Singapore's national water agency, the Public Utilities Board (PUB) is undertaking a two year study to look into the feasibility of building an underground drainage and water reservoir system to mitigate the impact of climate change and act as a buffer against drought.

The republic's Environment and Water Resources Minister Vivian Balakrishnan said at the Singapore International Water Week Technology and Innovation Summit on 16 June that although the island gets an average of 2.4 metres of rainfall annually, and despite having 17 reservoirs, Singapore still lacks space to store water.

During heavy showers, much of the rainwater ends up in the sea.

"Climate change increases the probability of both intense rainfall and prolonged periods of drought. So if we and indeed if water utilities and authorities all over the world simply embark on business-as-usual, climate change will reduce the yield of reservoirs and of water catchments all over the world in the decades to come."

Chua Soon Guan, deputy chief executive for policy and development at the PUB, said many countries have underground aquifers, naturally occurring caverns that store water. Singapore is therefore learning from other countries on how they manage underground water and aquifers, ChannelNewsAsia reported.

During a rainstorm, tunnels could transport excess storm water from drains, drop the water down deep vertical shafts and store it in underground caverns.

A pumped storm storage hydro power system could tap into the energy of the storm water in the tunnels as it drops into the cavern and the stored energy can be reused when the water needs to be pumped out, the news channel said.

The study will include geographical surveys on soil and rock properties, as well as the challenges involved in building such underground facilities.

The study is expected to be completed by the end of 2017.