Flood warnings on the Mahaweli Ganga come mostly between November and December.
Since 23 Nov 2025, its 6 gauges have recorded flooding on 13 days and alert levels on 30 days. The most recent flood was 18 Sep – 20 Sep 2026, at Nawalapitiya, Peradeniya (major flood).
Below each line is what the river gauges recorded; above it, our estimate of how high the rivers ran, going back to 2022. Updated 27 Oct, 1:00 am (Sri Lanka time). Live Mahaweli Ganga levels →
Taller bars mean more gauges were in warning that day. Tap or hover a day for details. Earlier years are estimates.
Gauge records start 23 Nov 2025
Share of days in each month with at least one gauge at alert or worse on the Mahaweli Ganga.
Runs of days with minor or major flooding, ranked by the worst day.
Mahaweli Ganga: about 32 affected days a year in gauge records since 23 Nov 2025.
Before 23 Nov 2025 there are no gauge records here; estimates suggest about 55 affected days a year in 2022–2024.
Affected means at least alert level. A day counts once, at the worst level any gauge reached. Years before the gauge records start are estimates.
Measured: the highest level each gauge reached that day, compared with the Department of Irrigation’s alert, minor-flood and major-flood levels.
Estimated: for years before the gauge records here begin, we estimate how high each river ran from a global river-flow model. These are not official warnings. They show the flood seasons and the big floods well, but can miss the exact day or gauge, especially on small rivers.
Sources: Department of Irrigation river gauges; earlier gauge readings saved by lk_irrigation; river-flow estimates by Open-Meteo. Download the daily records.