Reservoir-Induced Changes in Dynamics and Synchrony of River Water Temperatures Revealed by RQA and CRQA

Abstract

River water temperature is a key environmental determinant for aquatic biota. A range of and dynamic changes in temperature values through different temporal scales from diurnal to annual ones determine conditions of life and survival for fish and other aquatic organisms. As a result of heat exchange with the environment (mainly at the air-water boundary), river water temperature largely follows changes in local weather conditions and is related to the dynamics of local air temperature. A retention reservoir operating in a course of river can alter the dynamics of water temperature and the specific air-water relationship for a given site below that reservoir. But to what extent? Water and air temperatures measured some distance below a group of two reservoirs functioning on a mountain river were studied in two separate time periods—occurring before and after the reservoirs’ construction. Recurrence and cross-recurrence quantification analyses revealed that the reservoirs in question have significantly altered the temperature dynamics of water flowing out of them compared to the pre-dam period, and caused the weakening of synchronization between the air and water temperatures studied.