The monitoring network within this area

Hydrionis holds 450 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

450

Values held

1902–2026

Record spans

Gauges within the Marias 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 Marias River near Shelby MT

The highest instantaneous discharge the publisher recorded in each year — a flood peak as measured, not a daily average of one. 1902–2025.

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	Marias River near Shelby MT (m³/s)
1902	782
1903	221
1904	242
1906	116
1907	835
1911	248
1912	227
1913	183
1914	136
1915	75.3
1916	688
1917	283
1918	142
1919	110
1920	215
1921	148
1922	133
1923	114
1924	177
1925	217
1926	63.4
1928	183
1929	126
1930	80.7
1931	64.8
1932	198
1933	156
1934	459
1935	132
1936	89.5
1937	258
1938	142
1939	96.6
1940	65.4
1941	69.4
1942	158
1943	487
1944	88.9
1945	174
1946	81.0
1948	1,133
1949	108
1950	303
1951	343
1952	180
1953	620
1954	272
1955	196
1956	245
1957	180
1958	140
1959	197
1960	136
1961	170
1962	95.7
1963	85.5
1964	6,824
1965	249
1966	124
1967	255
1968	107
1969	155
1970	300
1971	168
1972	292
1973	115
1974	159
1975	2,144
1976	174
1977	32.8
1978	183
1979	187
1980	311
1981	303
1982	164
1983	90.0
1984	79.0
1985	125
1986	762
1987	106
1988	71.6
1989	219
1991	357
1992	58.0
1993	101
1994	181
1995	521
1996	183
1997	278
1998	118
1999	103
2000	62.0
2001	79.3
2002	586
2003	118
2004	52.1
2005	146
2006	115
2008	419
2009	121
2010	158
2011	532
2012	134
2013	161
2014	379
2015	89.5
2016	63.1
2017	112
2018	309
2019	473
2020	170
2021	114
2022	207
2023	113
2024	67.7
2025	58.6

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	1902–2025
Completeness	93.5% of the periods in that span are held. Gaps are drawn as breaks and never interpolated.
Known gaps	6 separate periods inside 1902–2025 hold no value. The longest runs from 1908 to 1910 — 3 years with no reading. They are drawn as breaks in the line and are never interpolated across.
Continuity	The record begins in 1902 and is not continuous from it: 124 years separate the first value from the last, and 94% 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 Marias River near Shelby MT, as a depth

The year's flow spread over the land draining to this gauge, in millimetres — the same unit rainfall is measured in. 1903–2024.

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	Marias River near Shelby MT (mm)
1903	169
1904	120
1906	100
1912	117
1913	135
1914	101
1915	82.0
1916	199
1917	185
1918	120
1919	70.0
1920	150
1921	108
1922	96.0
1923	116
1924	109
1925	163
1926	67.0
1927	244
1928	165
1929	83.0
1930	85.0
1931	48.0
1932	98.0
1933	130
1934	164
1935	101
1936	58.0
1937	75.0
1938	93.0
1939	68.0
1940	47.0
1941	52.0
1942	91.0
1943	179
1944	50.0
1945	94.0
1946	79.0
1947	147
1948	213
1949	87.0
1950	195
1951	227
1952	110
1953	182
1954	167
1955	126
1956	142
1957	112
1958	106
1959	170
1960	99.0
1961	86.0
1962	94.0
1963	71.0
1964	175
1965	160
1966	101
1967	161
1968	96.0
1969	113
1970	132
1971	133
1972	162
1973	63.0
1974	114
1975	231
1976	126
1977	36.0
1978	125
1979	110
1980	106
1981	98.0
1982	110
1983	57.0
1984	52.0
1985	100
1986	98.0
1987	87.0
1988	51.0
1989	129
1990	117
1991	150
1992	58.0
1993	92.0
1994	89.0
1995	150
1996	134
1997	138
1998	79.0
1999	90.0
2000	58.0
2001	45.0
2002	142
2003	71.0
2004	58.0
2005	64.0
2006	83.0
2007	57.0
2008	111
2009	80.0
2010	73.0
2011	175
2012	89.0
2013	80.0
2014	124
2015	74.0
2016	69.0
2017	102
2018	128
2019	118
2020	117
2021	76.0
2022	86.0
2023	65.0
2024	49.0

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	1903–2024
Completeness	95.1% of the periods in that span are held. Gaps are drawn as breaks and never interpolated.
Known gaps	2 separate periods inside 1903–2024 hold no value. The longest runs from 1907 to 1911 — 5 years with no reading. They are drawn as breaks in the line and are never interpolated across.
Continuity	The record begins in 1903 and is not continuous from it: 122 years separate the first value from the last, and 95% 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 Marias and what each holds
Gauge	Measures	Values	Record
Marias River near Shelby MT	burned area within 50 km, catchment area, annual maximum river flow, mean river flow	271	1902–2026
Marias River near Chester MT	burned area within 50 km, catchment area, annual maximum river flow, mean river flow	179	1921–2026

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 — 10030203. 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
Marias River near Shelby MT	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
Marias River near Chester MT	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	125	yes, 20 or more
Values held	450	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-06099500.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), Marias gauge records, accessed 2026-09-02, hydrionis.com/waters/united-states-marias/

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 Marias 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 confidence2025-05-12

Source: USGS — National Water Information System, USGS site 06099500, 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.