The monitoring network within this area

Hydrionis holds 1,347 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.

3

Gauges

1,347

Values held

1903–2026

Record spans

Gauges within the Walla Walla 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 MILL CREEK NEAR WALLA WALLA, WA

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	MILL CREEK NEAR WALLA WALLA, WA (m³/s)
1914	14.1
1915	13.0
1916	23.8
1917	31.7
1940	21.6
1942	25.5
1943	17.8
1944	20.4
1945	18.7
1946	40.8
1948	47.6
1949	17.0
1950	47.6
1951	37.7
1953	40.8
1955	11.6
1956	24.7
1958	39.1
1960	10.9
1961	29.7
1962	18.2
1963	12.2
1964	18.5
1965	104
1966	11.2
1967	17.3
1969	68.0
1970	34.3
1971	45.0
1972	32.3
1974	38.5
1975	49.3
1977	9.06
1979	26.4
1980	12.1
1982	44.7
1983	36.8
1984	19.5
1985	11.7
1986	60.6
1988	11.4
1989	23.6
1990	11.6
1991	22.1
1993	22.7
1994	14.9
1995	32.3
1996	180
1997	71.1
1999	25.6
2002	39.1
2003	55.2
2004	50.4
2005	13.8
2006	17.9
2008	15.0
2009	61.7
2010	23.3
2011	53.0
2013	36.5
2014	29.7
2015	37.1
2016	16.4
2017	39.6
2019	68.0
2020	211
2022	57.8
2023	18.7
2025	40.8

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	61.6% of the periods in that span are held. Gaps are drawn as breaks and never interpolated.
Known gaps	21 separate periods inside 1914–2025 hold no value. The longest runs from 1918 to 1939 — 22 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 62% 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 MILL CREEK NEAR WALLA WALLA, WA, as a depth

The year's flow spread over the land draining to this gauge, in millimetres — the same unit rainfall is measured in. 1914–2025.

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	MILL CREEK NEAR WALLA WALLA, WA (mm)
1914	447
1915	428
1916	625
1940	457
1941	342
1942	465
1943	550
1944	336
1945	570
1946	716
1947	581
1948	702
1949	635
1950	872
1951	669
1952	558
1953	659
1954	476
1955	509
1956	557
1957	527
1958	711
1959	624
1960	484
1961	582
1962	492
1963	377
1964	658
1965	585
1966	434
1967	428
1968	396
1969	546
1970	617
1971	600
1972	725
1973	503
1974	858
1975	871
1980	459
1981	480
1982	606
1983	466
1984	570
1985	423
1986	504
1987	331
1988	396
1989	526
1990	436
1991	503
1992	270
1993	463
1994	431
1995	714
1996	870
1997	920
1998	474
1999	603
2000	549
2001	403
2002	562
2003	618
2004	570
2005	344
2006	605
2007	384
2008	580
2009	734
2010	470
2011	726
2012	686
2013	546
2014	605
2015	406
2016	551
2017	758
2018	608
2019	584
2020	763
2021	544
2022	729
2023	507
2024	473
2025	506

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	Derived Computed by Hydrionis
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	2 separate periods inside 1914–2025 hold no value. The longest runs from 1917 to 1939 — 23 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.
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

The snow standing above this water

2 automated snow stations sit inside this drainage area, weighing the snowpack rather than measuring how deep it is.

1,536

Fullest snowpack recorded at Touchet, in 1997 (mm of water)

229

Thinnest, in 2005 (mm of water)

March

Month the pack is usually at its fullest

June

Month the pack has gone by, in half of years

Peak snowpack at Touchet

Water years 1981–2026. Each point is the fullest month of that snow season.

A water year runs October to September and is named for the year it ends, so the snow of one winter stays in one point. The value is the fullest month, not the fullest day: a pack that peaked sharply mid-month reads lower here than a single measurement taken at the right moment would.

View the data behind this chart

Underlying data
Period	Touchet (mm)
1981	374
1982	1,417
1985	1,130
1986	656
1987	698
1988	685
1989	989
1990	774
1991	597
1992	518
1993	794
1994	627
1995	820
1996	644
1997	1,536
1998	629
1999	1,372
2000	851
2001	579
2002	1,008
2003	604
2004	717
2005	229
2006	846
2007	616
2008	1,152
2009	978
2010	551
2011	833
2012	891
2013	643
2014	659
2015	260
2016	823
2017	889
2018	664
2019	757
2020	752
2021	828
2022	629
2023	834
2024	549
2025	759
2026	324

Read against the river

Touchet and SOUTH FORK WALLA WALLA RIVER NEAR MILTON,OREG. both sit in this drainage area, and their records overlap by 10 years. That is the span the two have in common, not a count of years both actually hold — either record may have gaps inside it. The two are shown separately rather than on one axis: millimetres of stored water and cubic metres per second are not commensurable, and a difference between them would mean nothing.

Being in the same drainage area does not put the snowpack upstream of the gauge. A subbasin is an area, and snow on one tributary can join the river below a gauge on another — so a weak relationship here may say more about which tributary was measured than about the snow.

Every gauge Hydrionis holds within this area

Gauges within the Walla Walla and what each holds
Gauge	Measures	Values	Record
MILL CREEK NEAR WALLA WALLA, WA	burned area within 50 km, catchment area, annual maximum river flow, mean river flow, mean river flow, water year	295	1913–2026
SOUTH FORK WALLA WALLA RIVER NEAR MILTON,OREG.	burned area within 50 km, catchment area, annual maximum river flow, mean river flow, mean river flow, water year	243	1903–2026
TOUCHET RIVER AT BOLLES, WA	catchment area, annual maximum river flow	44	1925–2026

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 — 17070102. 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
MILL CREEK NEAR WALLA WALLA, WA	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
SOUTH FORK WALLA WALLA RIVER NEAR MILTON,OREG.	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
TOUCHET RIVER AT BOLLES, WA	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	2	no
Years spanned	124	yes, 20 or more
Values held	1,347	yes, 1000 or more
Distinct measurements	6	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-14013000.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), Walla Walla gauge records, accessed 2026-10-05, hydrionis.com/waters/united-states-walla-walla/

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 Walla Walla 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 confidence2025-02-23

Source: USGS — National Water Information System, USGS site 14013000, 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.