Water-resources data for the 1998 water year (hereinafter 1998) for Minnesota consist of records of stage, discharge, and water quality of streams; and stage of lakes and reservoirs; and water quality of ground water. This volume contains discharge records for 102 stream-gaging stations; stage for 9 lakes and reservoirs; water quality for 22 stream-gaging stations; and peak flow data for 87 high-flow partial-record stations. These data represent a part of the National Water Data System collected by the U.S. Geological Survey and cooperating State and Federal agencies in Minnesota.
        This series of annual reports for Minnesota began with the 1961 water year with a report that contained only data relating to the quantities of surface water. For the 1964 water year, a similar report was introduced that contained only data relating to water quality. Beginning with the 1975 water year, the report was changed to present, in one volume, data on quantities of surface water, quality of surface and ground water, and ground-water levels.
        Prior to introduction of this series and for several water years concurrent with it, water-resources data for Minnesota were published in U.S. Geological Survey Water-Supply Papers. Data on stream discharge and stage and on lake or reservoir contents and stage, through September 1960, were published annually under the title "Surface-Water Supply of the United States, Parts 4, 5 and 6A." For the 1961 through 1970 water years, the data were published in two 5-year reports. Data on chemical quality, temperature, and suspended sediment for the 1941 through 1970 water years were published annually under the title "Quality of Surface Waters of the United States," and water levels for the 1935 through 1974 water years were published under the title "Ground-Water Levels in the United States." The above mentioned Water-Supply papers can be consulted in the libraries of the principal cities of the United States and may be purchased from the U.S. Geological Survey Branch of Information Services, Federal Center, Box 25286, Denver, Colorado 80225.

        Publications similar to this report are published annually by the USGS for all States. These official Survey reports have an identification number consisting of the two-letter State abbreviation, the last two digits of the water year, and volume number. For example, this volume is identified as the "U.S. Geological Survey Water-Data Report MN-98-1." For archiving and general distribution, the reports for 1971-74 water years also are identified as water-data reports. These water-data reports are for sale in paper copy or in microfiche by the National Technical Information Service, U.S. Department of Commerce, Springfield, Virginia 22161.

        Additional information, including current prices, for ordering specific reports may be obtained from the District Chief at the address given on the back of the title page or by telephone (612) 783-3100.

        The USGS and agencies of the State of Minnesota have had cooperative agreements for the systematic collection of streamflow records since 1909, for ground-water levels since 1948, and for water-quality records since 1952. Organizations that assisted in collecting data through cooperative agreement with the Survey are:

Assistance in the form of funds or services was given by the U.S. Army Corps of Engineers, U.S. Department of State, and the Federal Energy Regulatory Commission. Other organizations that supplied data are acknowledged in station descriptions.

        Most of Minnesota received near normal precipitation ("normal" being the statistical median based on data from 1961-90) during the 1998 water year (figs. 1 and 2). The greatest deviations were 4.7 inches below normal in the northeast, to 5.0 inches above normal in the southeast. Statewide, the precipitation totals for the 1998 water year averaged 1.4 inches below normal, or 95 percent of normal.

[figure 1]
[figure 2]
 

        Precipitation totals for the first quarter, October through December 1997, ranged from 60 percent of normal in the southeast, to 139 percent of normal in the northwest, with the statewide average of 80 percent of normal. Most locales did not experience any snowfall events with greater than 5 inches of snowfall. By the end of December most reporting stations had less than 6 inches of snow on the ground.

        Precipitation for the second quarter was an average of 146 percent above normal statewide. The southern one-third of the state had the most departure from normal with the southwest and southeast being 181 percent and 211 percent above normal, respectively. Severe storms toward the end of March accounted for most of this departure.

The remainder of the year, April 1 to September 30, saw quarterly precipitation totals near or below normal throughout the State. June was the only month to have some significant rainfall totals. One rain event in late June resulted in heavy rainfall totals, particularly in the southeast, where rainfall totals over 4 inches were common. Zumbrota reported nearly 8 inches of rain between June 27-28.

       Figures 3a and 3b show monthly-mean and annual-mean discharges for water year 1998 compared to normal (median of monthly-mean discharges for the period 1961-90) for 7 streamflow gaging stations. These stations are located in 4 major basins - Lake Superior, Red River of the North, Lake of the Woods, and the upper Mississippi River. The 1998 annual-mean discharges were greater than the normal medians for Red Lake River at Crookston, Chippewa River near Milan, and Crow River at Rockford; near normal for Mississippi River at Aitkin, and Des Moines River at Jackson, and below normal for Little Fork River at Littlefork and Pigeon River at Middle Falls.

[figure 3a]
[figure 3b]
 

        Monthly-mean discharges for the Pigeon River at Middle Falls near Grand Portage were below normal for every month except March, which was 126 percent of normal. Departures from normal for the remaining months ranged from 99 percent (April) to 21 percent (September) below normal. The annual-mean discharge for 1998 was 229 ft 3 /s, or 43 percent of normal. Annual runoff was 5.1 inches, a decrease of 6.3 inches from the previous year.

        Above normal monthly-mean discharges occurred every month except April, at the Red Lake River at Crookston, which is in the Red River of the North Basin. Flows in April were 62 percent of normal, while flows for the remaining months ranged from 102 percent of normal in September to 211 percent of normal in May. Annual runoff for 1998 was 5.07 inches, a decrease of 2.44 inches from the previous year. Annual-mean discharge was 1,968 ft 3 /s, which is 127 percent of normal.

        Monthly-mean discharges for the Little Fork River at Littlefork, which is in the Lake of the Woods basin, began in October at 73 percent of normal and ended in September at 17 percent of normal. Monthly-mean discharge was at normal in January and above normal for February and March. The remaining months were below normal. Annual-mean discharge for 1998 was 606 ft 3 /s, which is 52 percent of normal. Annual runoff for 1998 was 4.90 inches, a decrease of 6.06 inches from the previous year.

            Flows in the Mississippi River at Aitkin varied from 138 percent above normal in October to 35 percent below normal in May and fluctuated above and below normal the entire water year. The annual-mean discharge of 2,588 ft 3 /s for 1998 is 94 percent of normal and annual runoff was 5.72 inches or 3.98 inches less than last year.

Flows in the Crow River at Rockford, located about 30 miles west of the Twin Cities in the Mississippi River Basin, were above normal the entire year and ranged from 107 percent above normal in September to 572 percent above normal in February. The annual-mean discharge of 1,202 ft 3 /s for 1998 is 145 percent of normal. Annual runoff was 6.18 inches, or 3.32 inches less than last year.

In the Chippewa River near Milan, monthly-mean flows were above normal for the entire year. The month with the greatest departure from normal was February with a monthly-mean discharge of 432 ft 3 /s, which is 1,140 percent above normal. The annual-mean discharge for 1998 was 518 ft 3 /s, which was 170 percent of normal.

Flows in the Des Moines River at Jackson in southwest Minnesota fluctuated on both sides of normal throughout the year. October was the first month since May 1991 with flows below normal (80 percent of normal). Monthly-mean flows were as low as 54 percent below normal, in November, and as high as 391 percent above normal in February. The annual-mean discharge of 256 ft 3 /s for 1998 was 106 percent of normal.

One station, Cannon River at Welch, recorded the highest stage for the period of record. The stage of 15.05 feet occurred on June 27th and had a corresponding discharge of 23,500 ft 3 /s, which was the second highest on record. This was a result of heavy rains in late June (see Precipitation). High Island Creek near Henderson recorded the second highest discharge of record at 2,410 ft 3 /s on March 29. No other peak flows or minimum flows of record were noted.

        Boxplots for three USGS National Water-Quality Assessment (NAWQA) stations were used to depict, to a limited extent, variability in concentrations of dissolved solids and nitrate as nitrogen (figs. 4 and 5).

[figure 4]
[figure 5]
 

        Boxplots display the central tendency, variation, and skewness of a data set as well as the presence or absence of extreme values. A boxplot consists of a centerline (the median) dividing a rectangle whose ends are defined by the 75th and 25th percentiles. Whiskers extend from the ends of the box to the most extreme observation within 1.5 times the interquartile range (the distance from the 25th to the 75th percentile values) beyond the ends of the box. Values more than 1.5 interquartile ranges from the box ends may indicate extreme hydrologic and chemical conditions or sampling and analytical errors. Observations from 1.5 to 3 interquartile ranges from the box in either direction are plotted individually with a closed circle. Observations greater than 3 interquartile ranges from the ends of the box are plotted with an open circle.

        Current water year values are plotted with a triangle to show where these data lie with respect to the distribution of the historic data. These plots represent each sample collected and were collected monthly, or in some cases, two to three times per month.

Dissolved-solids sample concentrations for the Mississippi River near Royalton, Minnesota River near Jordan, and Mississippi River below Lock and Dam 2 at Hastings were collected for the Upper Mississippi River NAWQA program, and are shown in figure 4. In 1998, monthly-mean concentrations of dissolved-solids for Mississippi River at Royalton were at or above the historical median for all months except December. At the Minnesota River near Jordan, 1998 monthly means were above the historical monthly medians for the months of November through March. Samples collected in October, and July through September were below the median, while April through June had sample results on both sides of the median. At Mississippi River at Hastings, samples were significantly above the historical monthly medians for all months except December. In most months at Hastings the sample results were above the 75th percentile.

        Nitrate concentrations reported as nitrogen (analyzed for nitrite plus nitrate) are shown in figure 5. Sample concentrations in 1998 for the Mississippi River near Royalton ranged from 0.07 mg/L in August to 0.37 mg/L in March and were above the historical monthly medians for all months except December, February, April, June and August. Nitrate concentrations for the Minnesota River near Jordan ranged generally below the median for the first five months, then above the median the remaining seven months. Discrete values ranged from 0.05 mg/L in August to 13.0 mg/L in April from 0.13 mg/L in October to 10.3 mg/L in July. Nitrate concentrations for the Mississippi River at Hastings ranged from 0.85 mg/L in October to 8.35 mg/L in April, which was higher than historical monthly medians for all months except October, August, and September.

        Hydrologic Bench-Mark Network is a network of 50 sites in small drainage basins around the country whose purpose is to provide consistent data on the hydrology, including water quality, and related factors in representative undeveloped watersheds nationwide, and to provide analyses on a continuing basis to compare and contrast conditions observed in basins more obviously affected by human activities.

        National Stream-Quality Accounting Network (NASQAN) monitors the water quality of large rivers within four of the Nation's largest river basins--the Mississippi, Columbia, Colorado, and Rio Grande. The network consists of 39 stations. Samples are collected with sufficient frequency that the flux of a wide range of constituents can be estimated. The objective of NASQAN is to characterize the water quality of these large rivers by measuring concentration and mass transport of a wide range of dissolved and suspended constituents, including nutrients, major ions, dissolved and sediment-bound heavy metals, common pesticides, and inorganic and organic forms of carbon. This information will be used (1) to describe the long-term trends and changes in concentration and transport of these constituents; (2) to test findings of the NAWQA; (3) to characterize processes unique to large-river systems such as storage and re-mobilization of sediments and associated contaminants; and (4) to refine existing estimates of off-continent transport of water, sediment, and chemicals for assessing human effects on the world's oceans and for determining global cycles of carbon, nutrients, and other chemicals.

        The National Atmospheric Deposition Program/National Trends Network (NADP/NTN) provides continuous measurement and assessment of the chemical climate of precipitation throughout the United States. As the lead Federal agency, the USGS works together with over 100 organizations to accomplish the following objectives: (1) Provide a long-term, spatial and temporal record of atmospheric deposition generated from a network of 191 precipitation chemistry monitoring sites. (2) Provide the mechanism to evaluate the effectiveness of the significant reduction in SO2 emissions that began in 1995 as implementation of the Clean Air Act Amendments (CAAA) occurred. (3) Provide the scientific basis and nationwide evaluation mechanism for implementation of the Phase II CAAA emission reductions for SO2 and NOx scheduled to begin in 2000.

        Data from the network, as well as information about individual sites, are available through the World Wide Web at: http://nadp.nrel.colostate.edu/NADP

        The National Water-Quality Assessment (NAWQA) Program of the USGS is a long-term program with goals to describe the status and trends of water-quality conditions for a large, representative part of the Nation's ground- and surface-water resources; provide an improved understanding of the primary natural and human factors affecting these observed conditions and trends; and provide information that supports development and evaluation of management, regulatory, and monitoring decisions by other agencies.

        Assessment activities are being conducted in 53 study units (major watersheds and aquifer systems) that represent a wide range of environmental settings nationwide and that account for a large percentage of the Nation's water use. A wide array of chemical constituents will be measured in ground water, surface water, streambed sediments, and fish tissues. The coordinated application of comparative hydrologic studies at a wide range of spatial and temporal scales will provide information for decision making by water-resources managers and a foundation for aggregation and comparison of findings to address water-quality issues of regional and national interest.

        Communication and coordination between USGS personnel and other local, State, and Federal interests are critical components of the NAWQA. Each study unit has a local liaison committee consisting of representatives from key Federal, State, and local water resources agencies, Indian nations, and universities in the study unit. Liaison committees typically meet semiannually to discuss their information needs, monitoring plans and progress, desired information products, and opportunities to collaborate efforts among the agencies.

        Additional information about NAWQA is available through the World Wide Web at: http://wwwrvares.er.usgs.gov/nawqa/nawqa_home.html

The surface-water and ground-water records published in this report are for the 1998 water year that began October 1, 1997, and ended September 30, 1998. A calendar of the water year is provided on the inside of the front cover. The records contain streamflow data, stage and content data for lakes and reservoirs, water-quality data for the surface and ground water, and ground-water-level data. 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, whether stream site or well, in this report is assigned a unique identification number. This number is unique in that it applies specifically to a given station. The number usually is assigned when a station is first established and is retained for that station indefinitely. The system used by the USGS to assign identification numbers for surface-water stations and for ground-water well sites differ, but both are based on geographic location. The "downstream order" system is used for regular surface-water stations and the "latitude-longitude" system is used for wells and, in Minnesota, for surface-water stations where only miscellaneous measurements are made.

        Since October 1, 1950, the order of listing hydrologic-station records in USGS reports is in a downstream direction along the main stream. All stations on a tributary entering upstream from a main stream station are listed before that station. A station on a tributary that enters between two main-stream sections is listed between them. A similar order is followed by listing stations on first rank, second rank, and other order ranks of tributaries. The rank of any tributary on which a station is situated with respect to the stream to which it is immediately tributary is indicated by an indentation in a list of stations in front of the report. Each indention represents one rank. This downstream order and system of indention show which stations are on tributaries between any two stations and the rank of the tributary on which each station is situated.

        As an added means of identification, each hydrologic station and partial-record station has been assigned a station number. These are in the same downstream order in this report. 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 05041000, which appears just to the left of the station name, includes the two-digit part number "05" plus the six-digit downstream order number "041000."

        The eight-digit downstream order station numbers are not assigned to wells and miscellaneous sites where only random water-quality samples or discharge measurements are taken.

        The well and miscellaneous site numbering system of the USGS is based on the grid system of latitude and longitude. The system provides the geographic location of the well or miscellaneous site and a unique number for each site. 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 wells or other sites within a one-second grid. See figure 6. Each well site is also identified by a local well number, which consists of township, range, and section numbers, three letters designating 1/4, 1/4, 1/4 section location, and a two-digit sequential number.

[figure 6]

        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 discharge may be computed for anytime, 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 "High-flow 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, but they are presented separately in this report. Location of all continuous-record and high-flow partial-record stations for which data are given in this report are shown in figures 7 and 8.

[figure 7]
[figure 8]

        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 relations 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 relation 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.

        Records of stage are obtained with recorders that trace continuous graphs of stage or encode stage values at selected time intervals and store on a variety of media. Measurements of discharge are made with current meters using methods adapted by the USGS as a result of experience accumulated since 1880. These methods are described in standard textbooks, in U.S. Geological Survey Water-Supply Paper 2175, and in U.S. Geological Survey Techniques of Water-Resources Investigations (TWRI), book 3, chapter A6.

        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 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.

        At some stream-gaging stations the stage-discharge relation is affected by the backwater from reservoirs, tributary streams, or other sources. This necessitates the use of the slope method in which the slope or fall in a reach of the stream is a factor in computing discharge. The slope or fall is obtained by means of an auxiliary gage set at some distance from the base gage. At some stations the stage-discharge relation is affected by changing stage. At these stations the rate of change in stage is used as a factor in computing discharge.

        In computing records of lake or reservoir contents, it is necessary to have available from surveys, curves, or tables defining the relation 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 relation changes because of deposition of sediment in a lake or reservoir, periodic resurveys may be necessary to redefine the relation. Even when this is done, the contents computed may become increasingly in error as time since the last survey increases. Discharge over lake or reservoir spillways are computed from stage-discharge relations 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. 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."

        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 gage 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, given for only a few stations, 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 there are published records for the station or for an equivalent station. An equivalent station is one that was in operation at a time when the present station was not, and whose location was such that records from it can reasonably be considered equivalent with records from the present station.

REVISED RECORDS-- Published records, because of new information, occasionally are found to be incorrect, and revisions are printed in later reports. Listed under this heading are all reports in which revisions have been published for the station and 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)" means that only the instantaneous minimum was revised; and "(P)" means 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 National Geodetic Vertical Datum of 1929 (see glossary), and a condensed history of the types, locations, and datum of previous gages are given under this heading.

REMARKS-- All periods of estimated daily-discharge record will either be identified by date in this paragraph of the station description for water-discharge stations or flagged in the daily-discharge table. If a remarks statement 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, to conditions that affect natural flow at the station 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 USGS by a cooperating organization are identified here.

EXTREMES OUTSIDE PERIOD OF RECORD-- Included here is the 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 USGS.

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 Minnesota District office (address given on the back of title page of this report) to determine if the published records were ever revised after the station was discontinued. Of course, if the data 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 to 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, except for the listing of secondary instantaneous peak discharges in the EXTREMES FOR CURRENT YEAR paragraph, is now presented in the tabular summaries following the discharge table or in the REMARKS paragraph, as appropriate. No changes have been made to the data presentations of lake contents.

        Tables of peak discharges above base discharge are included for some stations where secondary instantaneous peak discharges are used in flood-frequency studies of highway and bridge design, flood control structures, and other flood related projects. The base discharge value is selected so an average of three peaks a year will be reported. This base discharge value has a recurrence interval of approximately 1.1 years.

Data Table of Daily-Mean Values

Statistics of Monthly-Mean Data

Summary Statistics

Identifying Estimated Daily Discharge

Accuracy of the Records

Other Records Available

Records of Surface-Water Quality    Top

Classification of Records

Arrangement of Records

On-Site Measurement and Sample Collection

Water Temperature

Sediment

Laboratory Measurements    Top

Data Presentation

Remark Codes    Top

PRINTED OUTPUT	REMARK
e	Estimated value
>	Actual value is known to be greater than the value shown
<	Actual value is known to be less than the value shown
K	Results based on colony count outside the acceptance range (non-ideal colony count)
L	Biological organisms count less than 0.5 percent (organisms may be observed rather than counted)
D	Biological organism count equal to or greater than 15 percent (dominant)
V	Analyte was detected in both the environmental sample and the associated blanks
&	Biological organism estimated as dominant.
Water Quality-Control Data

Blank Samples

Reference Samples

Replicate Samples

Spike Samples

Dissolved Trace-Element Concentrations

Change in National Trends Network Procedures

Records of Ground-Water Quality    Top

Data Collection and Computation

Data Presentation

Access to USGS Water Data    Top

Definition of Terms

Classification	Size (mm)	Method of analysis
Clay	0.00024 - 0.004	Sedimentation
Silt	.004 - .062	Sedimentation
Sand	.062 - 2.0	Sedimentation or sieve
Gravel	2.0 - 64.0	Sieve

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