What options are there for upgrading the traditional falaj irrigation
system in Oman?
Does anybody know of anybody who can advise on adapting the traditional irrigation systems (the falaj) in Oman? These irrigation systems are traditionally hand dug and provide water for date palm crops which only require water once a week but people are now trying to diversify the crops grown and would like to have a more efficient (less leaky) system and to have water on demand rather than once a week.
What options are there for upgrading the traditional falaj irrigation system?
My great thanks for interesting suggestions so far.
Please read my responses below to the points that have been raised by John, Martin and Ian.
John: You talk about assessing the resource potential of a wadi or seasonal river. There are three types of falaj in Oman: Ayni (water from a spring), Ghayli (water diverted from a wadi) and Daoudi (water accessed by hand-digging a tunnel – can be more than one or more kilometres long – such that the head of the tunnel taps the water table and the tunnel then flows by gravity to emerge at the village where traditionally some water was taken for domestic purposes and, again under gravity, most of the water is allocated to each garden in turn). We are working in Luzugh with a Daoudi falaj. Rainfall is low and very unpredictable in Oman. The strength of the Daoudi falaj is that the flow of water is ‘damped’ by the strata through which the rain water descends to the water table so although the falaj flow is quite varied it is very much more reliable than wadi flow. The Luzugh falaj seems never to dry up though the flow rate varies from 80l/s to under 10l/s over a series of years. Traditionally the villagers have coped by irrigating less land when the flow rate drops, but always giving priority to the date palm. But in these oil economy days dates form a much smaller proportion of the village diet and only minute proportion of the village economy.
John again: You also talk about undertaking a feasibility study. Quite a lot of people over the years, with varying levels of direct contact and discussion with villagers, have judged the potential value of changes to be made to the system. But to my knowledge only two attempts have been made to test change. One was too small and the other far too expensive – using high cost equipment whose use and maintenance was in no way sustainable. Our project in Luzugh is, essentially, a kind of feasibility study. I sometimes refer to the core of the project as being ‘action research’. On the basis of the best information available and in close discussion with the falaj managers and the falaj water users in Luzugh we want to test the feasibility (technically and socio-economically) of one or two action research (or pilot) projects to see whether in practice we can improve falaj water flow (less leakage and better distribution), and we want to monitor ... (more)
There are plenty of options. ..eg. sealing the tunnel in the conveyance part outside the source zone; using trickle irrigation in the fields. If crops need watering more than once a week, the order of watering could be changed... as long as the whole community using the system agrees. Talk to the falaj experts there - Mahmood Al Azri, Head of Falaj sectiion in Ministry of Water Resources; Abdullah Al-Ghafri at Nizwa University. I am copying them in on this. Harriet (Nash)
The system works on the basis that crops needing the most
year-round water and year to year are grown nearest the source ( palm trees). When there is
sufficient water in the system alfalfa etc are grown next, and wheat at the end in the best years,
as you outline. The distribution is complex and involves rented and owned water on the weekly or
half weekly basis, but is naturally geared to the seasonal and annual fluctuations in water table
levels, so there is never over abstraction. I think the best way to make it more flexible might be
to construct a ground storage tank to take some of the the amount allocated by right or rental and
use it when it is wanted for trickle or other irrigation but that would then need a pump on the
tank. Answer would depend on the resources of the families concerned and the size of the falaj
flow. A small elevated tank connected via a pump to a ground storage tank would let them irrigate
by gravity in small quantities at night or day for drip or even sprinkler irrigation for
vegetables if they want more than weekly irrigation and greater efficiency. Previously people
tended to make gardens beyond the falaj lands and dig a well for vegetables but protection zones
may now make that a problem? Since distribution channels do leak and trees are often over-watered
another option might be to dig a well in the groves to re-capture some of the wasted water?
Channel water losses can be reduced in smaller falajes by a) putting a cistern at the top end of
the open section and/or b) laying plastic sheet along the channel.floor (cheapest option). I am
happy to help if I can be of any assistance, but you have probably thought of these solutions!,
Where in Oman? I worked for 4 years on and down aflaj including on water losses and irrigation
efficiency there and would be interested to know how they are working now.
Best wishes Sally Sutton
My general view on upgrading traditional irrigation systems is “if it ain’t broke don’t fix it”. Generally traditional systems have grown up over time and have evolved a management system that works. Any imposed system that significantly alters the operation of a scheme may have disastrous consequences for management practices as well as traditional land and water rights. I was involved in a project to “modernise” irrigation schemes in Ethiopia and it is true that greater theoretical efficiencies can be achieved but tread carefully if there are any major changes. It is management systems rather than the hardware that generally causes the failure of communal irrigation schemes even if broken hardware is the symptom.
Having said the above if it is simply repairing what is already there then you will probably be OK.
As I understand it these systems are horizontal tunnels dug into a hillside to access an aquifer. There is probably not much you can do about the water resources available and any additional attempts to drain or pump more water might result in the existing systems running dry. What you can do is improve the efficiency of the use of what is flowing out of the hillside by one or more of the following options;
• Line, or repair the lining, of the transmission canals or even put the water into pipes which would reduce evaporation losses but might be expensive • Improve the in-field efficiency by changing from a flood irrigation technique to sprinklers or drip if the operating head is sufficient and there are suitable skills to maintain a more complex system • Reduce evaporative losses from the field surface by promoting mulching (if there is sufficient biomass) or even the more modern alternative of plastic sheeting.
The water on demand question could be a tricky one. I don’t know if the water flows and is used 24/7 or if there are periods when water is shut off, diverted into storage or flows to waste. In many irrigation systems there are night storage reservoirs to capture the overnight flow when the farmers leave their fields and go to sleep. It may be possible to increase the availability of water by introducing some storage but before you do that, check carefully about what downstream users are doing. Is any “waste” water being used by other farmers or animal herders further down.
Hope that this helps.
* Update *
It appears from Google that the hill is on the other side of a major dry river bed from the irrigated area and the scheme itself comprises a large area of palms with some well managed and well laid out market gardening plots using surface irrigation canals. Some of the plots appeared to be out of use at the time of the image implying perhaps a shortage of water. If the falaj cannot yield any more water and there are no improvements that can be made in the water conveyance or infield distribution systems there might be possibilities for ... (more)
Interesting question and quite a challenging objective to achieve. The
first step would be in establishing the design demand volume of the proposed system. This will
be determined partially by the types of crop and the type of farm water management selected
(e.g. flood irrigation, drip irrigation etc.), and partially by the how much of the crop water
demand is to be supplied by irrigation. For your interest the following link provides an outline
of the procedures that could be used for this. Unless you are a hydrologist I would skip the
mathematics and detail. I am a hydrologist and sincerely wish I could have skipped the
mathematics and detail! https://www.fao.org/docrep/x0490e/x0490e00.HTM
• It is important to realise that irrigation is as much about timing as quantity, so it would be preferable to get someone with experience of participatory methods to work with your communities in developing seasonal and cropping calendars at this stage. The following link gives a flavour of some of the participatory tools and approaches available (I could not find one on irrigation, but the principles are the same, even if the desired outcomes are different). https://www.unisdr.org/we/inform/publications/2299 • It is also important to note that the type of farm water management technology is determined as much by the communities capacities, traditional norms in land and water rights as it is by technical constraints. Irrigation on a meaningful scale uses large volumes of water and consequently infrastructure. The communities you are working with will be required to develop and maintain quite sophisticated institutions for your irrigation scheme to be successful. I cannot stress strongly enough the need to employ participatory approaches. • Once the design demand is established then you need to establish the supply volume available from your water source. Definitely hire an experienced hydrologist for this, it will be a critical determinant of the overall cost of your scheme. Water storage is expensive.
• In general the cost of your system will be determined by the efficiency required, which is a function of the ratio of supply to demand, storage and management arrangements. You should also carry out an EIA early in the project as irrigation in arid areas carries a high risk of soil sodicity and potential toxicity. For an overview of the issues you could check out https://www.fao.org/docrep/003/t0234e/T0234E00.htm#TOC. • For more specific guidance get in touch with the ministry of agriculture, ministry of the environment and natural resources. These ministries are likely to have carried out feasibility studies based on the hydrology and soil types in the area. I would suggest these as your first port of call, as they are also likely to have registers of engineering and professionals licensed to work on irrigation schemes. In my experience poorly planned irrigation projects with poorly executed feasibility studies are generally a waste of money. I hope the above helps to get you started. There is no ... (more)
Having worked in Oman on and off for several years I've seen some of the falaj systems that you're talking about.
I believe that in some cases it would be quite practical to line them with flexible polyethylene pipes, depending on the size and spacing of the access shafts, in the same way that thin polyethylene pipes are used to line sewers.
The minimum bending radius of PE pipes is in the region of 20 to 30 times the pipe OD. You would need to take this in to account when looking at whether it would be possible to get the liner pipes down the shafts and in to the falaj channel.
If you require any further information please drop me a line as I'm based across the border in Abu Dhabi and visit Oman several times a year.
The answer to this depends so much on local geography (rainfall, slopes, catchment size, geology, etc) and for what purpose the water is used for (just small-scale irrigation or domestic as well) but I recommend this book
If there are any specific technologies that you would like more advise on I'm happy to help
* Update *
Further to Martin’s post, may I suggest some technologies to consider for harvesting water from seasonal rivers
1) Sand dams and sub-surface dams. You can download the latest edition of our sand dam manual (NB it is still being reviewed).
2) Water abstraction from sand rivers. Further information on Water from Sand Rivers is available online.
3) Water spreading weirs. Further information on water spreading weirs is available online.
4) Spate irrigation. Further information is available from the spate irrigation network
The falaj question was put onto knowledge point by Neil Noble on my behalf. I had not known about KnowledgePoint before. I am very happy that the question elicited six responses and would like learn more about your different interests in the aflaj in Oman. We have an opportunity to work in one particular village in Oman and would like to move beyond just collecting local information - we would like to work with the local community to help make the falaj more productive. My email is email@example.com. Best wishes, Roderic Dutton
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