The Four National Taps of Singapore: A Holistic Approach to Water Resources Management from Drainage to Drinking Water K. N. Irvine, L. H. C. Chua and Hans S. Eikass Abstract 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: water from local catchment areas; imported water (from Malaysia); reused water (known as NEWater); and de- salinated water. Given the uncertainty of water imports, the remaining three national taps have become increasingly important and this paper begins with a general overview of the innovative programs implemented by PUB in support of these three taps. Stormwater runoff is captured from two-thirds of Singapore’s land area and stored in reservoirs for subsequent use. Stormwater management is an important component of the catchment area tap and extensive low impact development (LID) implementation has become a priority through the ABC (Active, Beautiful, Clean) Waters Program. Examples of several ABC Waters projects are dis- cussed. 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 steps of microfiltration, reverse osmosis and ultraviolet treatment for use primarily in industry, although a portion also is blended into the municipal reservoirs. Singapore’s single desalination plant currently meets 10% of its demand, with a second plant to be completed in 2013 that will more than double production. Also discussed are the results of recently completed pilot projects related to stormwater management including testing of E. coli in runoff from high density residential areas, a blind taste test and survey on acceptance of NEWater, and a survey of Singaporean understanding about stormwater management issues. Keywords: water supply, LID–BMP, water quality, stormwater, water treatment. 1 Introduction 2 Background to the Current Situation in Much has been written about the Singaporean economic miracle Singapore (e.g. Huff 1987; Krugman 1994; Chang 2003; Goh 2005; Siddiqui 2010) but less well known, at least in North America, is the innov- 2.1 History, Politics and Policy Development ative approach that Singapore has taken towards water resource To fully appreciate the current, innovative path that Singapore management. As such, the objectives of this paper are: has pursued with respect to water management it is important first to have a quick overview of Singapore’s recent history and 1. Outline Singapore’s closed loop, integrated systems associated politics. The first permanent settlement on the island approach to water management, locally known as appears to have been established in the late thirteenth century, the Four National Taps, explaining why the approach but the Lieutenant-Governor of Bencoolen (now Bengkulu) in was implemented and factors that have led to its Sumatra, Sir Thomas Stamford Raffles, is credited with establish- success; ing the current city-state in 1819. Raffles had been tasked with 2. Review the diversity of low impact development establishing a port of call as British traders needed a strategic (LID) technologies implemented as part of the Four location to provision their merchant fleet sailing between India National Taps, including a discussion of technology and China, and a strong foothold was desired to counter the performance; and Dutch presence in the region (Turnbull 1980; Murfett et al. 1999). 3. Summarize preliminary findings of some pilot stud- Soon, the island’s policy of free trade, as opposed to the restricted ies undertaken by students at the National Institute trade practiced by the Dutch and Spanish (Trocki 2006), attracted of Education, Nanyang Technological University, merchants from all over Asia and from as far away as the United related to Singaporean acceptance of NEWater, their States and the Middle East. The early beginnings of multicultur- understanding of stormwater issues, and stormwater alism were established, and this tradition carries on today with runoff quality characteristics. predominant ethnicities being Chinese (74.1%), Malay (13.3%), Irvine, K., L. Chua and H.S. Eikass. 2014. "The Four National Taps of Singapore: A Holistic Approach to Water Resources Management from Drainage to Drinking Water." Journal of Water Management Modeling C375. doi: 10.14796/JWMM.C375. © CHI 2014 www.chijournal.org ISSN: 2292-6062 1 Indian (9.2%), and others (including Europeans, 3.3%) (Singapore of the closing the loop philosophy is the Four National Taps, or Demographic Bulletin, April 2012, http://www.ica.gov.sg/data/ the four water supply sources for Singapore: resources/docs/Media%20Releases/SDB/SDB_April%202012.pdf). 1. Imported water from Malaysia; From 1824 through 1942 Singapore operated under British col- 2. NEWater (recycled water); onial rule, as Singapore was ceded in perpetuity to the East India 3. Water desalination; and Company by the Sultan of Johor (part of present day Malaysia). 4. Local catchments (i.e. stormwater runoff) and reser- On 15 February 1942 Singapore fell to Japan and was under voirs. Japanese rule until the end of World War II, at which time Britain regained control. However, the political climate in Southeast Asia was not the same after World War II (Ismail 2012) and Britain, facing post-war economic challenges and conflicting sentiment about colonial policy, granted the federated states of Malaya independence in 1957. By 1959 Singapore, under the leadership of Lee Kuan Yew and the People’s Action Party (PAP), was granted internal self government and subsequently joined the federated states of Malaya (now peninsular Malaysia), Sarawak and Sabah (eastern islands of Malaya) to form Malaysia in 1963. This union was short-lived, however, due to political differences, and Singa- pore was asked to leave, becoming an independent republic in 1965 (Liu et al. 2002). Interestingly, it was around this time (1961 and 1962) that the Johor water agreements were signed, which provided up to 350 mgd (15.3 m3/s) of raw water to Singapore from Malaysia (Ong 2010). The beginning of an independent Singapore republic was Figure 1 The PUB pproacha to closing water loop (from marked by the visionary leadership of Lee Kuan Yew, Singapore’s http://www.pub.gov.sg/water/Pages/default.aspx). first Prime Minister (1965–1990) (Oei 1998; Ang 2013). Low (2011) The first three taps will be described briefly in this paper, asserts that Lee’s focused initiatives to green Singapore have but the focus will be on the fourth tap (local catchments). An made good business sense by reducing pollution and cutting understanding of Singapore’s geography is a necessary prerequi- business costs. The Garden City was aptly named as its well- site to fully appreciate the magnitude of the country’s efforts in developed network of linked greenways and parks evolved from water resource management. Lee’s first greening program, Tree Planting Day (Tan 2006). Joshi et al. (2012) documented the steps towards the successful clean- up of the Singapore River between 1977 and 1986, emphasizing 2 Geography of Singapore that Lee’s vision required close coordination between govern- Singapore is a small island nation-state located at the southern ment agencies and different sectors in Singapore, and a holistic end of the Malaysian Peninsula. It has a total area of 715.8 km2, approach to urban development, environmental management, with an east–west length of only 49 km and a north–south length sustainability and economic opportunity. of 25 km. At a current total population of 5.3 million (up from 1.6 As part of Lee’s holistic approach to urban environmental million in 1960), Singapore’s population density of 7 257 people/ management, the Public Utility Board (PUB) was established in km2 is ranked the third most dense in the world, after Macau and 1963, initially to oversee the provision of electricity, water and Monaco. In comparison, the United States ranks 172nd with 34.3 piped gas (Khoo 2009). After a significant involvement with the people/km2 and Canada ranks 220th with 3.8 people/km2. Singa- Singapore River restoration, which also prompted the develop- pore’s per capita GDP in 2011 (adjusted for purchasing power ment of separate storm and sanitary sewer systems, PUB relin- parity and based on current international dollars) was higher, quished its mandate to manage electrical supply in 2001. This at $60 688 than either the United States ($48 112) or Canada marked the beginning of the Four National Taps water manage- ($40 370) according World Bank statistics (http://data.worldbank. ment strategy. org/indicator/NY.GDP.PCAP.PP.CD). The climate of Singapore is classified under the Koppen 2.2 The PUB Philosophy of Water Resources system as a tropical rainforest (Af) with no true dry season. Management Annual mean rainfall is approximately 2 343 mm and annual Singapore takes a holistic approach to managing its water resour- mean temperature is 27 °C. The annual maximum 60 min rainfall ces, essentially overseeing the entire hydrologic cycle through intensity 1980–2010, ranged between 70 mm/h and 130 mm/h. one agency, PUB. PUB has termed this approach closing the loop In keeping with its tropical rainforest classification, the mean and the philosophy is summarized in Figure 1. The core element number of days/month with rain ranges between 11 and 19, and 2 the minimum number of rain days per month is in the range 1 2009). Singapore currently has one seawater reverse osmosis to 3 (http://app2.nea.gov.sg/weather_faq.aspx, http://app2.nea. plant that produces 30 mgd (136 000 m3/d) and meets about gov.sg/weather_statistics.aspx). This amount of rainfall, and as- 10% of Singapore’s water needs (http://www.pub.gov.sg/water/ sociated runoff, presents management challenges and eclipses Pages/DesalinatedWater.aspx).