The energy-generating equipment of a hydropower plant (HPP) in long-term service is subjected to a variety of factors that may affect its operating conditions. One of these factors that deserves serious consideration in evaluating the performance efficiency of a power plant is the eventual change in conditions of the river bed formation. This concerns not only river stretches located in the afterbays (ABs) of integrated hydro schemes, but also those located downstream at a sufficiently remote distance from the stream flow regulating facilities. Reshaping of the river bed is determined by the ingress, in the afterbay, of a clarified water flow with an enhanced transport capacity as well as by the regulated stream flow conditions. Not infrequently, the river bed is used for recovering sand and pebble as the building material on a scale where the quarry area exceeds in size the natural bed, which results in severe deformation of the bed. In most cases, the reshaping manifests itself in a deepening of the river bed which results in a decreased afterbay flow rate ZAB (QAB and, consequently, in an increased water head. Along with favorable consequences of the bed reshaping (in particular, an increased power output against the rated design value), one should not overlook adverse effects associated with a change in HPP cavitation characteristic. The change in cavitation characteristic results in deteriorated operating conditions in subsurface machine rooms of the HPP building and a higher wear rate of the turbine equipment. In what follows we discuss results of an inspection of the operating conditions at the Votkinskaya HPP (in service since 1963) located in the Kama river. © 2002 Plenum Publishing Corporation.
