The monitoring network within this area

Hydrionis holds 1,053 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

1,053

Values held

1905–2026

Record spans

Gauges within the Middle San Juan 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 LA PLATA RIVER AT HESPERUS, CO

The highest instantaneous discharge the publisher recorded in each year — a flood peak as measured, not a daily average of one. 1905–2018.

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	LA PLATA RIVER AT HESPERUS, CO (m³/s)
1905	26.9
1906	28.3
1917	28.3
1918	6.80
1919	19.3
1920	21.0
1921	18.4
1922	14.7
1923	32.6
1924	19.8
1925	12.7
1926	13.0
1927	39.6
1928	11.5
1929	11.1
1930	6.54
1931	4.36
1932	18.4
1933	11.9
1934	3.37
1935	15.5
1936	11.4
1937	16.8
1938	18.6
1939	5.83
1940	7.08
1941	53.2
1943	16.5
1944	25.2
1945	12.8
1946	5.01
1947	12.5
1948	15.7
1949	24.1
1950	7.25
1951	14.7
1952	26.9
1953	8.10
1954	8.01
1955	5.86
1956	5.86
1957	32.3
1958	18.5
1959	4.30
1960	12.1
1961	9.83
1962	9.29
1963	5.80
1964	12.7
1965	15.1
1966	9.74
1967	6.65
1968	15.6
1969	9.74
1970	34.8
1971	4.39
1972	2.32
1974	5.27
1975	17.9
1976	6.06
1977	1.25
1978	10.3
1979	29.4
1980	26.6
1981	6.68
1982	11.6
1983	15.4
1984	16.5
1985	15.7
1986	16.7
1987	14.3
1988	8.21
1989	4.05
1990	5.61
1991	7.79
1992	11.3
1993	18.7
1994	8.47
1995	17.2
1996	4.76
1997	17.2
1998	6.60
1999	7.25
2000	6.34
2001	11.0
2002	2.78
2003	6.57
2004	8.69
2006	3.88
2008	11.0
2009	10.8
2010	8.35
2012	4.76
2013	4.93
2014	4.30
2015	7.79
2016	8.01
2017	7.90
2018	1.83

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	1905–2018
Completeness	86.8% of the periods in that span are held. Gaps are drawn as breaks and never interpolated.
Known gaps	6 separate periods inside 1905–2018 hold no value. The longest runs from 1907 to 1916 — 10 years with no reading. They are drawn as breaks in the line and are never interpolated across.
Continuity	The record begins in 1905 and is not continuous from it: 114 years separate the first value from the last, and 87% 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 LA PLATA RIVER AT HESPERUS, CO, as a depth

The year's flow spread over the land draining to this gauge, in millimetres — the same unit rainfall is measured in. 1918–2017.

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	LA PLATA RIVER AT HESPERUS, CO (mm)
1918	277
1919	550
1920	769
1921	613
1922	503
1923	703
1924	585
1925	398
1926	555
1927	731
1928	361
1929	533
1930	332
1931	228
1932	570
1933	308
1934	175
1935	552
1936	457
1937	505
1938	562
1939	229
1940	302
1941	1,053
1942	469
1943	454
1944	573
1945	393
1946	225
1947	391
1948	479
1949	660
1950	272
1951	248
1952	743
1953	312
1954	267
1955	262
1956	274
1957	771
1958	599
1959	191
1960	482
1961	391
1962	347
1963	269
1964	297
1965	678
1966	373
1967	268
1968	454
1969	508
1970	358
1971	315
1972	289
1973	713
1974	198
1975	629
1976	280
1977	94.0
1978	418
1979	676
1980	726
1981	250
1982	467
1983	640
1984	454
1985	618
1986	647
1987	579
1988	342
1989	262
1990	241
1991	366
1992	485
1993	669
1994	346
1995	592
1996	243
1997	643
1998	319
1999	430
2000	277
2001	378
2002	96.0
2003	262
2004	396
2005	656
2006	297
2007	335
2008	443
2009	317
2010	323
2011	351
2012	214
2013	195
2014	231
2015	331
2016	325
2017	491

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	1918–2017
Completeness	100.0% of the periods in that span are held.
Continuity	Continuous: every year from 1918 to 2017 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.

1,076

Fullest snowpack recorded at Columbus Basin, in 2019 (mm of water)

242

Thinnest, in 2018 (mm of water)

April

Month the pack is usually at its fullest

June

Month the pack has gone by, in half of years

Peak snowpack at Columbus Basin

Water years 1995–2026. 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	Columbus Basin (mm)
1995	1,004
1996	610
1997	867
1998	675
1999	534
2000	482
2001	801
2002	248
2003	524
2004	716
2005	1,047
2006	491
2007	524
2008	840
2009	650
2010	613
2011	636
2012	575
2013	431
2014	469
2015	411
2016	536
2017	875
2018	242
2019	1,076
2020	603
2021	378
2022	500
2023	920
2024	568
2025	387
2026	279

Read against the river

Columbus Basin and LA PLATA RIVER AT HESPERUS, CO both sit in this drainage area, and their records overlap by 23 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 Middle San Juan and what each holds
Gauge	Measures	Values	Record
LA PLATA RIVER AT HESPERUS, CO	burned area within 50 km, catchment area, annual maximum river flow, mean river flow, mean river flow, water year	340	1905–2026
LA PLATA RIVER AT COLORADO-NEW MEXICO STATE LINE	burned area within 50 km, catchment area, annual maximum river flow, mean river flow, mean river flow, water year	329	1920–2026

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 — 14080105. 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
LA PLATA RIVER AT HESPERUS, CO	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
LA PLATA RIVER AT COLORADO-NEW MEXICO 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 4 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	122	yes, 20 or more
Values held	1,053	yes, 1000 or more
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-09365500.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 San Juan gauge records, accessed 2026-10-05, hydrionis.com/waters/united-states-middle-san-juan/

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 San Juan 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 confidence2018-05-10

Source: USGS — National Water Information System, USGS site 09365500, 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.