©2010 Elsevier, Inc. Chapter 2 Properties of Water Dodds & Whiles

©2010 Elsevier, Inc. FIGURE 2.1 Bubbles formed in ice. This image reflects several properties of water. Surface tension forces the bubbles to be spherical, and gas that can dissolve in liquid water cannot do so in solid water. (Courtesy of Steven Lundberg).

©2010 Elsevier, Inc. FIGURE 2.2 Schematic of hydrogen bonding among water molecules. The black lines represent covalent bonds; the dashed lines represent hydrogen bonds. This is an approximate two-dimensional representation. In water, three-dimensional cage-like structures are formed. In liquid water, these structures form and break up very rapidly.

©2010 Elsevier, Inc. FIGURE 2.3 The density of water as a function of temperature from freezing to 80°C (A), from 0 to 40°C (B), and from 0 to 10°C to focus on the region of maximum density (C). At 0°C, ice forms with a density of g per milliliter. (Data from Cole, 1994).

©2010 Elsevier, Inc. FIGURE 2.4 Comparison of density change caused by temperature to that changed by salinity. The range of variation in density with temperature is represented by the gray box. Seawater has an approximate salinity of 3.5% (indicated by the point bounded by error bars); saline lakes can exceed this value by many times. (Data from Dean, 1985).

©2010 Elsevier, Inc. FIGURE 2.5 Viscosity as a function of temperature. Note that viscosity doubles when temperature drops from 30 to 0°C (i.e., a range of temperatures across seasons in temperate surface water). (After Weast, 1978).

©2010 Elsevier, Inc. FIGURE 2.6 Reynolds number as a function of size (A) and velocity (B) for a variety of aquatic organisms. Note the log scales. (Data from Vogel, 1994).

©2010 Elsevier, Inc. FIGURE 2.7 The concept of a flow boundary layer. (A) Arrows represent the velocity and direction of water flow. Inside the flow boundary layer, flow is approximately laminar and slows near the surface; outside the layer, turbulence increases. (B) The outer region of the flow boundary layer is where velocity is 99% of that in the open channel. Very close to the solid surface, water velocity approaches zero. (Modified from Vogel, 1994).

©2010 Elsevier, Inc. FIGURE 2.8 Schematic of thickness of the flow boundary layer as a function of surface roughness and distance from leading edge. Water is flowing from left to right. Picture the substrata as a rock in a stream. The thickness of the boundary layer increases with distance from the leading edge and is shallower over bumps and deeper over depressions.

©2010 Elsevier, Inc. FIGURE 2.9 Patterns of flow behind two differently shaped solid objects at three different ranges of Reynolds numbers. When the Reynolds number is low, turbulence is minimal. Vortices start to form with increased Reynolds number; vortices and turbulence are more prevalent with the cubic object (B and C) than with the streamlined object (E and F). Compare to Figure 2.10.

©2010 Elsevier, Inc. FIGURE 2.10 Water moving past an algal thallus at progressively higher velocities. Tracer particles allow visualization of turbulence. Velocities are 0.5 (A), 1.5 (B), 2 (C), and 3.5 cm s 21 (D). (From Hurd and Stevens, 1997; reproduced with permission of the Journal of Phycology).

©2010 Elsevier, Inc. FIGURE 2.11 Ventral view of a larval net-winged midge (order Diptera, family Blephariceridae), showing the suction discs that allow them to live in high water velocities in streams. (Reproduced with permission from Thorp and Covich, 2001).

©2010 Elsevier, Inc. FIGURE 2.12 Sinking velocities of spherical particles with two different densities and of a filamentous diatom, Melosira, as a function of volume. The diatom can be found suspended in water and has a density of approximately 1.2 g cm 23 (Data from Reynolds, 1984).

©2010 Elsevier, Inc. FIGURE 2.13 Schematic of wind-induced water movement in a lake illustrating the decrease in movement with depth from the surface, wave length, and wave height. The three-dimensional flow paths are more complex than in this simple diagram and will be discussed in Chapter 7.

©2010 Elsevier, Inc. FIGURE 2.14 Schematic showing how water movement is related to spatial and temporal scales. The x axis ranges from the size of a protein to the size of the Earth and the y axis from the time frame of molecular events to the age of the earth. This figure is not meant to imply that sharp boundaries exist between the adjacent regions. Rather, the regions should be viewed as fuzzy overlapping regions. Forces that drive the water movement are discussed in the text.