Abstract: A method and apparatus are disclosed for controlling and coordinating the power generated by a combined system of thermal units and hydro plants. In particular, hydro generation is determined for each of the hydro plants of the system as they are distributed in a plurality of groups, each group corresponding to a given river system. Because the amount of water flowing down a river system is dependent upon the amount of water released into the river system, calculation of the power generated by the hydro plants disposed upon a single river is conducted based upon the water flowthrough and power generated by a single plant termed a control plant. Assuming a set of lambdas, for example the lambdas calculated for the previous day, the water allocaion of not only the control plant but the remaining or dependent plants is determined by multiplying the incremental water rate curve of the control plant by an artificial cost variable gamma.