HydrionisGlobal Water Intelligence
Monitored reservoir

Alder Reservoir At Alder, WA

United States Geological Survey reservoir gauge 12085000 in WA, with published storage from 1965.

Storage record12085000

Storage now, against this reservoir's own record

226.87 Mm³
Stored, August 2026
37th
Percentile among 61 Augs on record
+6.1%
Against the Aug 1991–2020 average
+27.0%
Change over the 12 months to 2026-08

Storage in August 2026 was around the middle of the Aug record, ranked against 61 other Augs held for this reservoir.

Storage, 1965–2026

Monthly mean storage
730 monthly values, 1965 to 2026
Monthly mean storageMonthly mean storage: Alder Reservoir At Alder, WA in Mm³, from 1965.75 to 2026.5833333333333.0100200300Mm³1965.751973.51981.16666666666671988.83333333333331996.52004.16666666666672011.83333333333332019.5Year

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 730 periods, evenly spaced across the record. Every value is in the download and the API; a table of all 730 would be longer than this page and unusable with a screen reader.
PeriodAlder Reservoir At Alder, WA (Mm³)
October 1965248
January 1966157
May 1966259
August 1966285
November 1966144
February 1967264
May 1967166
August 1967285
November 1967249
February 1968275
June 1968284
September 1968280
December 1968266
March 1969118
June 1969280
September 1969273
December 1969185
March 1970239
June 1970230
September 1970253
December 1970205
March 1971254
June 1971250
September 1971269
December 1971131
March 1972243
June 1972255
September 1972273
December 1972191
March 1973122
July 1973243
October 1973179
January 1974241
April 1974187
July 1974269
October 1974227
January 1975251
April 1975136
July 1975271
October 1975254
January 1976258
April 1976139
July 1976279
October 1976222
January 1977151
April 1977181
July 1977280
October 1977188
January 1978193
April 1978178
August 1978282
November 1978220
February 1979187
May 1979276
August 1979237
November 1979178
February 1980241
May 1980278
August 1980262
November 1980231
February 1981243
May 1981281
August 1981250
November 1981220
February 1982259
May 1982261
August 1982246
November 1982211
February 1983247
May 1983241
September 1983259
December 1983222
March 1984245
June 1984269
September 1984244
December 1984205
March 1985137
June 1985278
September 1985204
December 1985161
March 1986264
June 1986270
September 1986192
December 1986233
March 1987239
June 1987260
September 1987201
December 1987212
March 1988217
June 1988279
October 1988204
January 1989245
April 1989232
July 1989258
October 1989177
January 1990238
April 1990257
July 1990273
October 1990192
January 1991232
April 1991260
July 1991279
October 1991194
January 1992207
April 1992229
July 1992181
October 1992119
January 1993138
April 1993233
July 1993248
November 1993132
February 1994174
May 1994222
August 1994168
November 1994169
February 1995227
May 1995237
August 1995200
November 1995220
February 1996225
May 1996237
August 1996204
November 1996157
February 1997213
May 1997231
August 1997253
November 1997224
February 1998213
May 1998231
August 1998237
December 1998229
March 1999214
June 1999252
September 1999227
December 1999229
March 2000198
June 2000246
September 2000179
December 200098.0
March 2001125
June 2001254
September 2001183
December 2001218
March 2002211
June 2002253
September 2002195
December 2002121
March 2003239
June 2003226
September 2003158
January 2004168
April 2004207
July 2004223
October 2004215
January 2005186
April 2005222
July 2005233
October 2005163
January 2006240
April 2006192
July 2006243
October 2006144
January 2007231
April 2007221
July 2007187
October 2007134
January 2008196
April 2008170
July 2008258
October 2008178
February 2009195
May 2009236
August 2009207
November 2009174
February 2010194
May 2010228
August 2010239
November 2010215
February 2011232
May 2011215
August 2011225
November 2011144
February 2012213
May 2012248
August 2012243
November 2012193
February 2013175
May 2013234
August 2013234
November 2013191
March 2014245
June 2014248
September 2014200
December 2014224
March 2015229
June 2015197
September 2015142
December 2015240
March 2016254
June 2016199
September 2016162
December 2016180
March 2017246
June 2017255
September 2017189
December 2017216
March 2018181
June 2018242
September 2018147
December 2018163
April 2019209
July 2019202
October 2019139
January 2020222
April 2020221
July 2020255
October 2020209
January 2021237
April 2021185
July 2021252
October 2021178
January 2022235
April 2022221
July 2022252
October 2022183
January 2023187
April 2023168
July 2023217
October 2023142
January 2024190
May 2024233
August 2024231
November 2024174
February 2025184
May 2025214
August 2025179
November 2025157
February 2026198
May 2026249
August 2026227

The reservoir's year

Seasonal storage profile
Each calendar month's reference average, against the most recent year
Seasonal storage profileSeasonal storage profile: 1991–2020 average, Most recent 12 months in Mm³, from 1 to 12.0100200Mm³123456789101112Month1991–2020 average 1: 201 Mm³1991–2020 average 2: 209 Mm³1991–2020 average 3: 206 Mm³1991–2020 average 4: 220 Mm³1991–2020 average 5: 232 Mm³1991–2020 average 6: 241 Mm³1991–2020 average 7: 232 Mm³1991–2020 average 8: 214 Mm³1991–2020 average 9: 189 Mm³1991–2020 average 10: 161 Mm³1991–2020 average 11: 169 Mm³1991–2020 average 12: 191 Mm³Most recent 12 months 1: 214 Mm³Most recent 12 months 2: 198 Mm³Most recent 12 months 3: 226 Mm³Most recent 12 months 4: 247 Mm³Most recent 12 months 5: 249 Mm³Most recent 12 months 6: 249 Mm³Most recent 12 months 7: 242 Mm³Most recent 12 months 8: 227 Mm³Most recent 12 months 9: 156 Mm³Most recent 12 months 10: 121 Mm³Most recent 12 months 11: 157 Mm³Most recent 12 months 12: 209 Mm³
  • 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
Period1991–2020 average (Mm³)Most recent 12 months (Mm³)
Jan201214
Feb209198
Mar206226
Apr220247
May232249
Jun241249
Jul232242
Aug214227
Sep189156
Oct161121
Nov169157
Dec191209

Why this page shows a volume and not a percentage

Rate and persistence

+4.02 Mm³
Mean change 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

Alder Reservoir At Alder, WA
Gauge location
Alder Reservoir At Alder, WAAlder Reservoir At Alder, WA — 226.87 Mm³Alder Reservoir At Alder, WA — 226.87 Mm³

About this data

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 existMeasured
Period held1965–2026
Completeness98.1% 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.
Continuity98% of the months between 1965 and 2026 are held. Monthly means of the publisher's own daily record.
Last read from the publisher2026-10-01
RedistributionPermitted by the upstream licences
Commercial reusePermitted by the upstream licences. No Hydrionis access tier can widen this.
MethodologyHow this was produced

Use this data

Use this data

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), Alder Reservoir At Alder, WA reservoir records, accessed 2026-10-05, hydrionis.com/reservoirs/reservoir-usgs-12085000/

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 Alder Reservoir At Alder, 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

730 monthly observations 1965–2026 Mm³
Spatially aggregatedHigh confidenceAugust 2026

Source: USGS — National Water Information System, 12085000. 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.

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