The monitoring network within this area

Hydrionis holds 836 values from 3 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

836

Values held

1901–2026

Record spans

Gauges within the Upper Chattahoochee huc8 subbasin

3 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 CHATTAHOOCHEE RIVER NEAR NORCROSS, GA

The highest instantaneous discharge the publisher recorded in each year — a flood peak as measured, not a daily average of one. 1901–2025.

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	CHATTAHOOCHEE RIVER NEAR NORCROSS, GA (m³/s)
1901	1,274
1903	920
1904	405
1905	456
1906	688
1908	578
1909	623
1910	351
1911	396
1912	864
1913	453
1914	320
1915	1,025
1917	685
1918	306
1919	1,549
1921	943
1922	396
1924	323
1925	476
1926	558
1927	323
1928	442
1929	881
1930	453
1931	552
1932	909
1934	900
1936	1,087
1937	770
1938	504
1939	419
1940	637
1941	264
1942	583
1944	637
1945	268
1946	1,557
1947	818
1948	470
1949	827
1950	311
1952	991
1953	447
1954	810
1955	490
1956	145
1957	243
1958	254
1959	223
1960	247
1961	253
1962	269
1964	374
1965	276
1966	269
1967	249
1968	297
1969	242
1970	263
1972	267
1973	345
1974	262
1975	317
1976	314
1977	297
1978	294
1979	300
1980	297
1981	241
1982	234
1983	267
1984	283
1985	262
1986	266
1987	250
1989	255
1990	311
1991	294
1992	289
1994	264
1995	268
1996	276
1997	252
1998	289
1999	214
2000	219
2001	211
2002	169
2003	297
2004	303
2005	323
2006	230
2007	174
2009	422
2011	246
2013	328
2014	238
2015	209
2016	282
2017	139
2018	271
2020	300
2022	262
2023	326
2024	340
2025	276

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	1901–2025
Completeness	85.6% of the periods in that span are held. Gaps are drawn as breaks and never interpolated.
Known gaps	18 separate periods inside 1901–2025 hold no value. They are drawn as breaks in the line and are never interpolated across.
Continuity	The record begins in 1901 and is not continuous from it: 125 years separate the first value from the last, and 86% 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 CHESTATEE RIVER NEAR DAHLONEGA, GA, as a depth

The year's flow spread over the land draining to this gauge, in millimetres — the same unit rainfall is measured in. 1930–2025.

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	CHESTATEE RIVER NEAR DAHLONEGA, GA (mm)
1930	644
1931	580
1941	407
1942	775
1943	838
1944	823
1945	642
1946	1,211
1947	645
1948	898
1949	1,080
1950	787
1951	651
1952	843
1953	735
1954	641
1955	572
1956	620
1957	773
1958	695
1959	818
1960	980
1961	1,043
1962	825
1963	873
1964	1,222
1965	721
1966	835
1967	1,109
1968	806
1969	855
1970	620
1971	935
1972	928
1973	1,235
1974	982
1975	942
1976	1,006
1977	939
1978	739
1979	1,140
1980	866
1981	447
1982	797
1983	932
1984	954
1985	537
1986	397
1987	569
1988	438
1989	943
1990	1,058
1991	1,072
1992	1,045
1993	860
1994	919
1995	892
1996	1,027
1997	824
1998	983
1999	475
2000	426
2001	466
2002	553
2003	938
2004	742
2005	997
2006	564
2007	445
2008	463
2009	935
2010	798
2011	660
2012	521
2013	1,220
2014	665
2015	870
2016	603
2017	482
2018	1,043
2019	1,152
2020	1,250
2021	1,082
2022	855
2023	668
2024	765
2025	619

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	1930–2025
Completeness	90.6% of the periods in that span are held. Gaps are drawn as breaks and never interpolated.
Known gaps	One period inside 1930–2025 holds no value: 1932 to 1940, 9 years with no reading. It is drawn as a break in the line and is never interpolated across.
Continuity	The record begins in 1930 and is not continuous from it: 96 years separate the first value from the last, and 91% 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 Chattahoochee and what each holds
Gauge	Measures	Values	Record
CHATTAHOOCHEE RIVER NEAR NORCROSS, GA	burned area within 50 km, catchment area, annual maximum river flow, mean river flow, mean river flow, water year	298	1901–2026
CHATTAHOOCHEE RIVER AT ATLANTA, GA	burned area within 50 km, catchment area, annual maximum river flow, mean river flow, mean river flow, water year	272	1901–2026
CHESTATEE RIVER NEAR DAHLONEGA, GA	catchment area, annual maximum river flow, mean river flow, mean river flow, water year	266	1907–2026

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 — 03130001. 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
CHATTAHOOCHEE RIVER NEAR NORCROSS, GA	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
CHATTAHOOCHEE RIVER AT ATLANTA, GA	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
CHESTATEE RIVER NEAR DAHLONEGA, GA	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	3	yes, 3 or more
Years spanned	126	yes, 20 or more
Values held	836	no
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-02335000.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 Chattahoochee gauge records, accessed 2026-10-05, hydrionis.com/waters/united-states-upper-chattahoochee/

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 Chattahoochee 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 02335000, 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.