The monitoring network within this area

Hydrionis holds 484 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.

Gauges

484

Values held

1890–2026

Record spans

Gauges within the American Falls 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 SNAKE RIVER NR SHELLEY ID

The highest instantaneous discharge the publisher recorded in each year — a flood peak as measured, not a daily average of one. 1890–2025.

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	SNAKE RIVER NR SHELLEY ID (m³/s)
1890	1,444
1892	1,538
1893	1,257
1894	2,124
1915	436
1917	1,042
1918	1,337
1919	388
1920	665
1921	861
1922	756
1924	311
1925	782
1926	405
1927	1,034
1928	1,036
1929	697
1930	348
1931	193
1934	185
1935	428
1937	399
1939	481
1940	268
1941	340
1942	462
1943	861
1944	620
1945	586
1946	705
1947	759
1948	782
1949	728
1950	793
1951	753
1952	838
1953	631
1954	784
1955	399
1956	852
1957	631
1958	467
1959	340
1960	263
1961	195
1962	470
1963	725
1964	688
1965	549
1966	498
1967	561
1968	609
1969	535
1970	680
1971	725
1972	617
1973	476
1974	733
1975	552
1976	1,906
1977	251
1978	507
1979	377
1980	620
1981	705
1982	663
1983	765
1984	850
1985	623
1987	394
1988	247
1990	323
1991	507
1992	314
1993	609
1994	351
1995	612
1996	708
1997	1,354
1998	600
1999	793
2000	360
2001	188
2002	221
2003	348
2004	416
2005	368
2006	614
2007	297
2008	538
2010	742
2011	915
2012	382
2013	445
2014	41.1
2015	473
2016	306
2017	787
2018	736
2019	629
2020	513
2021	354
2022	283
2023	436
2024	549
2025	360

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	1890–2025
Completeness	77.9% of the periods in that span are held. Gaps are drawn as breaks and never interpolated.
Known gaps	10 separate periods inside 1890–2025 hold no value. The longest runs from 1895 to 1914 — 20 years with no reading. They are drawn as breaks in the line and are never interpolated across.
Continuity	The record begins in 1890 and is not continuous from it: 136 years separate the first value from the last, and 78% of the years between them are held. The span is not the record.
Last read from the publisher	2026-08-31
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 SNAKE RIVER NR BLACKFOOT 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. 1911–2024.

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	SNAKE RIVER NR BLACKFOOT ID (mm)
1911	213
1912	260
1913	271
1914	229
1916	215
1917	256
1918	231
1919	98.0
1920	150
1921	193
1922	160
1923	154
1924	71.0
1925	198
1926	100
1927	211
1928	192
1929	114
1930	93.0
1931	36.0
1932	95.0
1933	84.0
1934	23.0
1935	69.0
1936	124
1937	72.0
1938	144
1939	86.0
1940	70.0
1941	69.0
1942	92.0
1943	205
1944	100
1945	131
1946	162
1947	136
1948	148
1949	135
1950	195
1951	207
1952	187
1953	120
1954	124
1955	96.0
1956	194
1957	138
1958	101
1959	88.0
1960	76.0
1961	63.0
1962	110
1963	109
1964	152
1965	220
1966	108
1967	128
1968	132
1969	152
1970	166
1971	311
1972	258
1973	128
1974	234
1975	210
1976	237
1977	67.0
1978	135
1979	119
1980	129
1981	101
1982	229
1983	273
1984	307
1985	170
1986	286
1987	89.0
1988	62.0
1989	81.0
1990	82.0
1991	78.0
1992	65.0
1993	106
1994	89.0
1995	134
1996	233
1997	363
1998	224
1999	226
2000	112
2001	59.0
2002	64.0
2003	71.0
2004	68.0
2005	69.0
2006	134
2007	80.0
2008	105
2009	155
2010	93.0
2011	267
2012	130
2013	81.0
2014	108
2015	94.0
2016	90.0
2017	236
2018	203
2019	136
2020	136
2021	90.0
2022	71.0
2023	95.0
2024	118

About this series

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	1911–2024
Completeness	99.1% of the periods in that span are held. Gaps are drawn as breaks and never interpolated.
Known gaps	One period inside 1911–2024 holds no value: 1915. It is drawn as a break in the line and is never interpolated across.
Continuity	The record begins in 1911 and is not continuous from it: 114 years separate the first value from the last, and 99% of the years between them are held. The span is not the record.
Last read from the publisher	2026-08-24
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

Every gauge Hydrionis holds within this area

Gauges within the American Falls and what each holds
Gauge	Measures	Values	Record
SNAKE RIVER NR BLACKFOOT ID	burned area within 50 km, catchment area, annual maximum river flow, mean river flow	252	1911–2026
SNAKE RIVER NR SHELLEY ID	burned area within 50 km, catchment area, annual maximum river flow, mean river flow	232	1890–2026

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 — 17040206. 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
SNAKE RIVER NR BLACKFOOT 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	2026-08-26
SNAKE RIVER NR SHELLEY 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	2026-08-26

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 3 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	137	yes, 20 or more
Values held	484	no
Distinct measurements	4	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-13069500.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), American Falls gauge records, accessed 2026-09-02, hydrionis.com/waters/united-states-american-falls/

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 American Falls 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 confidence2025-05-16

Source: USGS — National Water Information System, USGS site 13069500, 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 31 August 2026.