Luxembourg Reservoir Transparency

Luxembourg has essentially one functional surface-water reservoir of note: the Lac de la Haute-Sûre / Esch-sur-Sûre reservoir (~60 Mm³, managed by SEBES for drinking water and by SEO for hydropower). Its real-time water level (in metres above NN) is published via inondations.lu (Station 40, Sûre basin), which shows a current reading of 319.44 m NN as of 2026-05-28 within operational bounds of 317–320 m NN. The AGE also publishes a 'Measured Water Levels' dataset on data.public.lu (CC0 licence, updated daily, 11 files). However, these sources publish water surface elevation only — not volumetric storage (Mm³ or % full), not inflow/outflow, and not the Vianden PSP (1,296 MW pumped-storage) which is under German TSO Amprion/Creos jurisdiction for ENTSO-E purposes. SEBES's own website (sebes.lu) and the Energieauer national energy portal publish no operational storage data. Luxembourg does not submit 16.1.D reservoir filling data to the ENTSO-E Transparency Platform because its small run-of-river hydro capacity (~34 MW at Esch-sur-Sûre) falls below the meaningful threshold for aggregated reporting, and Vianden is reported under the German control area. The country's tiny reservoir footprint means most relevant metrics are near-absent from formal open data.

The AGE's water level dataset on data.public.lu is published under CC0 with 11 downloadable files and a WMS endpoint (layer 655 at wms.geoportail.lu). The community-built Héichwaasser API (JSON, open-source) reads this data and exposes it via river/station endpoints with time-range filtering. The inondations.lu monitoring site provides 15-minute updates in a browser interface but has no documented CSV export or REST API. Crucially, the data exposed is raw gauge height, not pre-computed volumetric storage, requiring end-users to apply capacity curves they must source separately. SEBES has no data download mechanism whatsoever.

Conservative capacity-weighted estimate applied 2026-05-29. Numerator/denominator: n_covered ≈ 65 / n_total ≈ 100 hm³. Luxembourg's reservoir estate is dominated by Lac de la Haute-Sûre/Esch-sur-Sûre (~60 hm³ total, ~53 hm³ effective, managed by SEBES for drinking water and SEO for hydropower) plus the Vianden Pumped Storage upper reservoir (~7 hm³ usable, under German Amprion control area for ENTSO-E purposes). LKW + Esch-sur-Sûre dam station are covered via inondations.lu real-time water level (15-min) and AGE data.public.lu Measured Water Levels (CC0, daily). Applying conservative downward adjustment (~-5 points) to recognise that the published metric is gauge elevation (m NN) rather than volumetric storage, Vianden upper reservoir has no Luxembourg-side publication, and several small dams (Müllerthal/Sauer-basin retention structures and minor industrial impoundments above the threshold) are absent from any public feed. coverage = round(100 × 65 / 100) = 65.

The inondations.lu station 40 page states it has been 'Operating Since 01.07.2013', implying roughly 13 years of potential gauge records. The AGE's data.public.lu dataset shows a creation date of September 2017 and 'Temporal coverage not set', making it unclear how far back the downloadable files extend. The monitoring system at the dam dates to 1989 (central computer installed September 1989), but whether pre-2013 or pre-2017 time series are digitally accessible to the public is not documented on any portal. No statistical minima/maxima for the station are published on inondations.lu ('No statistical values have been entered for this station'). Historical depth is therefore moderate at best.

The inondations.lu hydrometric network updates gauge readings every 15 minutes with forecasts recalculated at least every three hours. The AGE's open data dataset is described as updated daily. This is genuinely good operational frequency for flood-management purposes. However, the storage-relevant metric — volumetric fill — is never published by SEBES, SEO, or any public body. ENTSO-E 16.1.D weekly submissions are absent for Luxembourg. The high frequency of gauge-level updates is therefore only partially relevant to reservoir transparency.

The operational parameters for the Esch-sur-Sûre reservoir are publicly known (capacity 60 Mm³, effective 53 Mm³, summer max 320 m NN, winter max 317 m NN) from SEBES's website and Wikipedia. However, no public document explains how gauge height at station 40 maps to reservoir volume, what the bathymetric survey baseline is, or what counting methods are used for inflow estimation. The AGE's data is described as 'automatically captured without control' on inondations.lu, explicitly warning of quality issues. SEBES does not publish water quality or quantity monitoring methodology beyond stating that water quality is 'continuously monitored'. There is no open reservoir operations manual or data dictionary.

Luxembourg's open data portal (data.public.lu) is fully bilingual French/English with English as an equal interface language; inondations.lu is trilingual (French, German, Luxembourgish) with an English version. SEBES's website is trilingual (French, German, Luxembourgish) but lacks an English version. The Héichwaasser API documentation appears in Luxembourgish/French. For an international researcher, the data.public.lu portal and inondations.lu are accessible without language barriers, but the operator-level documentation at sebes.lu requires French or German.