“Turbines designed for low-flow situations would be wasteful in times of high water. Turbines designed for high efficiency at, say, five hundred cubic feet per second might be ineffective in times of low water. Under certain conditions, turbines can go into a state of cavitation, wherein vaporizing water creates bubbles that implode on the metal and riddle it with tiny holes. The ideal turbine for a little mill up a creek somewhere in inconsistent country would be one that was prepared to take whatever might come, to sit there and react calmly in any situation, to respond evenly to wild and sudden demands, to make the best of difficult circumstances, to remain steadfast in time of adversity, to keep going, above all to press on, to persevere, and not vibrate, fibrillate, vacillate, cavitate, or panic - in short, to accept with versatile competence what is known in hydroelectrical engineering as the run of the river.” TurbineHydro PowerHydro Book:Silk Parachute Source: Silk Parachute