Urban stormwater collection for potable use

Singapore is an island city-state with a limited land area of about 650 sq km. Almost half of its total land area has been utilised as water catchments. In its continuous efforts to meet the increasing demand for water, the Public Utilities Board (PUB) had embarked on a unique scheme to implement urban stormwater pond collection systems in suitable catchments. This is to exploit the harnessing of storm runoff from new townships to augment its limited water supplies. This scheme has been in use for over ten years. Urban stormwater collection systems are feasible through the implementation of a co-ordinated and integrated approach to development control and landuse planning, together with innovative design and effective catchment management. The Lower Seletar/Bedok Water Scheme was completed in 1986 with a total of eight stormwater collection ponds. Close monitoring and control of pollution through the adoption of stringent anti-pollution measures and enforcement actions have resulted in the collection of generally good quality raw water from these urbanised catchments with very low levels of heavy metals and low coliform counts as compared to raw water from largely forested catchments. Since then, newer urban stormwater pond collection stations have been implemented or are being planned in the northern and northwestern parts of Singapore to replace existing stream abstraction stations affected by urbanisation arising from public housing development. Additional features beyond utilitarian functions, such as better aesthetics and landscaping, and recreational facilities have been incorporated into these designs as well as land optimisation for competing uses. One unique facility is being built under the flyover ofan expressway interchange to utilise the land space which otherwise would be oflimited use. PUB is also designing a covered type of storrmwater pond at another location, the first of its kind, in order that the land above the functiona- l concrete pond can be used for other purposes such as schools' football fields and basketball courts.