Stream pool

[1] A stream pool may be bedded with sediment or armoured with gravel, and in some cases the pool formations may have been formed as basins in exposed bedrock formations.

[2] The depth and lack of water velocity often leads to stratification in stream pools, especially in warmer regions.

In warm arid regions of the Western United States, surface waters were found to be 3–9 °C higher than those at the bottom[3] This portion of a stream often provides a specialized aquatic ecosystem habitat for organisms that have difficulty feeding or navigating in swifter reaches of the stream or in seasonally warmer water.

Such pools can be important fish habitat, especially where many streams reach high summer temperatures and very low-flow dry season characteristics.

In warm and arid regions, the stratification of stream pools provide cooler water for fish that prefer low water temperatures, such as the redband trout (Oncorhynchus mykiss) in the Western United States.