Delaware River

The Delaware is one of our hemisphere’s most critical stopover points for migrating shorebirds.

The Delaware River begins its 400-plus-mile journey in New York’s Catskill Mountains, where cool springs establish the river’s East and West branches. Further south, the branches meet in Hancock, New York to form one of the only free-flowing major rivers remaining in the eastern United States.

With more than 300 miles designated as “wild and scenic,” the Delaware is a river of tremendous biological, economic and cultural significance. Nearly 20 million people along the East Coast rely on its water for drinking and industrial purposes. They share the resource with shad, sturgeon, eel and other species that migrate through the river. Anglers and kayakers enjoy the Delaware’s scenic beauty, protected in places by five national park properties.

Mammals including bobcat, beaver, bear and fox roam throughout this watershed that also contains an important segment of the Atlantic flyway. Each year, more than 200 species of birds spend part of their life cycle here.

The shores of the Delaware River Estuary, in Delaware and New Jersey, provide critical spawning grounds for horseshoe crabs and hosts one of the most critical stopover points for migrating shorebirds in the western hemisphere.


Although it remains undammed, the Delaware faces a variety of serious and growing threats, as human demands for water outstrip nature’s ability to provide. Among the many stresses on it are nutrient runoff and sedimentation from agricultural, industrial and residential sources, and invasive species which threaten the existence of many native species and natural communities. Further down the river, climate change poses another threat to the Delaware. Rising sea levels are causing serious concern that the Delaware’s “salt line” may move up the river, threatening Philadelphia’s water supply.

But one of the most challenging threats lies in the very way the river flows. Approximately 50 percent of its headwaters is diverted to New York City’s municipal water supply system, and never returns to the watershed.

The withdrawals and releases that accomplish this diversion cause profound changes in the natural flow of the river – the periodic changes of water level, volume, scouring and flooding that create the specific habitats upon which the river’s life depends. These flow alterations are threatening the survival of freshwater animals like mussels, crayfish and amphibians – among the species most at risk in the United States - and the health of the entire river system. 

Land use changes along the river’s edges also cause dramatic changes in the way the water moves. The river’s floodplains are rich stores of biodiversity, and serve as critical natural regulators of the water coursing down the river. Their thickly accumulated soils and dense floodplain forests slow the course of seasonal floods and help absorb the impact of storm events. 

But the Delaware’s floodplains have seen heavy development, and fewer are left to gentle the river’s rush. Recent years have seen unprecedented destruction from repeated heavy floods in the middle and lower stretches of the river. While the causes are many, one key part of the solution lies in conserving and restoring the floodplains that can help protect the river from the ravages of these events.

Taking Action – Everyone’s River

For decades, The Nature Conservancy has worked to protect and restore habitat in the Upper Delaware River watershed, conserving fens near Mount Bethel, seasonal wetlands in the Greater Minsi Lake Corridor, dramatic cliffs and hardwood forests at our Long Eddy River Edges Preserve, and a rich floodplain forest of increasingly rare butternut trees on Butternut Island. The new Cherry Valley National Wildlife Refuge, which The Nature Conservancy helped to establish, will assure permanent conservation for this lovely Delaware River tributary.

Now, the Conservancy is drawing on 50 years of experience in an effort to address the challenges of river management for the benefit of nature and people. We are using the Conservancy’s cutting-edge Active River Area analysis to identify the areas which are most important for protecting and restoring the Delaware’s natural physical and ecological processes.  This will provide powerful conservation guidance to the Conservancy, state and federal agencies and other partners in their efforts to ensure the health of the river and the well-being of communities downstream.

We have also contributed to the design of a “flexible flow management program” that allows water managers to mimic nature, providing the conditions needed for fish spawning and other natural events. Using this system, we have helped the four basin states, New York City, and the Delaware River Basin Commission to change the way reservoirs are managed so as to minimize disruption of the temperature and flow patterns further downstream. These actions – combined with ongoing efforts to connect important habitats, influence sustainable land uses and combat non-native vegetation – will go a long way in ensuring the Delaware River remains a healthy, abundant source of life-sustaining water for people and nature.


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