United States Snow Hydrology Dataset

What this looks like

One real series from the dataset, and real rows from the head of its published extract. Neither is a mock-up: the rows below are the same rows, unchanged, that are in the file you would download.

Sample rows

12 of 470,842 rows Taken from the start of observations-snow-ice-us-nrcs-snotel.csv. These are sample rows, not the dataset.

Sample rows from the United States Snow Hydrology Dataset extract
`metric_id`	`subject_id`	`subject_kind`	`value`	`censored`	`censor_operator`	`censor_threshold`	`censor_limit`	`censor_reported`	`unit`	`period_start`	`period_end`	`period_kind`	`basis`	`confidence`	`source_id`	`source_ref`	`qualifier`	`superseded`	`retrieved`
snow-water-equivalent	snotel-1000-or	geography	4.424516	—	—	—	—	—	mm	2000-10-01	2000-10-31	month	aggregated	high	us-nrcs-snotel	SNOTEL station 1000:OR:SNTL, snow water equivalent	—	—	2026-10-01
snow-water-equivalent	snotel-1000-or	geography	32.596667	—	—	—	—	—	mm	2000-11-01	2000-11-30	month	aggregated	high	us-nrcs-snotel	SNOTEL station 1000:OR:SNTL, snow water equivalent	—	—	2026-10-01
snow-water-equivalent	snotel-1000-or	geography	153.710968	—	—	—	—	—	mm	2000-12-01	2000-12-31	month	aggregated	high	us-nrcs-snotel	SNOTEL station 1000:OR:SNTL, snow water equivalent	—	—	2026-10-01
snow-water-equivalent	snotel-1000-or	geography	267.355484	—	—	—	—	—	mm	2001-01-01	2001-01-31	month	aggregated	high	us-nrcs-snotel	SNOTEL station 1000:OR:SNTL, snow water equivalent	—	—	2026-10-01
snow-water-equivalent	snotel-1000-or	geography	366.757857	—	—	—	—	—	mm	2001-02-01	2001-02-28	month	aggregated	high	us-nrcs-snotel	SNOTEL station 1000:OR:SNTL, snow water equivalent	—	—	2026-10-01
snow-water-equivalent	snotel-1000-or	geography	448.187097	—	—	—	—	—	mm	2001-03-01	2001-03-31	month	aggregated	high	us-nrcs-snotel	SNOTEL station 1000:OR:SNTL, snow water equivalent	—	—	2026-10-01
snow-water-equivalent	snotel-1000-or	geography	448.902667	—	—	—	—	—	mm	2001-04-01	2001-04-30	month	aggregated	high	us-nrcs-snotel	SNOTEL station 1000:OR:SNTL, snow water equivalent	—	—	2026-10-01
snow-water-equivalent	snotel-1000-or	geography	139.863871	—	—	—	—	—	mm	2001-05-01	2001-05-31	month	aggregated	high	us-nrcs-snotel	SNOTEL station 1000:OR:SNTL, snow water equivalent	—	—	2026-10-01
snow-water-equivalent	snotel-1000-or	geography	0	—	—	—	—	—	mm	2001-06-01	2001-06-30	month	aggregated	high	us-nrcs-snotel	SNOTEL station 1000:OR:SNTL, snow water equivalent	—	—	2026-10-01
snow-water-equivalent	snotel-1000-or	geography	0	—	—	—	—	—	mm	2001-07-01	2001-07-31	month	aggregated	high	us-nrcs-snotel	SNOTEL station 1000:OR:SNTL, snow water equivalent	—	—	2026-10-01
snow-water-equivalent	snotel-1000-or	geography	0	—	—	—	—	—	mm	2001-08-01	2001-08-31	month	aggregated	high	us-nrcs-snotel	SNOTEL station 1000:OR:SNTL, snow water equivalent	—	—	2026-10-01
snow-water-equivalent	snotel-1000-or	geography	0	—	—	—	—	—	mm	2001-09-01	2001-09-30	month	aggregated	high	us-nrcs-snotel	SNOTEL station 1000:OR:SNTL, snow water equivalent	—	—	2026-10-01

Download these rows as CSV — the same twelve, with the column header, for testing a loader before committing to the full file.

Methodology

Derived by Hydrionis from monthly snow water equivalent published by the NRCS Air and Water Database, and organised on the water year — 1 October to 30 September, named for the year it ends — because a calendar year cuts a snow season in half and makes every statistic from it meaningless. Peak is the largest monthly mean in the year, which is the fullest month rather than the fullest day. Peak month and melt-out month are counted from October, so that a December peak and a March peak can be subtracted from one another without crossing a year boundary. Melt-out is the first month after the peak at or below a tenth of that year’s own peak, a share of the year rather than a fixed depth, so that a thin year is measured against its own snowpack instead of being called melted-out before it ever accumulated. Each station is placed in a subbasin by the twelve-digit hydrologic unit code on its own station record, truncated to the first eight digits — a containment given by the coding hierarchy, not inferred by Hydrionis — and named from the USGS Watershed Boundary Dataset.

What this dataset cannot tell you

Read before relying on these figures

A snow pillow is a point on a mountain, not a catchment average. One instrument stands for a great deal of ground, and it can miss drifting and wind scour.
Snow water equivalent is not snow depth. A metre of fresh powder and a metre of settled spring snow hold very different amounts of water, and only the water is measured here.
This is water standing in the snowpack, not water that reaches a river. How much arrives depends on melt rate, how dry the ground beneath is, and how much sublimates without ever becoming liquid.
Peak is the fullest month, not the fullest day. A pack that peaked sharply mid-month reads lower here than a manual course visited at the right moment would record.
Being in the same subbasin as a gauge does not put a station upstream of it. A subbasin is an area, and snow on one tributary may join the river below a gauge on another.
A water year is published only where it holds nine of its twelve months and every month from February to July, and a year whose maximum falls in the first month held is refused outright — a maximum at the edge of a record is a maximum of the record rather than of the year. Six station-years peaking below one millimetre were also dropped, because melt-out is defined as a tenth of the peak and a tenth of nothing is nothing.
Melt-out is withheld where a month is missing between the peak and the crossing, or where the pack never falls that far before the water year ends. Neither case arose in this release: every one of the 31,222 published water years contained its own crossing, because these packs melt out completely and the zeros are recorded. The rule is exercised by test rather than by the corpus.

Coverage

Subjects	United States automated snow stations, chiefly the mountain West, in 331 named subbasins — 851 held
Period	1963–2025
Units	mm, months
Update cadence	Annually
Identifier	`us-snow-hydrology` v1.0.0

Fields

Data dictionary →

Every metric this dataset carries, with the unit it is stored in and the geography level it is reported at. Full definitions are in the data dictionary.

Identifier	Field	Unit	Reported at
`snow-water-equivalent-peak`	Peak snow water equivalent The largest monthly mean snow water equivalent recorded at a station in one water year — the fullest the snowpack got that year.	mm	monitoring-station
`snow-peak-month`	Month of peak snowpack How many months into the water year the snowpack reached its largest monthly mean — 1 is October, 6 is March.	months	monitoring-station
`snow-melt-out-month`	Month the snowpack went How many months into the water year the snowpack first fell to a tenth or less of that year’s peak — the point the melt was essentially over.	months	monitoring-station

Rights and access

Licence position

Open. Derivative use true; redistribution true; commercial reuse true.

Applies to material authored by US federal agencies. Third-party material carried within a federal product may be separately protected.

Permitted uses

Public display
Derived analysis
API delivery
Bulk download
Commercial use

Available to: Public, Developer, Research, Professional, Enterprise. These follow from the rights of the contributing publishers, not from a Hydrionis pricing decision — no access tier can widen what a publisher withheld.

Contributing sources

United States Department of Agriculture, Natural Resources Conservation Service — SNOTEL and snow course network — snow water equivalent (US Government work — public domain)

Attribution and citation

Cite and reuse →

Two different obligations, deliberately kept apart. One is a condition of somebody else's licence; the other is a request Hydrionis has no standing to enforce.

Suggested citation for Hydrionis

Hydrionis (2026), United States Snow Hydrology Dataset, version 1.0.0, accessed 2026-10-05, hydrionis.com/data/datasets/us-snow-hydrology/

Cite Hydrionis where you rely on values Hydrionis computed, on the method that produced them, or on the compilation itself. The underlying measurements remain the publishers’ and their attribution requirements apply to you directly.

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: United States Snow Hydrology Dataset 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.

Changelog

Version 1.0.0 — 2026-09-02

First release. The seasonal statistics are new; the monthly record they are computed from was already held and is unchanged.

Additions

31,222 water years of peak snow water equivalent, peak month and melt-out month across 847 stations.
Every station placed in a named subbasin on its publisher’s own hydrologic unit code, which is what makes the snowpack readable against the rivers in the same basin.

Use this data

Download snow-ice observations from NRCS (470,842 rows) (CSV)
Machine-readable JSON /api/v1/datasets/us-snow-hydrology.json
How to cite this, and who you must credit
How these figures were produced
Request this at a different scale, format or geography

Every bulk extract ships with a companion metadata file carrying this dataset’s version, its sources, their licences, the attribution you are required to give and the suggested citation — so the terms travel with the file rather than staying on this page.

About this data

The fields a professional user needs to judge whether this is fit for a particular purpose. Deliberately not a score.

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 Department of Agriculture, Natural Resources Conservation Service — SNOTEL and snow course network — snow water equivalent · US Government work — public domain
How the values came to exist	Derived Computed by Hydrionis
Period held	1963–2025
Known gaps	A snow pillow is a point on a mountain, not a catchment average. One instrument stands for a great deal of ground, and it can miss drifting and wind scour. Snow water equivalent is not snow depth. A metre of fresh powder and a metre of settled spring snow hold very different amounts of water, and only the water is measured here. This is water standing in the snowpack, not water that reaches a river. How much arrives depends on melt rate, how dry the ground beneath is, and how much sublimates without ever becoming liquid.
Continuity	Version 1.0.0, released 2026-09-02. 1 recorded version; breaking changes and corrections are listed in the changelog above.
Inputs last read	2026-10-01 · when the records this was computed from were last read from their publishers · publisher updates annually
Redistribution	Permitted by the upstream licences
Commercial reuse	Permitted by the upstream licences. No Hydrionis access tier can widen this.
Methodology	How this was produced