Water flowing over land into streams is described by which term?

• A. Lotic Ecosystem
• B. Runoff
• C. Percolation
• D. Pool

Answer: (B)

Overland flow of water from land into streams is runoff. When rain or snowmelt hits the ground, some water infiltrates the soil, but if the soil is saturated or the rainfall is intense, water cannot infiltrate quickly enough and instead flows across the surface toward lower elevations and into streams. This surface flow is a major pathway that delivers water, sediments, and nutrients to streams and shapes how watersheds respond to precipitation. A lot of attention in freshwater ecology is given to runoff because it links land use, soil properties, and hydrology to stream health. The other terms describe different things: a lotic ecosystem is the flowing-water environment itself, percolation is the downward movement of water into soil and groundwater, and a pool is a slow, deeper section within a stream.