Selected Water Quality Processes in Rivers and Streams - Hydro-Environmental Analysis: Freshwater Environments - page 136

Radiation terms Mass-dependent terms

Air-water
interface

Solar
shortwave
radiation

Atmospheric
longwave
radiation

Water
longwave
radiation

Conduction
and
convection

Evaporation
and
condensation

Net absorbed radiation Water-dependent terms

FIGURE 5.7 Heat exchange processes at the water surface. (After Chapra, S.C., Surface Water-Quality
Modeling , WCB McGraw-Hill, New York, 1997.)

the water mass is usually great enough that much more energy is required to cause a change in tem-
perature, so the impact is less. The result is that mid-order streams typically have a greater range of
maximum daily temperatures than low-order or high-order streams (Allan and Castillo 2007) (see
Figure 5.8).
Human impacts on the hydraulics of rivers and streams (hydromodiications) also have impacts
on temperatures. For example, damming a river can change a cold-water habitat to a warmwater
habitat. Conversely, releasing waters from the bottom of reservoirs in the south in hydropower
operations has changed many warmwater isheries to cold-water isheries (much appreciated by
southern trout ishermen). Thermal pollution, such as that due to temperature increases resulting
from the cooling operations of power generation facilities, has negatively impacted aquatic systems.
In the 2012 U.S. EPA's national summary of impaired waters and TMDL information, temperature
or thermal pollution is the tenth largest cause of water quality impairments in the United States, as
listed in the Causes of Impairment for 303(d) Listed Waters.

10
9
8
7
6
5
4
3
2
1
0

Maximum daily
temperature
range

12345678910 11 12
Stream order

FIGURE 5.8 Relationship between water temperature and stream order. (From Water on the Web, Monitoring
Minnesota Lakes on the Internet and training water science technicians for the future—A national on-line
curriculum using advanced technologies and real-time data. University of Minnesota, Duluth, MN, 2004.
Available at http://WaterOntheWeb.org. With permission.)