SINGAPORE - A detailed study of the environmental impacts of constructing a floating solar farm in Lower Seletar Reservoir - which could potentially be Singapore's largest - will soon be conducted.

National water agency PUB told The Straits Times that the reservoir has been identified by National Parks Board as a key corridor in facilitating animal movements among the core habitats of the Central Catchment Nature Reserve, Simpang-Khatib Bongsu and Coney Island.

PUB is therefore committed to conducting detailed environmental studies and impact assessment, to ensure that any solar panel deployment is done in an environmentally sensitive manner, said its spokesman.

To help Singapore meet its growing clean energy needs, the agency previously identified the Lower Seletar Reservoir as a potential site for a large-scale solar farm of 100 megawatt-peak (MWp) and Pandan Reservoir for a 44MWp system.

Feasibility studies are currently being planned to determine the viability of putting up solar panels at both reservoirs, as the Republic aims to install at least 2GWp of solar photovoltaic (PV) capacity by 2030.

Singapore's first large-scale floating solar farm was rolled out at Tengeh Reservoir in July last year, with a capacity of 60MWp.

PUB said the proposed installation of solar panels in Lower Seletar Reservoir would take up about a third of the reservoir's surface area, with detailed studies needed to determine the exact coverage and layout of the panels.

Its spokesman added that at Tengeh Reservoir, an environmental impact study and an environmental monitoring and management plan were conducted to minimise the impact of installing the solar panels during the construction and post-construction stages.

Findings and observations revealed that there has been no observable change in the reservoir's water quality, said PUB.

The solar PV system was also designed to allow sufficient sunlight and air to enter the water, thereby supporting aquatic life and minimising any impacts to the water quality of the reservoir, it added.

Aerators were also deployed to maintain the amount of dissolved oxygen in the water, with stringent requirements on material selection for the various components of the system. These plans will similarly be studied and carefully considered before deployment in other reservoirs.

"We have seen grey herons, white-bellied sea eagles, grey-headed fish eagles around the floating solar panel installation, with camera traps capturing otters on the solar panel system," said the PUB spokesman.

Nature enthusiasts, however, express concern that birds from forested areas surrounding the Lower Seletar Reservoir may experience a loss of feeding areas if the floating solar panels are deployed.

Dr Shawn Lum, president of Nature Society (Singapore), said the reservoir is bordered by secondary forests containing many albizia trees, which are tall, fast-growing and serve as an important habitat for large birds such as the white-bellied sea eagle and the locally endangered grey-headed fish eagle.

These eagles are dependent on areas where fish abound, such as in the catchment reservoirs. Other birds such as terns may also feed on fish, while swallows and bats may skim the water surface for insects.

These animals could be impacted by the loss of feeding areas, and an environmental impact assessment (EIA) would be needed to determine the extent to which such wildlife uses the Lower Seletar Reservoir, and the likely impacts of floating solar farms on these species, said Dr Lum.

PUB has launched a tender on government portal Gebiz for an EIA to be carried out at the Lower Seletar Reservoir, involving detailed water quality monitoring, baseline surveys of flora and fauna and other environmental indicators like microclimate parameters and noise levels.

An assessment of the solar panel deployment via these environmental indicators will be carried out, followed by mitigation measures along with an environmental monitoring and management plan. The entire EIA process is expected to take about 1½ years.

Dr Lum, however, pointed out that the EIA would not be able to address the "cumulative impacts" of water surfaces being gradually lost to floating solar farms.

"The assumption might be that if birds cannot feed at Lower Seletar, perhaps they could fly over to another reservoir or the Johor Strait to feed, but if much of our reservoir space is used for solar power generation, then reservoir-dependent wildlife would be impacted severely," he added.

This does not mean that Singapore should hold back on constructing floating solar farms - but instead it should have a "holistic view" of the ecosystem and wildlife impacts on a larger scale, to better assess the risks and mitigate or avert them if possible.

"At the very least, it would give us a realistic assessment of the ecological cost of solar power," he said.

Asked about whether an EIA will similarly be conducted at Pandan Reservoir, PUB said it would not be required as the solar PV system would not be deployed near areas with sensitive biodiversity or habitats and vegetation.

The agency will still be conducting studies such as water quality monitoring to ensure that the solar panel installation does not impact reservoir water quality.

Multiple biodiversity surveys to determine the food web at Pandan Reservoir have also been carried out, said its spokesman.