EXPLANATION OF THE RECORDS
Introduction
The surface-water records published in this report are for water
year 1996 that began October 1, 1995, and ended September 30,
1996. A calendar of the water year is provided on the inside of
the front cover. The records contain streamflow data and stage,
content, and water-quality data for lakes and reservoirs. The
locations of the stations where the data were collected are shown
in figures 1 and 2. The following sections of the introductory
text are presented to provide users with a more detailed
explanation of how the hydrologic data published in this report
were collected, analyzed, computed, and arranged for presentation.
Each data station in this report is assigned a unique
identification number. This number applies specifically to a
given station and to no other. The number usually is assigned
when a station is first established and is retained for that
station indefinitely. The systems used by the U.S. Geological
Survey to assign identification numbers for surface-water stations
is based on geographic location. Generally, the "
downstream-order" system is used for regular surface-water
stations and the "latitude-longitude" system is used for
surface-water stations where only miscellaneous measurements are
made.
Downstream-Order System
Since October 1, 1950, the order of listing hydrologic-station
records in Survey reports is in a downstream direction along the
main stream. All stations on a tributary entering upstream from a
mainstream station are listed before that station. A station on a
tributary that enters between two mainstream stations is listed
between them. A similar order is followed in listing stations on
first rank, second rank, and other ranks of tributaries. The rank
of any tributary with respect to the stream to which it is
immediately tributary is indicated by an indention in the "
List of Stations" in the front of this report. Each
indention represents one rank. This downstream order and system
of indention shows which stations are on tributaries between any
two stations and the rank of the tributary on which each station
is situated.
The station-identification number is assigned according to
downstream order. In assigning station numbers, no distinction
is made between partial-record stations and other stations;
therefore, the station number for a partial-record station
indicates downstream-order position in a list made up of both
types of stations. Gaps are left in the series of numbers to
allow for new stations that may be established; hence, the
numbers are not consecutive. The complete eight-digit number
for each station, such as 06342500, which appears just to the
left of the station name, includes the two-digit Part number
"06" plus the six-digit downstream-order number
"342500." The Part number designates the major river
basin; for example, Part "06" is the Missouri River
Basin. All records for a drainage basin encompassing more than
one State can be arranged in downstream order by assembling
pages from the various State reports by station number to
include all records in the basin.
Latitude-Longitude System
The identification numbers for miscellaneous surface-water sites
are assigned according to the grid system of latitude and
longitude. The number consists of 15 digits. The first six
digits denote the degrees, minutes, and seconds of latitude, the
next seven digits denote degrees, minutes, and seconds of
longitude, and the last two digits (assigned sequentially)
identify the sites within a 1-second grid. This
site-identification number, once assigned, is a pure number and
has no locational significance. In the rare instance where the
initial determination of latitude and longitude are found to be in
error, the station will retain its initial identification number;
however, its true latitude and longitude will be listed in the
LOCATION paragraph of the station description (fig. 6).
Miscellaneous Site Numbers
In this report, miscellaneous sites also are numbered according to
a system based on the location in the public-land classification
of the U.S. Bureau of Land Management. This system is used to
identify and locate miscellaneous measurement sites on maps that
use the public-land classification of the U.S. Bureau of Land
Management. The system is illustrated in figure 7. The first
number denotes the township north of a base line, the second
number denotes the range west of the fifth principal meridian, and
the third numeral denotes the section in which the site is
located. The letters A, B, C, and D designate, respectively, the
northeast, northwest, southwest, and southeast quarter section,
quarter-quarter section, and quarter-quarter-quarter section
(10-acre tract). For example, site 139-049-15ADC is in the
SW1/4SE1/4NE1/4 sec.15, T.139 N., R.049 W. Consecutive terminal
numbers are added if more than one site is recorded within a
10-acre tract.
Records of stage and water discharge may be complete or partial.
Complete records of discharge are those obtained using a
continuous stage-recording device through which either
instantaneous or mean daily discharges may be computed for any
time, or any period of time, during the period of record.
Complete records of lake or reservoir content, similarly, are
those for which stage or content may be computed or estimated with
reasonable accuracy for any time, or period of time. They may be
obtained using a continuous stage-recording device, but need not
be. Because daily mean discharges and end-of-day contents
commonly are published for such stations, they are referred to as
"daily stations."
By contrast, partial records are obtained through discrete
measurements without using a continuous stage-recording device
and pertain only to a few flow characteristics, or perhaps only
one. The nature of the partial record is indicated by table
titles such as "Crest-stage partial records," or
"Low-flow partial records." Records of miscellaneous
discharge measurements or of measurements from special studies,
such as low-flow seepage studies, may be considered as partial
records. Locations of all complete-record and crest-stage
partial-record stations for which data are given in this report
are shown in figure 1.
Data Collection and Computation
The data obtained at a complete-record gaging station on a stream
or canal consist of a continuous record of stage, individual
measurements of discharge throughout a range of stages, and
notations regarding factors that may affect the relationships
between stage and discharge. These data, together with
supplemental information, such as weather records, are used to
compute daily discharges. The data obtained at a complete-record
gaging station on a lake or reservoir consist of a record of stage
and of notations regarding factors that may affect the
relationship between stage and lake content. These data are used
with stage-area and stage-capacity curves or tables to compute
water-surface areas and lake storage.
Continuous records of stage are obtained with analog recorders
that trace continuous graphs of stage, with digital recorders
that punch stage values on paper tapes at selected time
intervals, with electronic data loggers that store data on an
electronic chip, or with satellite data platforms that store
data electronically and transmit the data periodically via
satellite to a computer based data processing facility.
Measurements of discharge are made with current meters using
methods adopted by the U.S. Geological Survey as a result of
experience accumulated since 1880. These methods are described
in standard textbooks, Water-Supply Paper 2175, and the U.S.
Geological Survey Techniques of Water-Resources Investigations
(TWRI's), Book 3, Chapter A1 through A19 and Book 8, Chapters
A2 and B2. The methods are consistent with the American
Society for Testing and Materials (ASTM) standards and
generally follow the standards of the International
Organization for Standards (ISO).
In computing discharge records, results of individual
measurements are plotted against the corresponding stages, and
stage-discharge relation curves are then constructed. From
these curves, rating tables indicating the approximate
discharge for any stage within the range of the measurements
are prepared. If it is necessary to define extremes of
discharge outside the range of the current-meter measurements,
the curves are extended using: (1) logarithmic plotting; (2)
velocity-area studies; (3) results of indirect measurements of
peak discharge, such as slope-area or contracted-opening
measurements, and computations of flow over dams or weirs; or
(4) step-backwater techniques.
Daily mean discharges are computed by applying the daily mean
stages (gage heights) to the stage-discharge curves or tables.
If the stage-discharge relation is subject to change because of
frequent or continual change in the physical features that form
the control, the daily mean discharge is determined by the
shifting-control method, in which correction factors based on
the individual discharge measurements and notes of the
personnel making the measurements are applied to the gage
heights before the discharges are determined from the curves or
tables. This shifting-control method also is used if the
stage-discharge relation is changed temporarily because of
aquatic growth or debris on the control. For some stations,
formation of ice in the winter may so obscure the
stage-discharge relations that daily mean discharges must be
estimated from other information such as temperature and
precipitation records, notes of observations, and records for
other stations in the same or nearby basins for comparable
periods.
In computing records of lake or reservoir contents, it is
necessary to have available from surveys, curves or tables
defining the relationship of stage and content. The
application of stage to the stage-content curves or tables
gives the contents from which daily, monthly, or yearly changes
then are determined. If the stage-content relationship changes
because of deposition of sediment in a lake or reservoir,
periodic resurveys may be necessary to redefine the
relationship. Even when this is done, the contents computed
may become increasingly in error as the lapsed time since the
last survey increases. Discharges over lake or reservoir
spillways are computed from stage-discharge relationships much
as other stream discharges are computed.
For some gaging stations, there are periods when no gage-height
record is obtained, or the recorded gage height is so faulty
that it cannot be used to compute daily discharge or contents.
This happens when the recorder stops or otherwise fails to
operate properly, intakes are plugged, the float is frozen in
the well, or for various other reasons. For such periods, the
daily discharges are estimated from the recorded range in
stage, previous or following record, discharge measurements,
weather records, and comparison with other station records from
the same or nearby basins. Likewise, daily contents may be
estimated from operator's logs, previous or following record,
inflow-outflow studies, and other information. Information
explaining how estimated daily-discharge values are identified
in station records is included in the next two sections, "
Data Presentation" (REMARKS paragraph) and "
Identifying Estimated Daily Discharge."
Data Presentation
Streamflow data in this report are presented in a new format that
is considerably different from the format in data reports prior to
the 1991 water year. The major changes are that statistical
characteristics of discharge now appear in tabular summaries
following the water-year data table and less information is
provided in the text or station manuscript above the table. These
changes represent the results of a pilot program to reformat the
annual water-data report to meet current user needs and data
preferences.
The records published for each continuous-record surface-water
discharge station (gaging station) now consist of four parts:
the manuscript or station description; the data table of daily
mean values of discharge for the current water year with
summary data; a tabular statistical summary of monthly mean
flow data for a designated period, by water year; and a summary
statistics table that includes statistical data of annual,
daily, and instantaneous flows as well as data pertaining to
annual runoff, 7-day low-flow minimums, and flow duration.
The manuscript provides, under various headings, descriptive
information, such as station location; period of record;
historical extremes outside the period of record, record accuracy,
and other remarks pertinent to station operation and regulation.
The following information, as appropriate, is provided with each
continuous record of discharge or lake content. Comments to
follow clarify information presented under the various headings of
the station description.
LOCATION.--Information on locations is obtained from the
most accurate maps available. The location of the gaging station
with respect to the cultural and physical features in the vicinity
and with respect to the reference place mentioned in the station
name is given. River mileages were determined by methods given in
"River Mileage Measurement," Bulletin 14, Revision of
October 1968, prepared by the Water Resources Council or were
provided by the U.S. Army Corps of Engineers.
DRAINAGE AREA.--Drainage areas are measured using the
most accurate maps available. Because the type of maps available
varies from one drainage basin to another, the accuracy of
drainage areas likewise varies. Drainage areas are updated as
better maps become available.
PERIOD OF RECORD.--This indicates the period for which
records have been published for the station or for an equivalent
station. An equivalent station is one that was in operation at a
time that the present station was not and whose location was such
that flow at it can reasonably be considered equivalent to flow at
the present station.
REVISED RECORDS.--Because of new information, published
records occasionally are found to be incorrect, and revisions are
printed in later reports. Listed under this heading are all the
reports in which revisions have been published for the station and
the water years to which the revisions apply. If a revision did
not include daily, monthly, or annual figures of discharge, that
fact is noted after the year dates as follows: "(M)"
means that only the instantaneous maximum discharge was revised;
"(m)" that only the instantaneous minimum was revised;
and "(P)" that only peak discharges were revised. If
the drainage area has been revised, the report in which the most
recently revised figure was first published is given.
GAGE.--The type of gage in current use, the datum of the
current gage referred to see level (see glossary), and a condensed
history of the types, locations, and datums of previous gages are
given under this heading.
REMARKS.--All periods of estimated daily discharge will
either be identified by date in this paragraph of the station
description for water-discharge stations or flagged in the daily
discharge table. (See next section, "Identifying Estimated
Daily Discharge.") If a REMARKS paragraph is used to identify
estimated record, the paragraph will begin with this information
presented as the first entry. The paragraph is also used to
present information relative to the accuracy of the records, to
special methods of computation, and to conditions that affect
natural flow at the station. In addition, information may be
presented pertaining to average discharge data for the period of
record; to extremes data for the period of record and the current
year; and, possibly, to other pertinent items. For reservoir
stations, information is given on the dam forming the reservoir,
the capacity, outlet works and spillway, and purpose and use of
the reservoir.
COOPERATION.--Records provided by a cooperating
organization or obtained for the U.S. Geological Survey by a
cooperating organization are identified here.
EXTREMES OUTSIDE PERIOD OF RECORD.--Included here is
information concerning major floods or unusually low flows that
occurred outside the stated period of record. The information may
or may not have been obtained by the U.S. Geological Survey.
REVISIONS.--If a critical error in published records is
discovered, a revision is included in the first report published
following discovery of the error.
Although rare, occasionally the records of a discontinued gaging
station may need revision. Because, for these stations, there
would be no current or, possibly, future station manuscript
published to document the revision in a "Revised Records
" entry, users of data for these stations who obtained the
record from previously published data reports may wish to contact
the District office (address given on the back of the title page
of this report) to determine if the published records were ever
revised after the station was discontinued. Of course, if the
data for a discontinued station were obtained by computer
retrieval, the data would be current and there would be no need to
check because any published revision of data is always accompanied
by revision of the corresponding data in computer storage.
Manuscript information for lake or reservoir stations differs
from that for stream stations in the nature of the "
Remarks" and in the inclusion of a skeleton stage-capacity
table when daily contents are given.
Headings for AVERAGE DISCHARGE, EXTREMES FOR PERIOD OF RECORD,
AND EXTREMES FOR CURRENT YEAR have been deleted and the
information contained in these paragraphs is now presented in
the tabular summaries following the discharge table or in the
REMARKS paragraph. No changes have been made to the data
presentations of lake contents.
The daily table of discharge records for stream-gaging stations
gives mean discharge for each day of the water year. In the
monthly summary for the table, the line headed "TOTAL"
gives the sum of the daily figures for each month; the line headed
"MEAN" gives the average flow in cubic feet per second
for the month; and the lines headed "MAX" and "MIN
" give the maximum and minimum daily mean discharges,
respectively, for each month. Discharge for the month also is
usually expressed in cubic feet per second per square mile (line
headed "CFSM"); or in inches (line headed "IN.
"); or in acre-feet (line headed "AC-FT"). Figures
for cubic feet per second per square mile and runoff in inches or
in acre-feet may be omitted if there is extensive regulation or
diversion or if the drainage area includes large noncontributing
areas. At some stations monthly and (or) yearly observed
discharges are adjusted for reservoir storage or diversion, or
diversion data or reservoir contents are given. These figures are
identified by a symbol and corresponding footnote.
A tabular summary of the mean (line headed "MEAN"),
maximum (line headed "MAX"), and minimum (line headed
"MIN") of monthly mean flows for each month for a
designated period is provided below the mean values table. The
water years of the first occurrence of the maximum and minimum
monthly flows are provided immediately below those figures. The
designated period will be expressed as "FOR WATER YEARS
_____-_____, BY WATER YEAR (WY)," and will list the first and
last water years of the range of years selected from the PERIOD OF
RECORD paragraph in the station manuscript. It will consist of
all of the station record within the specified water years,
inclusive, including complete months of record for partial water
years, if any, and may coincide with the period of record for the
station. The water years for which the statistics are computed
will be consecutive, unless a break in the station record is
indicated in the manuscript.
A table titled "SUMMARY STATISTICS" follows the
statistics of monthly mean data tabulation. This table consists
of four columns, with the first column containing the line
headings of the statistics being reported. The table provides a
statistical summary of yearly, daily, and instantaneous flows, not
only for the current water year but also for the previous calendar
year and for a designated period, as appropriate. The designated
period selected, "WATER YEARS _____-_____," will consist
of all of the station record within the specified water years,
inclusive, including complete months of record for partial water
years, if any, and may coincide with the period of record for the
station. The water years for which the statistics are computed
will be consecutive, unless a break in the station record is
indicated in the manuscript. All of the calculations for the
statistical characteristics designated ANNUAL (See line headings
below.), except for the "ANNUAL 7-DAY MINIMUM"
statistic, are calculated for the designated period using complete
water years. The other statistical characteristics may be
calculated using partial water years.
The date or water year, as appropriate, of the first occurrence
of each statistic reporting extreme values of discharge is
provided adjacent to the statistic. Repeated occurrences may
be noted in the REMARKS paragraph of the manuscript or in
footnotes. Because the designated period may not be the same
as the station period of record published in the manuscript,
occasionally the dates of occurrence listed for the daily and
instantaneous extremes in the designated-period column may not
be within the selected water years listed in the heading. When
this occurs, it will be noted in the REMARKS paragraph or in
footnotes. Selected streamflow duration curve statistics and
runoff data are also given. Runoff data may be omitted if
there is extensive regulation or diversion of flow in the
drainage basin.
The following summary statistics data, as appropriate, are
provided with each continuous record of discharge. Comments to
follow clarify information presented under the various line
headings of the summary statistics table.
ANNUAL TOTAL.--The sum of the daily mean values of
discharge for the year. At some stations the annual total
discharge is adjusted for reservoir storage or diversion. The
adjusted figures are identified by a symbol and corresponding
footnotes.
ANNUAL MEAN.--The arithmetic mean of the individual daily
mean discharges for the year noted or for the designated period.
At some stations the yearly mean discharge is adjusted for
reservoir storage or diversion. The adjusted figures are
identified by a symbol and corresponding footnotes.
HIGHEST ANNUAL MEAN.--The maximum annual mean discharge
occurring for the designated period.
LOWEST ANNUAL MEAN.--The minimum annual mean discharge
occurring for the designated period.
HIGHEST DAILY MEAN.--The maximum daily mean discharge for
the year or for the designated period.
LOWEST DAILY MEAN.--The minimum daily mean discharge for
the year or for the designated period.
ANNUAL 7-DAY MINIMUM.--The lowest mean discharge for 7
consecutive days for a calendar year or a water year. Note that
most low-flow frequency analyses of annual 7-day minimum flows use
a climatic year (April 1-March 31). The date shown in the summary
statistics table is the initial date of the 7-day period. (This
value should not be confused with the 7-day 10-year low-flow
statistic.)
INSTANTANEOUS PEAK FLOW.--The maximum instantaneous
discharge occurring for the water year or for the designated
period. Note that secondary instantaneous peak discharges above a
selected base discharge are stored in District computer files for
stations meeting certain criteria. Those discharge values may be
obtained by writing to the District office. (See address on back
of title page of this report.)
INSTANTANEOUS PEAK STAGE.--The maximum instantaneous
stage occurring for the water year or for the designated period.
If the dates of occurrence for the instantaneous peak flow and
instantaneous peak stage differ, the REMARKS paragraph in the
manuscript or a footnote may be used to provide further
information.
INSTANTANEOUS LOW FLOW.--The minimum instantaneous
discharge occurring for the water year or for the designated
period.
ANNUAL RUNOFF.--Indicates the total quantity of water in
runoff for a drainage area for the year. Data reports may use any
of the following units of measurement in presenting annual runoff
data:
Acre-foot (AC-FT) is the quantity of water required to
cover 1 acre to a depth of 1 foot and is equal to 43,560 cubic
feet or about 326,000 gallons or 1,233 cubic meters.
10 PERCENT EXCEEDS.--The discharge that has been exceeded 10
percent of the time for the designated period.
50 PERCENT EXCEEDS.--The discharge that has been exceeded 50
percent of the time for the designated period.
90 PERCENT EXCEEDS.--The discharge that has been exceeded 90
percent of the time for the designated period.
Data collected at partial-record stations follow the
information for continuous-record sites. Data for
partial-record discharge stations are presented in two tables.
The first is a table of annual maximum stage and discharge at
crest-stage stations, and the second is a table of discharge
measurements at low-flow partial-record stations. The tables
of partial-record stations are followed by a listing of
discharge measurements made at sites other than
continuous-record or partial-record stations. These
measurements are generally made in times of drought or flood to
give better areal coverage to those events. Those measurements
and others collected for some special reason are called
measurements at miscellaneous sites.
Identifying Estimated Daily Discharge
Estimated daily-discharge values published in the water-discharge
tables of annual State data reports are identified either by
flagging individual daily values with the letter symbol "e
" and printing a table footnote (e-Estimated) or by listing
the dates of the estimated record in the REMARKS paragraph of the
station description.
Accuracy of the Records
The accuracy of streamflow records depends primarily on: (1) The
stability of the stage-discharge relation or, if the control is
unstable, the frequency of discharge measurements; and (2) the
accuracy of measurements of stage, measurements of discharge, and
interpretation of records.
The accuracy attributed to the records is indicated under
"REMARKS." "Excellent" means that about 95
percent of the daily discharges are within 5 percent of their
true values; "good," within 10 percent; and "
fair," within 15 percent. Records that do not meet the
criteria mentioned are rated "poor." Different
accuracies may be attributed to different parts of a given
record.
Daily mean discharges in this report are given to the nearest
hundredth of a cubic foot per second for values less than 1 ft
3 /s; to the nearest tenth between 1.0 and 10 ft
3 /s; to whole numbers between 10 and 1,000 ft
3 /s; and to 3 significant figures for more than 1,000 ft
3 /s. The number of significant figures used is
based solely on the magnitude of the discharge value. The same
rounding rules apply to discharges listed for partial-record
stations and miscellaneous sites.
Other Records Available
Information used in the preparation of the records in this
publication, such as discharge-measurement notes, gage-height
records, temperature measurements, and rating tables is on file in
the North Dakota District office. Also, most of the daily mean
discharges are in computer-readable form and have been analyzed
statistically. Information on the availability of the unpublished
information or on the results of statistical analyses of the
published records may be obtained from the office whose address is
given on the back of the title page of this report.
Records of surface-water quality in this report represent a
variety of data types and measurement frequencies. Whenever
possible, records of surface-water quality are obtained at or near
stream-gaging stations because interpretation of surface-water
quality and seasonal variation is enhanced by knowledge of
corresponding discharge data. Locations of stations for which
records on the quality of surface water appear in this report are
shown in figure 2.
Classification of Records
Water-quality data for surface-water sites are grouped into one of
three classifications. A continuing-record station is a
site where data are collected on a regularly scheduled basis.
Frequency may be once or more times daily, weekly, monthly, or
quarterly. A partial-record station is a site where
water-quality data are collected systematically over a period of
years, but frequency of sampling is usually less than quarterly.
A miscellaneous sampling site is a location where samples
are collected one time or intermittently to provide better areal
coverage for defining water-quality conditions over a broad area
in a river basin.
A careful distinction needs to be made between "continuing
records," as used in this report, and "continuous
recordings," which refers to a continuous graph, a series
of discrete values punched at short intervals on a paper tape,
or electronically stored data from a data logger or satellite
data platform. Some records of water quality, such as
temperature and specific conductance, may be obtained through
continuous recordings; however, because of costs, most data are
obtained only monthly or less frequently. Locations of
stations for which records on the quality of surface water
appear in this report are shown in figure 2.
Arrangement of Records
Water-quality records collected at a surface-water daily record
station are published immediately following that record,
regardless of the frequency of sample collection. Station number
and name are the same for both records. Where a surface-water
daily record station is not available or where the water quality
differs significantly from that at the nearby surface-water
station, the continuing water-quality record is published with its
own station number and name in the regular downstream-order
sequence.
Onsite Measurements and Sample Collection
In obtaining water-quality data, a major concern needs to be
assuring that the data obtained represent the in situ quality of
the water. To assure this, certain measurements, such as water
temperature, specific conductance, pH, and dissolved oxygen, need
to be made onsite when the samples are taken. To assure that
measurements made in the laboratory also represent the in situ
water, carefully prescribed procedures need to be followed in
collecting the samples, in treating the samples to prevent changes
in quality pending analysis, and in shipping the samples to the
laboratory. Procedures for onsite measurements and for
collecting, treating, and shipping samples are detailed in the
TWRI Book 1, Chapter D2; Book 3, Chapter C2; and Book 5, Chapters
A1, A3, and A4. These references are listed in the "
Publications on Techniques of Water-Resources Investigations"
section of this report. These methods are consistent with ASTM
standards and generally follow ISO standards.
One sample can define adequately the water quality at a given
time if the mixture of solutes throughout the stream cross
section is homogeneous. However, the concentration of solutes
at different locations in the cross section may vary widely
with different rates of water discharge, depending on the
source of material and the turbulence and mixing of the stream.
Some streams must be sampled through several vertical sections
to obtain a representative sample needed for an accurate mean
concentration and for use in calculating load. All samples
obtained for the National Stream Quality Accounting Network
(see definitions) are obtained from at least several verticals.
Whether samples are obtained from the centroid of flow or from
several verticals depends on flow conditions and other factors
which must be evaluated by the collector.
Chemical-quality data published in this report are considered
to be the most representative values available for the stations
listed. The values reported represent water-quality conditions
at the time of sampling as much as possible, consistent with
available sampling techniques and methods of analysis. In the
rare case where an apparent inconsistency exists between a
reported pH value and the relative abundance of carbon dioxide
species (carbonate and bicarbonate), the inconsistency is the
result of a slight uptake of carbon dioxide from the air by the
sample between measurement of pH in the field and determination
of carbonate and bicarbonate in the laboratory.
For chemical-quality stations equipped with digital monitors,
the records consist of daily maximum, minimum, and mean values
for each constituent measured and are based upon hourly punches
beginning at 0100 hours and ending at 2400 hours for the day of
record. More detailed records (hourly values) may be obtained
from the U.S. Geological Survey North Dakota District office
whose address is given on the back of the title page of this
report.
Water Temperature
Water temperatures are measured at most of the water-quality
stations. In addition, water temperatures are taken at time of
discharge measurements for water-discharge stations. Large
streams have a small diurnal temperature change; shallow streams
may have a daily range of several degrees and may follow closely
the changes in air temperature. Some streams may be affected by
waste-heat discharges.
At stations where recording instruments are used, either mean
temperatures or maximum, minimum, and mean temperatures for
each day are published. Water temperatures measured at the
time of water-discharge measurements are published with the
water-quality records for each surface-water station in this
report.
Sediment
Suspended-sediment concentrations are determined from samples
collected by using depth-integrating samplers. Samples usually
are obtained at several verticals in the cross section. Although
data collected periodically may represent conditions only at the
time of observations, such data are useful in establishing
seasonal relations between quality and streamflow and in
predicting long-term sediment-discharge characteristics of the
stream. Records of the periodic measurements of the particle-size
distribution of the suspended sediment and bed material are
included for some stations.
Laboratory Analyses
Traditionally, dissolved trace-element concentrations have been
reported at the microgram per liter (mg/L) level. Recent
evidence, mostly from large rivers, indicates that actual
dissolved-phase concentrations for a number of trace elements are
within the range of 10's to 100's of nanograms per liter (ng/L).
Present data above the mg/L level should be viewed with caution.
Such data may actually represent elevated environmental
concentrations from natural or human causes; however, these data
could reflect contamination introduced during sampling,
processing, or analysis. To confidently produce dissolved
trace-element data with insignificant contamination, the U.S.
Geological Survey will begin using new trace-element protocols in
the near future.
Samples for biochemical-oxygen demand (BOD) and samples for
indicator bacteria are analyzed locally. Sediment samples are
analyzed in the U.S. Geological Survey laboratory in Iowa
City, Iowa. Al1 other samples are analyzed in the U.S.
Geological Survey laboratory in Arvada, Colo., the North Dakota
State Water Commission laboratory in Bismarck, N. Dak., or the
North Dakota Department of Health laboratory in Bismarck, N.
Dak. Methods used in analyzing sediment samples and computing
sediment records are given in TWRI, Book 5, Chap. C1. Methods
used by the U.S. Geological Survey laboratory are given in
TWRI, Book 1, Chap. D2; Book 3, Chap. C2; Book 5, Chap. A1,
A3, and A4.
Data Presentation
For continuing-record stations, information pertinent to the
history of station operation is provided in descriptive headings
preceding the tabular data. These descriptive headings give
details regarding location, drainage area, period of record, type
of data available, instrumentation, general remarks, cooperating
agencies, and extremes for parameters measured on a daily basis.
Tables of chemical, physical, biological, and radiochemical data
obtained at a frequency less than daily are presented first.
Tables of "daily values" of specific conductance, pH,
water temperature, and suspended sediment then follow in sequence.
In the descriptive headings, if the location is identical to
that of the stream-gaging station, neither the LOCATION nor the
DRAINAGE AREA statements are repeated. The following
information, as appropriate, is provided with each
continuous-record station. Comments that follow clarify
information presented under the various headings of the station
description.
LOCATION.--See Data Presentation under "Records of Stage
and Water Discharge"; same comments apply.
DRAINAGE AREA.--See Data Presentation under "Records of
Stage and Water Discharge"; same comments apply.
PERIOD OF RECORD.--This indicates the periods for which there
are published water-quality records for the station. The
periods are shown separately for records of parameters measured
daily or continuously and those measured less than daily. For
those measured daily or continuously, periods of record are
given for the parameters individually.
INSTRUMENTATION.--Information on instrumentation is given only
if a water-quality monitor, temperature monitor, pumping
sampler, or other sampling device is in operation at a station.
REMARKS.--Remarks provide added information pertinent to the
collection, analysis, or computation of the records.
COOPERATION.--Records provided by a cooperating organization or
obtained for the Geological Survey by a cooperating
organization are identified here.
EXTREMES.--Maximums and minimums are given only for parameters
measured daily or more frequently. None are given for
parameters measured weekly or less frequently, because the true
maximums or minimums may not have been sampled. Extremes, when
given, are provided for both the period of record and for the
current water year.
REVISIONS.--If errors in published water-quality records are
discovered after publication, appropriate updates are made to
the Water-Quality File in the U.S. Geological Survey's data
system, National Water Information System (NWIS), and
subsequently by monthly transfer of update transactions to the
U.S. Environmental Protection Agency's STORET system. Because
the usual volume of updates makes it impractical to document
individual changes in the State data-report series or
elsewhere, potential users of U.S. Geological Survey
water-quality data are encouraged to obtain all required data
from the appropriate computer file to insure the most recent
updates.
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Return to 1999 Data Report
