The monitoring network within this area

Hydrionis holds 274 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

274

Values held

1914–2026

Record spans

Gauges within the Upper San Antonio 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 San Antonio Rv at San Antonio, TX

The highest instantaneous discharge the publisher recorded in each year — a flood peak as measured, not a daily average of one. 1914–2025.

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	San Antonio Rv at San Antonio, TX (m³/s)
1914	130
1916	75.0
1917	4.16
1918	138
1919	67.4
1921	433
1923	11.0
1924	18.3
1925	18.2
1926	54.9
1927	23.9
1928	21.4
1929	16.7
1940	29.4
1941	41.6
1942	47.6
1944	35.7
1946	163
1948	80.4
1949	46.4
1951	51.0
1952	10.3
1953	45.6
1954	21.5
1955	22.9
1956	34.8
1957	52.4
1958	34.3
1959	21.9
1960	66.8
1961	96.6
1962	32.3
1963	42.5
1964	53.0
1965	128
1966	33.7
1967	63.4
1968	162
1969	152
1970	169
1971	73.9
1972	109
1973	172
1974	99.7
1976	99.1
1978	98.3
1979	31.7
1980	69.1
1981	87.2
1983	110
1984	82.4
1986	129
1987	118
1988	78.4
1989	77.0
1990	152
1991	90.9
1992	135
1993	127
1994	116
1996	86.4
1997	78.2
1998	76.7
2000	0
2001	0
2002	0
2003	0
2004	0
2006	0
2007	0
2008	0
2009	0
2010	0
2012	6.68
2013	9.91
2014	4.28
2016	123
2017	66.0
2018	36.8
2019	69.9
2020	60.9
2021	50.4
2023	56.1
2024	28.3
2025	72.2

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	1914–2025
Completeness	75.9% of the periods in that span are held. Gaps are drawn as breaks and never interpolated.
Known gaps	18 separate periods inside 1914–2025 hold no value. The longest runs from 1930 to 1939 — 10 years with no reading. They are drawn as breaks in the line and are never interpolated across.
Continuity	The record begins in 1914 and is not continuous from it: 112 years separate the first value from the last, and 76% 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 San Antonio Rv at San Antonio, TX, as a depth

The year's flow spread over the land draining to this gauge, in millimetres — the same unit rainfall is measured in. 1927–2024.

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	San Antonio Rv at San Antonio, TX (mm)
1927	258
1928	168
1940	185
1941	789
1942	849
1943	494
1944	494
1945	723
1946	681
1947	537
1948	223
1949	305
1950	209
1951	207
1952	178
1953	120
1954	97.0
1955	99.0
1956	87.0
1957	271
1958	340
1959	372
1960	378
1961	557
1962	189
1963	147
1964	198
1965	275
1966	186
1967	194
1968	361
1969	267
1970	210
1971	247
1972	309
1973	1,063
1974	705
1975	707
1976	763
1977	1,198
1978	519
1979	892
1980	247
1981	550
1982	318
1983	191
1984	163
1985	323
1986	426
1987	971
1988	295
1989	194
1990	327
1991	423
1992	1,878
1993	1,087
1994	453
1995	263
1996	111
2012	304
2016	243
2017	205
2018	219
2019	251
2020	231
2021	227
2022	196
2023	258
2024	242

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	1927–2024
Completeness	70.4% of the periods in that span are held. Gaps are drawn as breaks and never interpolated.
Known gaps	3 separate periods inside 1927–2024 hold no value. The longest runs from 1997 to 2011 — 15 years with no reading. They are drawn as breaks in the line and are never interpolated across.
Continuity	The record begins in 1927 and is not continuous from it: 98 years separate the first value from the last, and 70% of the years between them are held. The span is not the record.
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 Upper San Antonio and what each holds
Gauge	Measures	Values	Record
San Antonio Rv at San Antonio, TX	catchment area, annual maximum river flow, mean river flow, mean river flow, water year	241	1914–2026
San Pedro Ck at Furnish St, San Antonio, TX	catchment area, annual maximum river flow	33	1916–2026

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 — 12100301. 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
San Antonio Rv at San Antonio, TX	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
San Pedro Ck at Furnish St, San Antonio, TX	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 2 of them, which makes it a profile, not indexed.

Information-gain signals held for this water body
Signal	Held	Counts
Gauges holding a real record	1	no
Years spanned	113	yes, 20 or more
Values held	274	no
Distinct measurements	4	yes, 2 or more
Publishers measuring it	1	no
Official identifiers	1	recorded, not counted

Use this data

Machine-readable JSON /api/v1/observations/by-subject/gauge-usgs-08178000.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), Upper San Antonio gauge records, accessed 2026-10-05, hydrionis.com/waters/united-states-upper-san-antonio/

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 Upper San Antonio 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 confidence2025-06-12

Source: USGS — National Water Information System, USGS site 08178000, 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.