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

In the next hour the Kelani Ganga at Hanwella could fall to about 22.0 ft (22.0–22.1 ft). This is a forecast from the recent trend, the gauges upstream and rain, not an official warning.

What is the flood level at Hanwella?

The official marks for this gauge are alert 21.3 ft, minor flood 24.6 ft, major flood 31.2 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.

Hanwella Kelani Ganga water level

As of Tue, 27 Oct, 4:04 am (Sri Lanka time), the Kelani Ganga at Hanwella was 22.2 ft, above the 21.3 ft alert level, and steady.

In the next hour it could fall to about 22.0 ft (22.0–22.1 ft).

Official warning:

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

Irrigation Department

Reading at 4:04 am · 41 min ago

Alert

22.2 ft

Next hour

Falling

Next 24 hours

Could reach flood level in ~10 hours

Move valuables up, charge your phone

The river is above alert level and could reach minor flood level around 2 pm this afternoon (in about 9 hours).

Call 117 Colombo DMC office

Details

Above alert level now and could reach minor flood level around 2 pm this afternoon (in about 9 hours) (about 70% chance).

Published as 6.76 m (alert 6.5 m, minor flood 7.5 m, major flood 9.5 m)

Elevated river-flow outlook this week.

Is this right?

Each answer helps us improve the forecast for your area.

Water level

How this river reacts to rain

Rain close to Hanwella shows up in the river in about 7 hours.
Rain on the upper river (above Glencourse and Holombuwa) reaches here in about 7 hours.
About 35 mm of rain over 24 hours, averaged over the catchment, has usually come before a rise of 1 ft or more.
Each extra 10 mm has typically lifted it about 0.5 ft within a day, and more when the ground is already wet.

Learned from 11 months of readings and satellite rain. A guide, not a forecast.

This gauge’s forecasts: the next hour is typically off by about 0.06 ft; 24 hours ahead, by about 3.6 ft (last 30 days, 28 checks).

When does Hanwella flood?

Flood warnings come mostly in November.

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

Recent floods

22 May – 23 May 2026Minor flood
28 Nov – 2 Dec 2025Major flood
22 Oct – 24 Oct 2025Minor flood · estimated

Every day since 2022, year by year

Other stations

Along the Kelani Ganga

Arrows show the change over the last 3 hours.

Reservoirs upstream

In the newsNews reports, not official.

RiverSource: Daily Mirror26 Oct, 7:31 pm (9 h ago)
Flood warnings issued for Kelani, Attanagalu Oya basins(opens the news site in a new tab)
The Irrigation Department has issued a minor flood warning for low-lying areas of the Kelani River Valley, covering the Divisional…
RiverSource: Newswire26 Oct, 7:10 pm (10 h ago)
Amber flood warning issued for low-lying areas of Kelani and Attanagalu river basins(opens the news site in a new tab)
The Department of Irrigation has issued Amber flood warnings for low-lying areas in the Kelani River and Attanagalu Oya basins…

Towns that depend on this gauge

Common questions

Is Hanwella flooding now?: As of Tue, 27 Oct, 4:04 am (Sri Lanka time), the Kelani Ganga at Hanwella was 22.2 ft, above the 21.3 ft alert level, and steady.
Will the Kelani Ganga at Hanwella rise in the next hour?: In the next hour the Kelani Ganga at Hanwella could fall to about 22.0 ft (22.0–22.1 ft). This is a forecast from the recent trend, the gauges upstream and rain, not an official warning.
What is the flood level at Hanwella?: The official marks for this gauge are alert 21.3 ft, minor flood 24.6 ft, major flood 31.2 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?

In the next hour it could fall to about 22.0 ft (22.0–22.1 ft).

Common questions

Is Hanwella flooding now?: As of Tue, 27 Oct, 4:04 am (Sri Lanka time), the Kelani Ganga at Hanwella was 22.2 ft, above the 21.3 ft alert level, and steady.
Will the Kelani Ganga at Hanwella rise in the next hour?: In the next hour the Kelani Ganga at Hanwella could fall to about 22.0 ft (22.0–22.1 ft). This is a forecast from the recent trend, the gauges upstream and rain, not an official warning.
What is the flood level at Hanwella?: The official marks for this gauge are alert 21.3 ft, minor flood 24.6 ft, major flood 31.2 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.

In the newsNews reports, not official.

RiverSource: Daily Mirror26 Oct, 7:31 pm (9 h ago)
Flood warnings issued for Kelani, Attanagalu Oya basins(opens the news site in a new tab)
The Irrigation Department has issued a minor flood warning for low-lying areas of the Kelani River Valley, covering the Divisional…
RiverSource: Newswire26 Oct, 7:10 pm (10 h ago)
Amber flood warning issued for low-lying areas of Kelani and Attanagalu river basins(opens the news site in a new tab)
The Department of Irrigation has issued Amber flood warnings for low-lying areas in the Kelani River and Attanagalu Oya basins…

Water level

How this river reacts to rain

Rain close to Hanwella shows up in the river in about 7 hours.
Rain on the upper river (above Glencourse and Holombuwa) reaches here in about 7 hours.
About 35 mm of rain over 24 hours, averaged over the catchment, has usually come before a rise of 1 ft or more.
Each extra 10 mm has typically lifted it about 0.5 ft within a day, and more when the ground is already wet.

Learned from 11 months of readings and satellite rain. A guide, not a forecast.

This gauge’s forecasts: the next hour is typically off by about 0.06 ft; 24 hours ahead, by about 3.6 ft (last 30 days, 28 checks).

When does Hanwella flood?

Flood warnings come mostly in November.

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

Recent floods

22 May – 23 May 2026Minor flood
28 Nov – 2 Dec 2025Major flood
22 Oct – 24 Oct 2025Minor flood · estimated

Every day since 2022, year by year

Official warning:

Irrigation Department

Reading at 4:04 am · 41 min ago

Alert

22.2 ft

Next hour

Falling

Next 24 hours

Could reach flood level in ~10 hours

Move valuables up, charge your phone

The river is above alert level and could reach minor flood level around 2 pm this afternoon (in about 9 hours).

Call 117 Colombo DMC office

Details

Above alert level now and could reach minor flood level around 2 pm this afternoon (in about 9 hours) (about 70% chance).

Published as 6.76 m (alert 6.5 m, minor flood 7.5 m, major flood 9.5 m)

Elevated river-flow outlook this week.

Minor flood (24.6 ft): possible, about 7 in 10, from about 2:04 pm
Major flood (31.2 ft): unlikely, about 4 in 10

Local trend

-0.02 ft/h

Upstream avg

-0.3 ft/h

Rain that fell: 0.0 mm in the last 3 hours, 46 mm in the last 24 hours at this gauge (moderate rain) (heavy for this river)
Rain forecast: 13 mm in the next 24 hours over the catchment (moderate rain). Forecast model estimate.

Satellite estimate of rain over the catchment: 3.7 mm in the last 6 hours, 81.8 mm in the last 24 hours (to 4:30 am). It can differ from the gauges. GSMaP data by Japan Aerospace Exploration Agency (JAXA)

Deraniyagala 2.2mm · Glencourse 1.1mm

· 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 (15.4 ft); treat it as a rough guide.

How this is worked out
· Latest level at Hanwella and recent change, plus upstream gauges: Glencourse, Deraniyagala, Kithulgala.
· Forecast model estimate of catchment rain (Open-Meteo, area average over 8 grid cells above Hanwella): 63 mm modelled for the last 24 hours, 13 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.
· The 12, 24 hour steps read the rain the satellite measured over Hanwella's catchment (JAXA GSMaP, corrected for how it reads here), with rain beside the gauge and rain on the channels upstream timed separately (about 7 h from beside the gauge, about 7 h from upstream). Tested storm by storm it was closer than the version that reads the weather model's rain.
· Heavy rain upstream is part of the 12, 24 hour steps: rain that has fallen or is forecast over the catchment above Hanwella 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.

1h	22.0 ft	22.0 to 22.1	5:04 am
3h	21.5 ft	21.4 to 21.8	7:04 am
6h	20.5 ft	20.1 to 20.9	10:04 am
12h	19.5 ft	18.2 to 26.6	4:04 pm
24h	20.3 ft	17.8 to 39.1	4:04 am