Focusing on Japan from the 19th century onwards, this workshop investigates some issues related to water in its various forms. Rivers, rainfalls and seas encompass their own changing ecologies. Depending on one’s perspective, water can either be seen as a hydrological threat or as a vital element for everyday life and a benefit for agriculture. Water can provide a way to move away the wastes produced by industry but it can also serve as a channel bringing in and spreading unwanted pollution. Waterways and oceans produce frontiers that can hinder or enhance the exchanges between societies. In the same way, natural currents shape the flows of goods and people. The Meiji period deeply changed the Japanese society, marked an increase in the exploitation of natural resources and strengthened the industrialization process. These dynamics went on during the Taishō and Shōwa eras, with their own specificity, as this timeframe saw the building, the expansion and the collapse of the Japanese empire. Through a few case studies, this workshop aims at providing a better understanding of the changes and continuities in Japanese history throughout the Modern period from the perspective of water.