Hudson River Ecology

How does the Hudson River ecosystem respond to different types of changes over time? Are these changes permanent, and how will the ecosystem respond? Our curriculum addresses these questions through modules which combine unique and engaging Hudson River data collected by the Cary Institute and other scientists, investigations, readings, and visualizations.

Historic Pollution in the Hudson

One-two 45-minute class periods

Students will know how the pollution in the Hudson River has changed over time, and be able to explain the consequences of these changes.



Engagement: Students should read the excerpts from the New York Times, titled “A Poor Sewerage System” and “Albany’s Dangerous Basin”, along with a short synopsis of water quality in New York City. Reading (or discussion) questions are provided.

Divide students into pairs and ask them to brainstorm the effects of increased nitrogen and phosphorus on an aquatic system. If they have not done any work with water quality indicators, they should be asked to write down what they would need to know in order to answer the question. Review the ideas as a group, and discuss what the impacts of sewage discharge into the Hudson might be.

Exploration: You should decide whether you want to focus on the Upper Hudson or the Lower/Mid Hudson data. You can also have students compare data for both areas, although the concentrations are very similar when adjusted for population. Upper Hudson data includes the region from the source of the Hudson to the Federal dam at Troy. Mid Hudson starts at the Federal dam at Troy and ends at the Bronx-Westchester County boundary. Lower Hudson starts at the Bronx-Westchester County boundary and ends at the Verrazano-Narrows Bridge in the NYC harbor.

Students will open “History of Wastewater” in Excel. Students can graph all of the variables, or they can be split up into groups where each group completes one graph and then reports their results to the class. Give enough time for students to do some research on their topic(s): effluent, BOD (biochemical oxygen demand), TSS (total suspended solids), TN (total nitrogen), TP (total phosphorus). One group should be responsible for graphing the population changes.

Note: Graphing the Lower/Mid Hudson data with the Upper Hudson data eliminates much of the noticeable change in the Upper Hudson trends. Creating a secondary axis for these data is important if students want to see the changes more clearly. Remind students to label axes carefully since it can become confusing when there are different numbers of different y-axes. You can use the Excel tutorial in the Hudson River Ecosystem module of this curriculum for help with Excel.

Explanation: Population levels have been increasing since the 1900s as people move into the area and up into the suburbs of New York City. This data shows the mid and lower Hudson Valley grouped together (the area of the Hudson River Estuary from Troy to NYC), compared with the Upper Hudson. Primary water treatment plants were constructed in 1924 at Passaic Valley, New Jersey and in Yonkers, and an additional three were added by 1938. There were seven total primary treatment plants by 1952. After the 1972 Clean Water Act, upgrades were made to the plants and additional secondary treatment procedures were added. Dramatic improvements can be seen after the early 1970s. Unfortunately, coliform bacteria was not collected in a standardized fashion before 1974.

Extend: Students can graph additional parameters.

Evaluate: Based on their graphs, students should be able to answer the questions on the worksheet. 


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