Authors
Dale Alan McCullough
Report Citation
McCullough, D.A. 2011. The impact on coldwater-fish populations of interpretative
differences in the application of the United States Clean Water Act 1972 by individual
State legislatures. Freshwater Reviews. DOI: 10.1608/FRJ-4.1.159. pgs: 43-79. (https://www.fba.org.uk/journals/index.php/FRJ/issue/current/showToc).
Publication Date
June 2011
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The impact on coldwater-fish populations of interpretative differences in the application
of the United States Clean Water Act 1972 by individual State legislatures
Abstract
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The United States Clean Water Act (CWA) is one of the key legal means in the USA
to 'restore and maintain the chemical, physical and biological integrity of the
nation's waters'. Given the pervasive influence of human development and associated
climate change in increasing water temperatures in streams of the USA, salmonids
are particularly susceptible to reduction in productivity and geographic distribution.
Native and introduced, self-sustaining salmonid populations can be found in most
of the 50 States of the US. Despite this commonly shared resource, the highly similar
temperature sensitivity among salmonids, and the legal imperative under the CWA
to provide full protection to the most sensitive uses, the States supporting these
thermally sensitive species have adopted a wide range of standards. As these standards
are so divergent, even though the protection goal under the CWA applies uniformly
to all States, it is clear that water temperature standards have been developed
under conflicting interpretations of the best science available or there is a misunderstanding
of the level of protection needed. The current EPA Gold Book guidance for development
of protective standards, dating from 1973, still recommends the use of MWAT (maximum
weekly average temperature) as a means of assigning protective chronic temperature
standards to coldwater fisheries. MWAT, applied according to EPA guidance, is typically
used in conjunction with an acute upper limit. From its inception, evidence was
available to show that MWAT was inadequate to protect against chronic thermal impairment.
This review of temperature standards, applied across the 50 States, collectively
reveals a set of ecologically based principles that can be extracted from available
standards and would provide a better measure of protection. It is deduced that standards
might better apply to optimum temperatures for each life-history stage to protect
against chronic thermal effects. These should include: geographic identification
of core spawning and rearing areas, recognising cumulative warming from multiple
sources; a limit on rate of warming or cooling; special standards for salmonids
with exceptionally lower specific temperature requirements, requiring natural thermal
patterns on a daily, seasonal, and annual cycle; and regulating the frequency of
exceedence of standards on a multi-year basis. The diverse temperature standards
found in the statutes of individual States to protect fish species with highly similar
biological requirements are indicative of the failure of States to provide consistently
high levels of protection and of the EPA to ensure State application of the best
science through its standards approval process. In addition to appropriate standards,
monitoring, listing of streams as water quality impaired, and development of restoration
plans are essential to the success in protecting the coldwater fish resource.
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