Effect of Intake Elevation and Operation on Water Temperature

A graphical temperature prediction method based on simplifying assumptions is used to demonstrate how intake elevation and operation at certain times of the year influence outflow water temperature during a yearly cycle of temperature stratification build up and decay. Temperature predictions are made for three different intake elevations and three different years in which the hydrologic conditions require different reservoir operations. The method illustrates how intake elevation, reservoir operation and geometry, surface or bottom intake operation, inflow quantity and its annual distribution, inflow temperature, water surface elevation and climate influence outflow temperature. Additional applications are made to an existing reservoir to simulate a known operation and to check the reliability of the method. For the same reservoir, the outflow temperature of an assumed drastic operation change is predicted. The results show that dependent upon the combination of all factors, one and the same reservoir can produced a great variety of temperature patterns.