The United States Department of Energy and its associated technical activities support the development of technologies that will enable existing hydropower facilities to generate more electricity with less environmental impact. The biological effects of unnatural flow increases are usually irrelevant in regulating hydropower operations because public safety concerns justify more stringent regulations than biological concerns. Hydropower is controllable; that is, engineers can control the flow of water through the turbines to produce electricity on demand. Finally, hydropower impoundment dams create huge lake areas for recreation, irrigation of farm lands, reliable supplies of potable water, and flood control. Typical activities during operation of a hydropower plant include operation of the facility, power generation, and associated maintenance activities that would require vehicular access and heavy equipment operation when components are being replaced. The type of hydropower turbine chosen for a project is based on the height of standing water—referred to as head—and the flow, or volume of water, at the site.