The monitoring network within this area

Hydrionis holds 1,523 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

1,523

Values held

1909–2026

Record spans

Gauges within the Lower Cowlitz 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 COWLITZ RIVER AT CASTLE ROCK, WA

The highest instantaneous discharge the publisher recorded in each year — a flood peak as measured, not a daily average of one. 1927–2025.

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	COWLITZ RIVER AT CASTLE ROCK, WA (m³/s)
1927	1,164
1929	617
1930	855
1931	1,866
1932	1,438
1933	3,936
1934	1,750
1936	1,365
1937	1,388
1939	1,235
1940	748
1941	1,645
1942	1,713
1943	1,051
1945	1,283
1946	2,410
1947	1,090
1949	1,458
1950	1,552
1951	1,903
1952	1,172
1953	1,699
1955	1,419
1956	1,223
1958	997
1959	1,637
1960	1,826
1961	1,192
1962	1,894
1964	2,056
1966	816
1968	1,402
1969	1,141
1970	1,073
1971	1,416
1972	2,311
1974	1,943
1975	1,668
1977	425
1979	1,116
1980	2,747
1982	1,855
1983	1,405
1984	668
1986	1,775
1987	1,192
1988	668
1990	2,526
1992	765
1993	416
1994	490
1995	1,345
1996	3,171
1998	872
1999	1,181
2000	328
2001	1,455
2003	1,954
2004	1,079
2005	838
2006	1,591
2007	1,821
2009	3,002
2011	1,283
2012	1,331
2014	915
2015	1,090
2017	1,133
2019	736
2020	1,342
2021	1,291
2022	1,809
2023	1,269
2025	850

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	1927–2025
Completeness	74.7% of the periods in that span are held. Gaps are drawn as breaks and never interpolated.
Known gaps	25 separate periods inside 1927–2025 hold no value. They are drawn as breaks in the line and are never interpolated across.
Continuity	The record begins in 1927 and is not continuous from it: 99 years separate the first value from the last, and 75% 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 COWLITZ RIVER AT CASTLE ROCK, WA, as a depth

The year's flow spread over the land draining to this gauge, in millimetres — the same unit rainfall is measured in. 1927–2025.

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	COWLITZ RIVER AT CASTLE ROCK, WA (mm)
1927	1,608
1928	1,181
1929	957
1930	909
1931	1,144
1932	1,747
1933	2,169
1934	1,593
1935	1,096
1936	1,281
1937	1,561
1938	1,255
1939	1,162
1940	1,096
1941	961
1942	1,139
1943	1,205
1944	791
1945	1,349
1946	1,781
1947	1,423
1948	1,539
1949	1,482
1950	2,058
1951	1,539
1952	955
1953	1,705
1954	1,581
1955	1,864
1956	1,695
1957	1,166
1958	1,509
1959	1,656
1960	1,470
1961	1,644
1962	1,369
1963	1,153
1964	1,710
1965	1,201
1966	1,366
1967	1,452
1968	1,396
1969	1,387
1970	1,417
1971	1,804
1972	2,055
1973	1,188
1974	1,863
1975	1,833
1976	1,325
1977	1,290
1978	1,068
1979	1,039
1980	1,379
1981	1,364
1982	1,716
1983	1,642
1984	1,520
1985	1,123
2001	932
2002	1,330
2003	1,295
2004	1,213
2005	1,045
2006	1,681
2007	1,310
2008	1,406
2009	1,336
2010	1,450
2011	1,689
2012	1,957
2013	1,407
2014	1,610
2015	1,327
2016	1,607
2017	1,749
2018	1,264
2019	901
2020	1,516
2021	1,430
2022	1,520
2023	1,117
2024	1,215
2025	1,315

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	1927–2025
Completeness	84.8% of the periods in that span are held. Gaps are drawn as breaks and never interpolated.
Known gaps	One period inside 1927–2025 holds no value: 1986 to 2000, 15 years with no reading. It is drawn as a break in the line and is never interpolated across.
Continuity	The record begins in 1927 and is not continuous from it: 99 years separate the first value from the last, and 85% of the years between them are held. The span is not the record.
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.

2,032

Fullest snowpack recorded at Sheep Canyon, in 1999 (mm of water)

80

Thinnest, in 2015 (mm of water)

April

Month the pack is usually at its fullest

June

Month the pack has gone by, in half of years

Peak snowpack at Sheep Canyon

Water years 1984–2026. 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	Sheep Canyon (mm)
1984	1,133
1985	1,286
1986	371
1987	704
1988	913
1989	1,591
1990	1,207
1991	839
1992	403
1993	954
1994	772
1995	631
1996	228
1997	1,020
1998	926
1999	2,032
2000	1,225
2001	542
2002	1,225
2003	433
2004	810
2005	171
2006	1,240
2007	936
2008	1,942
2009	1,219
2010	795
2011	1,609
2012	1,410
2013	1,181
2014	657
2015	80.0
2016	729
2017	1,420
2018	1,161
2019	779
2020	959
2021	1,228
2022	1,167
2023	1,526
2024	912
2025	1,025
2026	381

Why the snow is not read against the river here

These two series do not overlap in time: Peak snow water equivalent runs 1983–2026 and Mean river flow, water year runs 1909–1978.

Every gauge Hydrionis holds within this area

Gauges within the Lower Cowlitz and what each holds
Gauge	Measures	Values	Record
COWLITZ RIVER AT CASTLE ROCK, WA	burned area within 50 km, catchment area, annual maximum river flow, mean river flow, mean river flow, water year	303	1927–2026
TOUTLE RIVER NEAR SILVER LAKE, WA	burned area within 50 km, catchment area, annual maximum river flow, mean river flow, mean river flow, water year	200	1909–2026

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 — 17080005. 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
COWLITZ RIVER AT CASTLE ROCK, WA	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
TOUTLE RIVER NEAR SILVER LAKE, WA	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	118	yes, 20 or more
Values held	1,523	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-14243000.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), Lower Cowlitz gauge records, accessed 2026-10-05, hydrionis.com/waters/united-states-lower-cowlitz/

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 Lower Cowlitz 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 confidence2025-02-25

Source: USGS — National Water Information System, USGS site 14243000, 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.