The monitoring network within this area

Hydrionis holds 1,403 values from 6 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.

6

Gauges

1,403

Values held

1925–2026

Record spans

Gauges within the Lower Kootenai huc8 subbasin

6 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 BOUNDARY CREEK NR PORTHILL ID

The highest instantaneous discharge the publisher recorded in each year — a flood peak as measured, not a daily average of one. 1929–2025.

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	BOUNDARY CREEK NR PORTHILL ID (m³/s)
1929	36.8
1930	28.9
1931	37.4
1932	47.6
1933	68.0
1934	49.8
1935	45.3
1936	42.2
1937	37.4
1938	64.3
1939	39.6
1940	34.0
1941	65.1
1942	45.6
1943	68.0
1944	21.1
1945	52.1
1946	55.8
1947	48.1
1948	71.6
1949	60.0
1950	63.7
1951	45.9
1952	43.6
1953	64.3
1954	66.5
1955	92.9
1956	73.9
1957	51.3
1958	54.1
1959	53.8
1960	49.0
1961	89.8
1962	39.6
1963	47.0
1964	55.8
1965	50.4
1966	49.6
1967	63.1
1968	100
1969	76.2
1970	52.4
1971	85.0
1972	79.6
1973	60.0
1974	92.3
1975	55.5
1976	84.1
1977	34.5
1978	52.7
1979	40.5
1980	92.6
1981	51.5
1982	66.3
1983	66.5
1985	58.3
1986	46.7
1987	75.6
1988	46.2
1989	60.9
1990	48.4
1991	71.6
1992	47.3
1993	53.5
1994	45.6
1995	49.8
1996	106
1997	107
1998	78.2
1999	80.7
2001	46.4
2002	76.2
2003	59.5
2004	44.5
2005	51.8
2006	101
2007	63.1
2008	90.3
2009	55.8
2010	73.3
2011	58.9
2012	85.8
2013	116
2014	59.7
2015	42.8
2016	45.9
2017	71.9
2018	101
2019	35.4
2020	51.8
2021	41.9
2022	64.8
2023	96.3
2024	0
2025	45.3

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	1929–2025
Completeness	97.9% of the periods in that span are held. Gaps are drawn as breaks and never interpolated.
Known gaps	2 separate periods inside 1929–2025 hold no value. They are drawn as breaks in the line and are never interpolated across.
Continuity	The record begins in 1929 and is not continuous from it: 97 years separate the first value from the last, and 98% 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 KOOTENAI RIVER AT PORTHILL ID TOTAL FLOW, as a depth

The year's flow spread over the land draining to this gauge, in millimetres — the same unit rainfall is measured in. 1929–2025.

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	KOOTENAI RIVER AT PORTHILL ID TOTAL FLOW (mm)
1929	276
1930	310
1931	232
1932	426
1933	514
1934	493
1935	387
1936	291
1937	296
1938	419
1939	318
1940	280
1941	283
1942	413
1943	437
1944	203
1945	296
1946	446
1947	482
1948	500
1949	346
1950	515
1951	558
1952	404
1953	407
1954	559
1955	429
1956	540
1957	368
1958	348
1959	545
1960	425
1961	484
1962	374
1963	385
1964	422
1965	437
1966	416
1967	476
1968	404
1969	509
1970	299
1971	483
1972	531
1973	238
1974	583
1975	402
1976	458
1977	274
1978	359
1979	288
1980	345
1981	460
1982	443
1983	404
1984	346
1985	333
1986	401
1987	307
1988	330
1989	353
1990	484
1991	552
1992	283
1993	313
1994	283
1995	449
1996	567
1997	533
1998	368
1999	484
2000	357
2001	196
2002	432
2003	321
2004	340
2005	369
2006	441
2007	433
2008	365
2009	295
2010	314
2011	490
2012	567
2013	419
2014	454
2015	323
2016	401
2017	461
2018	400
2019	262
2020	392
2021	321
2022	410
2023	274
2024	309
2025	292

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	1929–2025
Completeness	100.0% of the periods in that span are held.
Continuity	Continuous: every year from 1929 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

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.

1,208

Fullest snowpack recorded at Hidden Lake, in 2012 (mm of water)

471

Thinnest, in 2015 (mm of water)

April

Month the pack is usually at its fullest

June

Month the pack has gone by, in half of years

Peak snowpack at Hidden Lake

Water years 2001–2026. 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	Hidden Lake (mm)
2001	484
2002	991
2003	818
2004	836
2005	488
2006	1,090
2007	871
2008	945
2009	750
2010	847
2011	1,165
2012	1,208
2013	825
2014	1,003
2015	471
2016	827
2017	848
2018	1,166
2019	672
2020	1,001
2021	770
2022	833
2023	737
2024	748
2025	825
2026	634

Read against the river

Hidden Lake and KOOTENAI RIVER AT LEONIA, ID both sit in this drainage area, and their records overlap by 24 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 Lower Kootenai and what each holds
Gauge	Measures	Values	Record
BOUNDARY CREEK NR PORTHILL ID	burned area within 50 km, catchment area, annual maximum river flow, mean river flow, mean river flow, water year	324	1929–2026
KOOTENAI RIVER AT LEONIA, ID	burned area within 50 km, catchment area, annual maximum river flow, mean river flow, mean river flow, water year	238	1928–2026
KOOTENAI RIVER AT PORTHILL ID TOTAL FLOW	burned area within 50 km, catchment area, mean river flow, mean river flow, water year	231	1928–2026
KOOTENAI RIVER NR COPELAND ID	catchment area, annual maximum river flow	11	1925–2026
BALL CREEK NR BONNERS FERRY ID	catchment area, annual maximum river flow	9	1972–2026
MYRTLE CREEK NR BONNERS FERRY ID	catchment area, annual maximum river flow	2	2002–2026

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 — 17010104. 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
BOUNDARY CREEK NR PORTHILL ID	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
KOOTENAI RIVER AT LEONIA, ID	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
KOOTENAI RIVER AT PORTHILL ID TOTAL FLOW	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
KOOTENAI RIVER NR COPELAND ID	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
BALL CREEK NR BONNERS FERRY ID	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
MYRTLE CREEK NR BONNERS FERRY ID	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	3	yes, 3 or more
Years spanned	102	yes, 20 or more
Values held	1,403	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-12321500.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 Kootenai gauge records, accessed 2026-10-05, hydrionis.com/waters/united-states-lower-kootenai/

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 Kootenai 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 confidence2025-05-29

Source: USGS — National Water Information System, USGS site 12321500, 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.