What are shallow areas of swiftly flowing water called?

Swiftly flowing shallow areas of water are referred to as riffles. These are characterized by a rapid current and often have a rocky or gravelly bottom, which contributes to the turbulence of the water. Riffles play a significant ecological role in aquatic habitats, as they help to oxygenate the water, providing essential conditions for various aquatic organisms, including fish and invertebrates.

In the context of a stream or river, riffles are typically found between pools, where the water flow is slower, leading to a clear distinction between these two types of habitats. This differentiation is crucial for understanding the diverse environments present in aquatic systems, as it influences species distribution and behavior based on water depth, current speed, and substrate composition.