United States
Environmental Protection
  Office of Water
EPA 822-F-15-002
  February 2016
Draft  EPA-USGS  Technical  Report:
Protecting Aquatic Life from  Effects of
Hydrologic  Alteration
EPA and U.S. Geological Survey (USGS) are releasing
a draft technical report, Protecting Aquatic Life from
Effects of Hydrologic Alteration, for a 60-day public
comment period. The report provides information to
help states, tribes, territories, water resource
managers, and other stakeholders responsible for
the  maintenance of hydrologic flow regimes to
quantify flow targets for the preservation of aquatic
life and habitat. This report describes the
relationship between hydrologic condition and water
quality, and gives examples of what states have
done to address flow concerns using Clean Water
Act authorities and programs that can be used to
support the natural flow regime and maintain
aquatic life. The report provides a flexible,
nonprescriptive framework to quantify flow targets
to protect aquatic life from the effects associated
with flow alteration.

EPA and USGS partnered on this technical report on
hydrologic alteration, which can be an  important
contributor of impairment for water bodies that are
designated to support aquatic life. Stresses on
aquatic life associated with hydrologic alteration
may be further exacerbated through climate change.
Recent climate trends have included the change in
frequency and duration of extreme weather events,
such as droughts and floods, which can have an
impact on flow and affect aquatic life.
                            Technical Report Development
                            This document has undergone internal and external
                            peer reviews and is now being published in the
                            Federal Register for a 60-day public comment
                            period. Once the comment period has ended, EPA
                            and USGS will consider the comments, revise the
                            document, as appropriate, and then publish a final
                            document that will serve as a source of information
                            for states, tribes, territories, and other stakeholders.
                            Hydrologic Alteration
                            Hydrologic alteration is a change to an aquatic
                            system and can include an increase or decrease in
                            water volume, seasonal pulse flow disruption,
                            dramatic variation in water temperature, and other
                            Effects of Hydrologic Alteration
                            Hydrologic alteration can impact aquatic species'
                            ability to spawn, gather nutrients from a stream
                            system, access high-quality habitat, and more.
                            Why this Report is Important
                            This report is a nonprescriptive framework that can
                            be used to quantify targets for flow regime
                            components that are protective of aquatic life  and
                            their habitats. Flow targets can help states, tribes,
                            and territories prepare for changes in historic flow
                            patterns that can result from climate change.
                            Maintaining flow targets may help increase a
                            stream's  resilience to climate change by reducing or
                            avoiding  intensification of existing stresses.

How to View the Criteria Document and
Supporting Information
EPA has established an official public docket for this
action under Docket ID No. EPA-HQ-OW-2015-0335,
accessed at www.regulations.gov. You may also
download the document and supporting information
from EPA's aquatic life criteria website at:

Where to Find More Information
For more information, please contact EPA's Diana
Eignor by phone at (202)566-1143 or by email at
eignor.diana@epa.gov; or contact USGS' Jonathan
Kennen by phone at (609)771-3948 or by email at