The monitoring network within this area

Hydrionis holds 531 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

531

Values held

1889–2026

Record spans

Gauges within the Middle Potomac-Catoctin 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 POTOMAC RIVER AT POINT OF ROCKS, 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	POTOMAC RIVER AT POINT OF ROCKS, MD (m³/s)
1889	13,026
1895	1,940
1896	1,586
1898	3,596
1899	3,625
1900	1,634
1901	4,559
1902	6,201
1903	3,115
1904	1,260
1905	2,022
1906	2,302
1907	3,370
1908	4,304
1909	2,350
1910	4,757
1911	3,002
1912	2,701
1913	3,936
1914	2,093
1915	3,936
1916	3,511
1917	3,483
1918	3,596
1919	2,280
1920	3,087
1921	2,515
1922	2,231
1923	1,152
1924	7,844
1925	2,520
1926	1,713
1928	4,106
1929	5,097
1931	1,042
1932	4,474
1933	3,483
1934	1,039
1936	13,592
1937	8,778
1939	3,511
1940	2,650
1941	1,954
1942	3,540
1944	1,991
1945	3,936
1946	1,504
1947	1,192
1948	2,464
1949	3,738
1950	1,832
1952	3,596
1954	3,087
1955	6,060
1956	1,722
1957	1,960
1958	2,039
1959	1,577
1960	3,511
1961	2,888
1962	3,285
1963	3,540
1964	2,464
1965	2,769
1966	2,019
1967	4,078
1968	2,175
1969	787
1970	2,608
1971	2,447
1972	9,826
1973	3,738
1975	5,125
1976	3,087
1978	3,936
1979	5,040
1981	1,186
1982	2,605
1983	3,256
1984	5,635
1985	2,398
1987	4,332
1988	2,721
1989	2,291
1990	1,127
1991	2,407
1992	2,549
1993	4,729
1995	2,469
1996	8,778
1998	3,483
1999	1,150
2000	1,744
2001	1,886
2002	1,481
2003	4,248
2005	3,285
2007	2,718
2008	2,718
2009	2,832
2010	4,870
2011	4,078
2012	3,002
2014	4,106
2015	1,481
2016	2,492
2017	2,019
2018	4,955
2020	2,217
2021	2,580
2022	3,030
2023	983
2024	2,379
2025	4,361

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	83.2% of the periods in that span are held. Gaps are drawn as breaks and never interpolated.
Known gaps	19 separate periods inside 1889–2025 hold no value. The longest runs from 1890 to 1894 — 5 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 83% 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 POTOMAC RIVER AT POINT OF ROCKS, 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. 1896–2025.

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	POTOMAC RIVER AT POINT OF ROCKS, MD (mm)
1896	260
1897	380
1898	423
1899	362
1900	238
1901	505
1902	493
1903	443
1904	217
1905	269
1906	385
1907	482
1908	437
1909	228
1910	271
1911	291
1912	355
1913	339
1914	307
1915	372
1916	341
1917	293
1918	363
1919	280
1920	387
1921	253
1922	253
1923	196
1924	508
1925	245
1926	353
1927	396
1928	360
1929	384
1930	134
1931	180
1932	317
1933	395
1934	219
1935	355
1936	489
1937	534
1938	210
1939	320
1940	365
1941	209
1942	405
1943	316
1944	275
1945	344
1946	266
1947	191
1948	380
1949	392
1950	383
1951	372
1952	437
1953	334
1954	238
1955	339
1956	289
1957	258
1958	337
1959	204
1960	331
1961	353
1962	321
1963	243
1964	291
1965	253
1966	212
1967	340
1968	273
1969	164
1970	380
1971	427
1972	664
1973	474
1974	312
1975	464
1976	343
1977	255
1978	420
1979	573
1980	328
1981	196
1982	325
1983	430
1984	490
1985	371
1986	253
1987	344
1988	255
1989	347
1990	290
1991	274
1992	294
1993	483
1994	488
1995	271
1996	775
1997	302
1998	519
1999	202
2000	246
2001	222
2002	221
2003	709
2004	465
2005	293
2006	287
2007	263
2008	330
2009	301
2010	341
2011	485
2012	270
2013	352
2014	351
2015	273
2016	298
2017	278
2018	756
2019	422
2020	325
2021	287
2022	281
2023	184
2024	332
2025	280

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	1896–2025
Completeness	100.0% of the periods in that span are held.
Continuity	Continuous: every year from 1896 to 2025 is held.
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 Middle Potomac-Catoctin and what each holds
Gauge	Measures	Values	Record
POTOMAC RIVER AT POINT OF ROCKS, MD	burned area within 50 km, catchment area, annual maximum river flow, mean river flow	299	1889–2026
GOOSE CREEK NEAR LEESBURG, VA	burned area within 50 km, catchment area, annual maximum river flow, mean river flow	232	1910–2026

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 — 02070008. 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
POTOMAC RIVER AT POINT OF ROCKS, 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	2026-08-26
GOOSE CREEK NEAR LEESBURG, VA	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	138	yes, 20 or more
Values held	531	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-01638500.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), Middle Potomac-Catoctin gauge records, accessed 2026-09-02, hydrionis.com/waters/united-states-middle-potomac-catoctin/

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 Middle Potomac-Catoctin 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 confidence2025-05-15

Source: USGS — National Water Information System, USGS site 01638500, 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.