Securing a minimum volume of water for drinking and domestic purposes is vitally important in the aftermath of an earthquake. Currently, water supply systems across Japan are being reconstructed to ensure that they are earthquake-resistant. Disaster emergency wells are one means of supplementing basic water demand. Such wells are often privately owned, but are used for public purposes such as first-aid water supply in emergency situations. Although some case studies of disaster emergency wells have been reported after major earthquakes, how widely such wells are adopted in municipalities in Japan has not been investigated. This paper conducts a survey of the prevalence of disaster emergency wells in 20 ordinance-designated cities in Japan and describes evaluation of institutional effectiveness using criteria based on experiences following the 2016 Kumamoto earthquake. Survey results reveal that only 12 of those 20 cities have established disaster emergency wells and that Chiba, Kawasaki, Kumamoto, Nagoya, Sagamihara, and Yokohama cities have more effective institutions than other cities do. Finally, this paper presents future challenges for disaster emergency well management, including the need to increase their prevalence and, in combination with land use policy, to ensure their maintenance and their combined use with other water supplies.

　Although residence time is a key concept in hydrological studies, some confusion has arisen about similar terms. Here, we re-examine various concepts related to residence time and present a definition of each term and their characteristics in different systems. Then we recommend limited use of the term ‘residence time’ as general term involving ‘turnover time (i.e., conventional residence time),’ ‘age,’ ‘mean age,’ ‘transit time,’ and ‘mean transit time.’ We should distinguish these terms clearly when their values are shown. Additionally, we clarify correspondence among estimation methods and concepts/terms, and state remarks in interpreting estimation results. Finally, as ways forward in residence time studies, we emphasize the following: (1) combined use of tracers and numerical models and (2)appropriate selection and multi-faceted application of simple and well-defined indices of residence time.

　The Thai government enacted to a new Water Resources Law to address water issues in a comprehensive manner in December 2018. At the same time, the Thailand National Water Resources Management Strategy for 20 years (2018-2037) was announced. The points of the new Water Resources Law and the future water resources management strategy of Thailand were reported.