TD370
.E585167
United States
Environmental Protection
Agency
Office of Water
Regulations and Standards
Washington, DC 20460
September 1980
Water
vvEPA Intermittent Streams
OOOR80013
Water Quality Standards
Criteria Summaries
A Compilation
of State/Federal Criteria
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INTERMITTENT STREAMS
Water Quality Standards
Criteria Summaries
A Compilation of State/Federal Criteria
September 1980
U. S. Environmental Protection Agency
Office of Water Regulations and Standards
Washington, D. C. 20460
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NATIONAL SUMMARY
OF
STATE WATER QUALITY STANDARDS
INTERMITTENT STREAMS
PROVISIONS/POLICIES
SEPTEMBER, 1980
PREPARED FOR
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
CRITERIA AND STANDARDS DIVISION
401 M STREET, S. W.
WASHINGTON, D. C. 20460
PREPARED BY
NALESNIK ASSOCIATES INCORPORATED
505 ELEVENTH STREET, S. E.
WASHINGTON, D. C. 20003
Contract Number 68-01-6058
Project Number WA-80-A055
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INTRODUCTION
This digest is compiled to provide general information to the public as well as to
Federal, State, and local officials. It contains excerpts from the individual
Federal-State water quality standards establishing pollutant specific criteria for
interstate surface waters. The water quality standards program is implemented by
the U. S. Environmental Protection Agency where responsibility for providing
water quality recommendations, approving State-adopted standards for interstate
waters, evaluating adherence to the standards, and overseeing enforcement of
standards compliance, has been mandated by Congress.
Standards, a nationwide strategy for surface water quality management, contain
three major elements: the use (recreation, drinking water, fish and wildlife
propagation, industrial, or agricultural) to be made of the navigable water; criteria
to protect these uses; and an antidegradation statement to protect existing high
quality waters, from degradation by the addition of pollutants.
Water quality criteria (numerical or narrative specifications) for physical,
chemical, temperature, and biological constituents are stated in the July 1976 U. S.
Environmental Protection Agency publication Quality Criteria for Water (QCW),
available from the Government Printing Office, Washington, D. C. The 1976 QCW,
commonly referred to as the "Red Book," is the most current compilation of
scientific information used by the Agency as a basis for assessing water quality.
This publication is subject to periodic updating and revisions in light of new
scientific and technical information.
Intermittent streams provisions and policies in State water quality standards are
the subject of this digest. These provisions and policies are included into the
standards when a State wishes to qualify the applicability of its water criteria to
intermittently low flow streams. The Agency has recommended that water quality
standards should protect specified uses of a waterway in critical low flow
situations.* Additionally, for intermittent streams, the Agency recommends
criteria be adopted to that extent necessary to assure that conditions in the
streams or stream beds will not impair existing or designated uses in the stream or
in downstream waters. The Quality Criteria for Water (1976) recommends
pollutant criteria for the protection of aquatic life and other stream uses during
the minimum stream flow, which in many cases is the average seven-day low flow
which occurs once in ten years (i.e.7Q10).
Since water quality standards experience revisions and upgrading from time to
time, following procedures set forth in the Clean Water Act, individual entries in
this digest may be superseded. As these revisions are accomplished and allowing
for the States to revise their standards accordingly, this digest will be updated and
reissued. Because this publication is not intended for use other than as a general
* Guidelines for State and Areawide Water Quality Management Program
Development; Chapter 5, Water Quality Standards.
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information resource, to obtain the latest information and for special purposes and
applications, the reader needs to refer to the current approved water quality
standards. These can be obtained from the State water pollution control agencies
or the EPA or Regional Offices.
Individual State-adopted criteria follow:
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REFERENCES
A
California Water Quality Standards by River Basins, c.a. 1975
For more detailed information on selected basins, sub-basins
and stretches of streams and coastal areas refer to California
State Water Quality Standards.
g
Delaware Water Quality Standards, March 25, 1979
Q
Idaho Water Quality Standards, c.a. September, 1979
Missouri Water Quality Standards, c.a. February, 1978
£
American Samoa Water Quality Standards,
Revised July, 1973
p
Territory of Guam Water Quality Standards, Sept. 1975
^-1
Trust Territory of the Pacific Islands Water Quality
Standards, October 21, 1973
TJ
Virgin Islands Water Quality Standards, Aug. 1973
ENVIRONMENT REPORTER, The Bureau of National Affairs, Inc.
Washington, D. C. 20037
1 Pages 701:0501-0509, February 16, 1979
2 Pages 706:1004-1008, July 20, 1979
3 Pages 711:0542-0544, August 5, 1977
4 Pages 716:0603, March 26, 1976
5 Pages 726:1005, 1011-1013, March 7, 1980
Basic Water Quality Standards adopted May 22, 1979,
have not yet been submitted to EPA for formal approval.
6 Pages 731:1002-1009, September 8, 1978
7 Pages 746:1008-1014, October 19, 1979
8 Pages 751:0504-0505, January 25, 1980
9 Pages 765:0512-0515, January 30, 1976
10 Page 761:0503-0504, 1973
ni
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11 Page 766:0504-0509, October 5, 1979
12 Pages 771:0502-0504, September 29, 1978
13 Pages 776:0504-0506, April 10, 1979
14 Pages 781:0501-0502, May 18, 1979
15 Pages 786:0501-0502, August 29, 1975
16 Page 791:0583, May 26, 1978
17 Pages 796:0103-0108, February 16, 1979
18 Pages 801:1001-1002, Sept. 29, 1978
19 Page 806:1003, March 30, 1979
on
Page 811:1043, 1974
21 Pages 816:0602-0607, 0642-0648, 1974
99
Pages 821:0502-0505, June 30, 1978
0-J
Pages 831:0501-0510, February 21, 1975
94.
Page 836:0502, June 30, 1978
OK
Pages 841:0507-0537, December 7, 1979
26 Pages 846:0501-0508, November 17, 1978
27
Pages 851:1001-1023, December 15, 1978
98
Pages 856:1001-1002, July 18, 1978
OQ
Pages 861:1002-1007, August 11, 1979
Of)
Pages 866:1004-1009, December 28, 1979
31 Pages 871:0501-0506, November 25, 1977
°.9
Pages 876:1001-1043, May 26, 1978
oo
Pages 881:1001-1007, September 21, 1979
04
Pages 886:0513-0524, August 29, 1975
QC
Pages 891:1001-1129, November 16, 1979
-------
oc
Pages 901:0501-0505, November 3, 1978
07
J Pages 906:0501-0506, October 13, 1978
00
Pages 911:0501-0507, June 22, 1979
on
Pages 916:0541-0544, April 14, 1978
40
Pages 921:1001-1003, August 13, 1976
41 Pages 926:0541-0563, January 26, 1979
49
Pages 931:0501-0508, May 26, 1978
40
Pages 936:1001-1003, June 27, 1975
44 Pages 941:1001-1005, May 26, 1978
45 Pages 946:0501-0520, July 14, 1978
4fi
Pages 951:1002-1003, April 28, 1978
47 Pages 956:1001-1007, January 11, 1980
48 Page 741:1002, November 23, 1979
4Q
Pages 896:0301-0310, March 31, 1978
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INTERMITTENT STREAMS
PRO VISIO NS/POLICIES
State
Alabama
1
Alaska
Arizona1
Arkansas
CaliforniaA
Agricultural and Industrial Water Supply, Industrial
Operations.
This category includes watercourses in which natural flow
is intermittent and non-existent during droughts and which
may, of necessity, receive treated wastes from existing
municipalities and industries, both now and in the future.
In such instances, recognition must be given to the lack of
opportunity for mixture of the treated wastes with the
receiving stream for purposes of compliance.
Not Specified
When the entire flow in a watercourse that would other-
wise be dry at that time and place is effluent from a
wastewater treatment facility or agricultural irrigation
return flow or combination thereof, the Council may, upon
application, taking into consideration R9-21-206,
R9-21-207, and R9-21-208, determine that all or part of
such water quality standards do not apply where the
Council finds that such entire flow does not present a sub-
stantial danger to the health of the public.
When a watercourse that would otherwise be dry at the
time and place is the subject of excavation or other
activities in connection with retrieval of sand, gravel, or
other materials, these water quality standards shall not
apply to waters entering such excavations from occassional
streamflows or to such waters discharged therefrom.
Ephemeral Streams - Where there are streams with inter-
mittent flow, the treatment of waste discharged thereto
shall be no less than conventional secondary or equivalent.
Stream Flows - These standards are based upon the
assumption that existing flow conditions in streams shall
continue without material change. The Water Quality
Standards shall apply at all times except during periods
when flows are less than the average minimum 7-day low
flow which occurs once in ten years.
Not Specified
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Colorado"
Connecticut
Delaware
Florida7
Q
Georgia
Hawaii
.. , 10
Idaho
fllinois
B
Indiana
12
Iowa
13
Low Flow Exceptions - Water quality standards shall apply
at all times except where surface waters are below mini-
mum annual average seven-consecutive-day flow expected
to occur once in ten (10) years. For certain substances,
such as ammonia, the low flow exceptions may be based on
the seasonal average seven-consecutive-day low flow
expected to occur once in ten (10) years. Each season will
normally consist of a minimum of three months.
The minimum average daily flow for seven consecutive
days that can be expected to occur once in ten years under
natural conditions is the minimum flow to which the
standards apply except when a stream is regulated to result
in low flows below that level in which case the standards
apply to the absolute low flow resulting from such
regulation.
Not Specified
Not Specified
Specific criteria or standards set for the various para-
meters apply to all flows on regulated streams. On
unregulated streams, they shall apply to all streamflows
equal to or exceedng to 7-day, 10-year minimum flow.
Not Specified
Not Specified
Except as otherwise provided in this Chapter with respect
to temperature, the water quality standards in this Part
shall apply at all times except during periods when flows
are less than the average minimum seven day low flow
which occurs once in ten years.
All water quality standards in Section 6 of this Regulation,
except those provided in subsection 6(a), will cease to be
applicable when the stream flows are less than the average
minimum seven-consecutive-day low flow which occurs
once in ten years. This determination will be made using
Low-Flow, Characteristics of Indiana Streams by Paul B.
Rohne, Jr., 1972, United States Department of the Interior,
Geological Survey, or any additional information compiled
on a comparable basis.
Fish and aquatic life, wildlife, secondary recreation:
Chemical constituents shall not be exceeded at any time
the flow equals or exceeds the seven-day, ten-year flow
unless the material is from uncontrollable nonpoint
sources.
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Iowa (con't)
Water quality standards shall be met at all times when the
flow of the receiving stream equals or exceeds the average
seven-day low flow which occurs once in ten years.
Exceptions may be made for intermittent or low flow
streams. Where intermittent streams are classified for
Class B aquatic life protection the department may waive
the seven day, ten year low flow requirement and establish
a minimum flow in lieu thereof. Such waiver shall be
granted only when it has determined that aquatic resources
of the receiving waters are of no significance at flows less
than the established minimum.
Kansas
14
Kentucky
Louisiana
17
Maine
15
16
Maryland
18
For class A waters, the applicable criteria listed below
shall apply at all times. For class B streams, the appli-
cable criteria listed below shall apply at all times except
during periods when streamflows, including releases from
reservoirs, are less than the average minimum seven-day
low flow which occurs once in ten years, or when stream
flow is less than 1 cfs, whichever value is greater. Quality
criteria shall be met insofar as is practicable when stream-
flows are less than those stipulated.
All watercourses which reach zero natural flow annually
shall be exempted from water use classification and the
application of the Specific Criteria, Section VII except the
following water courses which shall be classified as Class B
waters: 1) those waters specifically listed in the State
Water Quality Standards; and 2) those waters where evi-
dence specifically indicates that aquatic life will be
supported because of pooling during periods of zero natural
flow.
Not Specified
Not Specified
Minimum Flow - Regulated Rivers and Streams: For
regulated rivers and streams, the Department may
establish a minimum flow necessary to maintain water
quality standards. This flow will be based upon achieving
the assigned classification, criteria and protection of the
uses of the stream. The Department will cooperate with
appropriate Federal, State and private interests in the
development and maintenance of stream flow
requirements.
(1) Discharges of effluent to intermittent streams is not
permitted if feasible alternatives are available.
(2) In instances where discharge to an intermittent
stream is permitted by the Administration, the dis-
charge shall comply with Effluent Limitations (Regu-
lation 08.05.04.05) as well as Receiving Water
Quality Standards (Regulation 08.05.04.03).
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Massachusetts
19
Michigan
20
Minnesota
21
The Division will determine the most severe hydrologic
condition at which water quality standards must be met. In
classifying the inland waters of the Commonwealth and in
applying these standards to such waters, the critical low
flow condition at and above which these standards must be
met is the average minimum consective seven day flow to
be expected once in ten years, unless otherwise stated by
the Division in these standards. In artificially regulated
waters, the critical low flow will be established by the
Division through agreement with the Federal, state or
private interest controlling the flow. The minimum flow
established in such agreement will become the critical low
flow under this section for those waters covered by the
agreement.
Protection of Low Flow Waters; Certain waters will be
designated by the Division in Regulation 5.5 of these
standards for protection under this section due to their
inability to accept pollutant discharges. New or increased
discharges of pollutants to waters so designated are prohi-
bited unless a variance is granted by the Division as
provided in Regulation 4.6
The accepted design streamflow to which the water quality
standards as prescribed by these rules shall apply are those
equal to or exceeding the ten-year recurrence of a mini-
mum low flow average of seven-day duration, except where
the commission determines that a more restrictive applica-
tion is necessary to protect a particular designated use.
Discharges of sewage, industrial waste or other waste
effluents shall be controlled so that the water quality
standards will be maintained at all stream flows which are
equal to or exceeded by 90 percent of the seven conse-
cutive daily average flows of record (the lowest weekly
flow with a once in ten year recurrence interval) for the
critical month(s). The period of record for determining the
specific flow for the stated recurrence interval, where
records are available, shall include at least the most recent
ten years of record, including flow records obtained after
establishment of flow regulation devices, if any. Such
calculations shall not be applied to lakes and their embay-
ments which have noncomparable flow recurrence interval.
Where stream flow records are not available, the flow may
be estimated on the basis of available information on the
watershed characteristics, precipitation, run-off and other
relevant data.
Allowance shall not be made in the design of treatment
works for low stream flow augmentation unless such flow
augmentation of minimum flow is dependable and con-
trolled under applicable laws or regulations.
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22
Mississippi
Missouri
Montana
23
Nebraska
24
All criteria contained herein shall apply to all stages of
streamflow greater than or equal to the 7-day, 10-year
minimum flow in unregulated, natural streams, and the
legally guaranteed minimum flow in regulated streams.
This requirement shall not be interpreted to permit any
unusual waste discharges during periods of lower flow.
(A) The general criteria shall apply to all waters of the
state at all times.
(B) The specific criteria for each use shall apply to all
waters, however, the Commission will consider exceptions
in the following cases:
1. Exception will be considered for streams when the
flow is equal to or below the 7-day, once-in-ten-years
low flow.
2. Exceptions will be considered in regulated-flow
streams if the flow falls below the minimum release
flow agreed upon by the regulating agencies.
3. Excpetions will be considered when the effluent
flow constitutes a majority of the stream flow.
4. Exceptions will be considered when the stream or
lake is subjected to non-point source pollutants due
to storm water runoff. The water quality manage-
ment process shall minimize the adverse effects of
storm water runoff. Exceptions during storm water
runoff shall not be construed as license to relax
point-source controls.
5. Exceptions are granted for the unavoidable chemi-
cal and physical changes that occur in the hypolim-
nion of lakes. Release waters from dams shall meet
specific criteria to protect downstream uses.
Streams that may cease flow in dry periods, but maintain
permanent pools which support aquatic life are identified.
Until such time as minimum stream flows are established
for dewatered streams, the minimum treatment require-
ments for discharges to dewatered receiving streams are to
be no less than the minimum treatment requirements
prescribed.
Treatment requirements for discharges to intermittent
streams are to be no less than the minimum treatment
requirements prescribed.
"The Water Quality Standards, except general criteria
(Rule 2.(2), will not apply to: ...
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Nebraska (con't)
Nevada
25
2fi
New Hampshire
27
New Jersey
28
New Mexico
New York
30
North Carolina
(b) Waters during periods when the flow is less than 0.1 cfs,
or when the flow is less than the 7-day-10-year low flow.
(c) Effluent dominated streams during periods when the
daily flow is totally composed of effluent, excluding minor
amounts of bank seepage."
The specified standards will not be considered violated
when the natural conditions of the receiving water are
outside the established limits, including periods of extreme
high or low flow. Where effluents are discharged to such
waters, the discharges shall not be considered a contributor
to substandard conditions provided maximum treatment in
compliance with permit requirements is maintained.
The water quality standards shall apply at all times except
during periods when receiving stream flows are less than
the minimum average ten-day flow which occurs once in
twenty years.
The levels of quality specified for various water uses,
where applicable, are expected to be maintained under
conditions comprising minimum consecutive seven-day
fresh water flows with ten-year recurrence intervals.
The Water Quality Standards apply at all flows unless
specified otherwise.
Water Quality Standards apply at all times.
The governing flow criterion for the water quality stan-
dards excluding dissolved oxygen and toxics shall be the
minimum average flow for a period of seven consecutive
days that has an average recurrence of once in ten years
(the seven day ten year low flow). The seven day ten year
low flow shall also be the governing flow for the dissolved
oxygen water quality standards during the summer dis-
charge period defined in 15 NCAC 2B.0404. The governing
flow for toxic water quality standards shall be the mini-
mum average flow for a period of 30 consecutive days that
has an average recurrence of once in two years. In cases
where the stream flow is regulated, the governing flow for
all water quality standards shall be the instantaneous
minimum flow or if deemed appropriate by the commission,
the minimum daily average flow.
These governing criteria are established specifically for
setting effluent limitations and for the design of waste-
water treatment facilities. In addition, the governing flow
also established a value below which deviations from water
quality standards can be anticipated.
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North Dakota
31
Ohio
32
Oklahoma
33
In the case of periods where the flow in the stream is less
than the 10-year, 7-day low flow level, the Department
reserves the right to make a case-by-case evaluation of
application of these standards. However, no substances
shall be present in concentrations or combinations that
materially interfere with, or that prove hazardous to, the
intended water usage.
Seasonal Warmwater Habitat: These are the waters
capable of supporting the propagation and habitation of
aquatic organisms on a seasonal basis. These waters have a
minimum annual 7 day average flow that has a recurrence
period of once in ten years (not attributable to discharges
and other hydraulic alterations) of 1 cubic foot per second
or less and having more than 50 per cent of the total flow
under such conditions composed of wastewater effluents.
Mixing zone standards, Rule 3745-1-06 of the Ohio Admini-
strative Code will not apply.
Limited Warmwater Habitat: These are waters incapable
of meeting criteria necessary for the support of popula-
tions of fish and associated vertebrate and invertebrate
organisms and plants either on a seasonal or year around
basis. This degraded condition may be due to relative low
stream flow coupled with heavily populated and/or indus-
trialized areas that have outdated sewer systems and/or
waste treatment facilities. However, exceptions from
Warmwater Habitat criteria will apply only to specific
criterion during specified time periods and/or flow condi-
tions. This will be determined on a case-by-case basis and
comply with all Federal and State water quality statutes.
This designation must be justified by significant economic
or technological rationale and is to be used only as a
temporary classification with upgrading of use designation
at the earliest possible time prior to July 1, 1983, where
attainable.
Standards for the support of this use designation will be the
same as the standards for the support of the use desig-
nation Warmwater Habitat. However, individual criterion
will be varied on a case-by-case basis and will supersede
the standards for other use designations where applicable.
The ammonia-N limit will correspond to the concentrations
in Table 2, where applicable, but the most stringest con-
centration to be met at any time will be the value set in
Section 3745-1-08(0(1) of the Ohio Administrative Code.
The numerical and descriptive (i.e. bioassay related) limits
shall be maintained at all times and apply to all perennial
streams of the State with the exception of when the flow is
less than the seven-day, two-year low flow value. For
intermittent streams, the numerical and descriptive limits
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Oklahoma
(con't)
~ 34
Oregon
35
Pennsylvania
Rhode Island
36
37
South Carolina
South Dakota
38
shall be maintained except when the flow is less than 1.0
cfs. All other general standards shall be maintained at all
times and apply to all perennial and intermittent streams
of the State except when conditions are attributable to
natural phenomena.
Not Specified
The accepted design stream flow, to which the water
quality criteria as set forth in this chapter shall apply, is
the actual or estimated lowest seven-consecutive-day
average flow that occurs once in ten years for a stream
with unregulated flow, or the estimated minimum flow for
a stream with regulated flows, except where the Depart-
ment determines that a more restrictive application is
necessary to protect a particular designated or existing
use. Where the lowest seven-consecutive-day average flow
that occurs once in ten years is zero, the Department shall
specify the design flow based on the identified or esti-
mated flow at that point where a use identified in section
93.4 of this title (relating to statewide water uses)
becomes possible.
The minimum average daily flow for seven consecutive
days that can be expected to occur once in ten years shall
be the minimum flow to which the standards apply.
Water Quality Testing - For the purposes of these regula-
tions, water quality criteria will be determined under the
most adverse conditions. For water quality parameters
most adverse conditions shall mean minimum dilution
predictable and complete disruption in operation of any
Waterwater Treatment Facility. Minimum dilution of flow
shall be the minimum average daily flow for seven con-
secutive days that can be expected to occur once in ten
years. For other water quality parameters, most adverse
conditions shall be defined by the director according to
sound engineering and scientific practices. Bacteriological
surveys of sea water should include sampling during periods
when the most unfavorable hydrographic and pollution
conditions prevail.
Specific water quality standards are not applicable where
natural flow conditions are lower than those which occur at
the minimum seven-day average flow that occurs with a
frequency of once in ten years.
Flow rates for high quality waters: When flow in streams
classified for the beneficial use of cold water permanent
fish life propagation, cold water marginal fish life propaga-
tion, or warm water permanent fish life propagation falls
below the minimum seven day average flow that can be
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South Dakota
(con't)
Tennessee
39
Texas
40
Utah
41
Vermont
42
expected to occur once in every twenty-five years, water
quality criteria shall not apply to the water but any
applicable effluent regulations shall remain in force.
Flow rates for low quality fishery waters: When the flow
in streams classified for the beneficial use of warm water
semipermanent fish life propagation or warm water margi-
nal fish life propagation falls below the minimum seven day
average flow that can be expected to occur once in every
five years but not less than 1.0 c.f.s., water quality criteria
shall not apply to the water but any applicable effluent
regulations shall remain in force.
The criteria set forth shall be applied on the basis of the
following stream flows:
Unregulated streams — stream flows equal to or greater
than the 3-day minimum, 20 year recurrence interval;
Regulated streams — all flows in excess of the minimum
critical flow occurring once in 20 years as determined by
an analysis of records of operation and approved by the
Commissioner of the Tennessee Department of Public
Health.
The dissolved oxygen concentrations represent minimum
values and shall apply at all times that the daily flow
exceeds the base flow condition. The base flow condition
is defined as either the 7-day minimum average flow for
the existing hydrologic conditions with a recurrence inter-
val of two years or 0.1 cfs, whichever is higher.
Temperature: Same as dissolved oxygen.
Other Parameters and General Criteria: The general
criteria and the numerical criteria not specifically dis-
cussed above shall apply at all times regardless of flow
unless specifically excepted.
Failure of a stream to meet water quality standards when
stream flow is either unusually high or less than the 7-day,
10-year minimum flow shall not be cause for action against
persons discharging wastes which meet both the require-
ments of PART I of these regulations and the requirements
of applicable permits.
Water quality classification standards and associated
requirements shall apply in all instances except during
periods when the low natural stream flow is less than the
consecutive seven (7) day mean low flow with a ten (10)
year return period. On those rivers and streams whose rate
of flow is artificially regulated, the flow shall not be
reduced to a point where these standards and requirements
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Vermont
(con't)
Virginia
Washington
44
45
West Virginia
46
Wisconsin
Wyoming
47
American Samoa
District of .
Columbia
E
governing water quality cannot be met nor shall such flow
be regulated in such a way as to produce erosion or
sedimentation with resulting discoloration or turbidity in
excess of the limits provided in these regulations. The
Secretary shall cooperate with appropriate federal, state,
municipal and private interests in the development and
maintenance of streamflow requirements.
This rule shall in no way be construed to permit less than
the normal design operation of any wastewater treatment
facility during periods of low stream flow or to otherwise
waive any discharge prohibitions or restrictions.
Not Specified
Not applicable.
Stream quality standards are to apply at all times when
flows are equal to or greater than the minimum mean 7-
consecutive-day drought flow with a 10-year return
frequency.
The Standards shall apply at all times except (a) during
periods when flows are less than the average minimum 7-
day low flow which occurs once in 10 years (7-day Q10),
and (b) in channels which convey a treated effluent to
natural surface waters. In determining the 7-day Q10 flow,
consideration will be given to streams subject to hydrau-
lically altered flow regimes.
Where stream flow data are availabe, these standards shall
apply at all times except during periods when flows are less
than the average of the minimum seven consecutive day
flow which has the probability of occurring once in ten
years.
During periods when stream flows are less than the mini-
mums described above the Wyoming Game and Fish
Department and the Department may require the dis-
charger to institute operational modifications as necessary
to insure the protection of aquatic life. Where stream flow
data are not available, the Department must take into
consideration the possible existence of markedly abnormal
flows when determining violations of these standards.
Not Specified
The criteria assigned to a stream applies to all flows equal
to or exceeding the 7-day, 10-year minimum flow except
where, and to the extent that, natural conditions prevent
their attainment.
-10-
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Guam Not Specified
49
Puerto Rico Water quality standards shall apply at all times, except for
surface waters during periods when their flows are less
than the average minimum seven-day low flow which
occurs once in ten years.
si
Trust Territories Not Specified
TT
Virgin Islands Not Specified
UU.S. GOVERNMENT PRINTING OFFICE: 1980-341-082/106 ~ 1 L~
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