Why are Pools of Water important?
Pools are a natural part of many stream types, and may be created by fallen trees, boulders, or natural stream erosion processes. Fish may rely on pools for long-lasting water sources or hiding places, and deep pools can be critical to the survival of species such as juvenile salmon and steelhead trout during the dry season. Birds and mammals may likewise seek water in pools to help sustain them through dry periods. However, not all pools are beneficial to native species. Pools that are very silty or have no associated vegetation cover may become too warm to provide good habitat. Functional, healthy pools contribute to overall stream complexity and are another sign of stream health.
How do we measure impact?
The presence of pools is one of several indicators of stream condition in the California Rapid Assessment Method (CRAM) for monitoring wetland condition. Pool depth and size are also important, with deeper larger pools providing cooler habitat needed for species like trout and salmon.