3.15 Restoration of traditional stone spouts

Technical Description

This technology is a traditional water system in the Kathmandu Valley of Nepal. A typical stone spout is illustrated in Figure 20.

Figure 20. A Stone Spout.

Stone spouts are beautifully carved stone elements, in the shape of a crocodile head (considered as a holy water animal - the carrier of the Goddess Ganga) or serpent head, installed in the front or side walls of sunken and stepped platforms for the purpose of channelling water for human use. Each platform, or hiti, may contain one or more spouts. The spout(s) projects about 20 cm to 50 cm from the wall in which the spout is installed. The platform is usually constructed of stone slabs or bricks paved with mortar and fitted with a shallow overflow or drainage channel (generally provided with an iron screen). The surrounding wall is of brick masonry. Stone sculptures, idols and images of gods and goddesses are laid over and under the spout(s), on the surrounding wall and elsewhere in the compound. Despite their age, the underground supply and drainage lines of many old systems are still functioning, nobly characterizing the technical and engineering skills of the ancient people of Nepal.

The supply of water to the hitis depends both on ground and surface water. Most stone spouts receive water from either an individual spring or nearby aquifer. A single aquifer may supply water to one or many stone spouts. The stone spouts may be located within a particular, defined aquifer of known extent, or, more often, within aquifers whose locations and extent are unconfirmed. The aquifers are largely dependent on rainwater for recharge and maintenance of the groundwater table. Draw down of the water table in shallow aquifers may cause some stone spouts to yield less or become dry during the dry season. Some stone spouts only flow during the rainy season and remain virtually dry in other seasons.

Figure 21. Typical Porous Brick Chamber and Supply Line

To provide a continuous and uninterrupted supply of water from the stone spouts, a porous brick chamber is usually constructed surrounding the location of the underground channel from the aquifer. The porous base and the surround of the chamber provide stability to the channel and protect it. The supply line is made of brick, timber or clay or a combination of these materials. The timber used in the supply line is generally grooved in a lengthwise direction, and brick or timber planks are used as lids to cover them (Figure 21). To avoid contamination of the underground supply by the entry of surface water, sewage or other contaminants through suction, percolation or seepage into the supply lines, the supply lines, and especially the joints, are carefully covered with clay or red soil of limited permeability. The supply lines are generally located between 1 m and 5 m below the ground surface. The supply lines are sloped to maintained the flow of water.

TABLE 12. Maximum (Wet Season) and Minimum (Dry Season) Discharges from Stone Spouts in Nepal.

In addition to protecting and ensuring a supply of groundwater for human use, the stone spouts provide for the filtration of the water. Water is conveyed through the supply line to vessels containing filter media placed just upstream of the spout(s). The technologies adopted to filter the water are not the same everywhere in Nepal, but can be categorized into two types of systems which have been popularly installed for filtration; namely, the sand filter and settling basin filter. The sand filter type consists of layered gravel and sand beds which act as the filtration media. Water from the supply line is passed through the layers, graded and placed from coarse to fine, which filter the water before it flows out from the spout (Figure 22).

Figure 22. Sand and Gravel Filter

The settling basin filter system consists of stone containers (whose shape, size and number may vary with the number of water spouts in a particular hiti) equipped with a hole or holes in the wall of the basin, set slightly below the brim. The supply line terminates at the stone container, which feeds directly to the spouts. The sand, soil or other foreign matter present in the water settle in this container and are retained, while freshwater flows through the spouts. This is how the water is filtered out using a stone container, as shown in Figure 23.

Extent of Use

Stone spouts have been extensively used in the Kathmandu Valley of Nepal since ancient times. A few are also scattered in other places such as Palpa in the western part of the country. However, time and the development of new technologies for water systems has brought further construction of stone spouts to a standstill. Thus, conservation of the existing spouts has been given priority by the government, which is expected to contribute to their maintenance and optimum utilization.

Figure 23. Settling Basin Filtration System.

Operation and Maintenance

To ensure the regular supply of water for irrigation, and to the pokharis and the stone spouts, a Watchman is appointed by the government and charged with the overall operation and maintenance of the supply canals. Thus, while the responsibility for the operation and maintenance of the system is borne by a municipality or the government, the day-to-day operation of the system rests with the community. Operation and maintenance activities, as a result, do not incur direct costs but are carried out voluntarily by the community.

Level of Involvement

It is of utmost importance to conserve and maintain the stone spouts, not only to augment freshwater resources but also to protect the spouts themselves, which are valuable national monuments. Government, the community and other non-governmental and private sector agencies often jointly mobilize their resources to protect and restore deteriorating traditional systems. Urban Development through Local Effort (UDLE), implemented under the Patan Conservation and Development Project (PCDP) and assisted by the German Agency Technical Co-operation (GTZ), has done commendable work in improving stone spouts and their allied water sources and pokharis in Patan, while the United Mission to Nepal (UMN) has undertaken a number of studies relating to groundwater resources. The conservation initiative of the community and municipality in recent years is also a praiseworthy step. The key element in ensuring a successful project is the effective coordination between all of the actors involved.

Effectiveness of the Technology

The effectiveness of any technology can be indicated by its performance. Water from the stone spouts is meant for drinking and other domestic purposes. Collection of water and bathing are usually allowed at all of the stone spouts; but cleaning utensils and washing clothes may not be allowed. However, the use of water is not limited to household purposes only; the spout waters are considered pure and holy and are used daily in religious functions, rites and rituals in temples and shrines. Some Baidyas (Ayurvedic homeopathic medical practitioners) also use water from certain spouts to prepare medicines, and there is a strong belief that the water has medicinal qualities used for treating diseases.

The stone spouts, traditionally built to supply water to a small population in a localised area, could take on much greater importance as the National Water Supply and Sewerage Corporation (NWSC) of Nepal is unable to supply the required amount of water to all of the population of Nepal due to the high rate of population growth and unplanned urbanization. Studies have shown that stone spouts benefit between 150 and 250 persons per spout in Kathmandu, and between 300 and 400 persons per spout in Patan, or between 3% and 4% and 4% and 6% of the total population, respectively, of Kathmandu and Patan. In the dry season, water from these spouts is carried in tankers and distributed in areas of water scarcity. Some stone spouts have shallow ponds, fed by overflow water from the spouts, located adjacent to them which are used widely for washing clothes, cleaning utensils, watering cattle and other purposes where high quality water is not essential, including the irrigation of downstream farmlands. Other stone spouts are connected to the municipal stormwater drainage system or directly discharged into rivers. Flows range from a minimum total daily discharge of about 1 575 m³/day during the dry season to a peak of about 4 596 m³/day during the rainy season. The average total daily flow is about 3 089 m³/day, a volume sufficient to theoretically supply some 31 000 people (assuming a per capita demand of 1001 per capita per day). While not all of this water is currently used for drinking (the volume of "useful water" is somewhat less than that of the average daily flow), the conservation and revitalization of the hitis could contribute to a reduction in the acute water shortage in Patan City.

Suitability

The stone spout technology is dependent upon the presence of an aquifer and the quality of the groundwater. Shallow aquifers are the primary source of water supplying the spouts, and should be free from possible contamination by surface water flows, seepage from sewer lines, etc. This technology is suitable in areas where the water table is not too low and where the groundwater quality is not disturbed by surrounding development.

Costs

No cost figures are available on the construction costs of the ancient spouts. However, the estimated cost of restoration of all of the spouts in the Valley is about $1 million.

Advantages

Revitalization of traditional water sources brings many benefits. Restoring the supply canals serves not only to fill the ponds which form a significant part of the traditional water supply network, but also serves to convey irrigation water to additional areas of fertile land, increasing crop yields and cropping intensity. Further, the abundant and permanent water in the ponds significantly contributes to the recharge of aquifers, stone spouts, wells and other small ponds. In addition, the revitalization work assists in the preservation of history, and restores the functions of the various elements of the ancient water supply systems to their original form. As the piped water supply system cannot reliably meet the full volume of water demand in Nepal, traditional water sources, such as the stone spouts and wells, remain potential, small-scale alternative sources of water supply. These sources can help to meet the water demand of the local community, and excess water can be redistributed to desired areas as needed.

Disadvantages

The restoration and revitalization of the stone spouts may involve the relocation of many buildings, constructed near the spouts, that are encroaching on public property. These buildings not only contribute to the disturbance of the natural aquifers and supply lines to the spouts as their impervious surfaces limit natural infiltration of rainwater, but also, since the spouts obtain water from shallow aquifers, to the contamination of the groundwater due to surface pollution. All of the spouts are reported to be contaminated in some way.

Cultural Acceptability

As the traditional stone spouts are believed to be a sacred heritage and as a system for their operation and maintenance exists among the local people of Nepal, cultural acceptability is not a problem with this technology. However, as water from some spouts is used for medicinal purposes and for sacred offerings to the gods and goddesses, conservation should be carried out with due regard to traditional societal beliefs.

Further Development of the Technology

If the stone spouts and the allied water sources are to be preserved and restored to function as historical water sources, reconstruction and restoration programmes must be carried out with due recognition to the hydrological cycle. The canals, which primarily serve to irrigate the land, also serve to recharge the ponds and aquifers, especially in the dry seasons. The revitalization of the canals, though not impossible, is a necessary and large-scale project which will make a significant and reliable contribution to the augmentation of the fresh drinking water supply available from stone spouts and wells.

Information Sources

G. B. Maharjan, (Local water user), Patan, Kathmandu, Nepal.

Dinesh Manandhar, D&M Associates, Post Office Box EPC4000, Kathmandu, Nepal, Tel. 977 1 410249, Fax: 977 1 410249, E-mail:[email protected].

Urban Development through Local Efforts, Project Office of UDLE/GTZ, New Baneshwor, Kathmandu, Nepal.