Chapter 2 - Properties of Water

Abstract

This chapter discusses the properties of water. One of the many unusual properties of water is that it exists in liquid form at the normal atmospheric temperatures and pressures encountered on the surface of earth. The density of liquid water, which is influenced by temperature and dissolved ions, can control the physical behavior of water in wetlands, groundwater, lakes, reservoirs, rivers, and oceans. Density also influences water flow and viscosity. Differences in density are important because less dense water floats on top of water with greater density. Such density differences can maintain stable layers. Formation of distinct stable layers is called stratification. Many aspects of life in aquatic environments can be discussed conveniently using the Reynolds number (Re). This number can quantify spatial- and velocity-related effects on viscosity and inertia. Small organisms have low values of Re and little inertia relative to the viscous forces they experience; the opposite is true for larger organisms. Biological activities, such as swimming, filter and suspension feeding, and sinking and many other aspects of aquatic ecology are constrained by properties of water that can be described by Re.