The monitoring network within this area

Hydrionis holds 1,586 values from 2 gauges within it. Discharge is a property of a gauge and its reach, not of this drainage area, so this page reports the network and its records rather than a single figure.

2

Gauges

1,586

Values held

1928–2026

Record spans

Gauges within the Tualatin huc8 subbasin

2 monitoring points, positioned as the publisher records them.

Flood peaks, as measured

This gauge's flood record, as measured. Unlike a daily mean it is the discharge at the moment the river was highest, which is the figure flood frequency analysis is built on.

Largest measured flow of each year at TUALATIN RIVER AT WEST LINN, OR

The highest instantaneous discharge the publisher recorded in each year — a flood peak as measured, not a daily average of one. 1929–2025.

Show relevant events (1 event)Shading marks when something was recorded, not what caused the line.

Published by the gauge's own operator from its sub-daily record; Hydrionis stores the figure rather than recomputing it. A year the gauge did not cover produces no value rather than a low one, and the gaps are stated below the chart. A peak is a property of this gauge and its reach: a larger flood upstream or downstream of it is not in this series.

What the shaded periods are (1 event)

A shaded period marks when something was recorded, not what caused the shape of the line. Where the two coincide, they coincided.

Documented record — A documented event, compiled from cited sources after it happened. The dates are as good as the record, which for older events can mean the month rather than the day.

Event	Type	Period	Standing	Authority
Hurricane Katrina water and sanitation collapse	Flood	2005-08-29 – 2005-09-30	Documented record	Compiled record

Not shown on this chart

The 1976 drought — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.
The 2022 drought — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.
Yorkshire drought — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.
Cantareira water crisis, São Paulo — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.
Cape Town Day Zero — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.
European drought — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.

View the data behind this chart

Underlying data
Period	TUALATIN RIVER AT WEST LINN, OR (m³/s)
1929	163
1930	135
1931	208
1932	232
1933	236
1934	279
1936	498
1937	215
1939	203
1940	231
1941	175
1943	326
1944	91.5
1945	204
1946	277
1948	294
1949	413
1950	314
1951	300
1953	326
1954	334
1955	127
1957	183
1958	215
1959	314
1960	247
1961	266
1963	233
1964	490
1966	294
1967	294
1971	331
1972	422
1974	631
1975	248
1976	203
1977	81.3
1979	140
1980	303
1982	334
1983	163
1984	177
1986	158
1987	309
1988	210
1989	125
1990	198
1991	242
1992	144
1993	125
1994	167
1995	191
1996	748
1997	583
1998	274
1999	445
2000	60.3
2001	216
2003	210
2004	148
2005	126
2006	385
2007	250
2009	211
2010	156
2011	214
2012	227
2014	212
2015	202
2017	283
2018	156
2019	160
2020	212
2021	256
2022	239
2023	211
2024	277
2025	189

About this series

Everything below is a property of the data rather than a rating of it. There is deliberately no single confidence score: how much a gap matters depends on what you are about to do with the series, and only you know that.

Source	United States Geological Survey — National Water Information System · US Government work — public domain
How the values came to exist	Measured
Period held	1929–2025
Completeness	80.4% of the periods in that span are held. Gaps are drawn as breaks and never interpolated.
Known gaps	17 separate periods inside 1929–2025 hold no value. The longest runs from 1968 to 1970 — 3 years with no reading. They are drawn as breaks in the line and are never interpolated across.
Continuity	The record begins in 1929 and is not continuous from it: 97 years separate the first value from the last, and 80% of the years between them are held. The span is not the record.
Last read from the publisher	2026-10-01
Redistribution	Permitted by the upstream licences
Commercial reuse	Permitted by the upstream licences. No Hydrionis access tier can widen this.
Methodology	How this was produced

How much of the rain came back out

A discharge in cubic metres per second cannot be compared with anything: the larger number may only mean the larger catchment. Divided by the area draining to the gauge it becomes a depth of water over that land, which answers a question a reader already has — of the rain that fell here, how much came back out as river?

Water leaving the catchment above TUALATIN RIVER AT WEST LINN, OR, as a depth

The year's flow spread over the land draining to this gauge, in millimetres — the same unit rainfall is measured in. 1929–2023.

Show relevant events (1 event)Shading marks when something was recorded, not what caused the line.

Computed by Hydrionis from the published annual mean flow and the catchment area the station's own publisher states. It is not a water balance: the difference between rainfall and runoff is not evaporation alone but also change in groundwater storage, water abstracted and taken elsewhere, and water imported by transfer schemes — which is why a catchment can yield more runoff than the rain that fell on it without anything being measured wrongly. A different area figure rescales every value here by the ratio between them.

What the shaded periods are (1 event)

A shaded period marks when something was recorded, not what caused the shape of the line. Where the two coincide, they coincided.

Documented record — A documented event, compiled from cited sources after it happened. The dates are as good as the record, which for older events can mean the month rather than the day.

Event	Type	Period	Standing	Authority
Hurricane Katrina water and sanitation collapse	Flood	2005-08-29 – 2005-09-30	Documented record	Compiled record

Not shown on this chart

The 1976 drought — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.
The 2022 drought — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.
Yorkshire drought — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.
Cantareira water crisis, São Paulo — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.
Cape Town Day Zero — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.
European drought — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.

View the data behind this chart

Underlying data
Period	TUALATIN RIVER AT WEST LINN, OR (mm)
1929	337
1930	309
1931	562
1932	791
1933	1,006
1934	794
1935	585
1936	586
1937	855
1938	750
1939	418
1940	665
1941	511
1942	640
1943	683
1944	300
1945	697
1946	874
1947	549
1948	909
1949	651
1950	1,079
1951	901
1952	501
1953	858
1954	840
1955	960
1956	833
1957	536
1958	739
1959	680
1960	714
1961	922
1962	618
1963	624
1964	819
1965	521
1966	832
1967	618
1968	951
1969	738
1970	843
1971	1,076
1972	879
1973	790
1974	966
1975	864
1976	576
1977	439
1978	548
1979	524
1980	764
1981	747
1982	1,024
1983	1,080
1984	746
1985	353
1986	547
1987	666
1988	457
1989	503
1990	617
1991	574
1992	430
1993	512
1994	623
1995	1,029
1996	1,340
1997	1,068
1998	1,055
1999	1,231
2000	522
2001	439
2002	637
2003	737
2004	489
2005	479
2006	1,082
2007	652
2008	601
2009	546
2010	921
2011	834
2012	1,086
2013	392
2014	696
2015	751
2016	973
2017	1,039
2018	584
2019	446
2020	535
2021	755
2022	724
2023	747

About this series

Everything below is a property of the data rather than a rating of it. There is deliberately no single confidence score: how much a gap matters depends on what you are about to do with the series, and only you know that.

Source	United States Geological Survey — National Water Information System · US Government work — public domain
How the values came to exist	Derived Computed by Hydrionis
Period held	1929–2023
Completeness	100.0% of the periods in that span are held.
Continuity	Continuous: every year from 1929 to 2023 is held.
Inputs last read	2026-10-01 · when the records this was computed from were last read from their publishers
Calculation date	2026-08-24 · when the calculation method was last versioned, not a reading of any publisher
Redistribution	Permitted by the upstream licences
Commercial reuse	Permitted by the upstream licences. No Hydrionis access tier can widen this.
Methodology	How this was produced

The snow standing above this water

2 automated snow stations sit inside this drainage area, weighing the snowpack rather than measuring how deep it is.

796

Fullest snowpack recorded at Saddle Mountain, in 2008 (mm of water)

5

Thinnest, in 2015 (mm of water)

February

Month the pack is usually at its fullest

April

Month the pack has gone by, in half of years

Peak snowpack at Saddle Mountain

Water years 1980–2026. Each point is the fullest month of that snow season.

A water year runs October to September and is named for the year it ends, so the snow of one winter stays in one point. The value is the fullest month, not the fullest day: a pack that peaked sharply mid-month reads lower here than a single measurement taken at the right moment would.

View the data behind this chart

Underlying data
Period	Saddle Mountain (mm)
1980	101
1981	30.0
1982	237
1983	70.0
1984	64.0
1985	437
1986	121
1987	96.0
1988	214
1989	251
1990	466
1991	88.0
1992	13.0
1993	438
1994	66.0
1995	163
1996	95.0
1997	113
1998	56.0
1999	525
2000	199
2001	44.0
2002	164
2003	22.0
2004	74.0
2005	34.0
2006	70.0
2007	95.0
2008	796
2009	220
2010	91.0
2011	496
2012	234
2013	332
2014	14.0
2015	5.00
2016	80.0
2017	253
2018	139
2019	275
2020	65.0
2021	133
2022	217
2023	439
2024	123
2025	55.0
2026	33.0

Why the snow is not read against the river here

OSWEGO CANAL NEAR LAKE OSWEGO, OREG. measures a canal, not a natural channel. What passes through it is an operating decision — how much was diverted, and when — so comparing it with what the sky or the mountain delivered would describe the operator rather than the hydrology.

Every gauge Hydrionis holds within this area

Gauges within the Tualatin and what each holds
Gauge	Measures	Values	Record
TUALATIN RIVER AT WEST LINN, OR	burned area within 50 km, catchment area, annual maximum river flow, mean river flow, mean river flow, water year	321	1928–2026
OSWEGO CANAL NEAR LAKE OSWEGO, OREG.	burned area within 50 km, annual maximum river flow, mean river flow, mean river flow, water year	161	1928–2019

How these gauges were attached to this water

Assigned by the publisher to a numbered basin Every gauge here is assigned to this drainage area by its own publisher, which issues the area an official code — 17090010. A drainage area is not a river: it contains the tributaries as well as the main channel, and a gauge in it may be on any of them.

What each gauge’s link to this water rests on
Gauge	Evidence	Established
TUALATIN RIVER AT WEST LINN, OR	Stated by the publisher — USGS site service, huc_cd field — https://waterservices.usgs.gov/nwis/site/ ; named from the USGS Watershed Boundary Dataset 8-digit HU (Subbasin) layer — https://hydro.nationalmap.gov/arcgis/rest/services/wbd/MapServer/4	2026-10-02
OSWEGO CANAL NEAR LAKE OSWEGO, OREG.	Stated by the publisher — USGS site service, huc_cd field — https://waterservices.usgs.gov/nwis/site/ ; named from the USGS Watershed Boundary Dataset 8-digit HU (Subbasin) layer — https://hydro.nationalmap.gov/arcgis/rest/services/wbd/MapServer/4	2026-10-02

What this record holds

Hydrionis decides which waters get a page, and which of those are offered to search, from what is actually held rather than from how the page reads. Five signals are counted; this record has 4 of them, which makes it a full profile.

Information-gain signals held for this water body
Signal	Held	Counts
Gauges holding a real record	2	no
Years spanned	99	yes, 20 or more
Values held	1,586	yes, 1000 or more
Distinct measurements	6	yes, 2 or more
Publishers measuring it	2	yes, 2 or more
Official identifiers	1	recorded, not counted

Use this data

Machine-readable JSON /api/v1/observations/by-subject/gauge-usgs-14207500.json
How to cite this, and who you must credit
How these figures were produced
Request this at a different scale, format or geography

No bulk download is offered here, which is a licence position rather than a product one: at least one contributing publisher does not permit redistribution. The values can be read on the page, cited, and pointed to at source.

Attribution and citation

Suggested citation for Hydrionis

Hydrionis (2026), Tualatin gauge records, accessed 2026-10-05, hydrionis.com/waters/united-states-tualatin/

Cite Hydrionis where you rely on values Hydrionis computed, on the method that produced them, or on the compilation itself. The underlying measurements remain the publishers’ and their attribution requirements apply to you directly.

Recommended, not required. Hydrionis does not claim rights over unmodified public data it relayed, and doing arithmetic on somebody else’s measurements does not make them Hydrionis’s. Cite the version and the access date: the Tualatin gauge records changes as publishers release and as methods are revised, and a citation without both cannot be checked later. Full guidance is on cite and reuse.

None of the contributing licences requires attribution. Crediting the publishers is still good practice and they are listed above.

Where these figures come from

MeasuredHigh confidence2025-01-03

Source: USGS — National Water Information System, USGS site 14207500, annual peak streamflow. Licence: Open.

Method: The instantaneous maximum discharge of each water year as published by USGS, dated to the day it occurred. One value per October-to-September water year; where the publisher lists both a systematic and a historic peak for a year, the larger is the annual maximum. Values the publisher marks as maximum daily averages are not held here, because they are not instantaneous peaks. Values marked as bounded rather than measured are held as censored observations carrying the bound. Cubic feet per second are converted to cubic metres per second and the publisher unit is recorded alongside.

Rating curves are extrapolated at extreme discharges, so the largest values in a peak series carry the largest measurement uncertainty. Data from the U.S. Geological Survey National Water Information System, a work of the United States government and therefore in the public domain.

Retrieved 1 October 2026.