These devices, consisting of operable gates with stems and operators, are used to regulate the water level within a impounded water body – a pond, lake or reservoir. Stop log structures are usually used in addition to gates to maintain a certain water level without constant supervision to the gate. Many different types of valves have been used over the years, especially on older dams it is a possibility to see a “sprocket driven slide gate” or even a slide gate made out of wood. Gate valves are also commonly used for smaller pipes as a low level outlet.