Hiroshi Yajima

CONTROL OF THERMAL STRATIFICATION IN A RESERVOIR USING A SELECTIVE WITHDRAWAL SYSTEM

A selective withdrawal system (SWS) is mainly used for the control of released water quality (e. g. temperature, SS, metals) released from a dam reservoir. Capacities of most Japanese dams are smaller than those of foreign countries. Therefore we can also use SWS to control the water quality in a reservoir by controlling thermal stratification. To demonstrate the efficiency of this process, we applied numerical simulations (using the onedimensional hydrodynamics model called DYRESM, developed by CWR) to various-shaped dam types. The results indicated that the heat budget in a reservoir is mostly affected by the difference of released water temperature corresponding to the SWS operation, and that the effectiveness of the control is dependent on the epilimnion volume and inflow rate.