{"nature":"This API supplies data organisation and trend description only. It is not a recommendation to act; the decision is yours. Purely descriptive - no judgement, no prediction. Official source plus record_hash; verify with the free /gauge/verify.","tier":"raw(free base)","record_hash_verifiable":{"mode":"via-endpoint","note":"This response is a projected delivery (some core fields are omitted to control size). Cross-check record_hash with the free /gauge/verify, or buy /gauge to get the complete core for offline recomputation."},"note":"The hydrology CURRENT reading is free (equivalent to the public USGS output). Cross-period comparison (previous/change/trend_7d, on the same basis: real-time against real-time), the official and statistical rulers (band/percentile), and source tiering plus independence labelling (source_tier / sources[].independent) are our added value, not public data. Add-ons: /gauge/ruler, /gauge/calibrated, /gauge/strata, /gauge/history, or pay once for the full /gauge. Current price of each endpoint is at /manifest.","deprecation":{"effective_date":"2026-08-08","enforced_date":"2026-09-12","fields_removed":["previous","change","trend_7d","sources","source_agreement_cv","source_tier"],"status":"enforced","reason":"Only current is equivalent to the public USGS output. Cross-period comparison (on the same basis: real-time against real-time), source tiering and independence labelling are our own processing.","use_instead":{"all":"/gauge (full single-signal delivery)","price_source":"/manifest"},"unchanged":"The hydrology current reading (current), record_hash, and source_ref stay free. This endpoint is limited to the single hydrology.* line and is kept as a try-before-you-buy shop window."},"signal_id":"hydrology.river-level","entity":"07010000","entity_name":"Mississippi River at St. Louis, MO","snapshot_date":"2026-10-09","observed_at":"2026-10-09T13:30:00.000Z","data_age_hours":0,"current":{"gauge_height_ft":19.24},"source_ref":"https://waterdata.usgs.gov/monitoring-location/07010000/","record_hash":"sha256:4a9233dd89f1f8c8305832386ae789eeea9ff163477d51a7c52b8e503490ed1c"}