The monitoring network within this area

Hydrionis holds 839 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.

2

Gauges

839

Values held

1929–2026

Record spans

Gauges within the Redwater 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 SPEARFISH CREEK AT SPEARFISH, SD

The highest instantaneous discharge the publisher recorded in each year — a flood peak as measured, not a daily average of one. 1947–2024.

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	SPEARFISH CREEK AT SPEARFISH, SD (m³/s)
1947	25.2
1948	11.8
1949	4.98
1950	3.28
1951	6.09
1952	26.8
1953	8.52
1954	4.16
1955	5.13
1956	8.50
1957	4.47
1958	16.2
1959	2.35
1960	2.44
1962	23.5
1963	18.7
1964	86.1
1965	120
1966	3.17
1967	6.51
1968	3.00
1969	13.2
1970	25.0
1971	6.63
1972	4.62
1973	8.13
1974	4.96
1976	110
1977	4.73
1978	6.51
1979	5.15
1980	2.41
1981	2.89
1982	59.7
1983	14.2
1984	8.07
1985	2.52
1986	2.94
1987	2.44
1988	3.34
1989	3.00
1990	2.32
1991	3.00
1992	1.98
1993	2.83
1994	4.96
1995	53.8
1996	5.78
1997	9.12
1998	25.5
1999	5.30
2000	4.30
2001	3.31
2002	4.84
2003	5.92
2004	2.12
2005	3.23
2006	5.27
2007	24.2
2008	27.6
2009	7.48
2010	7.28
2011	17.8
2012	2.92
2013	51.8
2014	15.7
2015	6.97
2016	3.51
2017	3.40
2018	4.90
2019	10.8
2020	9.09
2021	2.97
2022	8.33
2023	61.7
2024	5.86

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	1947–2024
Completeness	97.4% of the periods in that span are held. Gaps are drawn as breaks and never interpolated.
Known gaps	2 separate periods inside 1947–2024 hold no value. They are drawn as breaks in the line and are never interpolated across.
Continuity	The record begins in 1947 and is not continuous from it: 78 years separate the first value from the last, and 97% 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 SPEARFISH CREEK AT SPEARFISH, SD, as a depth

The year's flow spread over the land draining to this gauge, in millimetres — the same unit rainfall is measured in. 1947–2024.

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	SPEARFISH CREEK AT SPEARFISH, SD (mm)
1947	122
1948	102
1949	97.0
1950	88.0
1951	78.0
1952	99.0
1953	99.0
1954	81.0
1955	96.0
1956	79.0
1957	87.0
1958	80.0
1959	71.0
1960	64.0
1961	55.0
1962	84.0
1963	116
1964	133
1965	173
1966	113
1967	117
1968	103
1969	110
1970	148
1971	140
1972	149
1973	157
1974	118
1975	112
1976	132
1977	123
1978	136
1979	114
1980	95.0
1981	82.0
1982	185
1983	139
1984	141
1985	94.0
1986	99.0
1987	81.0
1988	86.0
1989	86.0
1990	86.0
1991	88.0
1992	78.0
1993	98.0
1994	124
1995	177
1996	171
1997	207
1998	194
1999	214
2000	177
2001	141
2002	114
2003	120
2004	95.0
2005	95.0
2006	115
2007	125
2008	172
2009	181
2010	189
2011	215
2012	160
2013	187
2014	238
2015	220
2016	170
2017	112
2018	132
2019	167
2020	175
2021	132
2022	127
2023	135
2024	118

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	Derived Computed by Hydrionis
Period held	1947–2024
Completeness	100.0% of the periods in that span are held.
Continuity	Continuous: every year from 1947 to 2024 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

The snow standing above this water

1 automated snow station sits inside this drainage area, weighing the snowpack rather than measuring how deep it is.

219

Fullest snowpack recorded at Cole Canyon, in 2020 (mm of water)

48

Thinnest, in 2026 (mm of water)

March

Month the pack is usually at its fullest

May

Month the pack has gone by, in half of years

Peak snowpack at Cole Canyon

Water years 2001–2026. Each point is the fullest month of that snow season.

A water year runs October to September and is named for the year it ends, so the snow of one winter stays in one point. The value is the fullest month, not the fullest day: a pack that peaked sharply mid-month reads lower here than a single measurement taken at the right moment would.

View the data behind this chart

Underlying data
Period	Cole Canyon (mm)
2001	126
2002	116
2003	126
2004	104
2005	68.0
2006	121
2007	114
2008	163
2009	168
2010	122
2011	203
2012	122
2013	111
2014	171
2015	76.0
2016	96.0
2017	82.0
2018	171
2019	161
2020	219
2021	100
2022	88.0
2023	203
2024	57.0
2025	142
2026	48.0

Read against the river

Cole Canyon and REDWATER CREEK AT WY-SD STATE LINE both sit in this drainage area, and their records overlap by 24 years. That is the span the two have in common, not a count of years both actually hold — either record may have gaps inside it. The two are shown separately rather than on one axis: millimetres of stored water and cubic metres per second are not commensurable, and a difference between them would mean nothing.

Being in the same drainage area does not put the snowpack upstream of the gauge. A subbasin is an area, and snow on one tributary can join the river below a gauge on another — so a weak relationship here may say more about which tributary was measured than about the snow.

Every gauge Hydrionis holds within this area

Gauges within the Redwater and what each holds
Gauge	Measures	Values	Record
SPEARFISH CREEK AT SPEARFISH, SD	burned area within 50 km, catchment area, annual maximum river flow, mean river flow, mean river flow, water year	271	1946–2026
REDWATER CREEK AT WY-SD STATE LINE	burned area within 50 km, catchment area, annual maximum river flow, mean river flow, mean river flow, water year	253	1929–2026

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 — 10120203. 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
SPEARFISH CREEK AT SPEARFISH, SD	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
REDWATER CREEK AT WY-SD STATE LINE	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 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	98	yes, 20 or more
Values held	839	no
Distinct measurements	6	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-06431500.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), Redwater gauge records, accessed 2026-10-05, hydrionis.com/waters/united-states-redwater/

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 Redwater 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 confidence2024-08-19

Source: USGS — National Water Information System, USGS site 06431500, 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.