Columbia University President Lee Bollinger and New York State Governor George Pataki announcing the launch of a center for rivers and estuaries research in Beacon, NY with satellites at Columbia and RPI, April 21 2003. Click HERE for the release from the Governor's office. Photo: Lester Millman, Photographer to Governor Pataki

The quantity, quality and security of Earth's fresh water supply, much of which rests in the world's rivers, is an ongoing and critical concern. Because many of the world's major cities lie along the banks of rivers and estuaries, these enormous tracts of water become extraordinarily vulnerable to the effects of pollution, shifts in ecology and innumerable other anthropogenic perils.

Researchers at the Lamont-Doherty Earth Observatory of Columbia University have formed a Hudson River research team to develop a systems approach to understanding the Hudson River and Estuary - the watershed that runs from the Adirondack Mountains of upstate New York through New York Harbor out to the shores of Long Island.

By studying the Hudson on multiple levels and scales, from its surface to its depths, from its mud to its marshes, these scientists hope to shed light on the complex relationships humans have to the rivers they live near and use for recreation, transportation and commerce and as drinking water supply sources.

In recent years, the Observatory has become a major contributor in New York State to the study of the Hudson River and its dynamic environs, where remnants of a glacial past, invasive zebra mussels, underwater dunes reminiscent of the Sahara Desert, and the presence of toxic waste come together.

Mapping the Hudson

Robin Bell and her colleagues have meticulously accounted for every curve, crevice, ridge and valley of over 90 miles of the river floor, from the Verrazano Bridge to the Federal Dam at Troy, including New York Harbor. Their map reveals a dynamic riverbed, with large dunes of sand and gravel, banks of oysters, archaeological artifacts and great swaths of the river that have been physically altered by centuries of human activity. This map has also identified places where recent mud has settled, since contaminants like PCBs tend to be found in recent mud.

In the spring of 2002, Michael Studinger and Frank Nitsche conducted the first systematic measurements of the magnetic field from just south of the Tappan Zee Bridge to 59th Street in Manhattan. The dramatic bends and folds in the map are produced by the bedrock in Westchester County driving beneath the river to depths of several hundred feet. Atop this natural backdrop, the map reflects the history of human use of the river, such as the crisscrossing of natural gas pipelines that power the lights of New York and New England, and long-collapsed piers.

Understanding the Hudson and Its Surroundings

Arnold Gordon is leading a team of researchers in a comprehensive study of the physical, chemical, geological and biological systems within Jamaica Bay - a complex salt marsh environment that is seriously threatened by its urban surroundings. Members of the team have already defined sediment terrains and characteristics of marsh loss and identified a number of island salt marshes that may be eroding or drowning.  Some researchers have amassed temperature, salinity and water current records, documenting the changing nature of the bay, while others have calculated a flushing time for contaminants that may be introduced into the region. The team has also focused on providing critical information on nutrient levels and the bay's biogeochemical responses to human activity while exploring the effects of urban development on the bay's wildlife habitats.

How Contaminants Move through the Hudson

In a recent series of experiments, a team of researchers, led by Peter Schlosser, David Ho and Ted Caplow, injected trace amounts of a harmless, inert gas into the Hudson River to see how quickly it would spread through the water.  During one such experiment in the summer of 2001, scientists were surprised to find that the highest concentration of gas did not move significantly from Newburgh, where it was first injected into the river, but that various amounts of the gas had spread throughout a large stretch of the river. This experiment has shown that the decrease in the concentration of the gas was caused not by the flow of the river but instead by the mixing of the river, which is linked to tidal motion. This result has tremendous implications for understanding the way in which contaminants move through the river and how best to follow them for cleaning.

These tracer field studies are augmented by numerical simulations of the spreading of perturbations in the Hudson River. The goal of these modeling studies is to put the measurements into a dynamic framework and to help with the interpretation of the evolution of the tracer distributions over time. First results are promising and suggest that the tidal forcing of the circulation in the Hudson River has significant impact on primary and secondary features of the observed tracer distributions. The modeling work is being performed in collaboration with the Department of Earth and Environmental Engineering and the Earth Engineering Center.

In a related study, Robert Houghton and colleagues have shown that the modulation of the mixing in the stratified lower Hudson by the spring/neap tidal variation is significantly greater than had originally been believed. As a consequence, the net up-river flow near the bottom is greater during neap (weak) tides and nearly absent during spring (strong) tides. Using a harmless dye tracer, scientists were able to measure the tidally driven flow in the Hudson River, including the weak but significant cross-channel (east/west) flow. Within hours, the tracer, injected near the bottom of the deepest portion of the river, the navigation channel on the east side, just north of Spuyten Duyvil, had moved across the river channel to shallow water on the west side. Their research suggests that this rapid movement contributes significantly to the mixing of pollutants introduced into the water.

The Environmental Geochemistry Group, a group of Observatory scientists led by James Simpson, has been analyzing components of Hudson geochemistry since the early 1970s. These researchers continue to study the impact on nutrient species distributions within the estuary as a result of very large discharges of sewage and other waste into the New York/New Jersey harbor complex. They have also measured dissolved gases to improve our understanding of how contaminants are influenced by microbial processes in river sediments and the water column. Over the years, Steve Chillrud and others have collected a large number of sediment cores from the Hudson River basin throughout the system downstream of Glens Falls, New York, paying considerable attention to persistent contaminants, such as heavy metals, polychlorinated biphenyls (PCBs), pesticides and anthropogenic radionuclides, which tend to accumulate in fine-grained sediments and can continue to mix with the water for many decades. In collaboration with Mount Sinai School of Medicine, the group has also investigated levels of lead, mercury and chlorinated organics in people who have consumed appreciable amounts of fish and shellfish from the Hudson.

Hudson History

The marshes are among the most crucial places in the Hudson, as they form the base of the food chain, protect young plants and animals, and protect the shoreline. Recently, Dorothy Peteet and her colleagues examined the vegetational and charcoal content of the marshes and found that over the last 4,000 years, these marshes have been strongly affected by drought. The Hudson's marshes are repositories of historic information about the regional New York climate and are especially valuable because they have a high sedimentation rate, which makes detailed sampling possible.

As part of a larger effort at the Observatory to understand the evolution of the Hudson Estuary and regional climate, Cecilia McHugh, Stephen Pekar and Lloyd Burckle are evaluating climate variability for the Hudson Valley for the past 6,000 years. They are estimating past salinity changes and fluctuations in freshwater discharge rates into the Hudson River using three proxies for salinity: diatom assemblages, foraminiferal biofacies and oxygen isotopes. Calibration to historical precipitation records that go back to the late 1800s shows a correlation to the pronounced mid-1960s and early 1970s droughts in the northeast United States. Documentation of historical droughts in the Hudson Valley will help scientists to understand future climate change and to evaluate the impact of anthropogenic activities on the environment.

In the summer of 2001, Suzanne Carbotte and other Observatory scientists sited and recovered deep samples from the ancient glacial lake that once flooded the Hudson Valley. Scientists identified the distinctive signature of the glacial deposits in the seismic data acquired in the spring.  With assistance from a local utility company, samples from the glacial lake were recovered and are now being analyzed at the Observatory's Core Laboratory. Scientists are looking for evidence of climatic cycles and the river's response to changing climate.

Carbotte is also examining the evolution of oyster populations in the Hudson River.  Although oysters are not present today, researchers have dated shell remains found in the Hudson from 600 to 2,500 years old and from 5,000 to 6,500 years old. Cores taken from the oyster beds reveal abrupt changes in sediments, resulting from sea level rise and climate change. From these cores, researchers have determined that oysters disappeared in the Tappan Zee region during cooler times, possibly due to more severe winters with extensive freezing and ice rafting within the river. In more modern times, the demise of oysters may be associated with the Little Ice Age, although pollution and over harvesting appear to have contributed to the early-20th-century demise of oysters within New York Harbor.

The Pulse of the River - A Riverscope

In the fall of 2001, Martin Visbeck and Robin Bell, working with Observatory engineers, installed the first node of a riverwide monitoring station just south of the Tappan Zee Bridge. The initial installation includes atmospheric observations, river observations and observations from sensors beneath the water surface. Real-time monitoring of the Hudson River may have widespread impact upon policy development and the prediction of short- and long-term impacts of environmental changes. Salt front movement and its relation to urban water supplies, PCB dredging in the upper Hudson and its impact on the entire river and estuary, and the invasion of exotic species such as zebra mussels and the subsequent shifts in local and regional ecosystems will be some of the issues studied. Other studies will focus on land-use impacts and the implications of climate change on the Hudson River and its surroundings.

Related Links

Hudson River Research at Columbia University