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Lithuania: LHMT

Documentation index · Usage
Provider lt_lhmt
Country Lithuania
Published by Lietuvos hidrometeorologijos tarnyba (LHMT), the Lithuanian Hydrometeorological Service under the Ministry of Environment
Read from Meteo.lt API (api.meteo.lt)
Quantities Historical daily mean discharge and stage
Stations in the catalogue 97. Availability depends on quantity and period
Station metadata Station name and water-body name. See Fields by provider
Credentials None
Licence stated by LHMT Creative Commons Attribution-ShareAlike 4.0 (CC BY-SA 4.0), unless stated otherwise
Agency documentation Meteo.lt API

RivRetrieve reads only the API's historical feed, so it provides nothing more recent than the latest published year; the API's separate feed of the last 30 days of readings is not read. Retrieve one week of published daily mean discharge at station nemajunu-vms, Nemajūnai on the Nemunas:

import rivretrieve as rr

selection = rr.find(
    provider="lt_lhmt",
    station="nemajunu-vms",
    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,+00:00,192.0,m3/s
2020-01-02T00:00:00.000000,+00:00,189.0,m3/s
2020-01-03T00:00:00.000000,+00:00,203.0,m3/s
7
()

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

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

Who measures, and who publishes

LHMT both measures and publishes these data. Its hydrology page describes Lithuania's hydrological observations as carried out by a network of water measuring stations (vandens matavimo stotis, abbreviated VMS) covering the whole country: currently 101 stations measuring water level, water temperature, air temperature, precipitation and discharge.

The Meteo.lt API publishes data measured at LHMT's hydrological and meteorological stations. RivRetrieve reads the API's historical hydrological observations. The API's hydrological station list, which the packaged catalogue follows, contained 97 stations on 2026-09-27. The API does not explain the difference from the 101 stations in the network description.

Station identifiers are the API's own codes, which are words rather than numbers, for example nemajunu-vms.

What you can retrieve

Quantity filter Source field / variant Frequency Statistic Source unit Returned unit
discharge waterDischarge Daily Mean m³/s m³/s
stage waterLevel Daily Mean cm m

The API documents both fields as daily means ("Vidurkis per parą"). RivRetrieve converts stage from centimetres to metres; discharge needs no conversion. The source_unit column keeps the published unit, cm, alongside the returned m. Stage is water level; RivRetrieve has not established its vertical reference or datum.

The catalogue lists both quantities at every station, because the station list does not say which quantities each station publishes. A station being listed does not guarantee data for every quantity or requested period. Some stations publish stage with discharge left empty; RivRetrieve returns those days as rows with value=null. On 2026-09-27, five stations, such as the Curonian Lagoon station juodkrantes-vms, reported no historical record range.

How far back, and how recent

The API documentation states:

Istoriniai hidrologinių stebėjimų duomenys teikiami nuo 2000 metų.

Duomenys už praėjusius metus pradedami teikti nuo einamųjų metų vidurio.

In English, unofficially: historical hydrological observations are provided from 2000; data for the previous year start to be provided from the middle of the current year.

Records start later than 2000 at many stations. On 2026-09-27, no station's historical record extended beyond December 31, 2024: data for 2025 had not appeared nine months after that year ended. Treat the stated timing as the API's description, not a guarantee.

A request for a period that has not been published returns no rows and a source.http_not_found warning, which reports that the API had no data for that month. It is not a network failure. Check issues before interpreting an empty result.

The API also has a separate measured feed that RivRetrieve does not read. It holds stage and water temperature for the last 30 days, with UTC timestamps, and no discharge. The historical feed that RivRetrieve reads has no water temperature. Making the measured feed available is on the roadmap (#402).

Time and data status

The API labels each daily mean with a date that it describes as UTC (observationDateUtc). RivRetrieve returns that date at midnight in time, paired with time_zone="+00:00". The API does not say when the averaging day starts and ends, so RivRetrieve leaves the day definition unknown. Do not assume the mean covers midnight to midnight UTC.

The historical feed carries no quality or approval flags. LHMT provides the data as they are, without warranty of their quality or fitness for a particular purpose. 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, reported alongside any successful records.

Rate limits

The API limits each IP address:

Užklausų kiekis iš vieno IP adreso ribojamas iki 180 užklausų per minutę. Prašome negeneruoti daugiau kaip 20.000 užklausų per vieną parą iš vieno IP adreso, nes viršijus nurodytą limitą Jūsų IP adresas gali būti užblokuotas be įspėjimo.

In English, unofficially: requests are limited to 180 per minute per IP address; please do not generate more than 20,000 requests a day from one IP address, as exceeding the limit may block the address without warning.

RivRetrieve sends one request per station and calendar month. Because each monthly response contains both discharge and stage, one fetch that selects both quantities shares that request; separate fetch calls for each quantity request the same months again. RivRetrieve also requests the neighbouring month when the selected period starts on the first or second day of a month, or ends on one of its last two days. If that extra month is unpublished, the request is not reported as an issue. Twenty years at one station take about 240 requests in a single fetch, whether it selects one quantity or both, so many stations add up quickly.

Terms and citation

LHMT's data-use conditions, on the API page, state that the data are publicly available and free for public use, distribution and further processing, on conditions including:

1) duomenys, jeigu nenustatyta kitaip, teikiami pagal Creative Commons Attribution-ShareAlike 4.0 (CC BY-SA 4.0) tarptautinę duomenų naudojimo licenciją, būtina susipažinti su licencijos sąlygomis;

5) publikuojant, pakartotinai atkartojant ar kitaip naudojant duomenis, būtina nurodyti, kad duomenų šaltinis yra Tarnyba.

In English, unofficially: unless stated otherwise, the data are provided under the CC BY-SA 4.0 international licence, whose conditions users must read; and when publishing, reproducing or otherwise using the data, LHMT must be stated as the source.

The conditions add that access may be withdrawn if the source is not stated, and that the data may be used only for lawful and defined purposes. The CC BY-SA 4.0 licence also requires adaptations to be shared under the same licence.

LHMT gives no formatted citation. Name LHMT and the Meteo.lt API as the source, and retain the station, quantity, requested period and access date to make the retrieved record traceable. This is practical guidance, not an LHMT citation template.

Sources

Publisher pages checked on 2026-09-27:

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 the limits of these checks.