Abstract
This paper is intended to address the need to pay more attention to water temperature conditions for environmentallysound river management. It discusses the importance of maintaining proper water temperature regimes for the health of aquatic life, and provides some insight into the impact of upstream control on downstream water temperature regimes. It suggests that adverse impact might be alleviated if upstream control is properly managed. To characterize instream thermal environment, a thermal diversity index is proposed. In addition, the inadequacy is pointed out of the current water temperature monitoring systems along major rivers in Japan.
