A year of the Danube, measured in Balatons

Daily mean discharge of the Danube at Budapest, 18 Jul 2025 – 17 Jul 2026 — and what it adds up to. Even in a drought year, 47 km³ of water flowed through the city: roughly one Lake Balaton every 15 days. Public OVF data retrieved by an AI agent through ovf-data-mcp. Operational data — preliminary, unchecked.

Daily mean discharge (m³/s)

Gauge Budapest (1026) · hover or focus + arrow keys for values

Cumulative volume through the year (km³)

Right-edge labels mark every fifth Lake Balaton (1 Balaton ≈ 1.9 km³) · hover or focus + arrow keys for values

Data table — daily discharge and cumulative volume

Date	Discharge (m³/s)	Cumulative (km³)	Balatons

How this page was made

An agent ran one server-side aggregation for the discharge metric — the coverage check shows this gauge's discharge record goes back to 1924:

vizugy observations coverage surface:1026 --metric discharge   # available from 1924
vizugy observations aggregate surface:1026 --metric discharge \
    --start 2025-07-18T00:00:00Z --end 2026-07-18T00:00:00Z \
    --interval daily --operation avg

These commands are the only data source. The agent then integrated the daily means (m³/s × 86,400 s) into volumes and wrote this page’s HTML, CSS, and JavaScript itself — no chart libraries, no build step.

Source: Országos Vízügyi Főigazgatóság (OVF) via the public VRAQuery API · station Budapest (1026), Duna, metric “Felszíni vízhozam” (discharge, m³/s), data type “operatív összefésült” · retrieved 2026-07-18 11:29 (UTC). Lake Balaton’s volume is taken as ≈1.9 km³ (a commonly cited approximation; it varies with the lake’s level). Cumulative volume integrates daily means, so sub-daily variation is smoothed. Operational values may be preliminary; for checked data follow OVF’s formal data-request process.