{"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. Every record carries an official source plus a record_hash (canonical sha256, recomputable offline for self-verification; cross-check with free /gauge/verify).","note":"Free sample: this is the COMPLETE REAL RECORD that the paid /gauge returns - it includes the common ruler (normalized_index, which quantifies how deep the reading is), the statistical ruler (same-season percentile), a self-verifiable record_hash, and provenance (age computed at request time plus the freshness criterion). Source independence is labelled per record in sources[].independent; source_agreement_cv measures cross-source agreement (null when only one independent source exists, a coefficient of variation otherwise). Try before you buy","sample":{"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},"previous":{"gauge_height_ft":21.19},"change":{"period":"vs_24h_ago (instantaneous vs instantaneous, same basis)","gauge_height_ft":{"delta":-1.95,"direction":"falling","direction_reason":null}},"trend_7d":[10.37,11.13,15.35,21.49,23.82,23.19,21.15],"sources":[{"name":"USGS Water Services","role":"sole data source (IV real-time current value; dv daily mean supplies trend_7d)","as_of":"2026-10-09T13:30:00.000Z","value":19.24,"weight":1,"independent":true},{"name":"NOAA NWS/NWPS","role":"Flood threshold and official classification provider; its observation is the official relay channel of the same USGS sensor (NWPS self-reports usgsId=07010000), not an independent second source","as_of":"2026-10-09T13:30:00Z","value":19.24,"weight":0,"relay_of":"USGS 07010000","independent":false}],"source_agreement_cv":null,"standard_ruler":{"band":"below_action","note":"Severity = normalized_index, comparable across sites on the same scale; thresholds are the official values, interpolation is plain arithmetic and never a forecast","unit":"ft","bands":["action","minor","moderate","major"],"scale":"flood_stage","metric":"gauge_height_ft","source":"NOAA NWS/NWPS","standard":"NWS flood category thresholds (official; not judged by this API)","thresholds":{"major":40,"minor":30,"action":28,"moderate":35},"index_basis":"normalized_index: piecewise linear (action=0/minor=1/moderate=2/major=3); below the first band = (value - first threshold) / first threshold, clamped to [-1,0); above the top band it is unbounded. pct_to_action = value / first alert threshold (bounded, 1 = at the first alert)","current_value":19.24,"pct_to_action":0.687,"normalized_index":-0.313,"official_category":"no_flooding","distance_to_action":8.76},"stat_ruler":{"doy":282,"note":"Purely descriptive statistics: where the current value falls against the same season of the last few years of official data (the seasonal window removes cyclical confounding). Not a forecast and not a risk judgement. Method and sample size are disclosed so you can recompute it yourself.","unit":"ft","basis":"day-of-year seasonal window","range":{"max":21.49,"min":-3.09},"scale":"empirical_percentile_seasonal","method":"Empirical percentile over the last 5 years of official daily means, using the same-season +/-15 day window (day-of-year=282), linearly interpolated. current_percentile = the share of days in that same-season history that are not above the current value.","metric":"gauge_height_ft","n_days":154,"source":"USGS Water Services daily values (official raw data; the seasonal percentile is computed by this API)","n_total":1802,"percentiles":{"p05":-2.54,"p10":-2.33,"p25":-1.482,"p50":-0.195,"p75":1.465,"p90":3.94,"p95":13.687},"source_tier":"T1","window_years":5,"current_value":19.24,"frequency_label":"unusual (tail, under 5% of the time)","current_percentile":0.994,"season_window_days":15},"summary_zh":"Mississippi River at St. Louis, MO 的 gauge_height_ft 為 19.24,較前值 falling。統一尺(flood_stage,ft;官方閾值):action 28 / minor 30 / moderate 35 / major 40;深淺 pct_to_action=0.687(0~1,1=達 action)、嚴重度 normalized_index=-0.313(action=0/minor=1/moderate=2/major=3,跨站可比)、band「below_action」;現距 action 8.76 ft;NWS 官方分類「no_flooding」(官方閾值+純算術內插,非本 API 判斷/預測,深淺可量化)。統計尺(近 5 年·同季節窗 ±15 日,n=154 日;經驗百分位):現值落在同季節第 99 百分位 → 屬「不尋常(尾端 <5% 時間)」;同季節區間 -3.09–21.49、中位數 -0.195(方法:USGS 官方日均值 day-of-year 季節窗線性內插百分位,可自算複核;純統計描述非預測)","source_ref":"https://waterdata.usgs.gov/monitoring-location/07010000/","source_tier":"T1","record_hash":"sha256:4a9233dd89f1f8c8305832386ae789eeea9ff163477d51a7c52b8e503490ed1c","hash_core_version":4,"ots_status":"pending","lifecycle":null,"summary_en":"Mississippi River at St. Louis, MO: 19.24 ft gauge height - no flooding, 8.76 ft below the first official alert (action stage 28 ft). seasonal percentile 0.994 (unusual). falling vs 24h ago.","provenance":{"served_from":"GAUGE stored snapshot (SQL) - not a live upstream API call at request time","data_as_of":"2026-10-09T13:30:00.000Z","oldest_leg_as_of":"2026-10-09T13:30:00.000Z","data_age_hours":0,"age_hours_now":1.3,"freshness":"fresh","freshness_basis":"cadence=daily; fresh<=24h; recent<=192h; dead_source>1440h; age_basis=request-time(now minus observed_at)","data_lineage":[{"signal":"hydrology.river-level","independent_dimension":"hydrology-riverflow","traceable_to":"USGS / NOAA NWPS","uncertainty":"single-source-no-CI","observed_at":"2026-10-09T13:30:00.000Z","record_hash":"sha256:4a9233dd89f1f8c8305832386ae789eeea9ff163477d51a7c52b8e503490ed1c"}],"validation_status":"not-yet-backtested (screening-level; framework Ch19 historical baseline still being built)","note":"Non-real-time decisions are served from stored data to avoid upstream API latency; use for decisions within this data cadence. Timestamps are UTC."}}}