The monitoring network within this area

Hydrionis holds 1,390 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

1,390

Values held

1923–2026

Record spans

Gauges within the Upper Henrys 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 HENRYS FORK NR LAKE ID

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	HENRYS FORK NR LAKE ID (m³/s)
1923	9.83
1924	21.0
1925	2.63
1926	25.7
1927	4.11
1928	10.9
1929	22.4
1930	10.6
1931	10.1
1934	8.72
1936	10.3
1942	9.03
1943	8.92
1944	13.0
1945	10.4
1946	7.62
1947	11.0
1948	10.3
1949	7.14
1950	10.6
1951	5.27
1952	10.0
1953	6.77
1954	4.76
1955	13.1
1956	8.33
1957	8.13
1958	14.1
1959	12.6
1960	8.47
1961	7.82
1962	3.74
1963	8.13
1964	8.89
1965	8.47
1966	8.41
1967	10.6
1968	8.47
1969	9.09
1970	9.71
1971	9.29
1972	7.42
1973	6.03
1974	9.29
1975	6.26
1976	4.56
1977	8.86
1978	3.60
1979	3.14
1980	6.46
1981	6.03
1982	9.43
1983	10.7
1985	8.47
1986	8.86
1988	6.09
1990	6.09
1991	6.40
1995	8.50
1997	7.31
1998	8.50
2000	3.51
2006	7.42
2007	5.21
2008	7.19
2009	6.00
2010	7.31
2011	10.4
2012	4.56
2013	4.56
2014	9.77
2015	2.41
2016	2.49
2017	5.18
2018	5.66
2019	5.21
2020	3.51
2021	2.17
2022	5.64
2023	4.87
2024	2.57
2025	2.15

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	79.6% of the periods in that span are held. Gaps are drawn as breaks and never interpolated.
Known gaps	10 separate periods inside 1923–2025 hold no value. The longest runs from 1937 to 1941 — 5 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 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 HENRYS FORK NR LAKE ID, as a depth

The year's flow spread over the land draining to this gauge, in millimetres — the same unit rainfall is measured in. 1930–2025.

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	HENRYS FORK NR LAKE ID (mm)
1930	209
1931	102
1932	155
1933	178
1934	108
1935	112
1936	110
1937	151
1938	121
1939	44.0
1940	172
1941	107
1942	152
1943	102
1944	260
1945	152
1946	184
1947	267
1948	242
1949	202
1950	132
1951	227
1952	295
1953	173
1954	139
1955	234
1956	106
1957	224
1958	280
1959	132
1960	265
1961	152
1962	82.0
1963	204
1964	249
1965	257
1966	193
1967	216
1968	242
1969	332
1970	276
1971	337
1972	290
1973	214
1974	228
1975	284
1976	225
1977	196
1978	121
1979	128
1980	198
1981	195
1982	229
1983	367
1984	381
1985	204
1986	301
1987	113
1988	117
1989	16.0
1990	130
1991	138
1992	245
1993	126
1994	167
1995	269
1996	264
1997	301
1998	293
1999	293
2000	152
2001	225
2002	19.0
2003	85.0
2004	140
2005	66.0
2006	244
2007	124
2008	114
2009	161
2010	146
2011	297
2012	197
2013	200
2014	88.0
2015	159
2016	117
2017	201
2018	222
2019	200
2020	181
2021	95.0
2022	148
2023	199
2024	130
2025	79.0

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	1930–2025
Completeness	100.0% of the periods in that span are held.
Continuity	Continuous: every year from 1930 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

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

615

Fullest snowpack recorded at Island Park, in 1997 (mm of water)

174

Thinnest, in 2026 (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 Island Park

Water years 1982–2026. 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	Island Park (mm)
1982	561
1983	512
1984	379
1985	394
1986	430
1987	235
1988	285
1989	443
1990	307
1991	295
1992	263
1993	392
1994	279
1995	506
1996	327
1997	615
1998	311
1999	464
2000	365
2001	203
2002	374
2003	276
2004	435
2005	311
2006	456
2007	284
2008	442
2009	360
2010	238
2011	474
2012	317
2013	284
2014	364
2015	250
2016	324
2017	327
2018	363
2019	478
2020	354
2021	330
2022	245
2023	503
2024	341
2025	320
2026	174

Read against the river

Island Park and HENRYS FORK NR LAKE ID both sit in this drainage area, and their records overlap by 43 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 Upper Henrys and what each holds
Gauge	Measures	Values	Record
HENRYS FORK NR LAKE ID	burned area within 50 km, catchment area, annual maximum river flow, mean river flow, mean river flow, water year	311	1923–2026
Big Springs At Big Springs ID	annual maximum river flow	4	1998–2022

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 — 17040202. 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
HENRYS FORK NR LAKE 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
Big Springs At Big Springs 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

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	1	no
Years spanned	104	yes, 20 or more
Values held	1,390	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-13039500.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), Upper Henrys gauge records, accessed 2026-10-05, hydrionis.com/waters/united-states-upper-henrys/

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 Upper Henrys 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 confidence2025-09-22

Source: USGS — National Water Information System, USGS site 13039500, 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.