:: Specific Design Brief

ITDG 4: Rainwate
r Harvesting - further information


Mahamaddawa is a village in north west Sri Lanka, a very dry part of the country. They have many months when there is no rain. Collecting and storing water efficiently is vital to them, especially for drinking.

The village. Mahamaddawa is a village of about 225 households in the north western region of Sri Lanka, not too far from Puttalam. There is an average household size of about five people. Work. It has a long tradition of subsistence farming, with households selling anything extra they produce in local markets, the nearest being about 10 kilometres away. Rice produced in paddy fields is most common. They cultivate home gardens and also plots in the higher land nearby. Some women work in the nearby tile, brick and timber factories and some of both sexes are self-employed craftspeople. Income. An average income for a household would be around 250-300 rupees per day for agricultural labourers (a little less than 2) whilst craftsmen such as builders or carpenters might receive 350 rupees per day. Cost of living. Although the cost of living is much lower, they are still poor families whose lives are made much worse when there is drought and no water saved. (
Example prices are: kilo rice = 48 Rupees, packet of dried milk = 17R, loaf of bread 13R, kilo of vegetables 60-80R, coconut = 18-25R. A bicycle would cost between 8-10,000R)

The village is 3 km away from the nearest public transport, which is not particularly reliable. The majority of households own a bicycle that is used to carry as many people as possible, and to carry goods and produce backwards and forwards. Housing. All the families own their own homes but most have only two or three rooms. A recent charity intervention has meant that over 60% now have tiled roofs but this is high compared with many areas. The remainder have traditionally thatched roofs made from coconut leaves and a mixture of local grasses including mara and iluk.

Rainfall patterns have been changing, with local officials claiming this has been the result of global warming. The island used to have two monsoons or rainy seasons every year but this is now far less predictable. Mahamaddawa is in one of the driest regions of the country, with an average rainfall of 1500 mm per annum, much lower than the capital, Colombo. Temperatures are often in the high 30s. There will usually be a period of three or months without any rain but often the dry season lasts even longer. There have been times when no rain has fallen at all in a year. Because of the low rainfall and its lack of predictability, being able to store water is crucial. During the dry season communal wells can dry up completely. However, a household's ability to store water is limited by the vessels it has available that are suitable.

Water requirements.
It is difficult to distinguish requirements for different purposes as most surveys look at total water needed. That includes drinking, cooking and washing. However, one household visited in the dry season uses 12 litres of water for six people, suggesting they are extremely economical with their use of water for drinking purposes. They would also need about 40 litres for cooking and approximately 1500 litres for bathing and 400 litres for washing clothes.

Traditional methods of collecting and using water
Most villages, including Mahamaddawa, have a large reservoir that has existed for centuries. This is usually used for bathing and washing clothes. It is a common sight at almost any time of the day to see people washing themselves or their clothes at the edge of reservoirs. However, that ancient tradition has not been transferred into reservoir use in modern times.

For cooking and drinking purposes, they collect water from the nearest well. In Mahamaddawa, most would have to walk a minimum distance of between half and one kilometre but for some the distance can be as great as five kilometres in each direction. This means that the amount of time spent per day collecting water can vary greatly depending on factors such as;
distance travelled
quantity of water capable of being carried per trip
who is involved in water collection
availability of transport.
It has been estimated that an average household may spend 4-5 hours per day collecting water.

Although there are several public wells, there is a problem with sedimentation, which limits the amount a well can hold, and salinity or contamination due to poor pipes. As a result there is only one well used by over 200 households for drinking purposes. It seems that there is an unwritten but strictly kept rule that this well is only used for household purposes, never for washing.

Traditionally, it was a woman's job to collect water, and it is evident that this tradition continues quite a lot of the time. Women collect water in aluminium containers that can usually hold between four and five litres. Each weighs about four to five kilos. The women traditionally carry them on their hips. Children of both sexes are also likely to help.

Increasingly, the task is being shared more equally. Men can carry more, and travel longer distances in the dry season. They are more likely to have access to bicycles, which also enables them to collect larger quantities.

Research suggests that in the wet season, households make between three and six visits per day to collect water. In the dry season it can be as many as ten visits.

Other problems during dry seasons or drought.
Inevitably, there is a temptation to use other impure water sources during hard times, with a consequent increase in water borne disease at this time. In compensation, however, cases of malaria fall. The necessity of boiling water is not a simple one, either, as villagers do most of their cooking on local fire systems.

Because of their dependence on subsistence farming, their crops are also hit badly at such times. The only way they can economise is through reducing the amount they eat. Surveys have shown that households reduce their eating from three meals to two per day during the dry seasons, with a consequent impact on their health. Since income is also reduced, they are less able to purchase essentials.

Traditional methods of rainwater harvesting.
It is highly unlikely that Mahameddawa will receive piped water in the foreseeable future so a different method of obtaining a more stable supply has recently been sought. There is a long tradition of using different methods of harvesting rainwater in the village and these are now being supplemented by some more modern techniques. The aim is to collect as much clean water as possible, so both the storage vessel and the means of collection is vital.

Royal palm leaves. People use local clay or bricks to construct a tank, usually with a capacity of about 1,250 litres, enough for 25-30 days' household use (drinking and cooking). They then use a very large palm leaf with a huge surface area to collect and filter the water. It can fill a tank in 3-4 hours of heavy rain. The palm is mounted on four sticks and sloped into the tank to collect rainwater directly. Although it does not bring impurities, the system is vulnerable to strong winds and very heavy rain. One leaf will last for about two weeks during the rainy season. A similar, but less effective system, involves the use of an upturned umbrella.

Tree trunk methods. Coconut and jak trees are preferred. Coconut leaves (which are also large) are tied around the trunks to intercept and harvest water coming down. This system yields about 35-45 litres per day in rains.

Gutters and tanks. People in the area are familiar with the use of guttering and have used their own versions for many years. Gutters are usually temporary and can be made out of hollowed bamboo, galvanised iron sheets, plastic sheets and, recently PVC guttering. They sometimes use some form of downpipe but at others simply allowed water from the gutter to drip into a tank below with the other end of the gutter closed off. Many users practice a system known as "first flush" which means that for the first 30 minutes of rain they don't collect the water, allowing the roof and gutter to be cleaned by the rain. A more permanent filtering system is now in operation in some houses thanks to charitable intervention.

Storing water is then the problem. Many use all available vessels. Others use barrels or cement formed tanks holding up to 300 litres. Once full, they are covered with leaves, polythene sheets or tin. Most last for 5-7 days for an average family.

The design problem. Modern houses with tiled roofs and guttering, can be adapted to rainwater harvesting methods relatively cheaply. ITDG (Intermediate Technology development Group) has joined forces with other non-government organisations, to bring 25 harvesting systems to various houses, as well as 25 for agricultural purposes. These systems can be seen in the accompanying photographs. The tanks cost 20,000 rupees. Most hold either 5,000 or 7,500 litres but they aim to increase the size to hold up to 12,500 litres. During a good year for rain it may be filled between 10 and 15 times but the average is five. People who have them are delighted and have learnt to economise with their use of the water for drinking so that the problem is now nothing like so severe in dry months. One woman told us that the health of her family had improved greatly since the introduction of the system. They now know they have access to clean drinking water as long as they don't overuse it.

However, it is more difficult to devise a system for the coconut thatch roof. An average roof is 50 square metres on one side. The thatch is waterproof so water still runs off well but the house structure lends itself less well to a guttering system, though it would be possible to design one. Particles from the coconut and grass thatching would mean a particularly efficient filtration system would be needed.

Materials available.
In the area they have the requisite skills of carpentry, masonry, pottery, cement mixing, bricklaying. Fortunately there is tile and brick making in the vicinity as well as a timber yard. Ropes made from coconut fibre are used to tie wooden struts together. Good quality coconut leaves are divided into two and intertwined to create a thatch. Roofs usually need to be replaced about every two years parts might need repair before that so any structure would need to be easily dismantled when re-roofing took place.

Coconut trees are everywhere, and fibre cheaply available. Bamboo of sufficient diameter is cheap and also locally available. Clay is available nearby and clay pipes could be made. Cement costs 425 rupees for a 50 kilo bag. Corrugated iron costs 350 rupees for a 10 ft x 2.5ft sheet. PVC guttering is available at 100 rupees per metre (3" diameter). Asbestos sheeting is also widely available. Rocks for tank construction can also be bought locally at relatively low cost.