Civil Engineering Technology Energy Facing a worldwide increasing power demand particularly in developing countries the significance of gaining energy by water power is rising accordingly. The spectrum of dams ranges from river dams and medium pressure hydro-electric power stations up to high pressure hydro-electric power stations in high mountain areas. Here, a multitude of different closing-off structures are used taking over a variety of functions and making different demands on the hydraulic drive. Since huge forces effect on constructions and buildings the technology demands a maximum of precision: e.g. for bottom outlet gates high pulling and pushing forces of several 1.000 kN are required. Both turbine intake gates and draft tube gates have to be losed at high velocities of 20 m/min or more and they must be moothly moved into their end position. Features and possibilities Dams Weirs