land area to catch and store the rainfall, and the absence of natural aquifers and lakes. Therefore, Singapore relies on four water sources, called the "Four National Taps": Rainfall, collected in artificial reservoirs that collect water from carefully managed catchment areas (200–300 million gallons per day, depending on rainfall), Imported water (up to per day, according to the 99-year agreement signed in 1962, plus an additional quantity under the 1990 agreement), Reclaimed water (producing what is called NEWater) (up to per day, officially only "30% of demand"), and Seawater desalination (up to per day, officially only "10% of demand"). This "four tap" strategy aims to reduce reliance on foreign water supply by increasing the volume supplied from the three other sources, or "national taps". Since water demand in 2011 was per day, Singapore could actually already have been water self-sufficient in 2011 except in years of very low rainfall. The official figures downplay the share of reclaimed and desalinated water in water supply, and thus the ability of the country to be self-sufficient. However, the Chairman of PUB admitted in 2012 that water self-sufficiency could be achieved well before the target year of 2061. In Singapore, water management is closely integrated with land management. The latter is tightly controlled in order to prevent any pollution of water resources through sewage, sullage or other sources of pollution. The management of water supply, sanitation and stormwater drainage is managed by a single agency, the Public Utilities Board, in an integrated and coordinated manner. Water from catchment areas Two thirds of the country's surface area are classified as partly protected catchment areas with certain restrictions on land use, so that the rainwater can be collected and used as drinking water. As of 2012, surface water was collected in 17 raw water reservoirs. Singapore's oldest reservoirs - MacRitchie, Lower Peirce, Upper Selatar as well as the more recently built Upper Peirce Reservoir - are all located in the Central Catchment Nature Reserve, a protected area that has been reforested to protect the water resources and act as a "green lung" for the city. The larger reservoirs, however, have been built after independence and are located in river estuaries that have been closed off by barrages. Reservoir water is treated through chemical coagulation, rapid gravity filtration and disinfection. Imported water Singapore's imported water comes through a pipeline that runs along a 1 km bridge, the