic content
and fertility. The notes given above on increasing fertility and reducing erosion/desertification should
also be considered.
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Table 4.1: Water flow test results
Table 4.2: Summary of flow losses
4.0 Irrigation System
4.1 Introduction
There are two concrete water collection tanks in the village which fill up overnight and are used to
distribute water to the fields during the day. The water source is an underground spring higher up in the
valley. Flow from the source is collected and reaches the tanks via approximately 300 metres of
underground channels (khettara) and then an open channel for 900m (seguia). From these tanks the
water is distributed to the fields via open earth channels and applied to the crops using flood irrigation.
The total flow arriving at the tank was estimated using several methods and the results are summarised
in Table 4.1 below, see appendix E1 for calculations.
Method Flow rate l/s
Measurement of seguia velocity 2.5
Depth of pipe flow (150mm UPVC) 3.5
Mannings equation (5) 4.0
Tank volume 3.3
50mm pipes at full bore 3.4
Average 3.34
One of the main aims of the project is to increase the flow in the irrigation system or, more importantly,
the amount of flow reaching the parcels. It is difficult to increase the amount of flow ebbing from the
springs, therefore the key to increasing water flow is understanding and pinpointing the main losses in
the system and reducing them. There are three main areas where water is lost; the khettara, the
concrete seguia and the earth channels. For each of these three elements, evaporation and infiltrationlosses were calculated. Table 4.2 below summarises the results and the calculations can be found in
appendix E2.
Element Losses (l/s) Losses (m3/day)
Evaporation Infiltration Total Evaporation Infiltration Total
Khettara 0 0.5 0.5 0 43.2 43.2
Seguia 0.017 0 0.017 1.35 0 1.35
Earth channels 0.018 0.6 0.618 1.5 52 53.5Total 0.035 1.1 1.135 2.85 95.2 98.05
The calculations of losses have been based on evaporation and infiltration rates measured on site. The
losses in the earth seguia are based on 300m of channel, this was chosen as an average distance of
each parcel from the supply tanks.
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4.2 Khettara
4.2.1 History
Khettara, or qanats, are underground tunnels that tap the groundwater and lead the water artificially to
a human settlement and agricultural lands using gravity flow conditions. The tunnels can be many
kilometres long and very deep. The longest qanatis more than 40 km long and 100m deep and can befound in Iran. In general a qanat system consists of an underground part and a part above ground
surface. The underground part is divided into the "water production section" and the "water transport
section". In the "water production section", the water is collected, either from a natural source or
infiltration of groundwater. This section is underneath the groundwater level of the surrounding area.
The "water transport section" transports the water to the surface. This section is usually lined on the
sides to prevent leakage of water. The gradient of the tunnel is very precise and should not exceed 5 %
in order not to let the flow erode the rock or sand in which the tunnel is dug. On the other hand, the
gradient should not be too low because then the water can not be transported to the surface as self
cleaning velocity is not achieved. The technique is similar to mining and originates from Old Persia
(present day Iran) around 3000 years ago. (6)
Figure 4.1: Khettara/qanat typical
Figure 4.2: Khettara/qanat typical
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4.2.2 Existing Khettara in Imi NTizghte
The system here uses three different underground springs. The mothershafts are 3m, 3.5m and 6m
deep, each being sited to collect water from the individual underground springs. Each spring is created
by water percolating through the earth and bedrock higher up in the mountains. The groundwatercontinues under gravity down the valley and eventually passes over a shallow section of impermeable
bedrock where the motherwell picks up the flow. Further investigation is required to confirm this which
would be difficult, expensive and at this point unnecessary.
There are two khettara in Imi nTizghte, both of which were built in the 1940/50s by the French. Figure
4.3 below shows the layout. The khettara from source 2 was originally built with 12km of pipe to supply
Tafraout with drinking water. This pipe was destroyed sometime afterwards by the villagers so they
could have retain all the water that they felt was rightfully theirs.
Key
River (Asif)
Khettara 1 (poor condition)
Khettara 2 (UPVC/Dimatit)
Barrage (sub river concrete dam
Seguia (300x300 concrete channel)
Manholes
Figure 4.3: Existing Khettara layout (See drawing 2011 in appendix F)
SOURCE 1
(6m)
SOURCE 2
(3.5m)
SOURCE 3
(3m - TBC)
SEGUIA
FLOW
RIVER
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Figure 4.4: Khettara 1 (MH11)
Figure 4.5: Khettara 2 (source)
Khettara 1
Khettara 1 is a stone lined channel approximately 400mm wide by
900mm high with a gravel and sediment invert. Six years ago, two 75mm
MDPE pipes of approximately 2l/s capacity each were added in the base
of this khettara between MH11 and the seguia to try to increase water
flow. We believe this had an initial impact of increasing flows to approx
3l/s because the total flow from both sources was measured as 6l/s
according to a local engineer in 2001. Today, based on a visual inspection
of the flow at MH06 (manhole 6, see drawing 2011), only one of the
pipes has a significant amount of flow, approx 0.4l/s (just less than half
bore). The khettara runs beneath a river which only flows as a seasonal
torrent during the rare periods of heavy rainfall in the area. During this
time water percolates through the khettara walls and into the channel
temporarily increasing flow. A dam running perpendicular to the river
flow also traps flow and directs it into the khettara. This dam is
supposedly broken, we were unable to confirm.
Khettara 2
Khettara 2 is a stone lined channel for the first 20m, it then becomes
simply a buried Dimatit pipeline. Most of the flow in the seguia comes
from this khettara, running at approximately 3l/s. In the 1980s the lower
section of Dimatit was replaced with UPVC. This khettara runs beneath a
smaller river at its upper section. Generally this khettara is in good
condition and will not be considered for renovation as part of this study.
4.2.3 Problems with Khettara 1Consider the khettara as having an upper section and a lower section. The lower section has 2No 75mm
MDPE pipes running along the invert, whereas the upper section is as originally constructed with stone
walls and gravel/sediment invert. The problem with the upper section is that the channel is unlined for
approximately 180m, therefore the infiltration losses are considerable (estimated at 0.5l/s equivalent).
The walls and roof have also deteriorated over time, leaving stones, rocks and debris in the channel
invert which, when not cleared, restrict water flow. To get past these obstacles the flow depth increases
which allows further water to escape through the khettara walls. The upper section has not been
cleaned since the 1980s.
The lower section has two main problems. Firstly the 75mm MDPE pipes have blocked over the last 7
years restricting the amount of flow able to pass down them, this is due to the low flow and lowgradient meaning self cleansing velocities are not achieved. Secondly, the original invert has not been
cleaned often enough, meaning that when flow percolates through the khettara walls it is quickly lost
through the invert due to infiltration as it cannot pass through the blocked channel.
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Figure 4.6: Khettara 1 section
Table 4.3: Khettara remediation Options
4.2.4 Khettara Remediation Options
The main aim of the remediation options are:
- Reduce/remove infiltration losses i.e. all flow gathered at source reaches seguia
- Stop the pipes and khettara silting up and blocking with stones and rocks.
- Retain permeable walls to allow for continued infiltration along the khettara length
All 4 options below include the new silt traps to be built at selected manholes (MH06 and MH11, see
drawing 2011), this will prevent the MDPE pipes silting up and ensure the silt gathers in a manholewhich can be accessed easily.
Option Description Advantages Disadvantages Cost
1
New MDPE pipework
from spring (Source 1)
to MH11
No infiltration losses in upper
section, cheap (pipe already exists on
site)
Does not allow fresh flow percolating
in to join the MDPE flow. Will sediment
up due to lack of flow velocity and
difficult to clean.
Labour
2Concrete lining entire
khettara invert
No infiltration losses, captures
percolating flow also.
Channel can still be blocked by falling
rocks, debris and sediments.
64740
(MDH)
3
Concrete lining entire
khettara invert, walls
and roof (re-build
khettara)
New long lasting infrastructure,
provides safe working and
maintenance area, channel no longer
blocks from falling stones/debris
Expensive, difficult construction (with
very limited access for machinery) and
complete removal of existing
infrastructure.
180000
(MDH)
4New 400mm concrete
perforated pipe.
New infrastructure, easier and safer
construction, allows for percolation
Removal of existing infrastructure, not
a proven technology in the area. Access
into manholes only (like a small sewer)
151900
(MDH)
5
Re-line invert with
perforated UPVC pipe,
gravel and PVC
membrane
Cheaper than concrete lining (option
2), also perforated pipe prevents
channels blocking with large stones
Tricky construction using straight pipe
sections in the meandering khettara.
Fig roots may grow in the perforations
and block the pipe this is TBC.
67710
(MDH)
FLOW LOSSES
FLOW IN
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Figure 4.7: Khettara remediation Options
Option 2 Option 3 Option 5
Option 4
4.2.6 Recommendation
Reline using UPVC pipe with perforations (option 5). It is not confirmed as to whether fig roots will
block the perforations, further study is required here to confirm before construction starts. If fig roots
are deemed a problem, then the pipes should be solid and maintenance improved to ensure thechannel is cleared annually (remove fallen stones/boulders). Regular maintenance will also be
required to remove collected silt as well as roots growing along pipe joints. See drawing 2012 in
appendix F for full details.
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Figure 4.8: Seguia and water tanks layout
4.3 Seguia and Water Tanks
4.3.1 Existing Infrastructure
The concrete seguia and storage tanks were built around 15 years ago. The seguia used to be the earth
channels like the ones seen between the parcels today. The open seguia runs for 900m from the
khettara outlet to the storage tanks.
Water from the seguia is used for irrigation, washing clothes and drinking. There is a pumping chamber
(Manhole C, see AutoCAD drawing) which raises the water to the header tank at the top of the village.
The Seguia details are shown below in figures 4.9 and 4.10. The seguia hugs a steep slope for most of its
course, traversing around regular rocky outcrops and changing in gradient to mirror the natural
contours. There are also several lateral outfalls (generally 100mm DIA holes) which, using stone dams,
can direct flow into parcels running next to the seguia.
N
IMI NTIZGHTE
ANBDOUR
PARCELS
Key
Concrete Seguia
Wash Area
Storage Tanks
Khettara 1
Khettara 2
River
Figure 4.9 Typical section through concrete seguia Figure 4.10 Seguia photo
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Figure 4.11: Tank 2 filling
& emptying via twist valve
Figure 4.12: Cracks and weeds Figure 4.13: Unlined sides Figure 4.14: Steep section
There are two water collection tanks. Tank 1, which is smaller and
higher up so the seguia water reaches it first, is sometimes by-
passed. Tank two, the larger tank shown in the photo, is 17mx 8.5mx
2.15m, therefore having a capacity of 310m. This tank is filled
overnight and discharged to fields each morning. Both tanks
can be bypassed if necessary using steel blanking plates. Tank
2 has three different outlets to serve different areas of
parcels, each controlled by cast iron twist valves. Each tank
has an emergency overflow and both have a build up of
sediment along the invert. Both tanks are in structurally good
condition and will not be considered further in this report.
4.3.2 Problems with existing Infrastructure
The 900m of open channel is all concrete lined but varies in quality with some sections having cracks
along the invert and sides. In general it does not look like there are any significant leakages. Most of the
cracks have allowed plants to cling to and grow within the channel. Therefore, as shown in table 4.2
infiltration losses are negligible. In some areas the walls are falling away or are no longer lined.
The gradient also varies along the length with some very steep sections. These create regions of fast
flowing water which accelerate the degradation of the concrete lining. To date however the lining is still
generally OK. There are also flat sections where flow is deep and slow, this causes deposition of
suspended sediments which slowly block the channel and slow the flow further.
Roots and plants growing within the channel also inhibit the flow and will gradually widen cracks in the
concrete lining, they also use the water. Where there are cracks and the flow is slow, there are oftenmany plants and weeds are growing. There is also lots of debris in the channel, generally dead leaves,
which further inhibit flow and could compromise the quality of the drinking water. Evaporation losses
from the seguia, as shown in table 4.2, are negligible.
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4.3.3 Remediation Options
There are four steps, or options, for remediation discussed here. Whichever scheme is chosen, it is vital
that first the channel is cleaned and all plant life removed. Option 1-Step 2 should not be carried out
with step 1 being carried out first.
Option 1 Step 1: Fix cracks and re-line base and walls where necessary
This involves fixing individual cracks by breaking out the cracked section, cleaning and scabbling the
area, then re-applying concrete and finishing until smooth with the existing channel. Sections where the
walls are not lined require new concrete lining, the walls should also be stabilized where they are falling
away due to the steep bank adjacent. This is a quick and cheap solution, however the results will not
last long unless the works are carried out to a high quality.
Option 1 Step 2: Improve gradients locally
There are three sections where the gradient would be unacceptable from a design perspective. These
sections could be removed by introducing new backdrop manholes or a series of steps set into the
existing channel. This would increase the life expectancy of the seguia. However the steps or manhole
would be in reinforced concrete and tricky to construct with limited working space, a dangerous slope
on one side and shallow bedrock.
Option 2 Re-line the whole seguia
This option is to effectively re-built the seguia with new concrete sections cast in-situ. The most cost
effective and quickest solution would be to line the existing channel with membrane and pour concrete
on top. The new concrete section requires expansion and contraction joints (bitumen filled) every 10m
and at each major bend/change in gradient. It is estimated that this could give a lifespan for the seguia
of at least 20 years, however the solution is time consuming and costly.
Option 3 Piped flow
A quick and cheap re-line solution is to pipe the flow for the 900m of seguia. The 150mm UPVC pipe
would sit within the existing channel with regular open sections at major bends, changes in gradient
and lateral connections. The solution is fairly simple to install and cheaper than option 3. However, the
pipe is aesthetically less pleasing, it removes the openness which helps local community trust
(everyone can see where the water is going) and it makes it more difficult to find/remove blockages.
Figure 4.15: Option 2-Backdrop Figure 4.16: Reline option 3 Figure 4.17: Option 2 Concrete Steps
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Figure 4.18: Concrete wash area
Figure 4.19: Contamination in channel
4.3.4 Costs
For full costing details see detail BOQ.
Option Description Cost (MDH)
1 Step 1 Fix cracks and re-line base and walls where necessary 3,800
1 - step 2A Improve gradients locally (backdrop manholes) 12,858
1 - step 2B Improve gradients locally (concrete steps) 11,150
2 Re-line the whole seguia in concrete 100,800
3 Piped flow (900m of new UPVC pipework + open sections) 75,080
4.3.5 Recommendations
Since the seguia is in decent condition, it is prudent that money is invested elsewhere before large
amounts are spent upgrading here. It is recommended that the channel is cleaned first including the
removal of all weeds growing in/near the channel. Then remediation option 1 - Step 1 carried out,which only tackles areas which are in need of repair. It is our understanding that the UPVC pipe
(option 3) has already been decided on in order to improve the quality of the drinking water.
Therefore recommend manholes at significant bends and changes in gradient to allow for access for
cleaning (sediment, etc) and repairs.
4.4 Clothes washing area
4.4.1 Existing usage and problems
The clothes washing area is used by many women in the village.Flow is diverted from the concrete seguia just upstream and runs
through the middle of the wash area in an open channel as
shown. This water is extracted by hand. The used soapy water
then rejoins the main irrigation channel and is used on the fields.
A small treatment section in the channel already exists just
downstream of the wash area. It consists of a series of four stone
dams which are supposed to filter the flow.
However the dams do not work effectively as all the suspended
sediments and soaps pass through the cracks in the rocks. Afterseeing the physical evidence and speaking with the local
population it is clear that contamination is an issue. According to
the DPA this contaminated water doesnt actually do much harm
to the trees but it does damage crops and vegetables.
Table 4.4: Seguia costs
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4.4.2 Remediation options
Option 1 is to make sure that none of the washing wastewater is used for irrigation by diverting the dirty
water into a new septic tank or soakaway. This would only be possible if there was a piece of land close
by available for this. One big disadvantage is the loss of water. Also the effectiveness of a septic tank or
soakaway is compromised by the antibacterial agents in the washing powder, especially when no other
bacteria are added (from a toilet, for example). This option includes new concrete washing sinks and
header tanks.
Option 2, suggested by the DPA, is to move the entire wash area to a position close to the river and to
use the soapy water to irrigate trees only. This option would be costly, require a large piece of land and
the backing of the community because it would change their usual habits, making it much further for
some people to walk. Although the water would be made use of it means less water is available for the
main fields where the crops are grown. It would also be difficult to set up a system where all of the
wastewater reaches trees only, especially if the system is entirely gravity fed.
Option3, is the purchase of washing machines particularly if it could be shown that they were economic
on water usage. It would be important that models chosen were modern energy and water efficient.
This option was chosen in another area of Morocco where they had the same problem, funded by a
French charity Leau de Desert. The used water would still need to be put into a soakaway or sewer.
There are the obvious benefits to the women of the village, giving them more time to work in the fields
for example, but it would take some organisation to avoid disputes and to agree on how much the use
of it would cost. There would need to be a building, electricity supply (possibly solar) and sewer system.
There would also need to be a strategy for the eventual repair and replacement of the machines.
Option 4 is to install a grease trap to remove the contamination. This would need to be cleaned
periodically, perhaps once a day, which would be a fairly quick and simple operation which involves
removing the top scum layer and putting it into a soakaway or cesspit (it is not recommended that the
waste is put into a septic tank as it will affect its operation). The settled sediments could be removed
around once per month depending on wash area usage. It is recommended that a temporary grease trap
is installed first to check the dimensions (the bigger it is, the less cleaning required) and the
effectiveness. This can then be replaced with either a new reinforced concrete unit or a system of
baffles cast into the existing outlet channel (where the stone dams exist today).
Figure 4.20: Temporary grease trap steel drum construction
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4.4.3 Costs
Option Description Cost (MDH)
1 New soakaway and concrete sinks/header yank 4,500
2 New wash area by river TBC
3 New washing machines 4,000 each
4 Grease trap - temporary steel drum Labour only
4 Grease trap Utilise existing concrete channel 1,775
4 Grease trap RC unit 5,050
4.4.4 Recommendations
It is recommended that the temporary grease trap is installed (option 4) and the community to be
consulted to decide the next step.
4.5 Earth Channels (Earth Seguia)
4.5.1 Existing Infrastructure and the problems
There is a network of over 2000m of earth channels delivering irrigation water to over 15ha of
agricultural land. The channels are lined with large stones and gravels. The less used channels have grass
growing in them. There are many steps and drop offs to allow the channels match the parcel terracing.
The channels are aesthetically pleasing and promote trust and openness with the water distribution.
The permeable invert also allows water to infiltrate into the surrounding soil and feed trees which live
adjacent to the seguia.
Figure 4.5: Contamination options - Costs
Figure 4.21: Section through existing earth seguia
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4.5.2 Problems with existing infrastructure
The earth seguias serve their purpose in transporting water to the fields but their efficiency is quite low.
The permeability test (see section 3.4) gave an infiltration rate of 6.7x10 -6m/sec for the soil. This test
was carried out on a dry earth seguia bed. The initial infiltration rate was 1.08x10
-5
m/sec which thensettled to 6.7x10-6m/sec. This means that, over say 300m of channel on average 300mm wide, 0.6l/s
should be lost (see table 4.2). Over a 12 hour day of irrigation that equates to 26m 3 of water wasted
(26,000 litres). If 3.4l/s leaves the tanks and 2.8l/s reaches the field, the efficiency is 82%. This
corresponds to data in The Civil Engineers Reference Book (7) which gives field canal efficiency of 80%
for unlined canals in blocks of up to twenty hectares. If the water has to travel further or the channel is
dry, which is often the case, the losses are greater. Other losses of water have also been observed, they
are hard to quantify but they mean that the total loss could easily be greater than 0.6l/s. The following
list gives the potential sources of inefficiencies which could be tackled:
1. Infiltration losses through channel invert.2. Undersizing of channels (flow spills over the edge).3. Losses at the many unlined steps and drop-offs.4. Wastage at stone dams/junctions which do not function correctly (flow dribbles into adjacent
lines, without actually reaching any fields and even if they did, the fields are not prepared).
5. Slow flow and pooling due to lack of gradient and high invert roughness (Mannings).
4.5.3 Options for re-lining channels
There are 4 re-lining options, all will reduce infiltration losses and increase water availability by up to
20%.
Option Description Advantages Disadvantages Cost (MDH)1 UPVC pipe lining Longevity and hard wearing Difficult to construct with many the bends, 132,700
2 PVC membrane Easy construction and cheap Vulnerable to punctures if not protected 42,700
3 MDPE pipes Very quick and easy constructionLose openness and aesthetics. Junctions
awkward (many valves would be expensive)115,500
4 Concrete lining Longevity and very hard wearing Expensive and long construction time 107,360
STONE DAM
WASTAGE
MAIN FLOW WASTAGE MAIN FLOW
Figure 4.22: Wastage at dams (4) Figure 4.23: Undersized channel (2) Figure 4.24: Poor drop-off design (3)
Table 4.6: Earth channel re-lining options (labour inc)
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As part of the re-lining there will need to be new junctions built. There are several options for this, the
cheapest and easiest to construction and maintain is as shown below. A concrete section with steel
baffle or piped sections with valves could also be used, though both incur greater costs.
4.5.4 Recommendations
Recommend re-lining with PVC membrane (option 2) with major junctions built as shown in figure
4.29 above. The channel needs to be well bedded and carefully covered with smooth stones to protect
the membrane. Recommend that a 200m section and one junction built first as a pilot (test) scheme.
Figure 4.25OPTION 1, UPVC half pipe Figure 4.26OPTION 2, PVC membrane
Figure 4.27OPTION 3, MDPE pipes Figure 4.28OPTION 4, Concrete lining
Figure 4.29 UPVC/concrete junction
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Figure 4.30 : Flood irrigation
4.6 Field Application
4.6.1 Existing Operation Strategy
The distribution is based on water rights. Each family has the right to a certain amount of water
depending on historic agreements; however this does not necessarily represent current needs. The
scope of this project does not include altering these rights however, only to increase the total quantityof water. The water rights have been the source of many disputes, especially when water levels are low.
Also, now that homes have tapped water without meters, water usage goes unmonitored and people
can be as inefficient as they like (many even use the tap water on their fields). To amplify the problem,
many villagers refuse to pay for the tap water.
During summer, when flow is low, each farmer is allocated certain time slots when they can extract
water from the seguia. This is measured in hours, the ancient method was to used a plate with a hole in
it. A plate full of water would take, on average, 7.5 minutes to empty, therefore they knew 8 plate-loads
was an hour of extraction time. Now the time is used. The distribution cycle during summer runs in 7
day loops (one farm in the morning, another in the afternoon)
During winter, when flows are higher, the time slots still exist,
however there is more water available per person. The distribution
cycle runs in 12 day loops. Winter is considered November to April
and the amount of rainfall varies from year to year, winter 2008 has
already seen more rain than the whole year preceding it (TBC by
DPA, Tafraout). The water is diverted from the earth seguias by
building temporary dams just downstream of their respective
lateral connections. This flow is channeled using stones/gravel
weirs. Once in the fields a variety of irrigation techniques are used
including flood irrigation, furrow irrigation and border irrigation.
4.6.2 Crop requirements and Irrigation Efficiency
As stated previously, the irrigation system is not performing to its full potential with flow losses from
source (khettara outlet) to destination (parcels). Presently, of the 3.4l/s leaving the khettara, only
2.77l/s arrives at the fields (based on EWB preliminary studies, see table 4.2 above). Based on crop
water requirements and irrigation efficiency it is possible to calculate the existing and potential
irrigatable area. The results were as follows; see Appendix E3 for full details.
Based on the Blaney and Criddle method, Crop water requirements in Imi nTizghte = 562mm/year
(based on average monthly temperatures and daily daylight hours, and a summer crop of tomato orsorghum. Millet, for example requires less water and has a shorter crop cycle, hence this value would be
reduced (7)).
This value does not take into account rainfall (8), hence we are assuming drought conditions. It does not
take into account any water added to the field between crops. Finally, this value does not take into
account the efficiency of the water application method. In this case we have an earth canal distribution
system (80% efficient) and flood irrigation (60% efficient). This increases the net annual crop water
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Figure 4.31 : Typical Drip by Drip layout (12)
requirement to 1171mm/year(562/(0.8*0.6)). To verify this, the Engineers In Emergencies design guide
was used (3), giving a value of 1092mm/year. We will work with the higher value.
2.77l/s gives a total water volume of87,355m3/yearavailable (arriving at the fields). The 2.77l/s takes
into account the distribution efficiency (previously taken as 0.8), therefore the crop water requirement
for every parcel becomes 0.937m3
per square metre/year (937mm/year), therefore the area which canbe adequately irrigated is 9.32 Ha. At present, approximately 15ha are irrigated with this 2.77l/s, which
means the crops are receiving around 60% of the water they need. This helps to explain the crop failures
and lack of fruiting trees in the summer 2008 harvest.
4.6.3 What is the potential?
There are two factors which can be looked at. That is to firstly increase the flow (reduce losses) and
hence the application efficiency. Secondly to improve the field application efficiency by, for example,
installing a Drip by Drip irrigation system.
By removing infiltration losses in the khettara and earth seguias, the flow arriving at the fields can be
increased to 3.87 l/s. This increases the annual water available to 122,044m3/year.
With a crop water requirement of 0.937m3 per square metre, it possible to irrigate an area of13.02Ha, a
large increase from 9.32Ha.
By installing Drip by Drip irrigation, field application efficiency increases to 0.8, the potential irrigation
area subsequently increases to 17.37Ha.
4.6.4 A note on Drip by Drip irrigation
Drip by Dip irrigation is an efficient irrigation method, it is a proven technology and many trees and
crops have very been successful under the system. The trickle system transports water through an
extensive pipeline network to the soil near the plant and puts the water directly into the root zone. The
main issue, however, is the cost and difficulty in construction. The most efficient and intricate systems
are generally used only for high value cash crops due to the high setup costs. Setting up a system to
work correctly in Imi nTizghte will
require a professional with the
correct knowledge, skills and
experience. It requires a hands
on approach, training the local
farmers in the process and would
most certainly benefit from a pilot
project on a few parcels (to test
construction methods and
effectiveness). INRA and DPA
involvement are absolutely
necessary here.
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4.6.5 Summary table, costs and Recommendations
SCHEMEAREA POSSIBLE
TO IRRIGATEADVANTAGES DISADVANTAGES
COST
(MDH)
Existing 9.32 Ha Costs nothingPoor efficiency, less crops, more
soils erosion
Free
Fix khettara an line
earth seguias13.02 Ha
Farming practices do not have to change,
more water available and more/better crops.Setup costs 114,210
As above + Drip by
Drip17.37 Ha Maximum efficiency
Difficulty setting up correctly and
high associated costs177,210
As shown in the table above, investment in the irrigation network can have a very significant impact on
the total area which could be effectively irrigated. At present the Boar fence design will contain an area
of 9.75 Ha. The total area covered by the channels is in excess of 15Ha (DPA, Fiche Techniques), it is
therefore recommended that firstly the khettara and earth seguia upgrades are completed. Followingthis, steps need to be taken to improve the irrigation efficiency further, via drip by drip or other forms of
water efficient irrigation. As a quick example, a Carob tree requires 350mm/year to fruit, so a flood
irrigation system (60% efficient) would demand 580mm /year (over the root area). To compare, a drip
by drip irrigation system (80% efficient) would need 438mm/year. This step, very much into the
unknown for many of the local farmers, needs be driven by INRA, DPA, AIDECO and the people of Imi
nTizghte.
In conjunction with this, it is suggested that steps are taken to encourage people to start using more
dryland crops. For example Pearl Millet (which can replace other grains such as wheat and corn), Carob
trees, and Cactus trees (prickly pear).
Finally, one of the main risks with flood irrigation is salinisation. This is when >0.1% salts (Na) exist in the
top 200mm of soil. Salinisation can be avoided by ensuring adequate surface and sub-surface drainage
to ensure no excess water pools and deposits salts. It is recommended that annual soil tests be carried
out by INRA (this could be organized by AIDECO/DPA/EWB each summer) to monitor salt levels and
irrigation/drainage modified as required. Remediation of salinisation is achieved in several ways, the
most appropriate and simple example is to flood the fields to flush excess salts out.
Table 4.7: Field Application options and costs
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Figure 5.2: AIDECOs sketch of boar fence
5.0Boar Fence5.1 Introduction
In recent years the wild boar population in the region has dramatically increased. A major factor in this is
the absence of natural predators such as wolves and jackels which have been completely wiped out. The
reproductive pattern of the boars has also amplified the problem. The boars are very destructive
because they eat most vegetables, even cactus, and also rummage in the ground for grubs which causes
further damage. Some people have built personal boar fences around their land. Materials seen include
stone walls, brambles, reeds, and wooden posts with chicken wire. Where there are these fences
vegetables seem to be successfully grown, however the vast majority of land remains unfenced.
There has been talk of building a perimeter boar fence for many years and it is something that many
people in the village say is the most important thing they would like to happen. The association had
sketched a suggested outline for the fence and then the EWB engineers surveyed the land to produce a
more accurate map. The total length of the perimeter was measured as 1430m. The terrain is
changeable and quite hilly and there is one length in particular that the slope is very steep,
approximately 30 degrees.
The original design produced by the DPA was a fence with
steel T sections as posts at 5m centres and galvanised steel
mesh (50x50). This design was not accepted by AIDECO who
thought it was excessive. See Appendix C for original fiche
techniques.The cost per metre was given as 80DH and the
total cost based on 1200m of fencing was 96000DH. The aim
of the EWB engineers was to propose a cheaper fence
design.
Figure 5.1: Existing Fence types in Imi nTizghte
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Figure 5.3: Wild Boar and electric fencing
Various options were looked at with each one have advantages and disadvantages in terms of cost,
appearance, effectiveness, time to construct, maintenance required and environmental impact.
5.2 Initial design considerations and materialsOne of the first things that was looked into was an electric fence as this is what is typically used in
France. The cost of this fence would be quite modest, as low as 20Dh/m, based on prices from a French
website (9). However it was decided that it would probably not be appropriate here because the
maintenance is so important for it to work correctly. With a wall or solid fence a small area of damage
might leave an area that can be breached but if an electric fence is not working the entire thing becomes
useless. Given the length of the fence and the relatively high level of maintenance required it was
deemed an inappropriate technology for the village. To back this, there is an electric fence somewhere
else in the valley which has proved ineffective, thought the reasons for the failure are unknown.
It was thought that local materials would be the cheapest
and have least environmental impact. There are fences that
have been built using the trunk of a date palm as the base
and then palm branches to as the barrier. This is ok for the
small fences some people have but there would not be
enough for the kind of lengths necessary.
The British CIRIA Wildlife Fencing Design Guide (10) and all
evidence of fencing seen in the UK is that timber fence posts
are used. This guide does also show examples of steel posts
but says that concrete is not suitable because it does not
perform well under tension. The problem here might be sourcing good quality timber and preservative.
Some of the electricity poles in the village are in timber and this type of timber would be suitable. It
should be found out where this timber comes from, what is its expected lifetime if treated and the cost.
Any timber sourced needs to be from a sustainable resource, a local managed forest is the ideal.
The other obvious local material is stone. All the traditional buildings are built from stone with an earth
based mortar. The advice from the DPA was that this option would be no cheaper because stone would
still have to be bought still that problems could be caused by people taking stone from existing terrace
walls. The opinion of the EWB engineers was that enough stone could be collected from the surrounding
area if there was enough of a volunteer labour force from the village.
Design 1:Dry stone walling with living barrier
EWB and DPA agreed on the merits of the option of dry stone walls along the river where there is an
abundance of stone. It is a traditional technique and could enhance rather than degrade the natural
landscape. There is also the advantage that in some places walls already exist which just need building
up to a suitable height. In addition to the walls prickly branches are placed on top to create a more
effective barrier. These could be Gigibier or Argan. A line of trees can also be planted on the inside of
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Figure 5.4: Section through river stone dry walling with trees
the wall which within a couple of years will grow to a height that the can be pruned to form a living
barrier over the top of the wall. It is hoped that these trees will require no irrigation and can be provided
by the Department dEau et Forets.
Environmental issues: One concern with this is that it may affect the river if too many stones are taken
from it though the DPA assured that this would not be a problem so long as stones are not taken from
the river banks as this could change the course of the river. These rivers actually only flow normally
about once a year and are used by most people to burn their rubbish, therefore the environmental
impact is considered negligible. The embodied energy in this option is almost zero (only the transport
required for labour and trees) and the planting of trees has a positive impact.
Cost: The cost of this wall is very much dependant on the labour since the materials are free. If there is
enough local know-how and people willing to volunteer the cost of the wall would be very low.
Otherwise due to the length of time it takes to build compared to a fence the cost would not be that
much less.
Maintenance: For this length a maintenance strategy would need to be in place with people assigned to
ensure that the Gigibier is intact, to make any repairs necessary to the walls and to prune the trees.
Design 2: Mesh fence
This is similar to the original design by the DPA however it is suggested that timber posts are used
instead of steel to reduce the cost and also as a material with lower embodied energy. Due to the
transparency of the mesh this fenceline would not have a big impact on the landscape. It is most
suitable for terrain which is reasonably flat. Mesh can be placed to a depth of 200mm in the ground and
attached to a tension cable to prevent the boars from digging underneath. On steeper ground masonry
walls could be built to provide to provide a horizontal base on which to place the fence.
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Figure 5.5: Elevation section of Timber post and 50mm mesh
In order for a mesh fence to be effective certain specification should be made and it is recommended
that the following advice is taken:
Posts at the start of a fence line or at a change of direction need to be at least 900mm below ground and
need to be supported with a strut and tie, see the figure.
For a boar fence the guide recommends a minimum of 200mm below ground and 900mm above ground
level. However it suggests that this may need to be increased in certain circumstances. The high
population and determination of the boars here would justify increasing this height.
It is important to specify a good mesh. If it is a woven mesh, the joints should be lock joints rather than
hinge joints so that verticals cant slip on the horizontals.
Foundations are not required if the posts can be driven into the ground without first digging out the soil.
It would be beneficial to source a mechanical post driver if possible to drive the posts into the hard
ground, this is made easier with pointed ended posts.
It is important that the mesh is attached to the outside of the fence, i.e. so that the animal pushes the
mesh onto the post rather than pushing it off.
Environment and Costs
The timber posts MUST be specified from a sustainable forest resource. For this scheme to become a
symbol of best practice then we must invest in protecting the environment wherever possible. The
openness of the mesh also helps to minimise the visual impact. As stated above, using timber also
helps to reduce the cost.
Maintenance
These fence sections will need to be checked regularly for weaknesses and breakages. The tension wire
can be tightened manually so it would be prudent to train a local person how to do this.
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Figure 5.6: Timber end post detail
Figure 5.7: Endpost
Design 3: Half blockwork wall half mesh
For the length of fence along the road a robust solution is necessary because
of the possibility of impact from vehicles and the amount of pedestrians
including children who frequent this route. A fence line with posts and mesh is
one option, although it might be subject to damage. There is also a reasonable
slope which is makes it difficult to accommodate the mesh. The DPA suggested
that a wall built in concrete blocks could work out to be cheaper, particularly if
a machine were purchased to produce the blocks in the village using sand
dredged from the river. This seems like a good suggestion however solid
concrete walls would not be very aesthetically pleasing, particularly because
they would block the view and give a closed atmosphere. Therefore the
proposed option is to have a block wall built to a height of 600mm 980mm
with a mesh for the upper half (the height of blockwork varies over each 5mlength according to the slope, 4 courses of blocks suggested as minimum). It is
recommended that the blocks are plastered and painted a similar colour to the
houses for a better look. The mesh required would not need to have such
small squares as the 50x50 suggested for a full height mesh fence because the
boars can exert more force if on the ground rather than if they have tried to
climb up. A mesh size of 100 x 100 is proposed.
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Figure 5.8: Elevation section, half blockwork wall half 100mm mesh
Environmental issues: One disadvantage of this wall is the amount of cement needed to construct it,
with the high embodied energy which that entails. A more environmentally friendly method would be touse earth blocks, or rammed earth. The DPA do not think that the soil here is appropriate for this use
but it is something that should be given more consideration before being completely ruled out,
particularly when earth has been used in the construction of the old houses here.
Cost: The cost depends on whether or not the blocks could be produced locally with a new machine.
This mesh size is cheaper than for the type of mesh required for a full height mesh fence.
Maintenance: Maintenance is quite low. Repainting of the wall every few years would improve the
appearance. The mesh may need some repairs and the posts may need replacing after 10-20 years
depending on the quality of timber and preservative.
Design 4: Masonry wall
This option was decided upon because it offers a stiff, robust solution on steep rocky ground. It is
expensive but it is a well known method used throughout the region and utilises local materials, hence it
fits well with the surrounding environment.
Environmental Issues: Embodied energy from the mortar and reinforced concrete posts. Using local
stones removes the need for quarrying and transportation. The wall fits in well aesthetically and its high
lifespan improve the overall environmental impact.
Costs: Are high due to the concrete and steel volumes. Can be made cheaper if local/volunteer labour is
used.
Maintenance: Low. This is as maintenance free as it gets. This wall will also last longer than any other
fence type discussed here.
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Figure 5.9: Mortared stone wall with concrete posts
Figure 5.10: Typical gate detail
(Timber with mesh infill)
Gates
The position of the gates along the fenceline should be
agreed with the community in order to ensure adequate
access. However the number of gates should be kept to
the minimum required because they represent a
weakness in the fence (continuity) and they can be left
open. They also increase the overall cost. A practical note;
you need to put end posts either side of a gate rather thanusing the gate posts as end posts. This is because the
endposts take the strain of the main cable and will move
over time, therefore the rigid gate would not last very
long under such conditions. The gate consists of timber
cross members with 50x50mm mesh infill and a 200mm
deep concrete footing linking the two gate-posts.
Maintenance issues
Problems are envisaged here because of problems in the community. The evidence of a very small
turnout to a presentation given on the fence and irrigation scheme suggests that a community meeting
to discuss maintenance would be impractical. A more likely outcome is that there will be a few
dedicated people in the village who end up doing all the work. If this were the case it would be fairer for
everyone to pay a small amount to pay these people for the work. Though again getting a consensus on
this would be difficult. In summary this is an area which need a lot more consideration and work from
AIDECO. It would be prudent to assign some budget to the upkeep of the fence.
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Table 5.1: Fence sections cost and appraisal
Figure 5.11: Fence sections and plan of Imi nTizghte
Section TERRAIN FENCE TYPE ADVANTAGES DISADVANTAGES COST MDH
A
235m
Riverside -
flat
Drystone wall (river
stones)
Cheap solution and longevity, also
aesthetically very pleasing and
sustainable material usage
Time consuming
construction, living part
needs maintenance. Takesup space on land.
8225
35Dh/m
B
222m
Roadside -
moderate
slope
Bottom half block work,
top half 100mm mesh
Suits sloping ground, longevity,
strong, keeps open view.High embodied energy.
22270
100Dh/m
C
206m
Roadside -
moderate
slope
As above As above As above19775
96Dh/m
D
72mFlat bare soil
50x50 mesh and timber
fenceposts
Quick and easy construction.
Low visual impact.
Relatively expensive,
vulnerable to vandalism
9479
132Dh/m
E
280m
Riverside
flatAs above (A) As above (A) As above (A)
11100
40Dh/m
F
35m
Steep rocky
section
Mortared wall with
concrete posts (5m c/c)
Longevity, aesthetics and extremely
robust
Costly, time consuming
construction
7685
220Dh/m
G
110m
Linkages
betweenhomes
Mortared wall with
concrete posts (10m c/c)
Longevity, aesthetics and extremely
robust
Getting agreement from
locals to use existing walls
14605
133Dh/m
H
119mFlat bare soil As above (D) As above (D) As above (D)
14426
121Dh/m
J
147m
Stepped Soil,
rocky
terraces
As above (B & C) As above (B & C) As above (B & C)14985
102Dh/m
TOTAL 122550
KEY STATS
1426 m LENGTH
122550 MDH TOTAL COST
86 MDH/m COST/M
98550 MDH MATERIALS
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Figure 6.2: Map showing
Pearl millet in Africa. Photos
of Pearl Millet (top) and Okra
6.0 Crops
Different crop types a critique with respect to Imi nTizghte
A number of different crop types are grown today in Imi nTizghte, this chapter looks at those species
which are grown, those which could be exploited further, and new crops which may not have been
considered before. The hope is to leave the local population with ideas for future agriculture to make
best use of the water whilst bolstering income.
6.1 Existing Crops
There is a limited variety of crops grown in Imi nTizghte today, generally due to the fact that the boars
eat most crops. They do not eat wheat, therefore it is the most popular crop. Some small parcels have
simple self maintained boar fences and they grow Courgettes, Aubergines, Squashes, Peppers and
various root vegetables. Alfalfa is also grown as animal feed.
The vast majority of the oasis is taken up by fruit trees including Argan, Olive, Almond, Date with a few
Carob and the occasional Pomigranite. There are also some fruiting cactus trees.
6.2 New crops
Suggestions for new crops include Pearl Millet, Pistachio tree,
Marama bean and Okra. These are all dryland crops, though
market value in the region requires further assessment. Pearl
Millet is often preferred to maize or wheat because of its
tolerance to difficult growing conditions such as
drought (it can survive on 200mmrainfall /year!), low
soil fertility and pH, high salinity levels and high
temperatures. It can be used as animal feeds, bread
and cous-cous making, and porridges. The Marama
bean is rich in oil and protein (rivaling soya) and
grows well in the Kalahari Desert. Okra is a another
dryland crop. It is a vegetable which grows wild in
Ethiopia and Egypt and is now grown and used for
cooking and making oil throughout the world.
Olive Almond Date Argan
Figure 6.1: Some trees of Imi nTizghte
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Fi
re
.
:T
e
r
ist
c
i
tree
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6.3 Future outlook
It is recommended that an effort is made to increase the numbers dryland cash crops in the area. This
can be in the form of the potential new crops mentioned in 6.2 and increasing numbers of certain
existing crops and trees such as Carob and Cactus. INRA are very interested in driving and monitoring
the use of the Prickly pear cactus. This i