The monitoring network within this area

Hydrionis holds 379 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

379

Values held

1909–2026

Record spans

Gauges within the Middle San Joaquin-Lower Chowchilla 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 JOAQUIN R BL FRIANT CA

The highest instantaneous discharge the publisher recorded in each year — a flood peak as measured, not a daily average of one. 1909–2025.

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 JOAQUIN R BL FRIANT CA (m³/s)
1909	869
1914	1,699
1915	450
1916	481
1917	442
1920	396
1921	433
1922	580
1923	371
1924	173
1925	326
1926	259
1927	405
1928	371
1929	348
1930	150
1931	95.7
1932	580
1933	252
1935	445
1936	708
1937	1,031
1939	133
1940	379
1941	476
1942	297
1943	317
1944	74.8
1945	185
1946	186
1947	85.5
1948	119
1949	142
1950	77.9
1952	227
1954	71.1
1956	202
1958	214
1959	7.19
1960	11.5
1962	21.6
1963	70.8
1964	5.18
1965	6.09
1966	4.56
1967	233
1968	6.23
1969	351
1970	55.5
1971	7.65
1972	5.89
1973	110
1974	39.1
1975	5.15
1976	8.13
1977	6.60
1978	216
1979	29.4
1980	228
1981	6.57
1982	234
1983	348
1985	5.10
1986	439
1987	5.55
1988	5.55
1989	6.37
1990	7.16
1991	7.36
1992	11.3
1993	115
1994	7.73
1995	354
1996	201
1997	1,708
1998	225
1999	79.3
2000	73.3
2001	25.8
2002	8.04
2003	83.3
2004	12.4
2005	248
2006	292
2007	10.4
2008	10.6
2009	10.9
2010	49.3
2011	242
2012	31.1
2013	30.3
2014	39.6
2015	57.2
2016	39.9
2017	271
2018	36.8
2019	201
2020	18.4
2021	13.2
2022	51.3
2023	294
2024	91.2
2025	31.1

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	1909–2025
Completeness	88.0% of the periods in that span are held. Gaps are drawn as breaks and never interpolated.
Known gaps	10 separate periods inside 1909–2025 hold no value. The longest runs from 1910 to 1913 — 4 years with no reading. They are drawn as breaks in the line and are never interpolated across.
Continuity	The record begins in 1909 and is not continuous from it: 117 years separate the first value from the last, and 88% of the years between them are held. The span is not the record.
Last read from the publisher	2026-08-31
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 JOAQUIN R BL FRIANT 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. 1941–2024.

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 JOAQUIN R BL FRIANT CA (mm)
1941	741
1942	635
1943	574
1944	310
1945	567
1946	436
1947	315
1948	291
1949	300
1950	308
1951	302
1952	591
1953	103
1954	63.0
1955	50.0
1956	341
1957	24.0
1958	335
1959	24.0
1960	29.0
1961	26.0
1962	21.0
1963	23.0
1964	21.0
1965	17.0
1966	18.0
1967	360
1968	17.0
1969	627
1970	25.0
1971	14.0
1972	21.0
1973	80.0
1974	39.0
1975	16.0
1976	24.0
1977	27.0
1978	381
1979	31.0
1980	277
1981	20.0
1982	324
1983	890
1984	95.0
1985	19.0
1986	275
1987	20.0
1988	23.0
1989	25.0
1990	29.0
1991	30.0
1992	36.0
1993	91.0
1994	34.0
1995	474
1996	131
1997	323
1998	468
1999	47.0
2000	54.0
2001	35.0
2002	32.0
2003	34.0
2004	33.0
2005	203
2006	392
2007	40.0
2008	39.0
2009	39.0
2010	120
2011	388
2012	83.0
2013	86.0
2014	121
2015	68.0
2016	72.0
2017	629
2018	83.0
2019	211
2020	83.0
2021	67.0
2022	144
2023	674
2024	104

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	1941–2024
Completeness	100.0% of the periods in that span are held.
Continuity	Continuous: every year from 1941 to 2024 is held.
Last read from the publisher	2026-08-24
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 Middle San Joaquin-Lower Chowchilla and what each holds
Gauge	Measures	Values	Record
SAN JOAQUIN R BL FRIANT CA	burned area within 50 km, catchment area, annual maximum river flow, mean river flow	232	1909–2026
CHOWCHILLA R BL BUCHANAN DAM NR RAYMOND CA	burned area within 50 km, catchment area, annual maximum river flow, mean river flow	147	1922–2026

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 — 18040001. 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 JOAQUIN R BL FRIANT 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	2026-08-26
CHOWCHILLA R BL BUCHANAN DAM NR RAYMOND 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	2026-08-26

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	118	yes, 20 or more
Values held	379	no
Distinct measurements	4	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-11251000.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 Joaquin-Lower Chowchilla gauge records, accessed 2026-09-02, hydrionis.com/waters/united-states-middle-san-joaquin-lower-chowchilla/

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 Joaquin-Lower Chowchilla 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 confidence2025-03-21

Source: USGS — National Water Information System, USGS site 11251000, 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 31 August 2026.