The estuary itself supports a great variety of thriving estuarine aquatic species; contrary to popular stereotypes, New York Harbor and its adjacent, interdependent waters are very much alive, and steadily recovering from pollution; ecologically it is true that these waters were once dead or extremely toxic but after 45 years of cleaning the estuary is in a much better state than it has been in a hundred years. Tidal flow occurs as far north as Troy, over 150 miles away. The salt front (dilute salt water) can reach Poughkeepsie in drought conditions and is present in the lower reaches of the Raritan River for most of the year.