Environmental Engineering Reference
In-Depth Information
All states have standards for temperature, which vary according to the degree of cold-water or
warmwater habitats. For example, for the Lower Columbia River in Oregon:
Temperature shall not exceed 20°C due to human activities. When natural conditions exceed 20°C no tem-
perature increases will be allowed which will raise the receiving water temperature by greater than 0.3°C.
While for Mississippi, the regulation (in part) reads:
The maximum water temperature shall not exceed 90°F (32.2°C) in streams, lakes and reservoirs,
except that in the Tennessee River the temperature shall not exceed 86°F (30°C). In addition, the dis-
charge of any heated waters into a stream, lake or reservoir shall not raise temperatures more than 5°F
(2.8°C) above natural background temperatures.
5.4 SEDIMENTATION
Sediments naturally occur in waters as a function of a variety of processes. However, excess sedi-
ments can result in degradation of the water quality. Under the CWA, state agencies are required to
identify and report to the U.S. EPA any waters of their states that are impaired (not meeting water
quality standards) under Sections 305(b) and 303(d) of the CWA. The U.S. EPA, in turn, prepares
a summary of the quality of the nation's waters and submits it to Congress. In the 2002 report
(Figure  5.9), sediment/siltation was listed as the number one cause of impairment in rivers and
streams, with over 100,000 mi. of rivers and streams impaired. In the 2004 report (Figure 5.10), the
Miles
Sediment/siltation
Pathogens
Habitat alterations
Metals
Nutrients
100,446
82,133
80,974
52,809
52,228
0510
15
20
25
30
35
Percent of impaired stream miles affected
FIGURE 5.9
Listing of causes of impairments from the national water quality inventory: Report to Congress
2002.
Miles
72,305
57,577
42,177
39,816
38,632
36,032
35,177
26,173
24,044
17,569
Pathogens
Habitat alteration
Organic enrichment or
oxygen depletion
Cause unknown—impaired biota
Nutrients
Metals
Sediment
Mercury
Flow alteration
Turbidity
0
5
10
Percent of impaired stream miles affected
15
20
25
30
35
FIGURE 5.10 Listing of causes of impairments from the national water quality inventory: Report to
Congress 2004.
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