46 with similar connection means the tubes 22 34 42 44 and 46 may be assembled in any desired orientation to accommodate any desired curvature of the dam 12 or any other structure similarly the cuffs 26 and 36 and pitons 28 and 38 may be constructed of any suitable dimensions and connection means to secure the final construction of the tubes 22 34 42 44 and 46 to the dam 12 alternately the tubes 22 34 42 44 and 46 may rest directly on the dam 12 or secured in relationship thereto by any other suitable means known in the art as shown in fig1 the fifth tube 46 is coupled to a variable control valve 48 although the variable control valve 48 may be of any type known in the art in the preferred embodiment the valve 48 is of the needle valve variety translating rotation of the needle valve into a modulation of fluid flow across the valve coupled to the valve 48 is a motor 50 although the motor 50 is preferably a vane motor it may be any suitable device for translating fluid pressure into mechanical motion preferably as shown in fig2 and 3 the motor 50 is provided with a drive shaft.