Author(s): Sang Yoon Han; David Hansen; William Cavers
Linked Author(s):
Keywords: Pool Number; Fish-habitat assessment; Hydraulic retention time; Lentic waters; Pools and riffles
Abstract: Pools are essential habitat elements for salmonids. Pools provide a complex of deep low- velocity areas, backwater eddies, and submerged structural elements that provide cover. This complex can provide salmon with safe areas in which to find refuge when low-flows and/or winter conditions inhibit their movement, or to find rest during floods. Because of the importance of pools as fish habitat, their behaviour has been studied by various investigators using several physical characteristics, including their depth, cross-sectional area, top width, and volume. A general index to describe the characteristics of pools as fish habitat would therefore be useful. In this study, a dimensionless Pool Number, P, was developed and applied to an on-going fish-habitat assessment. This number is defined using the nominal Hydraulic Retention Time (HRT), and is related herein to some of the variables mentioned above. The magnitude of Pool Number indicates how lentic, or pool-like, a given pool is. The question of critical Pool Numbers in connection with fine sediment and high temperature problems is addressed. P is related to Newcombe’s Stress Index. It is expected that the value of P will help to quantify the habitat quality of pools in a given stream system in a unified manner and could also be used to compare pools in different systems. However, the general utility of the Pool Number and the question of critical P values will require more data from different climatic zones and from pools of a wider range of sizes and shapes.
Year: 2005