Natural flows in river beds are important to human activity; friction loss in a stream bed has an effect on the height of the flow, particularly significant during flooding. The economies of pipelines for petrochemical delivery are highly affected by friction loss. The Yamal–Europe pipeline carries methane at a volume flow rate of 32.3 × 109 m3 of gas per year, at Reynolds numbers greater than 50 × 106.[2] In hydropower applications, the energy lost to skin friction in flume and penstock is not available for useful work, say generating electricity.