The Four National Taps of Singapore: A Holistic Approach to Water Resources Management from Drainage to Drinking Water

Singapore is a highly urbanized island country and as such faces significant water resource management challenges. Water resources in Singapore are managed following the principles of a closed-loop, hydrologic cycle by one agency, the Public Utility Board (PUB), which promotes its management philosophy through the “Four National Taps of Singapore” program. The Four National Taps are: i) water from local catchment areas; ii) imported water (from Malaysia); iii) reused water (known as NEWater); and iv) desalinated water. Given the uncertainty of water contracting and imports in the future, the remaining three national taps have become increasingly important and this presentation begins with a general overview of the innovative programs that have been implemented by the PUB in support of these three taps. Stormwater runoff is now captured from two-thirds of Singapore’s land area and stored in a number of reservoirs for subsequent use. One of these reservoirs, the Marina Barrage, was commissioned in 2010 and collects runoff from 10,000 ha of densely urbanized land. The reservoir was created through the construction of a 350 m wide dam across the Marina Channel to keep seawater out and subsequently infilling by stormwater runoff. Clearly, stormwater management (both quantity and quality) is an important component of the first national tap and extensive LID implementation and naturalization of the urban river system has become a priority through the ABC (Active, Beautiful, Clean) Waters program for catchment areas. Examples of several ABC Waters projects are discussed. NEWater currently supplies 30% of the country’s demand and this is projected to increase to 50% by 2060. NEWater plants take treated wastewater through the additional treatment steps of microfiltration, reverse osmosis, and ultraviolet for use primarily in industry, although a portion also is blended into the reservoirs. Singapore’s single desalination plant currently meets 10% of demand, with a second plant to be completed in 2013 that will more than double production.

The second part of this presentation provides preliminary results of some specific ongoing projects we are conducting related to stormwater management. In particular, we discuss levels and sources of E. coli, nitrate, and phosphate in runoff from a high density residential area and the positive results of a Nanyang campus taste test and survey on Singaporean acceptance of NEWater.