The monitoring network within this area

Hydrionis holds 315 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

315

Values held

1913–2026

Record spans

Gauges within the Ashtabula-Chagrin 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 Chagrin River at Willoughby OH

The highest instantaneous discharge the publisher recorded in each year — a flood peak as measured, not a daily average of one. 1913–2025.

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	Chagrin River at Willoughby OH (m³/s)
1913	694
1926	294
1927	252
1929	623
1930	303
1931	680
1932	166
1933	244
1934	124
1935	185
1940	194
1942	283
1943	231
1944	224
1945	247
1946	124
1947	408
1948	793
1949	143
1950	266
1952	294
1953	94.3
1954	320
1956	238
1957	419
1958	195
1959	623
1960	200
1961	271
1962	345
1963	226
1964	487
1965	198
1966	216
1968	176
1969	660
1970	131
1971	142
1972	275
1973	213
1974	161
1975	254
1976	323
1977	225
1979	230
1981	265
1982	159
1983	155
1984	216
1988	174
1989	677
1990	276
1992	155
1994	430
1996	269
1997	422
1998	197
1999	127
2002	140
2003	160
2004	228
2005	379
2006	541
2007	433
2008	493
2009	286
2010	182
2011	606
2012	230
2013	294
2015	309
2017	345
2018	328
2019	214
2020	345
2022	216
2024	199
2025	253

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	1913–2025
Completeness	69.0% of the periods in that span are held. Gaps are drawn as breaks and never interpolated.
Known gaps	18 separate periods inside 1913–2025 hold no value. The longest runs from 1914 to 1925 — 12 years with no reading. They are drawn as breaks in the line and are never interpolated across.
Continuity	The record begins in 1913 and is not continuous from it: 113 years separate the first value from the last, and 69% 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 Chagrin River at Willoughby OH, as a depth

The year's flow spread over the land draining to this gauge, in millimetres — the same unit rainfall is measured in. 1926–2024.

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	Chagrin River at Willoughby OH (mm)
1926	638
1927	538
1928	362
1929	524
1930	395
1931	308
1932	366
1933	288
1934	204
1940	496
1941	205
1942	534
1943	419
1944	308
1945	524
1946	312
1947	541
1948	454
1949	328
1950	712
1951	560
1952	484
1953	276
1954	595
1955	433
1956	576
1957	548
1958	408
1959	701
1960	410
1961	477
1962	358
1963	290
1964	369
1965	418
1966	386
1967	376
1968	456
1969	524
1970	448
1971	452
1972	615
1973	543
1974	615
1975	568
1976	529
1977	619
1978	449
1979	652
1980	450
1981	575
1982	643
1983	530
1989	518
1990	737
1991	377
1992	590
1993	567
1996	660
1997	502
1998	417
2002	373
2003	630
2004	686
2005	954
2006	814
2007	683
2008	773
2009	453
2010	454
2011	1,049
2012	564
2013	603
2014	644
2015	527
2016	447
2017	645
2018	784
2019	659
2020	724
2021	531
2022	591
2023	652
2024	494

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	1926–2024
Completeness	84.8% of the periods in that span are held. Gaps are drawn as breaks and never interpolated.
Known gaps	4 separate periods inside 1926–2024 hold no value. The longest runs from 1935 to 1939 — 5 years with no reading. They are drawn as breaks in the line and are never interpolated across.
Continuity	The record begins in 1926 and is not continuous from it: 99 years separate the first value from the last, and 85% 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

Every gauge Hydrionis holds within this area

Gauges within the Ashtabula-Chagrin and what each holds
Gauge	Measures	Values	Record
Chagrin River at Willoughby OH	catchment area, annual maximum river flow, mean river flow, mean river flow, water year	261	1913–2026
Ashtabula River near Ashtabula OH	catchment area, annual maximum river flow	54	1925–2026

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 — 04110003. 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
Chagrin River at Willoughby OH	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
Ashtabula River near Ashtabula OH	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 2 of them, which makes it a profile, not indexed.

Information-gain signals held for this water body
Signal	Held	Counts
Gauges holding a real record	2	no
Years spanned	114	yes, 20 or more
Values held	315	no
Distinct measurements	4	yes, 2 or more
Publishers measuring it	1	no
Official identifiers	1	recorded, not counted

Use this data

Machine-readable JSON /api/v1/observations/by-subject/gauge-usgs-04209000.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), Ashtabula-Chagrin gauge records, accessed 2026-10-05, hydrionis.com/waters/united-states-ashtabula-chagrin/

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 Ashtabula-Chagrin 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 confidence2025-06-14

Source: USGS — National Water Information System, USGS site 04209000, 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.