Sri Lanka Water Levels

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1. Rain on the hills
2. 2Reservoir
3. 3Gauges on the river
4. 4Your town, hours later
5. 5Rain on your street

• Where readings come from

  River gauges of the Irrigation Department, about every hour.

  We show each gauge’s latest reading. If a gauge goes quiet, we say how old its last reading is.

• What the colours mean

  Normal, Alert, Minor flood, Major flood: the Department of Irrigation's four official steps.

  Normal: below the alert mark (a gauge close to it still reads Normal, with a note). Alert: the river is high. Minor flood: low land starts to flood. Major flood: wide flooding. Your own street may flood earlier than the official step.

• How the forecast works

  River trend, rivers upstream and rain over the hills. Experimental.

  We look at how fast the river is moving, what rivers upstream are doing and the rain on the hills. It is experimental, and every hour we check our forecasts against what really happened.

• Reservoir releases

  Gates open, and the water arrives hours later downstream.

  Spill gates let extra water out of a full reservoir. It takes hours to travel down the river, so a calm gauge can rise fast. A cusec is one cubic foot of water a second, about 28 litres.

• Official warnings come first

  Follow the Disaster Management Centre and the Irrigation Department. Call 117.

  We repeat their warnings, we don’t replace them. If officials tell you to move, move.

• What we can’t promise

  Gauges can go offline and forecasts can be wrong.

  This is not an official service. Use it as an early hint, never as a guarantee.

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