What’s the difference between Olafur Eliasson’s 2008 East River Waterfalls

Image of Brooklyn Waterfall from Time
and Roosevelt Island’s 1969 Delacorte Fountain ?Image of Roosevelt Island Delacorte Fountain from Judy Seigel
The answer comes from this NY Times article:

The Waterfalls is not the first controversial water element to grace the citys shores and headlines. The philanthropist George T. Delacorte donated $400,000 to build a 450-foot geyser at the end of Roosevelt Island, then known as Welfare Island, that opened in 1969.

Upon learning that the source of the water was the East River, which then had 160,000 fecal coliform bacteria per 100 milliliters, the citys health department demanded that the water be chlorinated to reduce the risk to public health. The chlorine spray damaged a stand of 55 pine trees donated by residents of Sutton Place to improve their view. After occasionally failing, being vandalized and turning red from too much chlorine, the fountain fizzled out in 1987.

The Metropolitan Waterfront Alliance explains some of the reasons for a cleaner East River:

The water quality of the East River has improved considerably after the Clean Water Act of 1972. The water is well oxygenated, clearer, and the level of coliform bacteria, in dry weather conditions, is low enough to fish and boat. Bathing is not yet recommended.

The New York City Harbor Survey (since 1909) on East 23rd Street monitors the following parameters: Dissolved Oxygen, Fecal Coliform Bacteria, Chlorophyll a, and Secchi Transparency.

Those results have been achieved because today, industrial discharges are well regulated, and wastewater treatment plants have been improved. Along the East River there are five treatment plans: Newton Creek, Brooklyn; Red Hook, Brooklyn; Wards Island; Hunts Point, Bronx; and Tallman Island. They treat the water from different areas in the boroughs of Manhattan, Brooklyn, Queens and Bronx. These areas are highly populated and during wet weather, the storm water will thoroughly wash the hard land surface picking up dirt, chemicals, highway debris, unburned oils from vehicles, animal waste, and other pollutants. Part of the storm water runs off straight into the East River, the other part goes into the combined sewers that mix it with sewage and often discharge the untended overflow in the East River.

At the waterfront you can see the Combined Sewer Overflow outfall- the New York City Department of Environmental Protection (NYCDEP) marks them with green signs. One is encouraged to report discharge, during dry weather, by calling 311.

Maybe now, the Delacorte Fountain can be turned back on!