The monitoring network within this area

Hydrionis holds 576 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

576

Values held

1913–2026

Record spans

Gauges within the Lower 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 nr Falls City, TX

The highest instantaneous discharge the publisher recorded in each year — a flood peak as measured, not a daily average of one. 1926–2025.

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 nr Falls City, TX (m³/s)
1926	262
1927	62.9
1929	286
1930	36.5
1931	71.9
1932	47.0
1933	170
1934	96.3
1935	405
1936	459
1937	413
1938	122
1939	36.2
1940	105
1942	524
1944	146
1945	108
1946	1,342
1948	309
1949	419
1951	74.8
1952	59.5
1953	143
1954	55.2
1955	47.0
1956	102
1957	196
1958	207
1959	86.6
1960	148
1962	52.7
1963	50.4
1964	75.0
1965	268
1967	413
1968	490
1969	76.5
1970	90.0
1971	125
1972	214
1973	691
1974	231
1975	234
1976	205
1977	348
1978	191
1979	164
1980	145
1981	323
1983	183
1985	124
1986	405
1987	564
1988	71.9
1989	68.0
1990	114
1991	148
1993	337
1994	205
1995	123
1996	59.5
1997	326
1998	155
2000	110
2002	1,529
2004	343
2006	66.5
2007	748
2008	82.4
2009	64.8
2010	236
2011	41.6
2012	126
2013	436
2014	102
2015	292
2016	368
2018	277
2020	130
2021	178
2023	99.4
2024	114
2025	139

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	1926–2025
Completeness	83.0% of the periods in that span are held. Gaps are drawn as breaks and never interpolated.
Known gaps	17 separate periods inside 1926–2025 hold no value. They are drawn as breaks in the line and are never interpolated across.
Continuity	The record begins in 1926 and is not continuous from it: 100 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	2026-10-01
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 nr Falls City, 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. 1926–2025.

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	San Antonio Rv nr Falls City, TX (mm)
1926	49.0
1927	25.0
1928	26.0
1929	41.0
1930	20.0
1931	30.0
1932	30.0
1933	26.0
1934	33.0
1935	115
1936	131
1937	68.0
1938	47.0
1939	21.0
1940	46.0
1941	66.0
1942	100
1943	41.0
1944	46.0
1945	58.0
1946	131
1947	50.0
1948	33.0
1949	66.0
1950	29.0
1951	26.0
1952	23.0
1953	27.0
1954	15.0
1955	18.0
1956	18.0
1957	83.0
1958	110
1959	55.0
1960	64.0
1961	76.0
1962	36.0
1963	31.0
1964	39.0
1965	62.0
1966	37.0
1967	59.0
1968	101
1969	50.0
1970	52.0
1971	72.0
1972	85.0
1973	238
1974	102
1975	134
1976	137
1977	157
1978	98.0
1979	146
1980	62.0
1981	128
1982	66.0
1983	79.0
1984	64.0
1985	88.0
1986	116
1987	273
1988	55.0
1989	46.0
1990	69.0
1991	107
1992	356
1993	123
1994	78.0
1995	59.0
1996	39.0
1997	91.0
1998	150
1999	58.0
2000	72.0
2001	88.0
2002	330
2003	101
2004	205
2005	92.0
2006	39.0
2007	240
2008	53.0
2009	49.0
2010	105
2011	34.0
2012	63.0
2013	56.0
2014	42.0
2015	94.0
2016	153
2017	73.0
2018	105
2019	81.0
2020	47.0
2021	83.0
2022	33.0
2023	46.0
2024	44.0
2025	41.0

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	1926–2025
Completeness	100.0% of the periods in that span are held.
Continuity	Continuous: every year from 1926 to 2025 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

Every gauge Hydrionis holds within this area

Gauges within the Lower San Antonio and what each holds
Gauge	Measures	Values	Record
San Antonio Rv nr Falls City, TX	catchment area, annual maximum river flow, mean river flow, mean river flow, water year	301	1925–2026
San Antonio Rv at Goliad, TX	catchment area, annual maximum river flow, mean river flow, mean river flow, water year	275	1913–2026

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 — 12100303. 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 nr Falls City, 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 Antonio Rv at Goliad, 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	2	no
Years spanned	114	yes, 20 or more
Values held	576	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-08183500.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), Lower San Antonio gauge records, accessed 2026-10-05, hydrionis.com/waters/united-states-lower-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 Lower 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 confidence2025-06-15

Source: USGS — National Water Information System, USGS site 08183500, 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.