Will the Kelani Ganga at Glencourse rise in the next hour?

In the next hour the Kelani Ganga at Glencourse could fall to about 46.8 ft (46.5–47.2 ft). This is a forecast from the recent trend, the gauges upstream and rain, not an official warning.

What is the flood level at Glencourse?

The official marks for this gauge are alert 49.2 ft, minor flood 50.9 ft, major flood 62.3 ft. Alert means the river has reached the alert mark: move valuables up and charge your phone. Minor flood means water is spilling over low ground, and major flood means move to safety.

Where does this come from and how often does it update?

River readings come from the Department of Irrigation's gauges, roughly once an hour, and this page checks for new ones every minute. This site is independent and not an official warning service: follow the Disaster Management Centre and call 117 in an emergency.

Glencourse Kelani Ganga water level

As of Tue, 27 Oct, 5:05 am (Sri Lanka time), the Kelani Ganga at Glencourse was 47.4 ft, close to the 49.2 ft alert level, and falling.

In the next hour it could fall to about 46.8 ft (46.5–47.2 ft).

Official warning:

An amber warning says minor flooding may affect low-lying areas of the Kelani River Valley in Ruwanwella, Seethawaka, Dompe, Dehiowita, Eheliyagoda, Yatiyantota and Bulathkohupitiya within 24 hours; residents and motorists should exercise extreme caution.

Irrigation Department

Reading at 5:05 am · 42 min ago

Normal

47.4 ft

Near alert: 1.8 ft below the alert mark

Next hour

Falling

Next 24 hours

Small chance it reaches the alert level in ~8 hours (if the heavier rain comes)

Could reach minor flood level around 2 pm this afternoon (in about 8 hours) (about 40% chance).

Details

Could reach minor flood level around 2 pm this afternoon (in about 8 hours) (about 40% chance).

Published as 14.44 m (alert 15.0 m, minor flood 15.5 m, major flood 19.0 m)

Elevated river-flow outlook this week.

In	Level	80% range	At
1h	46.8 ft	46.6 to 47.2	6:05 am
3h	45.9 ft	44.9 to 47.5	8:05 am
6h	45.1 ft	42.4 to 49.0	11:05 am
12h	44.9 ft	38.6 to 58.1	5:05 pm
24h	45.8 ft	32.0 to 63.0	5:05 am

Alert (49.2 ft): possible, about 4 in 10, from about 1:05 pm
Minor flood (50.9 ft): possible, about 4 in 10, from about 2:05 pm
Major flood (62.3 ft): unlikely, about 1 in 10

Local trend

-0.6 ft/h

Upstream avg

-0.2 ft/h

Rain that fell: 0.0 mm in the last 3 hours, 76 mm in the last 24 hours at this gauge (heavy rain)
Rain forecast: 12 mm in the next 24 hours over the catchment (moderate rain). Forecast model estimate.

Satellite estimate of rain over the catchment: 1.8 mm in the last 6 hours, 72.3 mm in the last 24 hours (to 5:30 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 751 m3/s in its highest member within 7 days, above the 1-in-20 level (338 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 (44.6 ft); treat it as a rough guide.

How this is worked out
· Latest level at Glencourse and recent change, plus upstream gauges: Holombuwa, Deraniyagala, Kithulgala.
· Forecast model estimate of catchment rain (Open-Meteo, area average over 6 grid cells above Glencourse): 63 mm modelled for the last 24 hours, 12 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 Glencourse 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.

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Glencourse Kelani Ganga water level

Normal

Is this right?

Water level

When does Glencourse flood?

Recent floods

Along the Kelani Ganga

Reservoirs upstream

In the newsNews reports, not official.

Towns that depend on this gauge

Common questions

Along the Kelani Ganga

Common questions

In the newsNews reports, not official.

Water level

When does Glencourse flood?

Recent floods

Reservoirs upstream

Normal