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Czechia: CHMI

Documentation index · Usage
Provider cz_chmi
Country Czechia
Published by Český hydrometeorologický ústav (ČHMÚ), the Czech Hydrometeorological Institute (CHMI)
Read from CHMI open data, historical hydrology files (opendata.chmi.cz)
Quantities Daily mean discharge, stage and water temperature; hourly mean discharge and stage
Stations in the catalogue 831. Availability depends on quantity and period
Station metadata Station name, water-body name and drainage area. See Fields by provider
Credentials None
Licence stated by CHMI Creative Commons Attribution 4.0 (CC BY 4.0)
Agency documentation CHMI open data, hydrology, dataset descriptions

RivRetrieve reads CHMI's historical daily and hourly files. Retrieve one week of published daily mean discharge at station 0-203-1-180100, VD České Údolí on the Radbuza:

import rivretrieve as rr

selection = rr.find(
    provider="cz_chmi",
    station="0-203-1-180100",
    quantity="discharge",
    frequency="daily",
    statistic="mean",
)

result = rr.fetch(selection, start="2020-01-01", end="2020-01-07", cache="bypass")

preview = result.data.select("time", "time_zone", "value", "unit").head(3)
print(preview.write_csv(), end="")

print(result.data.height)
print(result.issues)

Output:

time,time_zone,value,unit
2020-01-01T00:00:00.000000,+00:00,1.7,m3/s
2020-01-02T00:00:00.000000,+00:00,1.54,m3/s
2020-01-03T00:00:00.000000,+00:00,1.5,m3/s
7
()

The request returned seven daily means in m³/s, one for each date from January 1 to 7. The preview shows the first three. The empty tuple () means that retrieval reported no issues; it does not establish the quality of the values. RivRetrieve reads the means CHMI publishes rather than calculating them from more frequent observations.

cache="bypass" requests CHMI rather than a local cache. This output was checked live on 2026-09-28. Published values can change, so a later retrieval need not reproduce it exactly. See Usage for general selection and result handling.

Who measures, and who publishes

CHMI establishes and operates state monitoring networks for the atmosphere and hydrosphere and processes their measurements. It publishes data from the national hydrometeorological database through its open-data service. This institutional role does not identify the operator of every station in the published catalogue.

For each station and calendar year, CHMI publishes separate files for daily and hourly observations. The daily file can contain mean discharge, stage and water temperature; the hourly file can contain mean discharge and stage. A file need not contain every quantity. For example, the daily file used above contains discharge and stage for 2020, but no water temperature.

Select a station using CHMI's station identifier, such as 0-203-1-180100 for VD České Údolí. RivRetrieve keeps these source identifiers unchanged.

What you can retrieve

Quantity filter Source field / variant Frequency Statistic Source unit Returned unit
discharge QD Daily Mean m³/s m³/s
stage HD Daily Mean cm m
temperature TD Daily Mean °C °C
discharge QH Hourly Mean m³/s m³/s
stage HH Hourly Mean cm m

Select frequency="daily" or frequency="hourly", with statistic="mean". CHMI's dataset description defines these as mean daily values (průměrné denní hodnoty) and mean hourly values (průměrné hodinové hodnoty). RivRetrieve converts stage from centimetres to metres. Discharge and water temperature need no unit conversion. Stage is water level; RivRetrieve has not established its vertical reference or datum.

The catalogue lists all five series at each station because the station metadata does not state which of these quantities are available. A station being listed does not guarantee data for every quantity or requested period.

How far back, and how recent

Availability depends on the annual files CHMI has published for a station and on the series within those files. RivRetrieve reads only the historical service, so requests cannot provide observations more recent than its published records. There is no fixed latest year imposed by RivRetrieve.

CHMI also publishes current observations in its recent and now folders and additional historical series that RivRetrieve does not yet read. Making these available is on the roadmap (#294).

Time and data status

CHMI's historical observation timestamps carry a UTC Z suffix. RivRetrieve returns their wall-clock labels in time, paired with time_zone="+00:00". Daily values have midnight labels. The boundaries of the averaging day are unknown, so do not assume a daily mean covers midnight to midnight UTC. Hourly values are published means, but whether their labels mark the start or end of the averaging hour is also unknown.

The historical records read here carry timestamps and values without observation-level quality or approval flags. Being in the historical service does not by itself establish a value's validation status. RivRetrieve makes no quality judgement of its own.

A published null remains a row with value=null. A date without a published observation supplies no row. A failed request remains an issue alongside any successful records. Check issues before interpreting an empty result.

Terms and citation

CHMI's open-data page states that its open data can be used free of charge under Creative Commons BY 4.0. Retrieval requires no personal credentials.

Its disclaimer and conditions of use state:

Produkty Českého hydrometeorologického ústavu dostupné na těchto webových stránkách podléhají licenci Creative Commons 4.0 CC-BY. Dílo smíte sdílet a upravovat za podmínky uvedení původu (zdroje ČHMÚ).

In English, unofficially: CHMI's products available on these websites are licensed under Creative Commons 4.0 CC BY; you may share and adapt the work on condition that you credit the origin (the source, ČHMÚ).

No formatted data citation was identified in these terms. Credit ČHMÚ and retain the station, quantity, requested period and access date to make the retrieved record traceable. This is practical guidance, not a CHMI citation template.

Sources

Publisher pages checked on 2026-09-28:

The station count describes the packaged catalogue. The example was retrieved live on 2026-09-28. The private verification archive retains commands, source checks, exact output and limitations.