Nuisance Posed by Chironomids from Pandan Reservoir

Ms Foo Mee Har asked the Minister for the Environment and Water Resources (a) what additional measures will the Ministry implement to mitigate the nuisance posed by chironomids from the Pandan Reservoir; and (b) how can residents living in the vicinity be updated on these actions and measures taken by PUB.

Chironomids or non-biting midges are a type of flying insects that thrive near water bodies such as canals, ponds and reservoirs. They are a natural part of the aquatic ecosystem and are food for fishes and birds. While they neither bite human beings nor spread any disease, they can pose nuisance when they swarm in large numbers. In recent months, the Public Utilities Board (PUB) has observed an increase in the emergence of chironomids around the Housing and Development Board (HDB) blocks near Pandan Reservoir, largely due to the intermittent hot and wet weather.

PUB has been actively monitoring the chironomid population and has stepped up measures to control the population and reduce inconvenience to nearby residents. These include regular removal of chironomid eggs from the reservoir's floating structures, increasing the frequency and dosage of the application of biological liquid larvicide Bacillus thuringiensis israelensis (Bti) from three times to five times per week along the reservoir perimeter to kill chironomid larvae, and increasing the frequency of fogging and misting around the reservoir dyke and surrounding vegetation to kill adult chironomids.

In addition, PUB has installed bright spotlights at the Pandan Reservoir pumping station and turned them on at night to attract the adult chironomids and deter them from flying into nearby residential areas. We will continue to monitor the situation closely and adjust our measures accordingly.

To keep residents living in the vicinity of Pandan Reservoir informed of the chironomid situation, PUB has recently issued a joint advisory with the National Environment Agency (NEA) and the West Coast Town Council on the measures taken by the agencies and actions residents can take within their premises. PUB also conducted a dialogue session with the residents on 28 August 2016 to address their concerns. Educational brochures have also been distributed to the residents around Pandan Reservoir.

I would like to assure members and the residents that PUB will continue to put in their best efforts to reduce the inconvenience caused by chironomids. Having said that, we may not be able to completely eradicate the chironomids, as they are a part of the natural aquatic ecosystem. Therefore, we also seek residents' understanding and tolerance, should they find these harmless chironomids in their homes.