The monitoring network within this area

Hydrionis holds 1,157 values from 9 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

1,157

Values held

1912–2026

Record spans

Gauges within the San Francisco Bay huc8 subbasin

9 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 ALAMEDA C NR NILES CA

The highest instantaneous discharge the publisher recorded in each year — a flood peak as measured, not a daily average of one. 1917–2025.

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	ALAMEDA C NR NILES CA (m³/s)
1917	289
1919	385
1920	30.3
1921	109
1922	394
1923	1.13
1925	82.1
1926	188
1927	103
1928	137
1929	8.16
1930	134
1931	3.03
1933	25.6
1934	59.5
1935	51.0
1936	154
1937	208
1938	297
1939	22.2
1940	244
1941	190
1942	156
1943	206
1944	79.9
1945	303
1947	4.73
1948	2.94
1949	21.4
1950	39.1
1952	688
1954	16.8
1955	19.5
1957	27.5
1958	722
1959	121
1960	60.0
1962	94.6
1963	326
1964	52.4
1965	21.4
1967	385
1968	64.0
1969	178
1970	197
1971	9.37
1973	236
1974	189
1975	117
1976	9.63
1977	12.2
1978	112
1979	58.3
1980	292
1981	29.4
1982	360
1983	354
1985	100.0
1986	464
1987	118
1988	41.6
1990	67.7
1991	97.1
1992	94.3
1993	286
1994	37.4
1995	425
1996	250
1997	303
1998	507
1999	129
2000	178
2001	45.0
2002	294
2004	170
2005	101
2007	80.1
2008	213
2009	97.7
2011	323
2012	83.3
2014	42.5
2016	127
2017	501
2018	56.4
2019	189
2020	41.9
2021	62.3
2022	629
2024	89.8
2025	188

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	1917–2025
Completeness	83.5% of the periods in that span are held. Gaps are drawn as breaks and never interpolated.
Known gaps	18 separate periods inside 1917–2025 hold no value. They are drawn as breaks in the line and are never interpolated across.
Continuity	The record begins in 1917 and is not continuous from it: 109 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 DRY C A UNION CITY CA, as a depth

The year's flow spread over the land draining to this gauge, in millimetres — the same unit rainfall is measured in. 1917–2024.

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	DRY C A UNION CITY CA (mm)
1917	48.0
1918	3.00
1960	24.0
1961	0
1962	75.0
1963	79.0
1964	50.0
1965	57.0
1966	13.0
1967	148
1968	32.0
1969	181
1970	136
1971	30.0
1972	19.0
1973	315
1974	159
1975	66.0
1976	0
1977	0
1978	140
1979	64.0
1980	127
1981	39.0
1982	299
1983	525
1984	74.0
1985	19.0
1986	157
1987	15.0
1988	2.00
1989	3.00
1990	0
1991	13.0
1992	32.0
1993	151
1994	13.0
1995	184
1996	224
1997	140
1998	400
1999	111
2000	161
2001	41.0
2002	44.0
2003	27.0
2004	58.0
2005	139
2006	216
2007	29.0
2008	41.0
2009	39.0
2010	106
2011	94.0
2012	68.0
2013	5.00
2014	56.0
2015	19.0
2016	91.0
2017	264
2018	28.0
2019	98.0
2020	3.00
2021	28.0
2022	65.0
2023	245
2024	99.0

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	1917–2024
Completeness	62.0% of the periods in that span are held. Gaps are drawn as breaks and never interpolated.
Known gaps	One period inside 1917–2024 holds no value: 1919 to 1959, 41 years with no reading. It is drawn as a break in the line and is never interpolated across.
Continuity	The record begins in 1917 and is not continuous from it: 108 years separate the first value from the last, and 62% 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 San Francisco Bay and what each holds
Gauge	Measures	Values	Record
ALAMEDA C NR NILES CA	burned area within 50 km, catchment area, annual maximum river flow, mean river flow, mean river flow, water year	257	1917–2026
DRY C A UNION CITY CA	burned area within 50 km, catchment area, annual maximum river flow, mean river flow, mean river flow, water year	240	1916–2026
ARROYO VALLE NR LIVERMORE CA	burned area within 50 km, catchment area, annual maximum river flow, mean river flow, mean river flow, water year	218	1955–2026
ARROYO MOCHO NR LIVERMORE CA	burned area within 50 km, catchment area, annual maximum river flow, mean river flow, mean river flow, water year	186	1912–2026
ARROYO DE LA LAGUNA A VERONA CA	burned area within 50 km, catchment area, annual maximum river flow, mean river flow, mean river flow, water year	161	1969–2026
SAN ANTONIO C NR SUNOL CA	catchment area, annual maximum river flow	34	1955–2026
ARROYO DE LA LAGUNA NR PLEASANTON CA	catchment area, annual maximum river flow	31	1970–2026
CALAVERAS C NR SUNOL CA	catchment area, annual maximum river flow	24	2002–2026
TASSAJARA C NR PLEASANTON CA	catchment area, annual maximum river flow	6	1979–2026

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 — 18050004. 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
ALAMEDA C NR NILES CA	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
DRY C A UNION CITY CA	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
ARROYO VALLE NR LIVERMORE CA	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
ARROYO MOCHO NR LIVERMORE CA	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
ARROYO DE LA LAGUNA A VERONA CA	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 C NR SUNOL CA	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
ARROYO DE LA LAGUNA NR PLEASANTON CA	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
CALAVERAS C NR SUNOL CA	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
TASSAJARA C NR PLEASANTON CA	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 5 of them, which makes it a full profile.

Information-gain signals held for this water body
Signal	Held	Counts
Gauges holding a real record	5	yes, 3 or more
Years spanned	115	yes, 20 or more
Values held	1,157	yes, 1000 or more
Distinct measurements	5	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-11179000.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), San Francisco Bay gauge records, accessed 2026-10-05, hydrionis.com/waters/united-states-san-francisco-bay/

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 San Francisco Bay 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 confidence2025-02-13

Source: USGS — National Water Information System, USGS site 11179000, 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.