|Sourcebook of Alternative Technologies for Freshwater Augmentation in some Asian Countries (UNEP-IETC, 1998)|
|Part B - Technology profiles|
|3. Freshwater augmentation|
In some villages in the hills of Nepal, drinking water is supplied to consumers through a bamboo piping system. In Barbotey Village, in the Dam District of Nepal, for example, water is supplied to two households (12 people) from a common source. A longitudinally cut bamboo tube, semi-circular in cross-section, serves as an intake. Water, drawn from the source, flow along about 100 In of open channel bamboo piping to a bamboo tap. Water flows by gravity down a 1% slope that follows the ground profile. The bamboo pipes, supports and ancillary plumbing fixtures are made from bamboo stems cut from the nearby forests.
The raw bamboo is cut in half to form a semi-circular pipe, and laid on the top of bamboo supports that carry the pipe down the slope to the consumers. At each change in direction (i.e., at the bends), the pipe is braced and supported by bamboo itself. At each socket joint, two bamboo lengths overlap and are again supported by bamboo bracing. At the bamboo tap, a bamboo inlet is inserted from the top and water is withdrawn hole at the bottom. A small HDPE pipe is also used in building the tap. This system is completely based on local technology using local materials.
Extent of Use
Bamboo conveyance systems are used throughout the hilly areas of the eastern region of Nepal.
Operation and Maintenance
Because bamboo decays as a result of its exposure to the weather and the scouring effect of the flowing water, all of the bamboo components have to be replaced each year. Thus, the annual operation and maintenance costs are the same as the capital cost, about $4.60 per year.
At present, two households have been operating and maintaining the system. They frequently visit the line to remove debris so that water flows smoothly. Surplus water is used for kitchen garden watering purposes. More than 50% of the water entering the system is lost due to leakage during the passage of the water from the source to the tap.
Level of Involvement
These distribution schemes may be implemented at the local community level, by the local users themselves. New techniques to improve the system have not been implemented, and the users are waiting for this scheme to be replaced by a piped water system. Nevertheless, there are some measures which could be considered fin order to improve the bamboo distribution system and the government could promote this technology in other areas where bamboo is commonly available.
The cost of the scheme is very low, as it only uses local materials. Total cost is about $4.60, and is incurred annually in the replacement of the bamboo.
Effectiveness of the Technology
At present, the system provides 0.201 per person of drinking water in the wet season. This volume diminishes to 10% of the wet season volume during the dry season. The system eliminated the need for the women of the households served to walk long distances to fetch water.
This technology is suitable in areas with a good natural source of water nearby, a steep topography, and a ready source of natural piping materials.
This technology is simple and uses local materials. Therefore, it is very cheap and can be implemented at the local level without skilled labour or specialised materials and equipment.
Since the bamboo piping is simply placed on top of the framework that supports the pipeline, high winds or broken branches can displace the piping and cause the system to break down. Further, because the pipeline is open, the chances of dirt, debris and tree leaves falling into, and contaminating, the water are extremely high. This potential for contamination requires that users screen and boil the water before they use it for drinking purposes.
Further Development of the Technology
This technology could be improved through the development of means to ensure that (i) the bamboo pipe is free from debris and contaminants, (ii) there is a continuous flow of water to minimize the rate of decay of the bamboo (bamboo left without water for more than 60 days decays rapidly), and (iii) there is provision for chlorination (at a rate of 10 mg/l chlorine) to improve water quality as well as preserve the bamboo from decay. Some improvements in this technology which have already been identified include the use of a fully enclosed bamboo pipe and plastic pipe joints between tube segments to control water loss due to evaporation and spillage. The use of fully enclosed bamboo tubes is impeded somewhat by the intemodes which grow naturally across the bamboo stem at intervals of about 1 m. These must be removed by drilling, adding a degree of complexity to the technology (the drilling can be accomplished using an hand auger attached to a steel bar, manually inserted into the bamboo tube from both the ends). Also joining the bamboo stems with polyethylene pipe of an appropriate size can control leakage through the joints. Bamboo pipes also can be reinforced with 3 mm diameter galvanized wire, which can also be used to anchor the pipeline to the supporting structures. In some situations, the pipe can be laid underground, but problems may arise due to the presence of fungi and termites. Applications of insecticides and anti-fungal agents can be applied to the trenches to control these pests, but at the increased risk of contamination of the supply.
Amar Neku, Engineer, District Water Supply Office, Dam District, Mechi Zone, Nepal.