The monitoring network within this area

Hydrionis holds 1,841 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

1,841

Values held

1909–2026

Record spans

Gauges within the Lower Henrys 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 FALL RIVER NR CHESTER ID

The highest instantaneous discharge the publisher recorded in each year — a flood peak as measured, not a daily average of one. 1920–2025.

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	FALL RIVER NR CHESTER ID (m³/s)
1920	92.3
1921	105
1922	92.6
1923	75.3
1924	43.9
1925	121
1926	66.0
1927	181
1928	128
1929	106
1930	99.1
1931	86.1
1932	161
1933	119
1934	37.1
1935	74.5
1936	106
1937	74.2
1940	96.8
1941	72.2
1942	79.9
1943	87.2
1944	73.9
1945	87.8
1946	71.6
1947	98.0
1948	117
1949	114
1950	95.1
1951	85.8
1952	108
1953	88.3
1954	97.4
1955	69.7
1956	98.8
1957	111
1958	95.1
1959	92.0
1960	125
1961	66.3
1962	88.3
1963	87.2
1964	123
1965	96.3
1966	77.3
1967	123
1968	130
1969	78.7
1970	162
1971	121
1972	106
1973	120
1974	179
1975	163
1976	149
1977	66.0
1978	139
1979	102
1980	87.5
1981	219
1982	113
1983	140
1984	149
1985	107
1986	108
1988	62.3
1989	122
1990	69.4
1991	118
1992	71.6
1993	137
1994	106
1995	104
1996	163
1997	153
1998	109
1999	135
2000	97.1
2002	106
2003	96.8
2004	71.1
2005	84.7
2006	117
2007	74.8
2008	147
2009	98.8
2010	218
2011	264
2012	106
2013	75.6
2014	104
2015	60.6
2016	68.5
2017	110
2018	108
2019	111
2020	98.8
2021	84.4
2022	131
2023	115
2024	73.9
2025	72.2

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	1920–2025
Completeness	96.2% of the periods in that span are held. Gaps are drawn as breaks and never interpolated.
Known gaps	3 separate periods inside 1920–2025 hold no value. The longest runs from 1938 to 1939 — 2 years with no reading. They are drawn as breaks in the line and are never interpolated across.
Continuity	The record begins in 1920 and is not continuous from it: 106 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 HENRYS FORK NR REXBURG 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. 1910–2024.

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	HENRYS FORK NR REXBURG ID (mm)
1910	257
1911	284
1912	322
1913	333
1914	300
1915	207
1916	272
1917	322
1918	265
1919	194
1920	204
1921	266
1922	227
1923	204
1924	120
1925	305
1926	176
1927	311
1928	264
1929	213
1930	151
1931	101
1932	200
1933	176
1934	82.0
1935	138
1936	186
1937	152
1938	231
1939	181
1940	187
1941	163
1942	181
1943	284
1944	212
1945	256
1946	242
1947	218
1948	248
1949	246
1950	263
1951	270
1952	294
1953	219
1954	206
1955	204
1956	256
1957	275
1958	207
1959	188
1960	168
1961	156
1962	235
1963	207
1964	254
1965	293
1966	176
1967	242
1968	258
1969	279
1970	308
1971	391
1972	366
1973	275
1974	356
1975	353
1976	376
1977	152
1978	256
1979	232
1980	247
1981	228
1982	356
1983	412
1984	479
1985	306
1986	390
1987	186
1988	178
1989	244
1990	184
1991	211
1992	161
1993	289
1994	182
1995	348
1996	338
1997	492
1998	374
1999	377
2000	235
2001	169
2002	194
2003	175
2004	200
2005	211
2006	296
2007	206
2008	268
2009	259
2010	209
2011	386
2012	252
2013	197
2014	230
2015	178
2016	176
2017	305
2018	281
2019	271
2020	231
2021	171
2022	169
2023	246
2024	212

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	1910–2024
Completeness	100.0% of the periods in that span are held.
Continuity	Continuous: every year from 1910 to 2024 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.

1,439

Fullest snowpack recorded at Grassy Lake, in 1982 (mm of water)

424

Thinnest, in 2026 (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 Grassy Lake

Water years 1981–2026. 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	Grassy Lake (mm)
1981	575
1982	1,439
1983	1,026
1984	857
1985	755
1986	1,022
1987	444
1988	678
1989	988
1990	683
1991	779
1992	560
1993	899
1994	614
1995	979
1996	967
1997	1,211
1998	807
1999	1,097
2000	761
2001	556
2002	695
2003	792
2004	879
2005	603
2006	999
2007	649
2008	990
2009	837
2010	547
2011	1,156
2012	790
2013	702
2014	1,043
2015	626
2016	691
2017	953
2018	828
2019	857
2020	850
2021	684
2022	581
2023	930
2024	680
2025	741
2026	424

Read against the river

Grassy Lake and HENRYS FORK NR ASHTON ID both sit in this drainage area, and their records overlap by 44 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 Henrys and what each holds
Gauge	Measures	Values	Record
HENRYS FORK NR REXBURG ID	burned area within 50 km, catchment area, annual maximum river flow, mean river flow, mean river flow, water year	367	1909–2026
HENRYS FORK NR ASHTON ID	burned area within 50 km, catchment area, annual maximum river flow, mean river flow, mean river flow, water year	326	1921–2026
FALL RIVER NR CHESTER ID	burned area within 50 km, catchment area, annual maximum river flow, mean river flow, mean river flow, water year	264	1920–2026
HENRYS FORK AT ST ANTHONY ID	burned area within 50 km, catchment area, annual maximum river flow, mean river flow, mean river flow, water year	261	1923–2026
FALL RIVER NR SQUIRREL ID	catchment area, annual maximum river flow	73	1949–2026

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 — 17040203. 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 REXBURG 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
HENRYS FORK NR ASHTON 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
FALL RIVER NR CHESTER 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
HENRYS FORK AT ST ANTHONY 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
FALL RIVER NR SQUIRREL 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 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	5	yes, 3 or more
Years spanned	118	yes, 20 or more
Values held	1,841	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-13056500.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 Henrys gauge records, accessed 2026-10-05, hydrionis.com/waters/united-states-lower-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 Lower 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 confidence2025-05-14

Source: USGS — National Water Information System, USGS site 13056500, 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.