The monitoring network within this area

Hydrionis holds 3,445 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

3,445

Values held

1923–2026

Record spans

Gauges within the Yellowstone Headwaters 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 Yellowstone River at Yellowstone Lk Outlet YNP

The highest instantaneous discharge the publisher recorded in each year — a flood peak as measured, not a daily average of one. 1923–2025.

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	Yellowstone River at Yellowstone Lk Outlet YNP (m³/s)
1923	130
1924	78.2
1925	204
1926	90.9
1927	210
1928	161
1929	105
1930	110
1931	70.2
1932	158
1933	133
1934	51.0
1935	128
1936	133
1937	102
1938	168
1939	91.5
1940	102
1941	77.9
1942	112
1943	196
1944	98.8
1945	113
1946	105
1947	128
1948	159
1949	150
1950	174
1951	145
1952	152
1953	120
1954	159
1955	117
1956	215
1957	151
1958	99.7
1959	159
1960	91.2
1961	107
1962	165
1963	151
1964	184
1965	194
1966	104
1967	187
1968	133
1969	129
1970	185
1971	234
1972	196
1973	99.1
1974	260
1975	182
1976	155
1977	62.9
1978	155
1979	105
1980	108
1981	121
1982	218
1984	147
1985	99.4
1986	209
1989	127
1990	122
1991	169
1992	79.6
1993	135
1995	165
1996	248
1997	282
1998	136
1999	192
2000	122
2001	73.9
2002	125
2003	140
2004	75.6
2005	102
2006	150
2007	77.9
2008	202
2009	199
2010	154
2011	271
2012	121
2013	108
2014	177
2015	104
2016	100
2017	210
2018	200
2019	135
2020	161
2021	91.7
2022	150
2023	136
2024	129
2025	104

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	1923–2025
Completeness	96.1% of the periods in that span are held. Gaps are drawn as breaks and never interpolated.
Known gaps	3 separate periods inside 1923–2025 hold no value. The longest runs from 1987 to 1988 — 2 years with no reading. They are drawn as breaks in the line and are never interpolated across.
Continuity	The record begins in 1923 and is not continuous from it: 103 years separate the first value from the last, and 96% 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 Yellowstone River at Yellowstone Lk Outlet YNP, as a depth

The year's flow spread over the land draining to this gauge, in millimetres — the same unit rainfall is measured in. 1927–2024.

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	Yellowstone River at Yellowstone Lk Outlet YNP (mm)
1927	595
1928	611
1929	380
1930	432
1931	259
1932	423
1933	362
1934	228
1935	382
1936	406
1937	328
1938	500
1939	383
1940	328
1941	356
1942	398
1943	616
1944	357
1945	418
1946	430
1947	511
1948	489
1949	494
1950	550
1951	595
1952	508
1953	378
1954	504
1955	391
1956	622
1957	493
1958	346
1959	423
1960	325
1961	348
1962	560
1963	484
1964	537
1965	633
1966	382
1967	555
1968	480
1969	490
1970	521
1971	677
1972	628
1973	380
1974	644
1975	513
1976	567
1977	248
1978	499
1979	378
1980	408
1981	395
1984	503
1985	396
1989	428
1990	412
1991	477
1992	334
1993	460
1994	302
1995	519
1996	682
1997	795
1998	512
1999	588
2000	399
2001	281
2002	392
2003	413
2004	351
2005	378
2006	448
2007	311
2008	551
2009	594
2010	450
2011	721
2012	427
2013	351
2014	608
2015	361
2016	336
2017	681
2018	618
2019	467
2020	508
2021	316
2022	448
2023	479
2024	413

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	1927–2024
Completeness	94.9% of the periods in that span are held. Gaps are drawn as breaks and never interpolated.
Known gaps	2 separate periods inside 1927–2024 hold no value. The longest runs from 1986 to 1988 — 3 years with no reading. 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: 98 years separate the first value from the last, and 95% 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

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

420

Fullest snowpack recorded at Northeast Entrance, in 1978 (mm of water)

119

Thinnest, in 2001 (mm of water)

March

Month the pack is usually at its fullest

May

Month the pack has gone by, in half of years

Peak snowpack at Northeast Entrance

Water years 1967–2026. 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	Northeast Entrance (mm)
1967	402
1968	293
1969	301
1970	415
1971	399
1972	361
1973	234
1974	343
1975	362
1976	419
1977	155
1978	420
1979	355
1980	255
1981	170
1982	376
1983	268
1984	223
1985	229
1986	297
1987	172
1988	200
1989	274
1990	253
1991	238
1992	249
1993	201
1994	216
1995	255
1996	374
1997	385
1998	202
1999	303
2000	260
2001	119
2002	172
2003	261
2004	152
2005	132
2006	244
2007	166
2008	270
2009	259
2010	126
2011	413
2012	240
2013	167
2014	355
2015	233
2016	183
2017	270
2018	351
2019	249
2020	249
2021	214
2022	133
2023	235
2024	132
2025	241
2026	164

Read against the river

Northeast Entrance and Yellowstone River at Yellowstone Lk Outlet YNP both sit in this drainage area, and their records overlap by 58 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 Yellowstone Headwaters and what each holds
Gauge	Measures	Values	Record
Yellowstone River at Yellowstone Lk Outlet YNP	burned area within 50 km, catchment area, annual maximum river flow, mean river flow, mean river flow, water year	325	1923–2026
Lamar River nr Tower Ranger Station YNP	burned area within 50 km, catchment area, annual maximum river flow, mean river flow, mean river flow, water year	287	1923–2026

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 — 10070001. 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
Yellowstone River at Yellowstone Lk Outlet YNP	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
Lamar River nr Tower Ranger Station YNP	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	104	yes, 20 or more
Values held	3,445	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-06186500.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), Yellowstone Headwaters gauge records, accessed 2026-10-05, hydrionis.com/waters/united-states-yellowstone-headwaters/

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 Yellowstone Headwaters 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 confidence2025-06-20

Source: USGS — National Water Information System, USGS site 06186500, 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.