#### STICHTING BAKENS VERZET

#### 1018 AM AMSTERDAM, THE NETHERLANDS

Director,

T.E.(Terry) Manning,

Schoener 50,

1771 ED Wieringerwerf,

The Netherlands.

Tel: 0031-227-604128

Homepage: http://www.flowman.nl

E-mail: (nameatendofline)@xs4all.nl : bakensverzet

## MODEL FOR SUSTAINABLE SELF-FINANCING INTEGRATED RURAL AND POOR URBAN DEVELOPMENT FOR THE WORLD'S POOR

Incorporating innovative social, financial, economic, local administrative and productive structures, numerous renewable energy applications, with an important role for women in poverty alleviation in rural and poor urban environments.

"Money is not the key that opens the gates of the market but the bolt that bars them"

Gesell, Silvio The Natural Economic Order

Revised English edition, Peter Owen, London 1958, page 228

Edition 11: 28 September 2006

(EN FRANÇAIS)

#### 05.37 NOTES ON RAINWATER HARVESTING SYSTEMS

This project does not cover all the possibilities offered by efficient rain-water harvesting. Instead, it assumes small-scale rainwater harvesting systems for agricultural purposes will be developed as a natural extension of economic activity in the area.

Rain-water is harvested both for irrigation and for drinking water. Some form of purification system is needed when it is used for drinking water as the water may come into contact with dirty surfaces and may need to be stored for quite long periods. Purification needs systematic technology application and careful management. The effects can be disastrous if these things are overlooked. That is why clean water from closed wells and boreholes has been preferred as a source of drinking water to harvested rain-water in this project.

The solar powered drinking water systems foreseen in this model project offer a limited capacity suitable for human consumption, small animals and small scale drip irrigation applied to high value cash crops. The project does not include water for irrigation and general agriculture for which the use of solar energy, taking into account the cost of PV panels and/or wind generators into account, is still relatively uneconomic.

Rain-water harvesting offers the possibility of providing a water supply suitable for agriculture. The use of gypsum composite water tanks and reservoirs made under the (LETS) systems means that users do not actually need to have any "money" to start and gradually expand their own rain-water harvesting systems.

The tanks can be gravity fed off roofs and/or slopes and/or road surfaces. This water would also be used for personal hygiene such as showers, and for the washing of clothes.

This project is limited to household water harvesting systems as a supplementary non-potable water supply for personal uses.

#### Sloping of surfaces

Surfaces such roofs, roads, squares need to be gently sloped so that water can run along gutters or other channelling material to one or more water collection points. The channelling materials used should be locally made gypsum composite materials to avoid financial leakage from the project area. In any case PVC must not be used. The collection surface(s) should be kept as clean as possible. Contamination of the surface by animals and waste products should where possible be avoided. Green or "living" roofs are ideal for rainwater harvesting. The number of water collection points will depend on the surface being drained and the maximum intensity of the rainfall. Purely indicatively one collection point should serve about 40m2 or 300 square.feet..

#### Filtering

The harvested water is intended for general household use and not for drinking. Should it be required for drinking purposes it must be boiled. Chlorination and other types of water treatment should be avoided except where the water in the rainwater tank is the only source of water available and it is known to be, or there is a reasonable risk that it be, bacterially infected. Even then treatment should only be carried out by a specialist.

The harvested water should however be filtered to keep organic materials, solids and particles in suspension out. This can be done is two phases:
a) At the collection point, with a fine metal grate together, eventually, with a suitable sponge-like material at the top of the down-water pipe.
b) Above the water tank, where the water can pass through a gypsum composite or other container (but not PVC!) filled with (locally available) shingle, sand, and charcoal.

The size of the filters will depend from case to case according to the maximum amount of flow reasonably foreseeable.

#### Down-water pipes

Their size will depend on the maximum amount of flow reasonable foreseeable, but will typically have an internal diameter from 3" to 6". Their length will depend on where the water tank is situated. They should be as short as possible. Where they are exposed to the sun's rays, the pipes must be resistant to them. Where possible the pipes should be made from locally available materials and supplied within the local LETS money systems. Do NOT use PVC material.

#### Water tanks

Where possible, the water tanks should be sealed and placed just under the roof, from where they can be gravity fed through pipes to outlet points in or around the house. Recipients can also be placed on a stand between roof level and floor level, so that gravity feeding is still possible. Where neither of these is feasible, ground level recipients can be used. This usually involves the use of lids, ladles, buckets and similar which may not be hygienic and the risk of infection and access by animals and insects is increased. Ground level tanks also occupy extra space.

The water tanks will normally be spherical in shape and made locally under the LETS systems from gypsum composite materials. Where they are esthetical in appearance and design, their position is irrelevant.

The first systems will be made in the gypsum composite factories and installed towards the end of the second year of project execution. This work will continue during the following 4-5 years until all of the (10.000) houses in the project area have been equipped.

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