The quality and safety of Hudson River water varies significantly from city to city, and often from spot to spot, according to new research.

The study will examine water quality at various locations on the Hudson.Riverkeeper, a nonprofit group that works to protect the Hudson River, noted the findings as part of its Swimmable River Campaign, which kicked off Thursday. The program aims to investigate the processes that control Hudson River water quality, begin to provide water quality data to the public, and inform the government's water quality management decisions with sound science.

Conducted with Columbia University's Lamont-Doherty Earth Observatory, the program is the first to regularly test Hudson River water quality from New York Harbor to Albany and make the data publicly available quickly.

The New York Times takes a closer look at Riverkeeper's work as well as the complexities of the Hudson.