The monitoring network within this area

Hydrionis holds 1,149 values from 4 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

1,149

Values held

1889–2026

Record spans

Gauges within the Conococheague-Opequon huc8 subbasin

4 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 CONOCOCHEAGUE CREEK AT FAIRVIEW, MD

The highest instantaneous discharge the publisher recorded in each year — a flood peak as measured, not a daily average of one. 1889–2025.

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	CONOCOCHEAGUE CREEK AT FAIRVIEW, MD (m³/s)
1889	623
1924	368
1929	220
1931	127
1932	133
1933	255
1934	303
1936	388
1937	402
1939	185
1940	193
1941	118
1942	182
1944	160
1945	225
1946	178
1947	133
1948	124
1949	189
1950	150
1952	439
1954	130
1955	221
1956	123
1958	213
1959	146
1960	183
1961	273
1962	146
1963	252
1964	177
1965	314
1966	340
1967	237
1968	117
1969	133
1970	306
1971	212
1972	917
1973	165
1975	447
1976	510
1978	208
1979	354
1981	184
1982	129
1983	166
1984	609
1985	166
1986	277
1987	220
1988	236
1989	219
1990	143
1992	121
1993	311
1995	131
1996	473
1997	385
1999	177
2000	155
2001	114
2002	58.6
2003	411
2004	394
2005	276
2006	210
2007	199
2008	276
2009	145
2010	408
2011	382
2012	274
2014	442
2015	135
2016	174
2017	151
2018	286
2019	177
2020	144
2022	204
2024	247
2025	276

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	1889–2025
Completeness	60.6% of the periods in that span are held. Gaps are drawn as breaks and never interpolated.
Known gaps	18 separate periods inside 1889–2025 hold no value. The longest runs from 1890 to 1923 — 34 years with no reading. They are drawn as breaks in the line and are never interpolated across.
Continuity	The record begins in 1889 and is not continuous from it: 137 years separate the first value from the last, and 61% 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 CONOCOCHEAGUE CREEK AT FAIRVIEW, MD, as a depth

The year's flow spread over the land draining to this gauge, in millimetres — the same unit rainfall is measured in. 1929–2025.

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	CONOCOCHEAGUE CREEK AT FAIRVIEW, MD (mm)
1929	479
1930	186
1931	229
1932	364
1933	484
1934	400
1935	327
1936	518
1937	609
1938	221
1939	351
1940	440
1941	268
1942	597
1943	403
1944	343
1945	434
1946	385
1947	331
1948	379
1949	365
1950	552
1951	492
1952	665
1953	468
1954	270
1955	369
1956	416
1957	307
1958	445
1959	240
1960	372
1961	412
1962	317
1963	266
1964	321
1965	270
1966	232
1967	415
1968	331
1969	204
1970	620
1971	496
1972	801
1973	717
1974	439
1975	705
1976	472
1977	357
1978	492
1979	692
1980	345
1981	291
1982	352
1983	488
1984	597
1985	335
1986	339
1987	298
1988	297
1989	424
1990	358
1991	299
1992	358
1993	666
1994	621
1995	328
1996	971
1997	384
1998	635
1999	316
2000	324
2001	239
2002	235
2003	819
2004	632
2005	407
2006	366
2007	302
2008	477
2009	375
2010	450
2011	716
2012	436
2013	349
2014	454
2015	268
2016	296
2017	381
2018	902
2019	567
2020	330
2021	353
2022	334
2023	231
2024	453
2025	323

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	1929–2025
Completeness	100.0% of the periods in that span are held.
Continuity	Continuous: every year from 1929 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

Every gauge Hydrionis holds within this area

Gauges within the Conococheague-Opequon and what each holds
Gauge	Measures	Values	Record
CONOCOCHEAGUE CREEK AT FAIRVIEW, MD	burned area within 50 km, catchment area, annual maximum river flow, mean river flow, mean river flow, water year	330	1889–2026
ANTIETAM CREEK NEAR SHARPSBURG, MD	burned area within 50 km, catchment area, annual maximum river flow, mean river flow, mean river flow, water year	325	1928–2026
POTOMAC RIVER AT SHEPHERDSTOWN, WV	burned area within 50 km, catchment area, annual maximum river flow, mean river flow, mean river flow, water year	271	1889–2026
BACK CREEK NEAR JONES SPRINGS, WV	burned area within 50 km, catchment area, annual maximum river flow, mean river flow, mean river flow, water year	223	1928–2026

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 — 02070004. 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
CONOCOCHEAGUE CREEK AT FAIRVIEW, MD	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
ANTIETAM CREEK NEAR SHARPSBURG, MD	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
POTOMAC RIVER AT SHEPHERDSTOWN, WV	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
BACK CREEK NEAR JONES SPRINGS, WV	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	4	yes, 3 or more
Years spanned	138	yes, 20 or more
Values held	1,149	yes, 1000 or more
Distinct measurements	5	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-01614500.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), Conococheague-Opequon gauge records, accessed 2026-10-05, hydrionis.com/waters/united-states-conococheague-opequon/

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 Conococheague-Opequon 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 01614500, 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.