| INTERMEDIATE TECHNOLOGY GROUP
ITDG 4: RAINWATER HARVESTING
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)
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.
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
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
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.
(Pictures would be
very useful here - check if Ramitha can get any.)
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
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.
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.
Images to be added