Denmark Reservoir Transparency

GEUS Jupiter is an open, public database publishing detailed groundwater-level measurements, well construction, geological logs and abstraction data for 280,000+ wells, free of charge and as part of Denmark's national Environment Portal. Danmarks Miljøportal's VanDa system additionally publishes river water level and streamflow. Granular, resource-wide groundwater-level data is genuinely available; the score is not higher only because the data is framed around wells and abstraction rather than a single national storage figure.

The technical layer is mixed. GEUS Jupiter offers open bulk downloads (PCJupiterXL data model) and WMS/WFS services, and Danmarks Miljøportal runs a documented REST API (VanDa Hydrometry, Swagger + GitHub wiki). However, the VanDa API requires OAuth2 client credentials tied to a Danish CVR (organisational) registration, which gates real-time programmatic access for international users, and the Jupiter search interface is Danish-only. Capable but not as turnkey or openly licensed as the best-in-class systems.

Editorial scope decision (2026): because ~99% of Denmark's water supply is drawn from groundwater rather than surface reservoirs, the national aquifer system is treated as the country's documented water-storage deposit. On that basis coverage is high — the GEUS Jupiter database catalogues 280,000+ wells nationwide with groundwater-level measurements, and the GRUMO national groundwater monitoring programme gives systematic spatial coverage of the resource that actually stores the nation's water. Held below the top band because well-level data is a distributed proxy for storage rather than a single capacity-referenced volume.

Denmark's water-data record is deep. GEUS publishes groundwater monitoring from 1989 onward (35+ years) under the GRUMO programme, updated daily, and river/watercourse monitoring for ecology and nutrients extends back to the early 1970s. Accessible historical depth for the covered groundwater resource is strong.

Groundwater data in GEUS Jupiter is updated daily, and the VanDa IoT hydrometry ecosystem (launched April 2024) pushes continuous logger data in real time. Refresh cadence for the covered resource is therefore frequent, though much of the historical groundwater monitoring network reports on periodic rather than continuous schedules.

GEUS publishes detailed methodology for its monitoring programmes: annual groundwater reports documenting abstraction figures, validation and network design, the Jupiter data model and station metadata in peer-reviewed literature, and Statistics Denmark documents its water-abstraction statistics methodology publicly. Documentation of how the stored resource is measured and quality-controlled is strong.

GEUS provides substantial English documentation (the Jupiter description, annual groundwater summaries) and Danmarks Miljøportal has an English site (noted as AI-translated). However, the Jupiter search interface, the VanDa system UI and the API wiki are largely Danish-only, so operational usability for international users is partial.