Erratum for “Water Reclamation and Reuse in Singapore” by Yue Choong Kog

Singapore is a very small country, with a size of slightly more than $700{\mathrm{km}}^2$. During World War II, a water shortage was a major reason leading to the Japanese occupation of Singapore. This historical event is a constant reminder of the importance of water supply to Singapore’s security (Simson 1970). Supplying water to the world’s population is estimated to cost $700 billion yearly (Tully 2000). Many believe that water will be a valuable commodity that affects the prosperity of countries in the 21st century. The manner through which a nation manages its water supply could influence its well-being. To be competitive, countries must maintain their water plants in good condition and run them at the minimum cost.

Water supply will always be critical to the security of Singapore, both economically and militarily. Rainfall is plentiful in Singapore, although year-to-year rainfall is highly variable. It rains at least 0.2 mm an average of 167 days each year, and the 1981–2017 long-term mean annual rainfall total was more than 2,100 mm. Singapore’s average annual rainfall total since 1980 has increased at an average rate of 100 mm per decade. Countries with water resources $<\mathrm{1,000}{\mathrm{m}}^3$ per year per person are defined as water-stressed (i.e., with insufficient resources to meet their needs) (Postel 1993). With only $172{\mathrm{m}}^3$ of water per person per year because of the limited land surface, Singapore is one of the most water-stressed countries, along with the Middle Eastern countries. In fact, in a recent study, Singapore was forecast to be the most water stressed in 2040 (Maddocks et al. 2015).