{"id":"poland-hydrology","slug":"poland-hydrology","name":"Poland Hydrological Observations Dataset","description":"Water level, discharge and water temperature for the Polish national gauging network, accumulated daily from a publisher that serves only the current state. Every station names the watercourse it gauges.","methodology":"Collected from the IMGW public data API under the Polish Open Data Act of 2021 and Commission Implementing Regulation (EU) 2023/138 on high-value datasets, which requires hydrological data to be free, machine-readable and reusable commercially. The interface serves the latest reading per station and nothing older, so this runs in accumulate mode and Hydrionis becomes the archive of a snapshot the API does not keep. Each quantity carries its own measurement timestamp and is filed under the day it was taken rather than the day it was fetched — level, discharge and temperature are read at different times and frequently on different days. Water level is published in centimetres above each station’s own gauge datum and converted to metres; the datum stays local. Readings older than a fortnight are refused, because a rolling snapshot repeats a stale value indefinitely.","domains":["river-flow","temperature"],"metricIds":["river-level","river-flow-mean","water-temperature"],"subjectScope":"Polish national hydrological gauging stations","cadence":"daily","version":"1.0.0","released":"2026-08-27","changelog":[{"version":"1.0.0","date":"2026-08-27","summary":"First release. Poland joins the platform with full water-body linkage.","additions":["Water level, discharge and water temperature for around 900 stations.","The watercourse each station gauges, carried onto every station as it is collected."]}],"limitations":["A rolling snapshot, not an archive. The record begins when Hydrionis began accumulating it, and says nothing about how long Poland has been gauging its rivers — which is far longer. IMGW holds the real archive and releases it on request.","These are single readings, not daily means. One measurement taken at one moment, filed under the day it was taken; calling it a mean would be a different statistic under the same name.","Water level is measured against each station’s own gauge datum. Two Polish stations reading the same level are not at the same height, and a level is not the depth of the water.","Discharge is reported for fewer stations than level, and is a property of the gauge and its reach rather than of the river.","The publisher also serves ice phenomena and the state’s own warning and alarm thresholds. Those are recorded on the station rather than as observations, because a threshold is a regulatory decision and not a measurement."],"observationCount":3249,"seriesCount":1640,"subjectCount":904,"from":2026,"to":2026,"sourceIds":["pl-imgw-hydro"],"units":["m","m³/s","°C"],"redistributable":true,"commerciallyReusable":true,"citation":"Hydrionis (2026), Poland Hydrological Observations Dataset, version 1.0.0. Retrieved from https://hydrionis.com/data/datasets/poland-hydrology/","downloads":[{"file":"/downloads/observations-river-flow-pl-imgw-hydro.csv","format":"CSV","label":"river-flow observations from IMGW-PIB (3,041 rows)"},{"file":"/downloads/observations-chemistry-pl-imgw-hydro.csv","format":"CSV","label":"chemistry observations from IMGW-PIB (208 rows)"}],"apiPath":"/api/v1/datasets/poland-hydrology.json","lastFetched":"2026-10-01","fields":[{"id":"river-level","name":"River level","definition":"Height of the water surface at a gauging station, measured against that station’s own zero point.","unit":"m","nativeGeography":["river-gauge"],"comparabilityNotes":"Level is measured against each station’s own zero point, which is set locally and is not a common datum. Two gauges reading 3 m are not at the same height, and a level is not a depth of water: it says where the surface sits relative to a reference, not how deep the river is. Read a level against that gauge’s own record, never against another gauge’s."},{"id":"river-flow-mean","name":"Mean river flow","definition":"Average volumetric discharge past a gauging station over a stated period.","unit":"m³/s","nativeGeography":["river-gauge"],"comparabilityNotes":"Flow is a property of a specific gauge on a specific reach, and cannot be attributed to a river as a whole. Two gauges on the same river can differ by an order of magnitude. Where a station measures flow through a sluice, lock or pumping station — much of the Dutch network does — discharge is signed and a negative value means water moving in the reverse direction, which is a real operating state and not an error. Managed flow of that kind is not comparable with discharge at a natural gauging station, because it reflects operational decisions as well as hydrology."},{"id":"water-temperature","name":"Water temperature","definition":"Temperature of the water body or supply at the point of measurement.","unit":"°C","nativeGeography":["monitoring-station","river-gauge","supply-zone"]}]}