Environmental Engineering Reference
In-Depth Information
In the U.S., the USEPA sets national criteria for various pollutants, such as the DO criteria in Table 9.6,
but the individual States have to set and enforce the DO standards applicable in that State. Despite the
USEPA (1986b) national criteria document indicating achievement of 3 mg/L of DO at all times may be
sufficient to maintain a warmwater fish community, most States have retained their 1970s standards requiring
5 mg/L of DO at all times.
Linkage between habitat and standards —The DO standards like Wisconsin's Warmwater Sportfish
and Forage Fish Communities and Ohio's Warmwater Streams are for aquatic life uses that meet the baseline
regulatory requirements in line with the Clean Water Act “fishable goal”. Many States have defined
lower levels of aquatic life use for which lower DO concentrations are acceptable. The basis of these
lower levels of aquatic life use typically is defined by physical habitat limitations on the potential aquatic
community of the water body. These approaches attempt to link physical, chemical, and biological
integrity, which is the original goal of the CWA. One of the best developed systems for defining alternate
life uses and DO standards has been developed by the State of Ohio. Ohio's approach is described in the
remainder of this subsection.
The Ohio Environmental Protection Agency developed the Qualitative Habitat Evaluation Index (QHEI)
as a means to evaluate the quality of habitat features for support of diverse aquatic ecosystems. The QHEI
considers and rates aspects of substrate, instream cover, channel quality, riparian/erosion condition, pool and
riffle conditions, and gradient to obtain a total habitat quality score for a given location. The individual
habitat metrics included in the QHEI are listed in Table 9.8, however, the details of the rating system are
beyond the scope of this chapter and readers are directed to Ohio Environmental Protection Agency (1989).
Ta b l e 9. 8 Component metrics and their score ranges in the qualitative habitat evaluation index of the ohio environmental
p rotection Agency (1989)
Metric
Score
Substrate
20 points
(1) Type
0 to 20
(2) Quality
-5 to 3
Instream Cover
20 points
(1) Type
0 to 9
(2) Amount
1 to 11
Channel Quality
20 points
(1) Sinuosity
1 to 4
(2) Pool-Riffle Development
1 to 7
(3) Channelization
1 to 6
(4) Stability
1 to 3
Riparian/Erosion Condition
10 points
(1) Width
0 to 4
(2) Floodplain Quality
0 to 3
(3) Bank Erosion
1 to 3
Pool and Riffle Condition
20 points
(1) Maximum Depth
0 to 6
(2) Current Available
-2 to 4
(3) Pool Morphology
0 to 2
(4) Riffle/Run Depth
0 to 4
(5) Riffle Substrate Stability
0 to 2
(6) Riffle Embeddedness
-1 to 2
Gradient
0 to 10 points
Total Score
0 to 100 points
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