A modification of Prych's mathematical model (1972) for predicting the spreading of cooling water froma surface outlet is presented. The main modifications area change in the calculation of the initial values after the zone of flow establishment, more realistic density calculations and the introduction of the fact that spreading of the jet's heat content takes place faster than the spreading of its velocity .

In the modified model the calculated plumes are noticeably narrower and thicker than in Prych's model. Furthermore, the jet's deflection by the ambient current is stronger and excess temperature on the surface diminishes faster.