ABSTRACT
Tenryuu River starts from Lake Suwa in Okaya, Japan. The river has six cascading dams. In order to carry out analysis on the scale of the system of cascading dams, a holistic approach is considered. In this paper, we present past and on-going efforts on maintaining the proper functioning of the river and its ecosystem based on continuous monitoring, research and development, regular field measurements, as well as applying numerical modelling tools. These efforts enable the operator to minimize the impacts of the dams, and at the same time, improve the operation to provide optimal ecosystem services; e.g. regulation of flow and provision of water use, biodiversity, aquaculture and environment.
The research work focuses on the retention capacity of the reservoirs and their influences on water quantity and quality, e.g. loss of storage, temperature stratification, sediment concentration in the reservoir. In addition, the work considers the natural flow regime, the hydrological alteration and sediment management including their effects on the morphological changes at the downstream reach leading to social, ecological and safety concerns.
This paper demonstrates how such a holistic approach is useful for the sustainable operation of a system of dams considering the fulfilment of the multisectoral stakeholders’ demand. The paper describes the development of monitoring programs and field campaign as well as the model development and application to understand various processes, quantify and predict the impacts, and subsequently propose possible measures and adaptation to be considered.
