|Sourcebook of Alternative Technologies for Freshwater Augmentation in some Asian Countries (UNEP-IETC, 1998)|
|Part B - Technology profiles|
|3. Freshwater augmentation|
The main objective of spring development and protection is to provide improved water quantity and quality for human consumption. Development of natural springs tends to improve their yield, in contrast to the generally-held belief that discharges decline if the springs are touched. Spring development activities include provision of storage tanks, tapstands, drainage, and catchment area protection. Thus, the design of a standard spring development and protection scheme includes the construction of an intake structure, collection tank, tapstand, and retaining wall, and the provision of drainage, fencing and grassed surround.
The intake structure is located at the source of the spring (called the eye, or the point within the spring where the spring flow is concentrated and follows a stable channel), and collects the water for transfer to the collection tank. The intake structure also protects the eye of the spring from immediate and future contamination. In concentrated springs, where the water appears in a single channel, water can be tapped easily using a standard catchment structure at the eye. In dispersed springs, where the water flow is diffused and an eye is not discernable, suitable channels may need to be constructed to divert water from diffused sources to the catchment area. A typical intake structure is constructed of a minimum of 2 In backfill above the source of the spring. In of which should be constructed of impervious clayey soil. This construct is protected from erosion by a dry stone retaining wall built to prevent the backfill area from being washed away. Immediately around the spring is constructed a filter bed of dry rubble. In dispersed springs, where the construction of a filter bed may not be possible, a dry-stone channel may be used to the direct water from the spring source to the catchment floor. The stone channel and catchment area are covered with heavy duty plastic sheets to stop the surface water from mixing with the spring water. A concrete pad is required below the filter bed whenever the soil conditions are in doubt. However, it is important to ensure that the concrete pad of the intake structure floor and walls is well drained in order to prevent seepage from undermining the concrete floor. Also, while small plants and grasses should be planted around the spring area to filter surface runoff and protect the spring from contamination, deep-rooted trees should be avoided as the root systems can clog the spring and damage the protection works. Finally, the outlet and overflow pipes placed into the intake structure should be sized so as to avoid the possibility of impounding the spring water during peak flow periods.
Spring water should be stored in an appropriate collection device. A small ferrocement tank of 500 or 1000 l capacity serves to store the water in most cases when the average discharge of the spring under consideration is below 0.1 l/s. If the flow of the spring exceeds 0.1 l/s then a storage tank may not be necessary and direct flow to the point of use could be provided. The size of the tank is determined based upon a minimum supply of 20 l per capita per day. Where a storage tank is provided, the top of the tank should be raised above ground level. The tank should be located as close to the catchment as possible, and the head difference between the intake and the tank should be sufficient to drain off the collected spring flow to the tank without causing a back-up or impounding of the water within the spring. The tank also should be protected by a fence.
An appropriate tapstand, including a washing platform with the provision for drainage, may also be constructed.
Extent of Use
The concept of spring development and protection was developed and initiated in Nepal during 1992 by the Department of Water Supply and Sewerage (DWSS). This technology has been used extensively in the Eastern Region of Nepal, moderately in the Central Region and rarely in the remaining three western regions, although the government has planned to implement spring protection projects in the all the regions of Nepal. This concept has been developed and is reflected in the policy and guidelines of DWSS.
Operation and Maintenance
Regular maintenance of the scheme is required and includes cleaning the storage tank regularly, protecting the storage tank and catchment area with fencing and grass plantings to minimise contamination, keeping the tap area clean and properly drained, and diverting surface water drainage away from the catchment area. Retaining walls should also be constructed on steep hillsides to mitigate landslides.
User participation in the project from the beginning, and contributions to the project by providing labour and locally available materials for its construction, ensures familiarity with the system. Users are trained in the operation and maintenance of the system, and one user is selected to act as the caretaker. This person is provided with some basic tools as part of the project cost. Since all the components of the scheme are located in close proximity to each other, the caretaker can maintain close observation of the users and the site, which reduces the chances of misuse of water or overuse of the system due to the limited capacity of the source. In many communities, users raise maintenance funds as part of the process of project implementation. However, some maintenance problems have been noticed due to the passivity of the users.
Level of Involvement
Spring protection schemes are generally implemented by the government, with active community involvement, with assistance from NGOs and international agencies such as UNICEF. Private construction has not been noticed as yet.
Direct capital costs include local and non-local materials, transportation, and labour. The average cost of a scheme is $500.
Effectiveness of the Technology
This technology is very effective and has brought about extensive improvements in the quality of water from the springs. The efficiency of utilisation has also improved due to the provision of storage capacity and conservation of water that previously was wasted during night.
This technology is suitable in hilly regions where small springs with minimum discharges of 0.01 l/s are available. However, it should be noted that spring protection, in general, is not considered as an alternative to piped distribution system as it does not reduce walking distances or ensure provision of an adequate water supply. People benefiting from spring protection systems may request a piped distribution system at a later date.
The technical advantages of the technology are:
- The technology is very simple and does not need any standard design procedure to be followed, making it replicable.
- It helps to augment available water resources which otherwise would not be used or considered "unhygienic" by the local people.
- The technology can be adapted to work in conjunction with other technologies such as gravity-flow, piped systems.
- Small springs can be developed to secure a supply of water during periods of extreme demand or when the main system fails for some time.
- There are fewer chances of disputes regarding the spring and its use as the users and developers of the water resource are the same.
- The entire construction can be completed within one week, once everything is available at the site.
- An high level of supervision and highly skilled operators are not necessary.
- The per capita costs are very low.
Though there are no major disadvantages to this technology, some minor disadvantages are:
- The exact shape and size of the catchment structure cannot readily be predicted before construction, and inexperienced contractors may not be able to trap the flow properly with respect to the quality and quantity expected.
- Since the spring becomes "user friendly" after development of the protection scheme, demand may increase, and, if the yield is low, frustrations may arise within the user community.
- Since the benefit of this technology is solely in terms of improved water quality and yield, the community may not accept it as a "water supply" project, since it does not reduce the distances between source and point of use.
- In some cases, it may be difficult to site and construct the components of the system due to a lack of area or required head.
In general, the technology is very acceptable to communities, and people are appreciative of the user friendly system with safe water (instead of a dirty pond from which they previously used buckets to collect water). However, in some cases, people have opposed the excavation of the spring for fear that the source may dry up if touched; practically, this is not true, if handled properly. Also, in some areas, people believe that stored water is not fresh, and, hence, is not suitable for morning ablutions and puja (worship), although such beliefs are slowly disappearing.
Further Development of the Technology
This technology is still experimental in Nepal and needs to be further developed in terms of technology, construction, management and adaptability. The following points should be considered for further development:
- A detailed study should be carried out, and detailed guidelines prepared, to facilitate the use of this technology in a range of specific site conditions.
- Spring development techniques should be designed and implemented in such a way as to form the basis for installation of a piped distribution system in the future, especially with regard to intake structure construction.
Planning Section, Department of Water Supply and Sewerage, Kathmandu, Nepal.