Is Thawalama flooding now?

As of Tue, 27 Oct, 4:02 am (Sri Lanka time), the Gin Ganga at Thawalama was 17.4 ft, above the 13.1 ft alert level, and falling.

Will the Gin Ganga at Thawalama rise in the next hour?

In the next hour the Gin Ganga at Thawalama could fall to about 17.3 ft (17.2–17.4 ft). This is a forecast from the recent trend, the gauges upstream and rain, not an official warning.

What is the flood level at Thawalama?

The official marks for this gauge are alert 13.1 ft, minor flood 19.7 ft, major flood 24.6 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.

Thawalama Gin Ganga water level today (live)

Official warning:

An amber warning says minor flooding may affect low-lying areas of the Gin Ganga Valley in Thawalama, Nagoda, Baddegama and Welivitiya-Divithura within 24 hours; residents and motorists should exercise extreme caution.

Irrigation Department

Reading at 4:02 am · 43 min ago

Alert

17.4 ft

Next hour

Falling

Next 24 hours

No estimate yet

Move valuables up, charge your phone

The river is expected to stay above the alert level for the next 24 hours.

Call 117 Galle DMC office

Details

Above alert level now and expected to stay there for the next 24 hours.

Published as 5.30 m (alert 4.0 m, minor flood 6.0 m, major flood 7.5 m)

Elevated river-flow outlook this week.

In	Level	80% range	At
1h	17.3 ft	17.2 to 17.4	5:02 am
3h	17.1 ft	16.8 to 17.5	7:02 am
6h	16.7 ft	16.2 to 17.4	10:02 am
12h	16.2 ft	15.4 to 17.4	4:02 pm
24h	17.4 ft	16.4 to 19.1	4:02 am

Minor flood (19.7 ft): unlikely, about 1 in 10
Major flood (24.6 ft): unlikely, about 1 in 10

Local trend

-0.07 ft/h

Upstream avg

n/a (top)

Rain that fell: 0.0 mm in the last 3 hours, 131 mm in the last 24 hours at this gauge (very heavy rain)
Rain forecast: 23 mm in the next 24 hours over the catchment (moderate rain). Forecast model estimate.

Satellite estimate of rain over the catchment: 27.2 mm in the last 6 hours, 158.2 mm in the last 24 hours (to 4:30 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 301 m3/s in its highest member within 7 days, above the 1-in-20 level (113 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 (13.1 ft); treat it as a rough guide.
· At 24 h nothing we tested beat 'level stays the same' for this gauge, so that is the line, with a range taken from how much the gauge has really changed over that time.
· Some rain is forecast over the catchment: about 23 mm in the next 24 hours (ensemble range 7 to 30 mm).

How this is worked out
· Latest level at Thawalama 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 5 grid cells above Thawalama): 47 mm modelled for the last 24 hours, 23 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.

Is this right?

Each answer helps us improve the forecast for your area.

Water level

This gauge’s forecasts: the next hour is typically off by about 0.2 ft; 24 hours ahead, by about 0.9 ft (last 30 days, 24 checks).

When does Thawalama flood?

Flood warnings come mostly between November and December.

It’s October: floods are less common than in November, but they do happen.

Recent floods

26 May – 29 May 2024Minor flood · estimated
23 May 2024Minor flood · estimated
11 Dec – 25 Dec 2023Major flood · estimated

Every day since 2022, year by year

Other stations

Along the Gin Ganga

Arrows show the change over the last 3 hours.

Towns that depend on this gauge

Thawalama

Common questions

Is Thawalama flooding now?: As of Tue, 27 Oct, 4:02 am (Sri Lanka time), the Gin Ganga at Thawalama was 17.4 ft, above the 13.1 ft alert level, and falling.
Will the Gin Ganga at Thawalama rise in the next hour?: In the next hour the Gin Ganga at Thawalama could fall to about 17.3 ft (17.2–17.4 ft). This is a forecast from the recent trend, the gauges upstream and rain, not an official warning.
What is the flood level at Thawalama?: The official marks for this gauge are alert 13.1 ft, minor flood 19.7 ft, major flood 24.6 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.