The IWSA International Workshop on Anti-Seismic Measures on Water Supply was held from 16 to 18 November 1998 in Tokyo. More than 170 people participated in this workshop from thirteen countries and regions all over the world. Three keynote lectures and thirty-eight papers were presented and vital discussions carried out, concerning earthquake-resistant measures of water supply such as risk assessment, diagnosis and retrofitting of existing facilities, dynamic behaviour of structures, emergency response, recovery and reconstruction, and earthquake-resistant design standards.

This resolution summarises and evaluates the current status of earthquake resistance of water supply systems and the directions towards which we have to make progress, based on the presented papers and discussions at the workshop.

Water supply is essential for human beings to sustain their lives. If a destructive earthquake such as the 1995 Kobe or 1994 Northridge earthquakes attacks highly urbanised areas, numerous facilities of water supply systems may be severely damaged, and a long-term paralysis of water supply seriously affects the residents and their social activities. Loss of function of water supply after an earthquake disables fire fighting and may result in disastrous spreading of the fire. Furthermore a long-period outage of water may result in tragic situation of epidemic disease spread.

Thus water supply is the key factor to protect lives of citizens at the time of a severe earthquake attack, and the minimal water supply and quick restoration of the functions after the disaster are essential. Therefore in order to achieve this goal, incessant efforts should be made by water supply utilities, central and municipal governments, concerned private sector bodies and residents.

2.1. It is important for water supply utilities, central and municipal governments and concerned private sector bodies to have a consensus with the residents about the importance of water supply and mutual roles at the time of a severe earthquake. Therefore the water supply utilities and governmental agencies should disclose information about the seismic risk and the reliability of the water supply system to the residents in order to obtain their understanding and cooperation.

2.2. In a close cooperation with the concerned governmental agencies, water supply utilities are requested to estimate the damage to the facilities and assess the risk of the loss of functions of water supply systems against future earthquakes, based on the investigation into the probability of seismic activity in the areas and diagnosis of the existing facilities.

2.3. Furthermore, based on the results of the damage estimate and the risk assessment, the water supply utilities are requested to prepare a total scheme for the most effective and economically acceptable measures for improvement of earthquake resistance of the water supply systems. Before implementation of these measures, sufficient explanation, particularly on the necessities and the cost, should be carried out in order to obtain the understanding of the residents.

2.4. A long-term strategy is essential for the management of the implementation of the measures for improvement of earthquake resistance of water supply systems, because a large number of facilities need diagnosis and retrofitting at very significant cost. A rational concept should be developed to share the cost properly between the current and future generations.

2.5. The technologies for diagnosis and retrofitting of existing facilities are most important for the reduction of the seismic risk. The advanced countries in the earthquake engineering, such as USA and Japan, are requested to develop effective and economical technologies.

2.6. Particularly the technologies for retrofitting of facilities in liquefiable ground and buried pipes crossing active faults should be promptly developed.

2.7. Since water supply systems consist of a large number of facilities which are spreading widely, it is impossible to perfectly mitigate the damage to the facilities against future earthquakes. Therefore proper maintenance of back-up facilities as well as redundancy are essential conditions for quick restoration of the functions of the damaged system. Furthermore, set-up of an emergency responding organisation that enables quick restoration and reconstruction works is important.

2.8. Emergency delivery of fresh and clean water should be implemented as soon as possible after an earthquake, and the technologies for the delivery and quality control of the water need to be developed.

2.9. Establishment of mutual cooperative relationships among concerned organisations for emergency delivery of fresh water and initiation of restoration efforts following an earthquake event is strongly recommended. These relationships should be established with regional as well as national and international entities and include both public and private sectors.

2.10. Establishment of methods and organization framework to acquire information and analyse damage of water supply systems, which enable effective and prompt activities just after the earthquake is recommended.

2.11. Disaster prevention training and education are important not only for the concerned professional people but also for the residents. Furthermore continuous and adequate maintenance of the facilities at the ordinary time and proper custody of drawings and design documents by a computer filing system are required.

2.12. Establishment of international cooperative relationships for research and development of earthquake resistant technologies of water supply systems as well as for recovery and reconstruction after earthquake disasters is important.

At this workshop many experts who understand the importance of earthquake counter-measures gathered from all over the world. Not a few crucial studies were presented and energetic discussions were held. We believe that all the participants of the conference had a fruitful time and got precious information to proceed anti-seismic measures more effectively.

Finally we propose that IWSA should hold this kind of conference regularly from now on to deliberate on reinforcing the safety and stability of water supply systems against earthquakes.

T. Shirozu (Chairman), H. Kameda (Co-chairman), M. Hamada (Co-chairman), D. Diemer, D. Lee,

Y. Taguchi, H. Tanaka, M. Yamanouchi, K. Murakami, T. Iwamoto, N. Suzuki, R. Isoyama.

T. Shirozu, K. Yune, K. Takenaka, T. Tomioka, M. Ohniki.