Previously the only source of water was contaminated and had to be carried over long distances. Mortality rates from disease and malnutrition were high despite World Vision clinics and food aid projects. The problem had to be tackled at the source to give a sustainable solution.
World Vision with the financial support from AusAid and the Australian public had built a water supply system in the Likimse region, to supply fresh clean water to 54,310 people from points close to village centres. Surplus water was available for irrigation.
Flood irrigation was not effective, as most of the water was lost by evaporation or seepage before it even reached the plot, and even then it gave a poor water distribution with sometimes the water not even reaching the end of the run.
1) transport the water without losses
2) distribute the water uniformly
3) to schedule the irrigation so that the right amount of water was applied for plant needs
4) to select crops that would provide the basic nutritional requirement from the limited water plus some market orientated crops such as coffee, paw paws and banana
5) The system had to be simple and use locally available material.
6) It had to be cheap, the aim was to be able to provide food for a capital $2 per person
a process called micro-flood, gravity fed irrigation but with small areas being irrigated in sequence
Water is transported by thin walled plastics pipe. In this case made from recycled plastics bags manufactured by Visy Plastics, although the plan is to make this in Ethiopia. It is like a long skinny but, tough plastics bag.
It is laid in a trench, then back filled with soil, forming essentially a lined channel, but about 1/10 the cost of conventional pipe and works just fine.
Note the small diameter. This is possible because of the 'tilt valve'.
The tilt valve may look crude but is an amazing device which allows each irrigation zone to be irrigated in sequence. The balance tube is slowly filled and after a certain amount of water has flowed, it will snap shut diverting flow to the next, so each zone is automatically irrigated in turn. This enables large areas to be irrigated from a small diameter transport pipe. The major cost is the four bolts which are 30 cents each (but we are working on that).
The author showing how to use drinking straw as an emitter. One straw gives four emitters so the total cost is under 0.1 cents each. This may seem a bit nit picking but when the average income is only $100 per year your first worry in the morning is not about scratching your BMW. The entire system had to be designed to use locally available materials at minimum cost.
The straw gives a simple but accurate way of controlling flow. High flow rate with short run time give a wide spread of the water without water
passing the root zone
Water can be directed to point sources, to water an individual tree like this pawpaw
or into rows for growing row crops or spread over an area
Maize is the main crop, however there was simply not enough water to irrigate the entire area under cultivation. Rather than irrigate a small area of maize it was decided to focus on growing selected vegetables considering their nutrient value and water consumption.
Once the crop is decided then we can think about he best way to irrigate, looking at irrigation depth, (set by the root depth), water requirements and frequency of irrigation. This helps decide the best way to irrigate and influences the best way to transport the water to the site.
This gave a great opportunity to rethink an entire irrigation system from a clean start.
Conventional flood irrigation was not practical as there was simply not enough water, drip was far too expensive and the associated items like pumps and filters are just not viable. There is no electricity, (or telephone or email), fuel is imported and there is not the hard currency. Gravity feeding was the only option.
Shallow rooted vegetables are going to be grown in this section so it is important that the water spreads rapidly with no water lost beyond the root zone. A saw tooth design was chosen so that each bay had a significant gradient. This also helps drainage and avoid soil erosion in periods of heavy rain.
Tractors are a rarity in Ethiopia, but the ground was soon prepared and ready for its first soaking, before planting.
The great thing about working in Ethiopia is the enthusiastic support from the World Vision Ehtiopian staff and community members. The demonstration site was commissioned within three days by local volunteer labour, and was inspected by the President and directorate team of World Vision on the day it was completed.
The 'disturbed' soil was first consolidated by an initial thorough wetting. After planting, only the upper soil will be worked- allowing a hard base to form which assist lateral movement of the soil.
With a fine tilth to the upper soil and a firmer base there should be no surface water, rather the water should move through this tilth.
Experience has shown that water can move at least 10 meters through the upper surface without surface water.
Micro flood differs from conventional flood in that there should be no surface water and differs from drip in that water moves by gravity rather than surface tension or wicking. This is why the pipes can be so widely spaced.
It is still gravity fed so there are no pumps or filters or expensive components requiring high maintenance.
The pawpaw tress on the left are irrigated from the same system but there was no need to rework the levels, just place an emitter at each tree.
-
More production, the water only has to move a small distance so the soil is kept moist by small but more frequent irrigations rather than the traditional deep cycle (saturate and dry out) irrigation.
-
The flow in the feeder channels is small but consistent allowing small and cheap lay flat feeder pipes.
-
A tilt valve automatically stops flow after set volume of water had flowed, allowing sequential irrigation with continuous flows in transport pipe.
-
A simple evaporation meter with a set point to show when to irrigate (see upcoming feature on scheduling)
-
A combination of high nutrient vegetables were selected to make best use of the water.
click
here
