{'fraction_non_alphanumeric': 0.033515412697977, 'fraction_numerical': 0.03584859048612445, 'mean_word_length': 4.79020979020979, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 1, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 9, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Historical Streamflow and Stage Data Compilation for the Lower Columbia River, Pacific Northwest

The U.S. Geological Survey (USGS) mined data from a variety of national and state agencies including USGS, Oregon Water Resources Department, National Oceanic and Atmospheric Administration, Washington Department of Ecology, Pacific Northwest National Laboratory, Portland State University, and U.S. Army Corps of Engineers (USACE). A comprehensive dataset of streamflow, stage, and tidal elevations for the Lower Columbia River basin was compiled. Data were compiled from gaging stations in Oregon and Washington along the Columbia River from Astoria to The Dalles and along the Willamette River from Salem to Portland. Tidal gages along the Washington, Oregon, and California coasts were also compiled. Seasonal maximum values were calculated for both streamflow and stage for the winter (November–March) and spring (April–July) flow seasons, as well as for the full water year when underlying data were available. The aggregated datasets are available at https://doi.org/10.5066/P9R6RT0Z.


Introduction
The U.S. Geological Survey (USGS) supported the U.S. Army Corps of Engineers in compilation of streamflow and stage data along with quality assurance of acquired data to be used by USACE in a reanalysis of the current flood profiles for the Lower Columbia River (LCR) basin. Flood profiles, also known as "stage-frequency curves," are defined as the annual probability the water level at a given river mile will exceed a specific elevation. The use of accurate flood profiles is important for floodplain management and levee risk assessments. The flood profiles currently used for the Lower Columbia and Willamette Rivers were first developed in 1990 as part of the Columbia River and Tributaries Study 1963 (U.S. Army Corps of Engineers, 1991).

Purpose and Scope
The purpose of this study was to compile an up-to-date dataset of daily mean streamflow, annual peak streamflow, stage, and tidal elevations that will allow for USACE to reanalyze flood profiles and update estimates of uncertainty. The updated profiles will support the mission of the U.S. Army Corps of Engineers (USACE) and other public agencies in the study area involved with the mitigation of flood impacts. All findings are summarized in this report with data published in Boudreau and others (2021). Additionally, three USGS stations were analyzed to provide additional information for future hydrologic modeling efforts in the study area.

Study Area
The LCR basin includes all watersheds draining into the Columbia River from its mouth to downstream of the Bonneville Dam (river mile 146). While much of the study area was in the LCR basin, a few additional areas, upstream of Bonneville Dam to the Dalles along with some tidal stations along the California, Oregon, and Washington coasts, were included. Tidal stations were included for this study in order to look at potential effects from tides and surges on the interior gages. The study area ( fig. 1) includes the Columbia River from Astoria to The Dalles, the Willamette River from Salem to Portland, and portions of the California, Oregon, and Washington coasts. For easier viewing, the study area ( fig. 1) was divided into sub-regions, which included gages from all data sources for the designated regions: Coastal Washington and Oregon

Methodology
Streamflow data were gathered as daily-mean streamflow and annual peak streamflow along the Columbia River from The Dalles to Astoria and along the Willamette River from Salem to Portland. Data were not collected from stations that did not contain sufficient period of record length or were not in locations needed for future modeling efforts. When available, finerresolution streamflow data (sub-daily) were collected for a selection of historic flooding events that occurred on December 1933, December 1964, January 1974, February 1982, February 1986, February 1996, January 1997, and January 2006. Stage data were gathered at a finer resolution (sub-daily) from available locations on the Columbia River below Bonneville Dam and along the Willamette River below Willamette Falls. Hourly tidal data were gathered from sites along the Oregon and Washington coasts as well as from sites on the Columbia River from Vancouver, Washington, to Astoria, Oregon (fig. 2).
All data were compiled in a HEC-DSSVue (U.S. Army Corps of Engineers, 2018a) database file. HEC-DSSVue is a java-based program allowing the user to both visualize and manipulate data in the database file format (.dss). Each dataset is saved in HEC-DSSVue with an associated pathname that follows the format /A/B/C/D/E/F. The various parts, A-F, are described in more detail in  Pathname parts A or B could be blank if a river name or station identifier/location were not available from the data source. Names were not added to these records in order to avoid future confusion when referencing the original data. For part C, the data parameter, see table 3 for explanations of the abbreviations used and their expanded descriptions. In some instances, part D, the data time range, could differ slightly in the pathname versus the actual dataset if the original data file was edited after upload. The time interval, part E, abbreviations are explained in table 3B. Part F, the additional user-defined information, was used to note the source where the data were retrieved from for this study. Table 3 describes the abbreviated part F sources with an expanded description.

Data Sources
This section summarizes sources from which data were compiled. Gages were not identified as being tidally influenced or regulated during this data compilation.

United States Geological Survey (USGS)
Data from 65 USGS gages were compiled for this study (table 4; figs. 4, 5, 6, 7, and 8). Multiple sources were used when compiling data from USGS stations. The USGS National Water Information System (NWIS) website was used for both historical and recent readily available data (U.S. Geological Survey, 2018). The USGS internal NWIS database was used to download stage data which has historically not been available on NWIS. Historical data that were not available in NWIS or electronic format were requested from the National Federal Data Archive (NFDA). An inventory of available data was searched, and a request made to the NFDA for temporary use of the archived records of interest. These records included pre-digital, analog recordings of gage height, such as mechanical stage recorders, paper copies of daily flow values, historic gage documentation, and paper copies of stage-discharge rating tables. Some historical stage-discharge rating tables (table 5) were recreated in the internal USGS database so they could be expanded to determine streamflow from historic stage data. For the historic flooding events of interest, 45 USGS gages had at least 1 flooding event where finer resolution (sub-daily) data were retrieved. Table 6   Daily mean streamflow, annual peak streamflow 1 Station still active at the time of data compilation Table 5. Historical paper rating tables that were recreated within the internal U.S. Geological Survey database to expand and determine instantaneous discharge for flooding events.
[Rating number: Rating numbers were historically labeled as the date they were implemented, but the U.S. Geological Survey later switched to labeling them by numeral. Dates  Oregon Water Resources Department (OWRD) Twelve OWRD gages were compiled for this study (table 7; fig. 6). Data were downloaded for the stations of interest from the OWRD website (Oregon Water Resources Department, 2018a). Data prior to approximately 2016 could be downloaded from Historical Streamflow and Lake Level Data web application (Oregon Water Resources Department, 2018b), while more recent data could be found on the Near Real Time Hydrographics Data web application (Oregon Water Resources Department, 2018c). Daily-mean flows were available and retrieved from all 12 of the stations of interest. Annual peak flow files were available for 11 of the stations. All data were compiled in local standard time (PST).  1933 1964 1974 1982 1986 1996 1997 2006 14105700 Columbia River at The Dalles, OR 6-1-1878 Hood River at Tucker Bridge, Near Hood River, OR 10-20-1897 1 3-5-2018 -  1933 1964 1974 1982 1986 1996 1997 2006 14211720 Willamette River at Portland, OR 10-1-1972 Station still active at the time of data compilation

National Oceanic and Atmospheric Administration (NOAA)
Of the 12 long-term NOAA tidal gages compiled for this study, 6 were coastal locations in Washington, Oregon, and California, and 6 were river locations in the Columbia and Willamette Rivers (table 8; fig. 2). Data were downloaded for each station from the NOAA tides and currents webpage (National Oceanic and Atmospheric Administration, 2018a). All data were compiled in local standard time (PST) and in station datum (STND), an arbitrary fixed base elevation.

Washington Department of Ecology (WA-DOE)
Thirteen WA-DOE gages were compiled for this study (table 9; figs. 3, 4, 5, and 8). Data were downloaded from each available year of data from the WA-DOE Flow Monitoring Network webpage (Department of Ecology State of Washington, 2018). Daily-mean streamflow values were retrieved from 12 of the gages, and 15-minute stage data were retrieved from 6 of the gages. All gages were established after January 2000; therefore, only the January 2006 flooding event was available and retrieved from six of the gages. All data were compiled in local standard time (PST) and all stage data were compiled at an arbitrary datum.

Pacific Northwest National Laboratory (PNNL)
Thirty-nine PNNL elevation gages were compiled for this study (table 10; (Talke and Jay, 2017). Data from four elevation gaging stations were compiled for this study (table 11; figs. 2, 3, and 7). Data directly retrieved from the NOAA webpage were used to populate the Astoria Tongue Point, OR station (9439026). The corrected data file for 9439026 includes a stage datum correction applied to documented instability of BM1 noted in Burgette and others (2009). The data were supplied in Greenwich Mean Time (GMT) with a gage datum of NAVD 88 in meters.

United States Army Corps of Engineers (USACE) Dataquery
Data (table 12; figs. 2, 4, 5, 7, and 8) to supplement and (or) extend data records at five sites were provided by the USACE in the form of HEC-DSS files that were retrieved from the Dataquery/Corps Water Management System (U.S. Army Corps of Engineers, 2018b). Table 13 details a selection of digitized paper files from post-flood report data compiled by USACE that were also included as part of this data compilation (U.S. Army Corps of Engineers, 1943Engineers, , 1949Engineers, , 1956Engineers, , 1957Engineers, , 1963Engineers, , 1966Engineers, , and 1975Columbia Basin Inter-Agency Committee, 1966;Northwest Hydraulic Consultants and others, 1997). Seasonal peak stages (winter and spring) for Willamette at Portland (PRTO) and Columbia at Vancouver (VANW) were digitized from USACE drawing CL-03-112 and CL-03-116. USACE also operates a network of stage gages on the Lower Cowlitz River since the mid-2000s, these were not included in this analysis because they are located on the tributary and not the main stem along with the shorter period of record. High-water marks along the Columbia for the 1948, 1956, and 1996 floods exist in USACE records, but are not included here because they representative of the whole river and are not tied to a specific gage. Additional daily data from Dataquery containing maximum, mean, and minimum stage at VANW are also included , though other datasets should take precedence during periods of overlap due to uncertainty about the source of these data.

Review and Quality Assurance/Quality Control (QA/QC) of Acquired Datasets
General Data Review HEC-DSS software was used to review data for accuracy, and any points deemed erroneous, based on hydrologic judgement, were removed ( fig. 9). Nearby gages, if available, were also used for comparison to help evaluate areas of uncertainty where the data appeared to deviate from the general trend. If erroneous data were removed from a dataset, the source file was duplicated to maintain an unaltered file. Both the original and final datasets were published as HEC-DSS database files (Boudreau and others, 2021). The time datum of all data compiled were reviewed and adjusted when needed to get all datasets consistently in the PST time datum. The gage elevation datums were also reviewed and adjusted when possible to get all datasets into a consistent datum (NAVD 88).

Time Datum Adjustments
For this study, most data were collected in or shifted to Pacific Standard Time (PST). The data from both PNNL and PSU were obtained in GMT and shifted accordingly, including date adjustments where needed. The USACE Dataquery files were supplied in local time, both PST and Pacific Daylight Time (PDT). USACE data in PDT were not shifted because the one-hour time difference was surmised to have negligible impact on the calculated summary maximums.

Vertical Gage Datum Adjustments
Most data were collected in or adjusted to North American Vertical Datum of 1988 (NAVD 88) in feet (ft). The data from both PNNL and PSU had gage heights obtained in NAVD 88 in meters. A conversion factor of 3.281 was used to convert data from meters to feet. NOAA tidal stage data were obtained in Station Datum (STND), an arbitrarily established fixed base elevation, and are converted to NAVD 88 using conversion values from . WA-DOE gage height data were referenced to an arbitrary datum and left as is. USGS data were found in multiple datums: Columbia River Datum (CRD), NGVD 29, and NAVD 88. Data in CRD and NGVD 29 were converted to NAVD 88 using VERTCON 2.0 software downloaded from National Oceanic and Atmospheric Administration (2018b). The values determined by VERTCON 2.0 are supplied in table 14.  (14243000), needed additional adjustments. The stage data at 14243000 were collected in NAVD 88 for most of the record except for the period of May 23, 1980, to June 29, 1997, where the USGS datum notes stated the water-stage recorder was at present site at datum, 23.65 ft higher. For the period in question, 23.65 ft was added to the gage datum to create a continuous NAVD 88 dataset.

Data Review by Data Source
Stage and streamflow data were scanned for erroneous periods and data were removed when deemed necessary. Erroneous data, often referred to as "data spikes," were removed based on hydrologic judgement. Nearby stations, if available, were also used to support the decision to remove the data spikes. The following sections detail the edits made, if needed, to each of the sources of data compiled for this study.

U.S. Geological Survey (USGS)
Historically, the USGS published streamflow data but not stage data. Because stage data were not published and were only used as an intermediate step in the calculation of streamflow, historical stage records did not undergo the same level of editorial clean-up and may contain some erroneous data. Erroneous data could have resulted from instances where the equipment used to measure stage failed or due to environmental conditions. If this occurred, the streamflow data may have been estimated or calculated without the use of the standard relationship between stage and streamflow. In such instances, the stage data might not reflect the true stage of the stream for that period-of-time. Specific edits to records are detailed below.
For the 1974 flooding event, Butte Creek at Monitor, OR (14201500), stage data, used to compute the sub-daily streamflow record, contained a string of repetitive stage values on the recession of the streamflow flooding event peak, suggesting the stage data were erroneous. It was determined this was the result a stage recorder malfunction and the corresponding streamflow data were removed. The 1982 flooding event at Tualatin River near Gaston, OR (14202500), also had signs of a stage recorder malfunction on the recession of the streamflow flooding event peak. The corresponding streamflow during the time of stage recorder malfunction was also removed from the record.
Erroneous stage-data spikes were removed from the record in 1990, 1991, 1992, and 1998. Cowlitz River at Castle Rock (14243000) had erroneous stage data spikes removed from the record in the following years: 1989, 1990, and 1995. For the stage data at Willamette River above the Falls, at Oregon City (14207740), the stage recorder appeared to be failing during two periods of data, one in 1991 and one in 1994, the data were removed from the record. Erroneous data points were removed from the stage record at Willamette River below the Falls, at Oregon City (14207770) in 1990, 1994, and 1996. Due to changes in rounding values over time, as well as the subjective process of visual interpretation of stage values from paper tape chart line plots, the recreated sub-daily streamflow data for flooding events may not match the historically computed daily records. Stage values were physically read off the paper tape chart line plots, so a certain degree of uncertainty could be related to those stage values "picked off the line" and the corresponding streamflow.

Oregon Water Resources Department (OWRD)
OWRD data were reviewed for erroneous data. No edits were deemed necessary.

National Oceanic and Atmospheric Administration (NOAA)
NOAA tidal data were reviewed for erroneous data. No edits were deemed necessary.

Washington Department of Ecology (WA-DOE)
Data from WA-DOE were reviewed for erroneous data, and edits were made as deemed necessary. Data collection during high flow events is not the primary mission of WA-DOE. Therefore, field measurements are often not taken during high flow events, reducing the accuracy of the rating curves and flow data for large events. Edits and review documentation are detailed below broken into sub-sections for stage and streamflow. WA-DOE provided a list of defined codes that were used when qualifying the stage and streamflow data (J. Shedd, WA-DOE, written communication, May 11, 2020). These codes were considered when analyzing the data for data edits.

Stage
The early portion of data from Chinook River at Chinook Valley Road (24N070), collected from December 2014 to July 2015 and from August to October 2015, diverged significantly from the rest of the record. After an email response from WA-DOE staff, it was determined that during this period the tide gates were fully raised so that a contractor could install a lid on a culvert on highway 101. During this period, the gage infrastructure was modified so that all tidal changes would be recorded (J. Shedd, WA-DOE, written commun., July 13, 2018). During some periods of 2015, missing data had been coded as "below instrument threshold" by WA-DOE.
From October 2005 to June 2006, there was a large portion of data missing from Abernathy Creek near Mouth (25E060). These data had been coded by WA-DOE as "estimated data-unreliable" and were therefore removed from the record by WA-DOE. The stage data during low flow periods prior to June 2006 appears lower than the stage data after it. The station had been moved to a new location on June 28, 2006, which accounted for this change in the stage values observed. No adjustments were made to the stage data to account for the station moving.
At Mill Creek at Mouth (25F060), two periods (May 14, 2011-July 19, 2011and March 31, 2012-May 9, 2012 were coded by WA-DOE as "backwater flow conditions" and, therefore, no data were reported by WA-DOE. From March to June 2017, stage data differ from the surrounding periods with a more pronounced oscillation. The Mill Creek stage data were plotted against a nearby site, Coweeman River at Kelso (26C075), and the oscillations were not observed there. The data were coded as "good quality provisional data" by WA-DOE. This period also coincides with backwater conditions when the Columbia River stage was high. To stay consistent with previous periods where WA-DOE had removed backwater effected areas these data were also removed.
In February 2012 a period of data that had been coded as "questionable estimate" by WA-DOE was removed from the dataset at Washougal River at Hatahway Park (28B080). It deviated from the general trend, and similar patterns were not observed at nearby sites Coweeman River at Kelso and Mill Creek at Mouth. Additional periods of missing data were noted in March 2012; there were two periods coded by WA-DOE as "instrument impaired," but the data in-between was coded as "good quality provisional data." The "good quality provisional data" did not follow the trends of nearby sites and was removed as potentially suspect.

Streamflow
Chinook River near Houchen Street (24N100) had a few streamflow peaks which appeared to be outliers. During these periods, December 2014, January 2015, and November 2016, the data were coded by WA-DOE as "above rating, over 2x." The data were compared with a nearby USGS gage, Naselle River near Naselle, WA (12010000), these higher peaks corresponded to similar peaks of differing magnitudes at the USGS gage and were therefore kept in the record.
Some high streamflow peaks were also observed at Grays River near Mouth (25B060) during 2006-09. For the periods in question the data were coded by WA-DOE as "above rating, over 2x." The data were again compared with USGS gage 12010000 with similar corresponding peaks, of differing magnitude, being present. Notes were also found in WA-DOE documentation that USGS gage Chehalis River near Doty, WA (12020000), stage data had occasionally been used to compute streamflow when stage data were missing at Grays River near Mouth. The streamflow at 12020000 was found to have similar high flow peaks supporting the peaks at 25B060, and they remain in the record. High flow peaks were not present from the end of 2009 through 2013 as the data had been deleted by WA-DOE with the data being coded as "estimated data -unreliable." The following sites had minor data gaps throughout the period of record: Elochoman River at Monroe Drive (25C060), Germany Creek at Mouth (25D050), Abernathy Creek near Mouth (25E060), Mill Creek at Mouth (25F060), EF Lewis near Dollar Corner (27D090), Rock Creek at Stevenson (29A070), and Wind River at Stabler (29C070). These gaps were associated with data flags of "rating table exceeded (data will not be reported)," "incomplete day," or "estimated data -unreliable." Mill Creek at Mouth also had a few small gaps in 2011 and 2012 associated with a data flag of "backwater flow conditions." Coweeman River at Kelso (26C075) had streamflow peaks which appeared to be outliers during 2006-09. These peaks corresponded to data periods flagged as "above rating, over 2x" by WA-DOE. A nearby USGS gage, Cowlitz River at Castle Rock, WA (14243000), was used as a comparison site and found corresponding similar peaks, at differing magnitudes, were present. This supported keeping the peaks at 26C075 in the record.
Washougal River at Hathaway Park (28B080) had a combination of some higher flows in 2006 and 2009 associated with data coded as "modeled flow-calibrated results exceed 20 percent of measured flow." A nearby USGS gage, Sandy River near Marmot, OR (14137000), was used for comparison and displayed similar high flow peaks of differing magnitudes, this provided the support for keeping the peaks in the record. Due to not knowing the methods WA-DOE uses to model flow at this station, calculated streamflow values were assumed accurate and retained. Minor periods of missing data were associated with data coded as either "rating table exceeded (data will not be reported)," "incomplete day," "bankfull discharge exceeded," or "estimated data-unreliable." A few periods of high flow were observed at Little Klickitat near Wahkiacus (30C070) in 2007, 2009, 2011, 2012, and 2017. These are all associated with data coded as "modeled flow." Data from 2017 were also coded as "estimated from another station, same variable." Similar high flow peaks at the USGS gage Klickitat River near Pitt, WA (14113000), were found to correspond, at differing magnitudes, to the higher flows observed at 30C070. This provided the 27 support for keeping the higher flows for 30C070 in the record. Various data throughout the period were missing and associated to codes "instrument impaired," "rating table exceeded," and "ice impacted data."

Pacific Northwest National Laboratory (PNNL)
The following stations had erroneous points, in the form of data spikes, that were removed from the elevation records using hydrologic judgement: Baker Bay Marsh, Bradwood Slough Marsh, Burke Island Marsh, Clatskanie River Marsh, Cunningham Lake Marsh, Fort Clatsop Dike-Breach Marsh, Gee Creek Riparian Wetland, Karlson Island Dike-Breach Marsh, Reed Island Slough Marsh, Sauvie Willow Bar Marsh, Walluski River Dike-Breach Marsh, Walluski River Marsh, Welch Island Marsh Slough, and Whites Island Marsh. Stations were compared to others in the area for evaluating when to remove spikes.
Data were typically recorded in 30-minute or 1-hour increments, and typically recorded on the hour. Three stations had hourly data but on slightly differing recording marks: Chinook River Marsh (CHM-HOBO) on the 20-minute mark, Lord Island Marsh 2 (LI2-HOBO) on the 45-minute mark, and Walluski River Dike-Breach Marsh (WRB-HOBO) on the 14-minute mark. Times were not adjusted for these stations.
The snap to time function was used within the HEC-DSS software when the data files from PNNL appeared to have a slight time offset during various deployment periods. This allowed the irregular time series to be adjusted to a regular time series. The time shifts were anywhere from 1 to 13 minutes. The following sites had time shifts applied: Crooked Creek Swamp (CCS-HOBO), Goat Island Marsh (GIC-HOBO), and Seal Slough Swamp (SSS-HOBO2). The first deployment period for the Secret River Marsh (SRM-HOBO) was set to 30minute data. and all other deployments were set to 1 hour. The 30-minute data were snapped to hourly data to create a regular complete final dataset at a 1-hour interval. The original 30-minute dataset was retained as an unaltered file.

Portland State University (PSU)
Data provided by PSU had been reviewed by their staff and were assigned a quality assurance level of "good," based on a qualitative scale of "light," "good," or "excellent." Datasets were qualitatively reviewed for this study, and no edits were deemed necessary.

U.S. Army Corps of Engineers (USACE)
Data provided by USACE via Dataquery files in HEC-DSS format were typically in local standard time. Some data supplied by USACE from Dataquery were found to have stage values off exactly by a factor of 10. In such instances, stage values were divided by 10 to match the stage from periods either before or after the period in question. USACE staff confirmed (R. Cahill, USACE, written commun., October 18, 2018) this approach. Erroneous data points were removed from the supplied records using hydrologic judgement and by comparing data from nearby locations. The following stations each had some data where this manipulation was needed to correct the data back to within reason: Bonneville (BON), Columbia at Columbia City (COCO), Columbia River at Camas (CAMW), Wauna (WAUO/9439099), Willamette River above the falls, at Oregon City (ORC/14207740), and Willamette River below the falls, at Oregon City (ORCO/14207770).

Combining Data from Multiple Sources
On a few occasions, data from the same station were available from multiple data sources (table 16). When possible, the data were combined to extend the dataset and form a continuous period of record. The primary and secondary data sources are listed in table 13. In all instances, the primary data source is presented in Pacific Standard Time and the secondary data source is in local standard time. These 1-hour discrepancies in time were deemed to be inconsequential for the purpose of this project compilation; therefore, no time adjustments were made to the secondary data source. The elevation data were combined at the Willamette River at Portland, OR, gage between USACE Dataquery (PRTO) and USGS (14211720) data files. The Dataquery file was used exclusively from 14:00 on October 1, 1976, to 18:00 on September 30, 1988, to extend the station dataset further back in time from where the USGS data began. An observable time difference of approximately 10 hours with the Dataquery file from October 1976 to December 1992 was visible in the overlapping portions of the two datasets. During four additional time periods where USGS data were currently unavailable, the Dataquery files were used to fill in missing periods: January-April 1993, July-September 1994, March-May 1995, and November 1995 During these time periods, the data were found to coincide well with only the slight 1-hour time difference noted.
Columbia River at Vancouver elevation data were extended as a combination of Dataquery (VANW) and USGS (14144700) files. There was a small period of overlap between the two datasets where the time datum lined up. Dataquery files from 15:00 on November 1, 1974, to 15:00 on February 4, 1998, were used to extend the NOAA dataset back further in time.
For the Cowlitz River at Castle Rock, WA, gage, a Dataquery file was used for the early portion of the elevation dataset from 13:30 on October 31, 1988, to 12:15 on July 29, 1997. The remainder of the dataset from 12:30 on July 29, 1997, to present is from the USGS.
Willamette River above the Falls, at Oregon City USGS (14207740) Seven gages are currently being operated by OWRD after being previously operated by USGS. Those datasets were combined between the two sources to form a continuous record for both daily mean streamflow and the annual peak streamflow at the gages involved. Table 17 details the USGS gages now operated by OWRD and the corresponding time periods of each agency's operation of the gage. behind why continuous streamflow has not been part of the historical record at the gage and discusses two methods that could be used to produce a record of continuous streamflow. An evaluation of the gage data at Willamette River at Portland (14211720) and Columbia River at Vancouver (14144700) was completed along with a re-survey at each gage location to associated benchmarks (Appendix 2). The USGS gage datum at 14211720, which had previously been described as 1.55 ft above NGVD29, has since been adjusted to 1.48 ft above NGVD29 or 4.96 ft above NAVD88. The vertical gage datum at 14144700 is CRD, and the reported conversion was previously described as 1.82 ft above NGVD29. This datum has since been updated to 1.77 ft above NGVD29 or 5.22 ft above NAVD88.

Summary
A total of 402 datasets from 7 national and state agencies were compiled into a HEC-DSSVue database file. These included daily streamflow, annual peak streamflow, streamflow from various historic flooding events, along with elevation and stage data. The datasets were reviewed for any potential erroneous data before being accepted into the final database. The database files are available at Boudreau and others (2021).         Gage height data at Willamette River above the Falls at Oregon City, Oregon, and Willamette River at Newberg, Oregon, illustrating the effect of the flashboards for summer 2017 in which the flashboards were installed in mid-July.

Summary of Key Gaging activities at Willamette Falls
From 1909 to 1912 the USGS published daily water level data furnished by Portland Railway, Light and Power Company, a precursor to Portland General Electric (PGE). In the USGS's early Water Supply reports and archived files at the USGS office in Portland, the location was simply referred to as Willamette River at Oregon City. The gage locations were described as below Willamette Falls at a "vertical staff at the foot of the locks" or "vertical staff gage on the left bank about 1 mile above Willamette Falls." Values were published from both locations.
During 1909-12, streamflow measurements were made by the USGS on the Willamette River either below the mouth of the Clackamas River, about 1.4 miles downstream of Willamette Falls, or at the historical location of a railroad bridge 7 miles downstream of Willamette Falls. Measurements were made by boat, and inflows were subtracted as necessary, so the results represented river discharge at Willamette Falls.
The U.S. Department of Agriculture and the Weather Bureau, a precursor to the National Weather Service (NWS) also recorded water levels at this location. Their readings were made from the staff plate located below the locks (USGS files).
In 1927, the USGS, at the request of the U.S. Army Corps of Engineers made 18 streamflow measurements as well as velocity verification measurements for the turbines. More recently between 1992 and 2001, the USGS made 14 streamflow measurements above the Willamette Falls and above the Tualatin River.
The USGS has recorded water levels at both Willamette River above the Falls at Oregon City (14207740) and Willamette River Below the Falls at Oregon City (14207770) since 1976. Continuous streamflow was not computed for either of these locations. The gage above Willamette Falls is located on the right bank (from the reference frame looking downstream), 0.2 mi upstream from Willamette Falls, 1.6 mi downstream from Tualatin River, and at river mile 26.8. The gage below Willamette Falls is located on the right bank, 0.5 mi downstream from Willamette Falls, 1.4 mi upstream from Clackamas River, and at river mile 26.2

Streamflow Ratings and Streamflow
Upstream of the Willamette Falls a stage-streamflow relationship is unreliable due to backwater caused by the installation of flashboards and bladders. It appears early efforts to measure streamflow (1909-12 and 1927) were made downstream due to dangerous boating conditions above Willamette Falls. The measurements from 1992-2001 were made above the Tualatin River during non-flood conditions. Downstream of Willamette Falls, the Willamette River is tidally influenced ( fig. 1.2), preventing the development of an accurate stage-streamflow rating required to compute streamflow. Developed stage-streamflow ratings would have limited use outside of flood conditions. The USGS developed stage-streamflow ratings in 1912 and 1927. The ratings of data collected above Willamette Falls are only valid when flashboards are not installed due to the backwater conditions.
Of the 14 streamflow measurements made by the USGS between 1992 and 2001, 13 were correlated with available stage data from Willamette River above the Falls (14207740; fig. 1.3). The NWS uses a synthetic streamflow rating at Willamette Falls for internal purposes. They do not use this rating when the flashboards are in place during the summer and fall months (Stephen King, National Weather Service, written communication, Apr. 2, 2019).
The Willamette River at Newberg streamflow gage (14197900) began operation in 2001 to establish continuous streamflow data above Willamette Falls. This gage is located at river mile 50.0 and is 23.4 miles above Willamette Falls. Stage, at this location, is not affected by the flashboards or bladders.
Stage-streamflow ratings above Willamette Falls are only reliable without the flashboards or bladders. Stage-streamflow ratings below Willamette Falls are only reliable during flood conditions.

Summary of Drainage Area and Inflows between Willamette River at Newberg and Willamette Falls & Monthly Water Balance Comparisons.
The Willamette River above the Falls streamflow gage (14207740) is at river mile 26.8 with a drainage area of 10,100 square miles. The closest streamflow gage, upstream of the Willamette Falls gage, is Willamette River at Newberg (14197900). The Newberg gage is at river mile 50.0 with a drainage area of 8,350 square miles. Major inflows between the two gages consist of the Tualatin River and the Molalla River. The Tualatin River at West Linn streamflow gage (14207500), with a drainage area of 706 square miles, accounts for 99 percent of the total drainage for the river when compared to the drainage area at the mouth of Tualatin River. On the Molalla River, two upstream gages; Molalla River near Canby (14200000) and Pudding River at