Ben MacIntyre, biologist with the U.S. Army Corps of Engineers Nashville District Regulatory Division's Western Branch, verifies a stream delineation April 13, 2021 by looking for macroinvertebrate insect larvae (the aquatic lifecycle phase of certain types of insects) in a stream in Mt. Juliet, Tennessee. Many of these larvae live on the bottom side of rocks within streams. Each species requires a certain amount of time living in water, which can indicate the amount or duration of flow in a stream, depending on the species observed. Stream flow regime (ephemeral, intermittent or perennial) is used in part to assess a stream’s function, from which impact debits are tabulated to calculate the amount of mitigation required to offset a project’s impacts to aquatic resources. (USACE Photo by Sammy Iskrzycki)