The monitoring network within this area

Hydrionis holds 1,427 values from 3 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.

3

Gauges

1,427

Values held

1910–2026

Record spans

Gauges within the Lower Clark Fork huc8 subbasin

3 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 Clark Fork near Plains MT

The highest instantaneous discharge the publisher recorded in each year — a flood peak as measured, not a daily average of one. 1912–2025.

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	Clark Fork near Plains MT (m³/s)
1912	2,110
1913	3,256
1914	1,897
1915	1,073
1916	3,256
1917	3,002
1918	2,832
1919	2,090
1920	2,090
1921	2,832
1922	3,228
1923	2,733
1924	2,274
1925	3,002
1926	1,354
1927	3,313
1928	3,568
1929	1,906
1930	1,339
1931	1,339
1932	2,367
1933	3,398
1934	2,175
1935	2,016
1936	2,316
1937	1,416
1938	2,492
1939	1,926
1940	1,362
1941	912
1942	2,095
1943	2,619
1944	1,025
1945	2,121
1946	2,008
1947	2,945
1948	3,794
1949	2,721
1950	3,115
1951	2,721
1952	2,047
1953	2,653
1954	2,566
1955	2,118
1956	3,002
1957	2,461
1958	2,696
1959	2,628
1960	2,155
1961	2,650
1962	1,914
1963	1,657
1964	3,625
1965	2,577
1966	1,665
1967	2,704
1968	1,971
1969	1,943
1970	2,532
1971	2,537
1972	3,256
1973	895
1974	3,200
1975	3,030
1976	2,481
1977	597
1978	1,889
1979	2,070
1980	2,413
1981	2,687
1982	2,563
1983	1,974
1984	1,736
1985	1,574
1986	2,175
1987	1,014
1988	827
1989	1,665
1990	1,866
1991	2,098
1992	852
1993	1,430
1994	895
1995	2,087
1996	2,557
1997	3,115
1998	1,668
1999	1,784
2000	1,206
2001	830
2002	2,441
2003	1,880
2004	1,155
2005	1,977
2006	2,115
2007	1,419
2008	2,149
2009	1,645
2010	1,657
2011	2,945
2012	2,132
2013	1,804
2014	2,345
2015	1,036
2016	1,249
2017	2,325
2018	2,917
2019	1,928
2020	2,240
2021	1,662
2022	2,407
2023	1,583
2024	1,158
2025	1,017

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	1912–2025
Completeness	100.0% of the periods in that span are held.
Continuity	Continuous: every year from 1912 to 2025 is held.
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 Clark Fork near Plains MT, as a depth

The year's flow spread over the land draining to this gauge, in millimetres — the same unit rainfall is measured in. 1911–2025.

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	Clark Fork near Plains MT (mm)
1911	333
1912	330
1913	416
1914	310
1915	263
1916	485
1917	418
1918	411
1919	247
1920	323
1921	381
1922	333
1923	339
1924	276
1925	423
1926	240
1927	485
1928	467
1929	248
1930	248
1931	189
1932	338
1933	426
1934	399
1935	288
1936	277
1937	213
1938	298
1939	273
1940	196
1941	175
1942	289
1943	427
1944	179
1945	252
1946	340
1947	424
1948	430
1949	323
1950	448
1951	451
1952	322
1953	303
1954	396
1955	340
1956	454
1957	333
1958	303
1959	490
1960	348
1961	347
1962	350
1963	301
1964	402
1965	461
1966	318
1967	380
1968	336
1969	398
1970	342
1971	436
1972	465
1973	224
1974	483
1975	407
1976	425
1977	200
1978	364
1979	316
1980	322
1981	379
1982	385
1983	318
1984	307
1985	311
1986	328
1987	231
1988	222
1989	316
1990	369
1991	393
1992	224
1993	292
1994	222
1995	311
1996	485
1997	507
1998	295
1999	334
2000	270
2001	170
2002	337
2003	258
2004	258
2005	278
2006	336
2007	277
2008	345
2009	292
2010	276
2011	492
2012	399
2013	291
2014	393
2015	273
2016	285
2017	396
2018	429
2019	282
2020	344
2021	277
2022	345
2023	237
2024	227
2025	230

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	1911–2025
Completeness	100.0% of the periods in that span are held.
Continuity	Continuous: every year from 1911 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

1 automated snow station sits inside this drainage area, weighing the snowpack rather than measuring how deep it is.

2,301

Fullest snowpack recorded at Bear Mountain, in 1997 (mm of water)

614

Thinnest, in 2015 (mm of water)

April

Month the pack is usually at its fullest

July

Month the pack has gone by, in half of years

Peak snowpack at Bear Mountain

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	Bear Mountain (mm)
1984	1,043
1985	1,566
1986	933
1987	1,355
1988	1,290
1990	1,449
1991	1,848
1992	1,038
1993	1,158
1995	1,564
1996	1,317
1997	2,301
1998	1,211
1999	2,268
2000	1,599
2001	725
2002	1,998
2003	1,471
2004	1,322
2005	1,017
2006	1,729
2007	1,416
2008	1,653
2009	1,258
2010	1,083
2011	1,899
2012	1,895
2013	1,433
2014	1,475
2015	614
2016	1,159
2017	1,270
2018	1,615
2019	1,039
2020	1,620
2021	1,163
2022	1,287
2023	1,015
2024	1,119
2025	1,456
2026	874

Read against the river

Bear Mountain and CLARK FORK AT WHITEHORSE RAPIDS NR CABINET ID both sit in this drainage area, and their records overlap by 29 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 Lower Clark Fork and what each holds
Gauge	Measures	Values	Record
Clark Fork near Plains MT	burned area within 50 km, catchment area, annual maximum river flow, mean river flow, mean river flow, water year	381	1910–2026
CLARK FORK AT WHITEHORSE RAPIDS NR CABINET ID	burned area within 50 km, catchment area, annual maximum river flow, mean river flow, mean river flow, water year	263	1928–2026
Thompson River near Thompson Falls MT	burned area within 50 km, catchment area, annual maximum river flow, mean river flow, mean river flow, water year	246	1948–2026

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 — 17010213. 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
Clark Fork near Plains MT	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
CLARK FORK AT WHITEHORSE RAPIDS NR CABINET ID	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
Thompson River near Thompson Falls MT	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	117	yes, 20 or more
Values held	1,427	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-12389000.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 Clark Fork gauge records, accessed 2026-10-05, hydrionis.com/waters/united-states-lower-clark-fork/

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 Clark Fork 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 confidence2025-05-13

Source: USGS — National Water Information System, USGS site 12389000, 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.