Data collection

World Bank World Development Indicators

• Outside plausible range: 37

Examples:

• Municipal share of withdrawal for Brunei, 2022: 164.673913 outside 0–100
• Municipal share of withdrawal for Brunei, 2021: 164.673913 outside 0–100
• Municipal share of withdrawal for Brunei, 2020: 164.673913 outside 0–100
• Municipal share of withdrawal for Brunei, 2019: 164.673913 outside 0–100

Environment Agency Water Quality Archive

• Outside plausible range: 52

Examples:

• Nitrate as nitrogen for SPT FOR MISCELLANEOUS RIVER SAMPLES (DOES NOT INCLUDE CONTAMINATED SW) IN MERSEYSIDE, 2010: 826.2457333333333 outside 0–200
• Orthophosphate as phosphorus for MISC RIVER SAMPLES LUNE/WYRE, 2022: 67.63900000000001 outside 0–50
• Orthophosphate as phosphorus for SPT FOR MISCELLANEOUS RIVER SAMPLES (DOES NOT INCLUDE CONTAMINATED SW) IN CHESHIRE, 2019: 57.139346153846155 outside 0–50
• Orthophosphate as phosphorus for SPT FOR MISCELLANEOUS RIVER SAMPLES (DOES NOT INCLUDE CONTAMINATED SW) IN DISTRICT 7, 2001: 55.804964285714284 outside 0–50

Hub'Eau Hydrométrie — French river flow

• Outside plausible range: 6

Examples:

• Mean monthly river flow for L'Yser en Belgique [Roesbrugge], 2026: -0.004 outside 0–250000
• Mean monthly river flow for Le Lignon à Yssingeaux [QNR Versilhac-la-Valette], 2009: -0.011 outside 0–250000
• Mean monthly river flow for Le Lignon à Yssingeaux [QNR Versilhac-la-Valette], 2017: -0.171 outside 0–250000
• Mean monthly river flow for L'Allier à Monistrol-d'Allier [QNR], 2020: -0.001 outside 0–250000

SEPA — Scottish river flow, rainfall and groundwater

• Outside plausible range: 7

Examples:

• Monthly precipitation for Inchnadamph No 2, 2007: 6442451123 outside 0–3000
• Monthly precipitation for Inchnadamph No 2, 2008: 1610613060.8 outside 0–3000
• Monthly precipitation for Bogmuchals, 1993: 1610612764.6 outside 0–3000
• Monthly precipitation for Newtown Sewage Works, 2008: 1610612797.3 outside 0–3000

Hub'Eau Prélèvements — French water abstraction

• Outside plausible range: 1

Examples:

• Water abstracted, all purposes for France, 2013: 1018589.933046 outside 0–1000000

EIA — United States thermoelectric cooling water

• Outside plausible range: 1

Examples:

• Facility water consumption for Paradise, 2019: 3669.1617881133598 outside 0–2000

Bureau of Reclamation reservoir operations

• Outside plausible range: 105

Examples:

• Reservoir release for Willow Creek Reservoir, 1988: -0.015528593292387097 outside 0–250000
• Reservoir release for Willow Creek Reservoir, 2012: -0.9059047446273768 outside 0–250000
• Reservoir release for Willow Creek Reservoir, 2012: -3.74192969289984 outside 0–250000
• Reservoir release for Willow Creek Reservoir, 2012: -1.7924107169403867 outside 0–250000

Met Office HadUK-Grid areal series

• Publisher last updated: 03-Aug-2026 09:28

World Bank World Development Indicators

• Dropped 318 sector-share values across 106 country-years where the three shares did not sum to 100% (e.g. country-alb|2016-01-01, country-alb|2015-01-01, country-atg|1998-01-01). This is an upstream inconsistency, not a Hydrionis one, and the whole triple is withheld rather than a guess published.
• World Bank data is CC BY 4.0. Several water indicators are relayed from FAO AQUASTAT or the WHO/UNICEF JMP; the originating body is recorded on every observation.

Environment Agency Hydrology Data Explorer

• waterFlow: 356 stations collected of 356 selected; 972,537 daily readings failed quality control; 7,594 months withheld as incomplete
• groundwaterLevel: 409 stations collected of 409 selected; 127,047 daily readings failed quality control; 11 readings rejected as impossible for their own borehole

Environment Agency Water Quality Archive

• Nitrate as N: 1,253,837 results read, 33,220 below detection limit; 3,923 points published, 9,776 dropped as too short a record, 40,829 point-years dropped as too few samples, 1,347 dropped as mostly below detection
• Orthophosphate, reactive as P: 1,358,271 results read, 165,130 below detection limit; 3,877 points published, 11,102 dropped as too short a record, 44,569 point-years dropped as too few samples, 8,717 dropped as mostly below detection
• Ammoniacal Nitrogen as N: 1,419,959 results read, 501,106 below detection limit; 3,003 points published, 12,868 dropped as too short a record, 45,942 point-years dropped as too few samples, 27,317 dropped as mostly below detection
• Oxygen, Dissolved as O2: 1,242,781 results read, 59 below detection limit; 4,244 points published, 10,050 dropped as too short a record, 42,399 point-years dropped as too few samples, 0 dropped as mostly below detection
• Oxygen, Dissolved, % Saturation: 1,328,762 results read, 69 below detection limit; 4,470 points published, 11,104 dropped as too short a record, 45,676 point-years dropped as too few samples, 0 dropped as mostly below detection
• pH: 1,382,827 results read, 28 below detection limit; 4,637 points published, 11,751 dropped as too short a record, 49,736 point-years dropped as too few samples, 0 dropped as mostly below detection
• Temperature of Water: 1,452,858 results read, 10 below detection limit; 4,633 points published, 11,327 dropped as too short a record, 46,119 point-years dropped as too few samples, 0 dropped as mostly below detection
• Conductivity at 25 C: 775,159 results read, 31 below detection limit; 1,586 points published, 12,528 dropped as too short a record, 43,526 point-years dropped as too few samples, 0 dropped as mostly below detection
• Alkalinity to pH 4.5 as CaCO3: 930,523 results read, 16,866 below detection limit; 2,347 points published, 11,660 dropped as too short a record, 47,044 point-years dropped as too few samples, 1,031 dropped as mostly below detection
• Turbidity: 114,363 results read, 3,995 below detection limit; 373 points published, 2,595 dropped as too short a record, 3,242 point-years dropped as too few samples, 136 dropped as mostly below detection
• Solids, Suspended at 105 C: 776,426 results read, 140,639 below detection limit; 2,075 points published, 8,970 dropped as too short a record, 19,415 point-years dropped as too few samples, 5,036 dropped as mostly below detection
• BOD : 5 Day ATU: 828,897 results read, 214,720 below detection limit; 1,291 points published, 9,849 dropped as too short a record, 21,082 point-years dropped as too few samples, 8,562 dropped as mostly below detection
• Carbon, Organic, Dissolved as C: 186,334 results read, 233 below detection limit; 359 points published, 5,923 dropped as too short a record, 6,959 point-years dropped as too few samples, 10 dropped as mostly below detection
• Nitrogen, Total Oxidised as N: 1,394,836 results read, 45,326 below detection limit; 4,502 points published, 10,868 dropped as too short a record, 45,281 point-years dropped as too few samples, 1,696 dropped as mostly below detection
• Nitrite as N: 1,308,307 results read, 195,277 below detection limit; 3,576 points published, 10,767 dropped as too short a record, 40,747 point-years dropped as too few samples, 10,735 dropped as mostly below detection
• Phosphorus, Total as P: 234,853 results read, 14,706 below detection limit; 342 points published, 4,112 dropped as too short a record, 1,580 point-years dropped as too few samples, 501 dropped as mostly below detection
• Lead, Dissolved: 182,317 results read, 104,542 below detection limit; 153 points published, 4,924 dropped as too short a record, 6,437 point-years dropped as too few samples, 10,264 dropped as mostly below detection
• Cadmium, Dissolved: 141,613 results read, 73,494 below detection limit; 125 points published, 4,641 dropped as too short a record, 6,487 point-years dropped as too few samples, 6,760 dropped as mostly below detection
• Mercury, Dissolved: 52,655 results read, 46,790 below detection limit; 2 points published, 800 dropped as too short a record, 1,274 point-years dropped as too few samples, 4,718 dropped as mostly below detection
• Nickel, Dissolved: 183,035 results read, 74,933 below detection limit; 335 points published, 4,756 dropped as too short a record, 6,443 point-years dropped as too few samples, 7,045 dropped as mostly below detection
• Zinc, Dissolved: 173,989 results read, 32,130 below detection limit; 332 points published, 4,961 dropped as too short a record, 6,653 point-years dropped as too few samples, 2,722 dropped as mostly below detection
• Copper, Dissolved: 651,392 results read, 96,849 below detection limit; 2,234 points published, 6,176 dropped as too short a record, 7,642 point-years dropped as too few samples, 8,440 dropped as mostly below detection
• Arsenic, Dissolved: 68,828 results read, 40,501 below detection limit; 100 points published, 1,346 dropped as too short a record, 1,985 point-years dropped as too few samples, 3,962 dropped as mostly below detection
• Chromium, Dissolved: 166,937 results read, 122,385 below detection limit; 80 points published, 4,832 dropped as too short a record, 6,093 point-years dropped as too few samples, 12,727 dropped as mostly below detection
• Iron, Dissolved: 183,568 results read, 40,113 below detection limit; 565 points published, 4,147 dropped as too short a record, 6,715 point-years dropped as too few samples, 3,901 dropped as mostly below detection
• Manganese, Dissolved: 89,810 results read, 23,133 below detection limit; 128 points published, 3,781 dropped as too short a record, 5,354 point-years dropped as too few samples, 2,077 dropped as mostly below detection
• Aluminium, Dissolved: 48,957 results read, 13,199 below detection limit; 22 points published, 3,112 dropped as too short a record, 3,439 point-years dropped as too few samples, 1,119 dropped as mostly below detection
• Chloride: 584,681 results read, 810 below detection limit; 1,353 points published, 10,028 dropped as too short a record, 8,263 point-years dropped as too few samples, 27 dropped as mostly below detection
• Sulphate, Dissolved as SO4: 37,374 results read, 7,808 below detection limit; 107 points published, 1,801 dropped as too short a record, 1,875 point-years dropped as too few samples, 671 dropped as mostly below detection
• Sodium, Dissolved: 40,140 results read, 39 below detection limit; 136 points published, 1,885 dropped as too short a record, 2,118 point-years dropped as too few samples, 2 dropped as mostly below detection
• Calcium, Dissolved: 99,232 results read, 672 below detection limit; 92 points published, 4,214 dropped as too short a record, 6,228 point-years dropped as too few samples, 63 dropped as mostly below detection
• Magnesium, Dissolved: 74,163 results read, 29 below detection limit; 70 points published, 3,609 dropped as too short a record, 5,401 point-years dropped as too few samples, 0 dropped as mostly below detection
• Potassium, Dissolved: 40,446 results read, 23 below detection limit; 135 points published, 1,915 dropped as too short a record, 2,119 point-years dropped as too few samples, 1 dropped as mostly below detection

USGS National Water Information System

• 13 sites publish the same statistic under more than one USGS time series identifier; the longest series was used for each. 26 annual values differed between identifiers by more than 0.1% and were not reconciled — the shorter series was discarded rather than merged.
• 1750 United States gauges collected from 50 states; 566 sites dropped where the published statistics were shorter than 50 years
• Monthly means are available from the same service and are deliberately not collected: they would multiply the observation count roughly twelvefold for a marginal gain.

Hub'Eau Hydrométrie — French river flow

• 892 sites retained (360+ months, at most 10 per department); 828 qualifying sites were dropped by the per-department cap, 2532 had shorter records and 5031 had no published monthly series.
• Discharge is published in litres per second and stored in cubic metres per second, with the publisher’s unit recorded on every series.
• 3487 retained sites have been measured by more than one station. The longest series is used for each; the alternative stations are not blended, because their values for the same month frequently differ.

SEPA — Scottish river flow, rainfall and groundwater

• Q: 309 stations retained of 320; 10 had fewer than 120 months of record.
• Precip: 358 stations retained of 382; 23 had fewer than 120 months of record.
• GWLVL: 45 stations retained of 58; 13 had fewer than 120 months of record.
• Scottish coverage uses SEPA under the Open Government Licence. The National River Flow Archive holds a longer and better Scottish record but its licence forbids republishing it, so it is recorded in the source registry as assessed and refused rather than used.

USGS reservoir storage

• 92 reservoirs retained across 14 states, selected as the 12 longest records in each state meeting a 25-year threshold.
• Storage is stored as a volume rather than as a percentage of capacity, because the capacity figures published alongside do not state whether they are gross, usable or conservation storage, and the three differ substantially.
• 0 reservoir records and 4 state listings could not be fetched on this run and are carried forward.

Hub'Eau Prélèvements — French water abstraction

• 1,236,887 abstraction declarations aggregated into 491 annual series across 101 departments and France as a whole.
• 0 declarations were recorded by the water agency as not abstracted and were excluded rather than counted as withdrawals.
• 13,658 declarations carried a purpose outside the five mapped categories. They are included in the total and not attributed to any purpose.
• These are withdrawals, not consumption, and declared volumes, not licensed entitlement.

Hub'Eau Indicateurs des services — French water service performance

• 68,064 SISPEA service-year returns aggregated into 783 series for 101 departments and France.
• 129 returns carried none of the indicators Hydrionis holds and contributed nothing.
• Figures are medians across reporting services, not population-weighted means: the SISPEA served-population field is empty on every record this API returns, so no defensible weight exists and none was invented.
• 4,474 returns carried no resolvable commune code and contributed to the national figures only.
• The observatory publishes returns for 2008 to 2019 and has released nothing later through this API, so these series end there rather than being extended. Later years are requested on every run and will appear without a code change if they are published.

Hub'Eau Qualité de l'eau potable — French drinking water

• 732,942 regulatory results for 5 determinands across 101 departments, aggregated into 1387 annual series.
• 146,520 results (20.0%) were reported as below the laboratory detection limit. They are counted, published as a quantified-share series, and excluded from every mean rather than substituted with zero.
• 4,563 results carried no parsable numeric value and are counted in the denominator only.
• Only complete calendar years up to 2025 are aggregated; the current year is excluded rather than published as a partial annual figure.

Hub'Eau Piézométrie — French groundwater levels

• 641 piezometers held from a national network of 23,330, selected as the 10 longest records in each department meeting a 30-year and 1000-reading threshold.
• Capping per department trades some of the very best records for national coverage: a purely national ranking would concentrate in the Paris and Rhône basins and leave large regions unrepresented.
• 17 selected boreholes were read too irregularly to support monthly means and were not stored.
• 1 borehole records and 0 department listings could not be fetched on this run and are carried forward.

PEGELONLINE — German federal waterway gauges

• W (water level): 737 gauges stored of 737 carrying the series.
• Q (discharge): 92 gauges stored of 92 carrying the series.
• PEGELONLINE serves roughly 31 days of measurement however much history is requested, so this run holds about one month per gauge. Each run adds its window to what is already stored, so the German record deepens over time rather than sliding forward. Hydrionis does not hold decades of German history.
• 95 German waterways were recorded from the gauge network. They are held as registry candidates rather than published: the river profile is still the generic entity page, and a page per waterway is worth adding only once there is a profile worth visiting.
• GKD Bayern holds the deep Bavarian record under CC BY 4.0 and is not collected: its bulk download requires an email address and acceptance of terms through a form, and Hydrionis does not complete access-consent flows programmatically. It is registered as assessed and blocked.

Environment Agency — English water company resources performance

• Read 2 of 2 report editions. Matched 13 of 22 tables to a known measure by header text; the remainder are national summaries or measures Hydrionis does not hold. Collapsed 36 figures the report prints twice at different precision, keeping the finer printing.
• Only two editions of this report exist, so this is seven indicators over two regulatory years — not the long series Ofwat holds and does not serve to automated requests. Two years does not meet the five common years a composite utility index requires, so this deepens the utility layer without triggering an index.
• Figures use the English regulatory year running April to March and the company-reported water balance. They are not comparable with international non-revenue water percentages, which use a different denominator, nor with the French linear leakage index and network efficiency indicators, which normalise by network length rather than by property or person.

Rijkswaterstaat Waterinfo — Dutch national water monitoring

• WATHTE (water level): 328 stations stored of 705; 377 returned nothing for the selected years. Rejected 6,312,728 readings from predicted rather than measured series — Rijkswaterstaat returns astronomical tide predictions alongside measurements at the same timestamps, and only the process type distinguishes them; rejected a further 1,838,461 measured against a reference plane other than NAP; 25 stations offered more than one measured series and the longest was taken rather than interleaving instruments. Rejected 830,132 readings the publisher did not mark quality code 00, including its .999999E+38 no-measurement marker. Collapsed 1,004,534 repeated timestamps from overlapping response blocks, and found 2496 repeats whose values disagreed — the first was kept and the disagreement is reported rather than resolved. Refused 1,223 days with fewer than 108 readings; 186 days held more than one validation state and used the stronger alone rather than averaging across them.
• Q (discharge): 115 stations stored of 199; 84 returned nothing for the selected years. Rejected 69,355 readings from predicted rather than measured series — Rijkswaterstaat returns astronomical tide predictions alongside measurements at the same timestamps, and only the process type distinguishes them; 7 stations offered more than one measured series and the longest was taken rather than interleaving instruments. Rejected 142,942 readings the publisher did not mark quality code 00, including its .999999E+38 no-measurement marker. Collapsed 232,789 repeated timestamps from overlapping response blocks, and found 10734 repeats whose values disagreed — the first was kept and the disagreement is reported rather than resolved. Refused 892 days with fewer than 108 readings; 19 days held more than one validation state and used the stronger alone rather than averaging across them.
• Holds the 2025 calendar year. Rijkswaterstaat retains its record back to about 2013 at ten-minute resolution and does not discard it, so the depth Hydrionis does not yet hold remains available: one location-year is roughly 16 MB, and the full archive across the network is on the order of 190 GB. Hydrionis does not hold the 2013-present Dutch archive. Further years are added in batches, and each addition deepens the record instead of overwriting it.

SMHI — Swedish river discharge

• 694 stations stored of 720; 24 publish no corrected archive, almost all of them closed or very short-lived gauges; 2 returned a header with no values. 9,507,623 daily values across 87 main drainage basins.
• Quality as SMHI marks it: 9,109,579 checked and approved, 21,148 roughly checked, 376,896 not yet checked. All three published levels are kept, because the roughly-checked values sit inside continuous records rather than at their ends — dropping them would leave silent holes. Each series states which of its periods are which.
• Stored as one file per main drainage basin. Sweden’s daily archive is roughly 200 MB, which in a single file would be eight times the largest Hydrionis holds; split by basin, a page about one Swedish river reads only that river’s data.

OPW waterlevel.ie — Irish hydrometric network

• 450 stations stored of 450 carrying an OD sensor. Rejected 17,208 unparseable readings; refused 500 partial days.
• Every sensor’s parameter is confirmed against the publisher’s own station page before its values are read. The interface identifies a series only by a code, and the codes are not self-explanatory: sensor 0003 returns values around 12.9 that read perfectly as a water temperature and are the station’s battery voltage.
• The OPW serves about five weeks per station here; its longer record is on the separate Hydro-Data site, which Hydrionis does not scrape. Each run adds to what is already held, so the Irish record deepens over time rather than sliding forward. Hydrionis does not hold Ireland’s historical archive.

Syke — Finnish river discharge

• 3 basins exceeded 1,000,000 values and were split on Syke's own sub-basin boundaries: kokemaenjoki, kymijoki, vuoksi. A page about one gauge reads the whole file its series lives in, so a basin is divided before that becomes expensive rather than after.
• 671 stations stored of 711 listed; 40 hold fewer than 365 usable days. Basins: 62.
• Refused 622 values that Syke itself flags as possibly erroneous, and 0 that were empty or unparseable. Stored 35,586 interpolated values, which are a stated method rather than a doubt, and which each series describes.
• Daily discharge is taken exactly as Syke publishes it. Every station record also names the main drainage basin it sits in, so Finnish gauges join the water graph as they are collected rather than through a separate linkage pass.

Eurostat — European freshwater abstraction

• 405 series across 40 countries, from 23,447 cells; skipped 459 cells for aggregates and units Hydrionis does not hold as countries; skipped 14,710 for sector and source combinations without a metric; deferred 131 to a national register Hydrionis already holds in more detail.
• Every value is reported actual abstraction. Eurostat publishes no licensed or authorised volumes, so nothing here can be confused with an entitlement. Abstraction is also not consumption, and no return flow is estimated.
• The sector codes double-count by design — manufacturing cooling is part of manufacturing, and irrigation and aquaculture are parts of agriculture. Only the leaves Hydrionis holds a metric for are stored, so a page cannot sum a country’s sectors to more than its own total.

EIA — United States thermoelectric cooling water

• 838 generating stations with at least one complete reported year, from 160,585 monthly rows across 11 annual workbooks. 441 distinct named water sources.
• Refused 488 plant-years in which the operator reported fewer than twelve months. A year assembled from part of itself is a different quantity with a year's name on it.
• Refused 2 plant-years reporting negative consumption. EIA derives the figure as a difference, so a plant returning more than it withdrew reports below zero; that is a real outcome and not one this metric can hold, since consumption is the part of a withdrawal that did not come back.
• Refused a further 104 plant-years reporting more water consumed than withdrawn, which cannot happen. Both figures are dropped for those years: one of the two is wrong, nothing says which, and correcting an operator's statutory return is not Hydrionis's to do.
• Withdrawal, consumption and reclaimed water are stored as three separate metrics and are never combined. For cooling water the difference between withdrawal and consumption is a factor of a hundred at a once-through plant, so substituting one for the other is not a rounding matter.
• 788 of 838 facilities carry an operator name, a position and an ownership record from the companion EIA-860 return. Ownership is a percentage a named company filed about a specific generator, not a corporate hierarchy Hydrionis assembled.
• These are facility figures. A utility operating fifteen plants appears fifteen times and the fifteen are never summed here: a company-wide total is assembled on a different basis and belongs to the company, not to any of its sites.

IMGW — Polish hydrological network

• 898 stations stored of 913 listed: 875 water levels, 646 discharges, 104 water temperatures. Refused 71 readings older than 14 days — a rolling snapshot repeats an old value indefinitely, and storing it on every run would fill the record with one ancient point per station.
• 898 of 898 stations name the watercourse they gauge, so Polish gauges join the water graph as they are collected rather than through a separate linkage pass.
• IMGW serves the latest reading per station and nothing older. Each run adds to what is already held, so the Polish record deepens over time rather than sliding forward. Hydrionis does not hold Poland’s hydrological archive, which IMGW releases on request.

NOAA GHCN-Daily — daily climate at stations near Hydrionis water measurement

• 146 of 146 stations fetched. 17,979 values were withheld because they failed NOAA's own quality checks.

NOAA nClimDiv drought indices by US climate division

• phdi: climdiv-phdidv-v1.0.0-20260806, 344 divisions.
• pdsi: climdiv-pdsidv-v1.0.0-20260806, 344 divisions.
• spi-1: climdiv-sp01dv-v1.0.0-20260806, 357 divisions.
• spi-12: climdiv-sp12dv-v1.0.0-20260806, 357 divisions.

FAOSTAT — crop production, irrigated area and land cover

• 140,057 values held across 3781 series for 6 crops, two irrigated-area measures and eight land-cover categories.
• 62,746 values imputed by a receiving agency were not held: Hydrionis does not backfill, and holding an upstream backfill is the same act at one remove.
• 1,126,182 rows were FAO's own regional and world aggregates, which are not adopted under Hydrionis region names. Sub-Saharan Africa is among them despite an area code below the usual aggregate threshold.
• 44 FAOSTAT areas did not resolve to a Hydrionis country and were skipped: Belgium-Luxembourg (M49 058, no ISO3); China (M49 159, no ISO3); China, Taiwan Province of (M49 158, no ISO3); Cook Islands (COK, not a Hydrionis country); Czechoslovakia (M49 200, no ISO3); Ethiopia PDR (M49 230, no ISO3); French Guiana (GUF, not a Hydrionis country); Guadeloupe (GLP, not a Hydrionis country); Martinique (MTQ, not a Hydrionis country); Niue (NIU, not a Hydrionis country); Réunion (REU, not a Hydrionis country); Serbia and Montenegro (M49 891, no ISO3); Sudan (former) (M49 736, no ISO3); USSR (M49 810, no ISO3); Yugoslav SFR (M49 890, no ISO3); American Samoa (ASM, not a Hydrionis country); Anguilla (AIA, not a Hydrionis country); Aruba (ABW, not a Hydrionis country); Ascension, Saint Helena and Tristan da Cunha (SHN, not a Hydrionis country); Bermuda (BMU, not a Hydrionis country); Bonaire, Sint Eustatius and Saba (BES, not a Hydrionis country); British Virgin Islands (VGB, not a Hydrionis country); Cayman Islands (CYM, not a Hydrionis country); Channel Islands (M49 830, no ISO3); Curaçao (CUW, not a Hydrionis country); Falkland Islands (Malvinas) (FLK, not a Hydrionis country); Gibraltar (GIB, not a Hydrionis country); Isle of Man (IMN, not a Hydrionis country); Mayotte (MYT, not a Hydrionis country); Montserrat (MSR, not a Hydrionis country); Netherlands Antilles (former) (M49 530, no ISO3); Norfolk Island (NFK, not a Hydrionis country); Northern Mariana Islands (MNP, not a Hydrionis country); Pacific Islands Trust Territory (M49 582, no ISO3); Pitcairn (PCN, not a Hydrionis country); Saint Barthélemy (BLM, not a Hydrionis country); Saint Martin (French part) (MAF, not a Hydrionis country); Saint Pierre and Miquelon (SPM, not a Hydrionis country); Sint Maarten (Dutch part) (SXM, not a Hydrionis country); Tokelau (TKL, not a Hydrionis country); Turks and Caicos Islands (TCA, not a Hydrionis country); United States Virgin Islands (VIR, not a Hydrionis country); Wallis and Futuna Islands (WLF, not a Hydrionis country); Western Sahara (ESH, not a Hydrionis country).

Wildfire burned area near Hydrionis measurement points

• 34 pages fetched; 67,544 perimeters returned, 66,934 usable for 1984–2019.
• 610 records were outside the covered years or carried no usable area or centroid, including a sentinel year of 9999.
• 1881 of 2638 United States measurement points had at least one fire within 50 km; the rest are not given a series rather than being given a row of zeros.

Environment Agency freshwater macroinvertebrate indices

• 2,611 of 30,693 sites met the record-length rule of at least 30 samples across at least 15 years; 10,444 series over 2,611 sites were built from 118,168 of their samples.
• 162,462 samples belong to sites with too short a record to show change and are not held. They are not lost data: the archive remains complete at the publisher, and the rule is about what Hydrionis can say rather than what exists.
• 1,816 field replicate values shared a site, date and version with a value already held and were dropped rather than averaged into a figure the Agency did not publish.

Environment Agency freshwater fish density

• 5,412 series over 1,804 sites, from 24,937 qualifying electrofishing depletion surveys and 3 species.
• 26,145 values are densities from a published estimate and 48,666 are zeros reconstructed from surveys that qualified but recorded no row for that species. The zeros are the majority for every species and are the whole point: a row exists only where a species was caught, so holding only those would have published Atlantic salmon as a widespread species on the strength of the 3,863 surveys that found it while discarding the 21,074 that did not.
• 120 of those surveys caught no fish of any species at all, which the publisher flags directly.
• Excluded as not comparable with a depletion estimate: 182,173 rows of another survey strategy, mostly single-catch; 28,668 rows caught by seine net or fixed trap; 1,943 rows from species-selective surveys, where a species being absent may mean nobody looked for it.
• 265 rows fished less than 50 m², where dividing by the area extrapolates a river from a few square metres. The extreme case is 58 trout in one square metre, which would have been published as 5,800 per 100 m².

Defra water and wetland bird indices

• 16 series held: 8 for the UK and 8 for England, across 8 water and wetland bird groups.
• The unsmoothed index is held. The smoothed trend line published beside it is a model with the year-to-year variation removed, and that variation is where a drought or a hard winter would show.
• Wetland Bird Survey site counts, which the wintering indices are built from, are available only through a data request service and are not openly licensed. The indices derived from them are official statistics under the Open Government Licence and are what is held.

Environment Agency aquatic insect richness

• 2,611 series from 118,168 samples at the same 2,611 long-record sites the community indices use.
• 9,611 of those samples contained no mayfly, stonefly or caddisfly at all and are held as zero. They are results rather than gaps — a reach too degraded for any of the three sensitive orders — and dropping them would have raised every site's richness and hidden the worst rivers.
• 2,159,881 EPT taxon records were read from 7.6 million and discarded after counting; no taxon list is stored. 487 EPT taxa appear in the publisher's dictionary and 484 of them resolve to a family.
• 652 records identified no further than the order contributed no family and were skipped rather than counted as one.
• 1,180,930 EPT records belong to samples at sites with too short a record to show change and are not held.
• Total abundance and Odonata richness were both computed and refused: a three-minute kick is semi-quantitative, and its dragonfly catch is incidental — the median sample containing any Odonata holds one taxon.

EPA CASTNET air chemistry and dry deposition

• 1132 series over 123 sites with at least 200 weekly samples: five measured concentrations and five modelled dry deposition fluxes, kept as separate metrics because a concentration and a flux are different quantities.
• 725,524 measured concentrations and 699,911 modelled flux values held.
• 8,263 weeks were below the detection limit and are held as censored observations, carrying the operator, the threshold and the kind of limit rather than a number. Nitrate is the most affected at 3.2% of weeks, then sulphur dioxide at 1.3%; the rest are under 1%.
• 29,966 values were flagged invalid, not analysed, or with failed flow, and carry no observation at all — which is a different absence from a week below detection.
• 58,686 of the flux weeks had their deposition velocity entirely substituted for missing inputs. They are held as the publisher publishes them, but the fluxes are modelled throughout and the substitution is concentrated in recent years.
• 40 chemistry records belong to sites absent from the site file or lacking coordinates and are not held.

USGS annual peak flow and catchment area

• 2236 gauges with an instantaneous annual peak series, 175008 peaks in total
• 8455 published peaks are marked by USGS as maximum daily averages rather than instantaneous maxima and are not held under this measure. A daily average is lower than the instantaneous peak of the same day, and holding the two together would understate every flood in the series that contained them.
• 133 peaks are published as a bound rather than a value — the discharge was known to be above or below a figure but not measurable — and are held as censored observations carrying that bound.
• 3436 peaks are marked by USGS as estimates rather than measurements. They are held, because an estimated peak is the publisher's best account of a real flood, and the qualification travels with the series.
• 926 published peaks carry a year but not an exact day, and are not held. Placing them on the first of the month would be inventing the date of a flood.
• 2257 catchment areas collected, of which 495 are contributing areas the publisher distinguishes from the topographic basin. The area is what allows a discharge to be expressed as a depth over the land that produced it, and so compared with rainfall.

NRCS SNOTEL snow water equivalent

• 847 automated snow stations collected, 375923 station-months from 1963; 38 stations held fewer than 60 usable months and were not stored
• 124527 of those months are zero, which is the summer at almost every station: the snowpack has melted and the instrument reports that it has. Those months are stored as measurements rather than as absences, because they are what shows when the melt finished.
• The same service publishes snow water equivalent from manual snow courses, some reaching back to 1910. Those are a different measurement — a person taking cores near the first of the month rather than an instrument weighing a pillow daily — and are deliberately not mixed into this record.

United States Drought Monitor

• 51 areas collected — the contiguous United States and each state — with 70941 weekly assessments from 2000-01-04 to 2026-08-25
• These are the Drought Monitor’s own categories, which are cumulative: the share shown for a category includes every area in a more severe one. Hydrionis stores them as published rather than converting them into exact bands.
• Drought status here is an assessment made weekly by named author agencies, and is deliberately held apart from the drought indices Hydrionis calculates. Hydrionis does not derive a drought status of its own, and nothing in its own indices should be read as one.
• 2 weekly figures did not follow the publisher's cumulative ordering, where a more severe category covered more area than a less severe one. They are stored as published and counted here, because the ordering is the publisher's to define.

USGS groundwater levels

• 43 observation wells held across 36 states, selected as the 12 longest records in each state meeting a 25-year threshold.
• Depth to water is stored rather than groundwater elevation, because it is the quantity the United States actually publishes: 4,462 wells report a daily mean depth against 510 on the 1988 vertical datum and 203 on the 1929 one. The two are not interchangeable and are not combined.
• Capping per state trades some of the longest records for national coverage: of the wells meeting the span threshold, roughly a fifth are in Georgia and a seventh in New Jersey, and a national ranking would have returned little else.
• 2 selected wells were read too irregularly to support monthly means and were not stored.
• 43 wells are held without aquifer or construction detail. Their water tables are complete; only the descriptive record is missing, because the publisher's request allowance was reached before it could be collected.
• 2 well records could not be fetched on this run and are carried forward.
• The publisher's hourly request allowance was reached partway through this run, so 213 wells were not asked for. Everything already held is retained and the remaining wells are carried forward to the next run rather than being treated as withdrawn.

Bureau of Reclamation reservoir operations

• 273 operating series held for 91 federal reservoirs, selected as the 25 longest-record reservoirs in each Reclamation region meeting a 20-year threshold.
• Storage is published as a volume and not as a percentage of capacity. The Bureau publishes no reservoir capacity of any kind — of the 782 quantities in its catalogue, the only ones named capacity are the generating capacity of the powerplants, in kilowatts — so there is no denominator to divide by, and Hydrionis does not invent one.
• Reservoir levels are held against each operator’s own datum, which differ: most are the 1988 national vertical datum, but Lake Mead is published on a local datum established at Hoover Dam in 1912. Levels are not comparable between reservoirs.
• 25 catalogued series are model output rather than measurement — basin-study projections running as far as 2099 under the same names as the observed record — and are not held. Hydrionis stores what was observed at these reservoirs, not what a study projects for them.
• 251 catalogued series report a reservoir quantity as a daily volume rather than as a rate. They are left alone rather than divided by a day length the publisher did not state.
• 25 series could not be fetched on this run and are carried forward.