SINGAPORE - Green algal growth was spotted in Kranji Reservoir on Tuesday (Oct 17), but water agency PUB has assured the public that such growth is not uncommon and poses no danger.

Photos sent in by a reader of The Straits Times, taken on Tuesday, show murky waters at the reservoir coated with a thick green hue.

A spokesman for PUB confirmed with ST that the photos show algal growth.

Singapore's weather creates favourable conditions for such growth, and the appearance of algae depends on weather conditions.

According to PUB, nutrients from sources in water catchments such as from pet waste, food waste, fertilisers, detergents and sediments, are food for algae, which are microscopic aquatic organisms.

"When these nutrients are available and when conditions are favourable, such as (when there is) warm water and sufficient sunlight, algae may grow rapidly," said PUB in an advisory on its website.



The water at the reservoir was tinted green. PHOTO: ST READER



The green tint created comes from the chlorophyll, a photosynthetic pigment in algal cells which they use to make food.

This is why algae is more visible from the early morning to the mid-afternoon, when sunlight is plentiful.

Algae tends to concentrate on the surface of calm waters, and can often appear as a concentrated green layer known as scum at certain reservoir shores or canal edges due to wind directions.

PUB assured the public in its advisory that it monitors water quality closely with real-time water quality sensors in reservoirs and major waterways, collecting samples to analyse algae and chlorophyll levels.

Related Story Algae turn Singapore River green

PUB removes algal scum in reservoirs and works with the National Environment Agency's Department of Public Cleanliness to clean waterways daily.

It is also working on an improved algal management plan, including enhanced monitoring tools and ways to manage algal growth.

The waters from the reservoirs undergo several layers of treatments, removing algae effectively, PUB said.

Earlier this month, parts of the Singapore River turned green because of algal overgrowth, startling several passers-by.