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Abstract The problem of thermal poliution has become increasingly imporr..&·E due to the tremendous grov.1h in the use of de~r:ical generating stations. This of course leads to z.n h”1Crease in the water temperarure which by sequence affects nearly eve:y physical property of concern in the water quality management and, unfortunately. an increase in water temperature is associated with undesired change in these properties. Therefore it is necessa...:· for the engineer to ·Je able to predict the effect that a proposed heat source will have on water system. As direct qnamatiYe measurements are expensi,·e and not a1ways possible. ETiathematical models are usually adopted a~ a. reaso112.ble basis for impa:::: assessment. The temperature distributions in a natural riYer do”·nstream of a r..l}ermal discharge are determined by the hydrodynamic characteristics of the stream and the meteorological conditions preYailing in the region. The physical processes .::;f surfc.ce heat exchange inch.:.de results ::::~ radiati·Jn. eYapora~ior.. c:ondu::t:o:1. aiJ.C. aGYe.:::t:o:-L Each c{ t1.ese processes v.·ill be s.ho\•.::-1 to depeud ~pon t\\-o facLJrs 1- The nan.;ral condicions which a:-e not affected b;, man s acti,·ities T~~e ex-:ess temperature of ul.e \\’2.:er which is c:aused by man· s inter12.ce \\·ith the system. The defin1~ior. of excess temperature then corresponds tc the te!!1peratt:.re rise ·v.·hich is sub1ect to restri:::ioill imposed by goYe;nrr,.ents. Th.e differential equation \\-l1ich governs the distribution i.J_J. titue and space of the excess temperature is deri,·ed. The manner in which the surface transfer coefficient for excess heat Yaries with meteorological and hydraulic variables is illustrated. |