Abstract
Two decades or more ago, numerous technical papers were written on the then popular subject of hydro versus steam power, but more recent discussions, presented both in society journals and in other engineering publications, have emphasized the advantages of the co-ordinated use of hydro and steam. These later papers have explored and charted that wide range of existing conditions where co-ordinated operation of hydro and steam will be more economical than use of either alone; and today the general principles involved in such co-ordinated operation are understood and applied in many regional power systems. In the first part of this paper, the historical development and the present status of co-ordinated operation in a specific regional power system are reviewed. This is followed by discussion of a possible approach to the use of pondage at run-of-river hydro plants as part of the system reserves, such use being predicated upon the probabilities of noncoincidence of maximum system loads, minimum river flows, and severe forced outage of steam capacity.
