Mud Mountain Lake, WA — storage

Storage now, against this reservoir's own record

0.02 Mm³

Stored, September 2026

30th

Percentile among 44 Seps on record

-73.1%

Against the Sep 1991–2020 average

-11.7%

Change over the 12 months to 2026-09

Storage in September 2026 was around the middle of the Sep record, ranked against 44 other Seps held for this reservoir.

Storage, 1982–2026

Monthly mean storage

521 monthly values, 1982 to 2026

Monthly means of the publisher's daily record. Volume, not percentage of capacity — see below for why.

What the shaded periods are (0 events)

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

240 of 521 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 521 would be longer than this page and unusable with a screen reader.
Period	Mud Mountain Lake Near Buckley, WA (Mm³)
October 1982	2.43
December 1982	0.801
February 1983	0.315
May 1983	0.513
July 1983	0.454
September 1983	0.124
November 1983	0.946
January 1984	3.18
March 1984	0.573
June 1984	8.16
August 1984	2.54
October 1984	1.83
December 1984	1.73
February 1985	1.50
April 1985	2.01
July 1985	3.16
September 1985	0.121
November 1985	0.690
January 1986	0.273
March 1986	1.41
June 1986	9.39
August 1986	2.44
October 1986	1.98
December 1986	1.84
February 1987	0.856
April 1987	13.5
July 1987	0.175
September 1987	0.277
November 1987	0
January 1988	0.068
March 1988	0.592
May 1988	2.17
August 1988	1.52
October 1988	1.53
December 1988	0.152
February 1989	0.126
April 1989	1.77
July 1989	0.087
September 1989	0.078
November 1989	0.391
January 1990	3.25
March 1990	0.928
May 1990	1.14
August 1990	0.047
October 1990	0.145
December 1990	0.827
February 1991	4.84
April 1991	0.672
June 1991	0.974
September 1991	0.067
November 1991	0.647
January 1992	0.538
March 1992	0.088
May 1992	0.091
July 1992	0.083
October 1992	0.072
March 1993	0.074
May 1993	0.120
July 1993	0.117
September 1993	0.102
December 1993	0.064
February 1994	0.060
April 1994	0.077
June 1994	0.068
August 1994	0.053
November 1994	1.10
February 1995	7.54
April 1995	0.134
June 1995	0.256
August 1995	0.147
October 1995	1.35
December 1995	15.4
March 1996	20.6
May 1996	0.733
July 1996	0.297
September 1996	0.132
November 1996	1.11
March 1997	15.8
May 1997	2.40
July 1997	0.116
September 1997	0.140
November 1997	1.41
January 1998	0
May 1998	0.402
July 1998	0.197
September 1998	0.131
November 1998	0.238
January 1999	1.70
March 1999	0.017
June 1999	0.532
August 1999	0.010
October 1999	0
December 1999	1.11
February 2000	0.0068
May 2000	0.158
July 2000	0
September 2000	0
November 2000	0
January 2001	0.118
March 2001	0.292
June 2001	0.234
August 2001	18.0
October 2001	0.130
December 2001	0.196
February 2002	0.043
April 2002	2.36
July 2002	0.0082
September 2002	0
November 2002	0
January 2003	0.163
March 2003	0.169
June 2003	0.021
August 2003	1.35
October 2003	0.012
December 2003	0
February 2004	0.855
April 2004	0
July 2004	0.0059
September 2004	0.155
November 2004	0.010
January 2005	3.78
March 2005	0
May 2005	0
August 2005	0
October 2005	0.0038
December 2005	1.58
February 2006	0.152
April 2006	0
June 2006	0.060
September 2006	0.123
November 2006	26.2
January 2007	1.92
March 2007	1.61
May 2007	0.895
August 2007	0.142
October 2007	0.141
December 2007	0.513
February 2008	0.589
April 2008	0.413
June 2008	0.405
September 2008	0.254
November 2008	12.6
January 2009	23.4
March 2009	0.973
May 2009	0.219
July 2009	0.085
October 2009	0.037
December 2009	0.050
February 2010	0.145
April 2010	0.168
June 2010	0.190
September 2010	0.139
November 2010	0.205
January 2011	12.9
March 2011	2.58
May 2011	3.97
July 2011	7.77
October 2011	0.032
December 2011	0.234
February 2012	1.94
April 2012	0.069
June 2012	0.034
August 2012	0.0059
November 2012	0.036
January 2013	0.033
March 2013	0.049
May 2013	0.026
July 2013	0.0088
October 2013	0.020
December 2013	0.768
February 2014	0.0095
April 2014	0.046
June 2014	0.060
August 2014	0.0059
November 2014	2.18
January 2015	2.36
March 2015	1.54
May 2015	0.122
July 2015	1.24
September 2015	0.027
December 2015	8.32
February 2016	21.4
April 2016	0.064
June 2016	0.055
August 2016	0.0043
November 2016	0.050
January 2017	0.063
March 2017	2.59
May 2017	0.117
July 2017	0.026
September 2017	0.031
December 2017	0.471
February 2018	6.12
April 2018	0.066
June 2018	0.047
August 2018	0.032
October 2018	0.027
January 2019	0.036
March 2019	0.035
May 2019	0.059
July 2019	0.0071
September 2019	0.0032
November 2019	0.029
February 2020	27.5
April 2020	0.049
June 2020	0.068
August 2020	0.0058
October 2020	0.0071
January 2021	0.785
March 2021	0.042
May 2021	0.060
August 2021	0.0038
October 2021	0.0045
December 2021	0.031
March 2022	3.39
May 2022	0.099
July 2022	0.055
September 2022	0.0022
November 2022	1.09
January 2023	0.026
April 2023	0.091
June 2023	0.035
August 2023	0.030
October 2023	0.0100
December 2023	1.23
March 2024	0.039
May 2024	0.050
July 2024	0.022
September 2024	0.027
November 2024	0.033
January 2025	0.041
April 2025	2.11
June 2025	0.047
August 2025	0.031
October 2025	0.026
December 2025	39.9
February 2026	0.0067
May 2026	0.053
July 2026	0.033
September 2026	0.024

The reservoir's year

Seasonal storage profile

Each calendar month's reference average, against the most recent year

1991–2020 average
Most recent 12 months

Twelve separate averages, one per calendar month. A January average describes Januaries only. Months are plotted 1–12.

View the data behind this chart

Underlying data
Period	1991–2020 average (Mm³)	Most recent 12 months (Mm³)
Jan	2.36	8.59
Feb	4.51	0.0067
Mar	2.18	18.7
Apr	0.880	1.59
May	0.590	0.053
Jun	0.480	0.017
Jul	0.690	0.033
Aug	0.790	0.028
Sep	0.090	0.024
Oct	0.240	0.026
Nov	2.37	0.164
Dec	2.01	39.9

Why this page shows a volume and not a percentage

Percentage full is a division, and the denominator is missing

“Percentage full” is the figure a drought is discussed in, and it is stored volume divided by capacity. Capacity is published on several different bases — gross, usable, live, and the figure at a particular spillway or licence condition — and dividing a stored volume by the wrong one produces a percentage confidently wrong by the ratio between them, at exactly the moment the number matters most.

Hydrionis holds storage measurements for this reservoir and does not hold a compatible authoritative capacity figure for it, so percentage full is not calculated. The volume above is what was actually measured. Where you need a percentage, take the publisher’s own capacity on its own stated basis and divide it yourself — the source is linked below, and knowing which basis you used is the whole point.

Rate and persistence

-0.00 Mm³

Mean drawdown per month over 12 months

7 of 24

Recent months below the 20th percentile for their own month

Rates are computed only across an unbroken run of months, so a rate is never divided by a period in which some of the change was not observed. Percentile counts compare each month with the same calendar month in every other year held.

Location

Mud Mountain Lake Near Buckley, WA

Gauge location

About this data

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	1982–2026
Completeness	96.5% of the periods in that span are held. Gaps are drawn as breaks and never interpolated.
Known gaps	Storage is a managed quantity. A falling line can be a rule curve, a scheduled release or a transfer to another system rather than a shortage of water, and nothing here distinguishes them. No capacity figure on a stated basis is held for this reservoir, so no percentage of capacity is computed.
Continuity	96% of the months between 1982 and 2026 are held. Monthly means of the publisher's own daily 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

Use this data

Machine-readable JSON /api/v1/observations/by-subject/reservoir-usgs-12098000.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), Mud Mountain Lake Near Buckley, WA reservoir records, accessed 2026-10-05, hydrionis.com/reservoirs/reservoir-usgs-12098000/

Cite Hydrionis where you rely on the compilation, the normalisation, the eligibility judgements or a chart. Where you use an unmodified published value, the publisher’s attribution is the one that is required; crediting Hydrionis as well is welcome and is not something Hydrionis can require of you.

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 Mud Mountain Lake Near Buckley, WA record 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 this comes from

521 monthly observations 1982–2026 Mm³

Spatially aggregatedHigh confidenceSeptember 2026

Source: USGS — National Water Information System, 12098000. Licence: Open.

Method: Monthly mean of daily reservoir storage published by the USGS in acre-feet and converted to millions of cubic metres. Months with fewer than 20 days of record are not published rather than averaged from a partial month.

Reservoir storage is managed as well as observed: a drawdown may reflect an operating rule, flood-control rule curve or scheduled release rather than a shortage. Compare a month against the same month in other years, and do not read a fall as a supply signal without knowing the operating regime.

Retrieved 1 October 2026.

Monthly mean of daily reservoir storage published by the USGS in acre-feet and converted to millions of cubic metres. Months with fewer than 20 days of record are not published rather than averaged from a partial month.