Singapore experiences an average of 167 rain days in a year, including 31 to 73 days classified as heavy rain days (based on 10 years of data).
Today, PUB is relying on 81 units of rain gauges across 710 km2 of land area to monitor rainfall across the entire island. Due to World Meteorological Organization’s requirements as well as limited suitable sites for installing rain gauges, there will be locations where rain gauges are sited as far as 3-5km away from each other. This results in the problem whereby the nearest rain gauges are too far to give representative readings of the rain intensity in certain areas.
Due to the convective nature of Singapore’s weather system, the rainfall in Singapore can vary significantly spatially and temporally. It is important that PUB obtains adequate rainfall data to support decisions to deploy flood management resources. The existing density of the rain gauge network does not provide enough resolution of the rainfall distribution and therefore, there have been instances in which the nearest rain gauge does not capture the actual rainfall at a location at a particular moment because it is sited outside the localised heavy rain area.