Environmental Issues in New York City - Water Supply

Water Supply

Many of the city's environmental assets are related to geography and a long tradition of environmental stewardship in the mountain ranges north of the city. Because the watershed is in one of the largest protected wilderness areas in the United States, the natural water filtration process remains intact. As a result, New York is one of only five major cities in the United States with drinking water pure enough to require only chlorination to ensure its purity at the tap under normal conditions.

However, all groundwater entering New York City's distribution system is treated with chlorine, fluoride, food grade phosphoric acid, and, in some cases, sodium hydroxide. New York City uses chlorine to meet the New York State Sanitary Code and federal Safe Drinking Water Act disinfection requirements. Fluoride, at a concentration of one part per million, is added to help prevent tooth decay and has been added since 1966 in accordance with the New York City Health Code. Phosphoric acid is added to create a protective film on pipes that reduces the release of metals such as lead and copper from household plumbing. Additionally, a sequestering phosphate is applied at several wells to prevent the precipitation of naturally occurring minerals, mostly iron and manganese, in the distribution mains and customers' household piping. Air stripper facilities can be operated at several wells to remove volatile organic compounds (VOCs). The only well in operation in 2007 had an air stripper in operation.

The complex New York City water supply system — with 19 reservoirs bringing mountain water from as far as 125 miles (201 km) away through a gravity-fed web of aqueducts — consists of three different systems. The Croton system, the oldest and smallest section, sits in Westchester and Putnam Counties. The second oldest is the Catskill system. In the early years of the 20th century, the city and state designated thousands of acres the eastern Catskills to build two reservoirs that more than doubled the city's capacity. In the 1950s and 1960s, the city expanded again, tapping the east and west branches of the Delaware River and other tributaries to create the newest and largest of its three systems.

The Croton system is the source of some turbidity issues for the city's water. The turbidity problem stems largely from conditions that have been present in the Catskill system from the beginning. Engineering studies in 1903 recognized that the clay of the steeply sloped Eastern Catskills turned the clear waters of the Schoharie and Esopus Creeks muddy after storms.

Engineers decided to go ahead anyway, devising a two-reservoir system with built-in turbidity controls. The city has sought to restrict development throughout its watershed. One of its largest watershed protection programs is the Land Acquisition Program, under which the New York City Department of Environmental Protection has purchased or protected through conservation easement over 70,000 acres (280 km²) since 1997.

In the 12 months that ended on June 30, 2006, daily consumption averaged 1.086 billion US gallons (4,110,000 m3) in the city, a decline of 5.2% since 2002 and the lowest total daily use since 1951, when the city had about 7.9 million people and New York was experiencing a severe drought. Daily consumption peaked at 1.512 billion US gallons (5,720,000 m3) in 1979; in the next year’s census, the city’s population was 7.1 million, its lowest since 1930. Despite having grown to a population of 8.2 million in 2006, the city is now using 28% less water than it did in 1979. The drop in consumption is mostly a result of city policy; water-saving plumbing fixtures and devices in renovations and new construction are required, the city has been more diligent in finding and fixing leaks, and since the late 1980s it has been metering residential customers’ water use. The city uses sonar and other equipment to more efficiently find and fix leaks in its millions of feet of water mains and has taken steps like installing sprinkler caps on fire hydrants during the summer, letting overheated kids cool off without torrents of gushing water.