The monitoring network within this area

Hydrionis holds 3,855 values from 5 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.

5

Gauges

3,855

Values held

1922–2026

Record spans

Gauges within the Lewis huc8 subbasin

5 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 LEWIS RIVER AT ARIEL, WA

The highest instantaneous discharge the publisher recorded in each year — a flood peak as measured, not a daily average of one. 1924–2025.

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	LEWIS RIVER AT ARIEL, WA (m³/s)
1924	844
1926	750
1927	1,773
1928	464
1930	609
1931	866
1932	1,181
1933	983
1934	1,076
1936	966
1937	1,390
1939	697
1940	1,045
1941	1,150
1942	1,631
1944	530
1945	1,212
1946	1,906
1948	872
1949	742
1950	1,138
1951	705
1953	1,354
1955	572
1957	767
1958	518
1959	929
1960	1,365
1961	337
1962	2,138
1964	501
1966	337
1968	881
1970	1,184
1971	660
1972	1,031
1974	1,688
1975	634
1976	334
1977	2,036
1978	334
1980	340
1982	1,152
1983	765
1985	626
1986	784
1987	348
1989	331
1990	1,189
1992	357
1993	340
1994	334
1995	753
1996	2,447
1997	966
1998	1,017
1999	1,011
2001	274
2003	1,396
2004	331
2005	467
2006	847
2007	515
2009	1,141
2010	360
2011	1,002
2012	648
2014	748
2015	898
2017	745
2018	340
2020	592
2021	637
2022	481
2024	614
2025	345

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	1924–2025
Completeness	74.5% of the periods in that span are held. Gaps are drawn as breaks and never interpolated.
Known gaps	26 separate periods inside 1924–2025 hold no value. They are drawn as breaks in the line and are never interpolated across.
Continuity	The record begins in 1924 and is not continuous from it: 102 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 LEWIS RIVER AT ARIEL, 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. 1924–2025.

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	LEWIS RIVER AT ARIEL, WA (mm)
1924	1,840
1925	2,178
1926	1,874
1927	2,531
1928	2,148
1929	1,475
1930	1,441
1931	1,622
1932	2,796
1933	3,618
1934	2,549
1935	1,838
1936	1,868
1937	2,539
1938	2,032
1939	1,804
1940	1,885
1941	1,681
1942	1,827
1943	2,007
1944	1,324
1945	2,233
1946	2,845
1947	2,192
1948	2,256
1949	2,281
1950	3,407
1951	2,538
1952	1,488
1953	2,895
1954	2,510
1955	2,808
1956	2,836
1957	1,996
1958	2,165
1959	2,511
1960	2,514
1961	2,756
1962	2,242
1963	2,084
1964	2,605
1965	1,961
1966	2,247
1967	2,339
1968	2,716
1969	2,294
1970	2,287
1971	2,910
1972	3,109
1973	2,124
1974	3,155
1975	2,840
1976	2,048
1977	2,079
1978	1,841
1979	1,790
1980	2,115
1981	2,124
1982	2,611
1983	2,801
1984	2,383
1985	1,708
1986	1,921
1987	1,806
1988	1,914
1989	1,898
1990	2,497
1991	2,124
1992	1,435
1993	1,701
1994	2,012
1995	2,793
1996	3,005
1997	3,007
1998	2,515
1999	2,961
2000	1,908
2001	1,550
2002	2,010
2003	2,228
2004	1,941
2005	1,704
2006	2,589
2007	1,996
2008	2,033
2009	1,965
2010	2,320
2011	2,474
2012	2,805
2013	1,905
2014	2,562
2015	2,010
2016	2,440
2017	2,881
2018	2,066
2019	1,506
2020	2,233
2021	2,200
2022	2,192
2023	2,155
2024	2,146
2025	2,084

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	1924–2025
Completeness	100.0% of the periods in that span are held.
Continuity	Continuous: every year from 1924 to 2025 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

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

2,150

Fullest snowpack recorded at Surprise Lakes, in 1999 (mm of water)

241

Thinnest, in 2005 (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 Surprise Lakes

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	Surprise Lakes (mm)
1980	1,018
1981	327
1982	1,653
1983	1,430
1984	1,482
1985	1,292
1986	917
1987	950
1988	565
1989	1,449
1990	1,095
1991	885
1992	661
1993	1,011
1994	1,030
1995	1,199
1996	797
1997	1,903
1998	1,367
1999	2,150
2000	1,523
2001	796
2002	1,453
2003	1,016
2004	1,220
2005	241
2006	1,830
2007	1,206
2008	1,771
2009	1,174
2010	1,188
2011	1,653
2012	1,512
2013	1,167
2014	953
2015	255
2016	1,337
2017	1,614
2018	1,238
2019	861
2020	940
2021	1,285
2022	1,061
2023	1,403
2024	930
2025	1,188
2026	558

Read against the river

Surprise Lakes and MUDDY RIVER BELOW CLEAR CREEK NEAR COUGAR, WA both sit in this drainage area, and their records overlap by 45 years. That is the span the two have in common, not a count of years both actually hold — either record may have gaps inside it. The two are shown separately rather than on one axis: millimetres of stored water and cubic metres per second are not commensurable, and a difference between them would mean nothing.

Being in the same drainage area does not put the snowpack upstream of the gauge. A subbasin is an area, and snow on one tributary can join the river below a gauge on another — so a weak relationship here may say more about which tributary was measured than about the snow.

Every gauge Hydrionis holds within this area

Gauges within the Lewis and what each holds
Gauge	Measures	Values	Record
LEWIS RIVER AT ARIEL, WA	burned area within 50 km, catchment area, annual maximum river flow, mean river flow, mean river flow, water year	343	1923–2026
EAST FORK LEWIS RIVER NEAR HEISSON, WA	burned area within 50 km, catchment area, annual maximum river flow, mean river flow, mean river flow, water year	324	1929–2026
MUDDY RIVER BELOW CLEAR CREEK NEAR COUGAR, WA	burned area within 50 km, catchment area, annual maximum river flow, mean river flow, mean river flow, water year	238	1927–2026
LEWIS RIVER ABOVE MUDDY RIVER NEAR COUGAR, WA	catchment area, annual maximum river flow	48	1927–2026
CANYON CREEK NEAR AMBOY, WA	catchment area, annual maximum river flow	32	1922–2026

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 — 17080002. 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
LEWIS RIVER AT ARIEL, 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
EAST FORK LEWIS RIVER NEAR HEISSON, 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
MUDDY RIVER BELOW CLEAR CREEK NEAR COUGAR, 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
LEWIS RIVER ABOVE MUDDY RIVER NEAR COUGAR, 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
CANYON CREEK NEAR AMBOY, 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 5 of them, which makes it a full profile.

Information-gain signals held for this water body
Signal	Held	Counts
Gauges holding a real record	3	yes, 3 or more
Years spanned	105	yes, 20 or more
Values held	3,855	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-14220500.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), Lewis gauge records, accessed 2026-10-05, hydrionis.com/waters/united-states-lewis/

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 Lewis 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 confidence2025-02-21

Source: USGS — National Water Information System, USGS site 14220500, 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.