Ratnapura Kalu Ganga water level

Above minor flood level now and could reach major flood level around 7 am this morning (in about 6 hours) (about 60% chance).

Published as 8.63 m (alert 5.2 m, minor flood 7.5 m, major flood 9.5 m)

Elevated river-flow outlook this week.

• Major flood (31.2 ft): possible, about 6 in 10, from about 7:10 am

Rain that fell

0.0 mm in the last 3 hours, 129 mm in the last 24 hours at this gauge (very heavy rain)

Rain forecast

26 mm in the next 24 hours over the catchment (moderate rain). Forecast model estimate.

Satellite estimate of rain over the catchment: 46.1 mm in the last 6 hours, 105.0 mm in the last 24 hours (to 12:30 am). It can differ from the gauges. GSMaP data by Japan Aerospace Exploration Agency (JAXA)

• · Outlook: the GloFAS global flood model has river flow at 461 m3/s in its highest member within 7 days, above the 1-in-20 level (285 m3/s). This is a heads-up only; it does not change the levels above.
• · Part of the range is above the highest level this model has seen (20.7 ft); treat it as a rough guide.
• · Some rain is forecast over the catchment: about 26 mm in the next 24 hours (ensemble range 7 to 38 mm).

• How this is worked out
• · Latest level at Rathnapura and recent change. No gauge sits upstream of it (or none reports in step with it), so the catchment rain is its upstream signal.
• · Forecast model estimate of catchment rain (Open-Meteo, area average over 6 grid cells above Rathnapura): 54 mm modelled for the last 24 hours, 26 mm forecast for the next 24 hours, with ECMWF ensemble spread.
• · The 1, 3, 6, 12, 24 hour steps use this gauge's own recent changes and the other gauges on the river (fitted to about 11 months of hourly readings, including the November 2025 Ditwah floods); where this was tested against 'level stays the same' it missed by less.
• · Heavy rain upstream is part of the 1, 3, 6, 12, 24 hour steps: rain that has fallen or is forecast over the catchment above Rathnapura raises the level, and the top of the range allows for the heavier forecast rain. Tested storm by storm (leaving each storm out, Ditwah included) it was closer than the river's own trend alone.