Hydrionis API | Hydrionis

Endpoints

Endpoint	Returns
/api/v1/index.json	Service index: available endpoints, record counts and build metadata.
/api/v1/metrics.json	Every metric with its definition, unit, native geography, aggregation rules and comparability notes.
/api/v1/sources.json	The full source registry including structured rights for each source.
/api/v1/geographies.json	Every geography: world, continents, regions, countries, UK nations, councils, utility areas, basins and oceans.
/api/v1/entities.json	Every entity: utilities, water bodies, aquifers, infrastructure, events, enforcement, bottled waters, sectors, standards and more.
/api/v1/observations.json	Every observation with metric, subject, period, value, unit, basis, source, confidence and retrieval date.
/api/v1/observations/by-metric/{metricId}.json	All observations for one metric.
/api/v1/observations/by-subject/{subjectId}.json	All observations for one country, place or entity.
/api/v1/guides.json	Guide index with slugs, sections, summaries and search intents.
/api/v1/diagrams.json	Diagram index with titles, summaries and text alternatives.
/api/v1/tools.json	Tool registry with method and caveats for each.

Example

curl https://hydrionis.com/api/v1/observations/by-subject/country-gbr.json

{
  "subjectId": "country-gbr",
  "count": 8,
  "observations": [
    {
      "id": "renewable-water-resources::country-gbr::1990-01-01",
      "metricId": "renewable-water-resources",
      "value": 147,
      "unit": "km³/yr",
      "period": { "start": "1990-01-01", "end": "2022-12-31", "kind": "multi-year" },
      "basis": "derived",
      "sourceId": "fao-aquastat",
      "confidence": "medium",
      "qualifier": "transcribed-pending-ingestion",
      "retrieved": "2026-08-23"
    }
  ]
}

Fields you should not ignore

basis — whether the value was measured, reported, calculated, derived, aggregated, estimated, modelled or inferred. The last three are not observations.
qualifier — currently carries transcribed-pending-ingestion on values hand-loaded from published sources rather than ingested automatically.
confidence — high, medium or low, set per observation.
sourceId — resolves against /api/v1/sources.json, which carries the licence terms governing what you may do with the value.