The Hudson River at the Bear Mountain Bridge. Photo: Eric Ortner

Stream and River Temperature Trends


We compiled and evaluated the second longest river temperature record in the world. We also synthesized long-term temperature trends for streams and rivers across the United States. The results of the project were presented to the scientific community, environmental groups, school children through organized educational activities, and the general public including through news and social media.

Project Status


Project Description

While there are many long-term air temperature data from numerous weather stations in the United States, similar records for water temperature are rare. Such a record, however, exists for the Hudson River based on direct measurements of the river temperature made daily at the Poughkeepsie Water Treatment Facility (PWTF). This record goes back to 1908 and provides an opportunity to analyze temperature change and to benchmark river temperatures relative to future climate that will likely be much warmer.

The Hudson water temperature data were initially assembled in 1990 by Donna Ashizawa, a Research Experience for Undergraduate (REU) student, at the Cary Institute of Ecosystem Studies (then named the Institute of Ecosystem Studies). Working with Jonathan Cole and with help from PWTF personnel, Ashizawa computerized daily temperature values from written and printed records, many of which were stored in dusty old boxes. In 2007, I updated the temperature data of Ashizawa and Cole with the help of Mathew Geho of PWTF. I also reviewed other temperature data from the Hudson including continuous temperature measurements made by the United States Geological Survey (USGS) at a number of sites on the river over shorter time periods. I found that the annual mean temperature of the Hudson River has increased and that the rate of warming is accelerating. This research was conducted while I was an REU student at the Cary Institute with Michael Pace.

We then worked on a synthesis of river temperature trends across the United States, an effort led by Sujay Kaushal. We compiled and analyzed historical records from 40 sites and found that 20 major streams and rivers have shown statistically significant, long-term warming. Rates of warming were often most rapid in urbanizing areas. Long-term increases in stream water temperatures were typically correlated with increases in air temperatures.

Distribution of river temperature trends: most rivers are warming

This project provides important context for those seeking to understand the influence of climate warming on rivers and streams. The warming trends we identified in this project have implications for a large number of ecosystem patterns and processes including effects on eutrophication (ecosystem degradation due to nutrient pollution), ecosystem processes such as biological productivity and stream metabolism, contaminant toxicity, and loss of aquatic biodiversity.

Broader Impacts

Popular Article

  • With Michael Pace, I wrote a popular article about long-term warming in the Hudson River. The article appeared in the Newsletter of the Hudson River Environmental Society (HRES). The HRES is a nonprofit, non-advocacy organization that communicates the science behind Hudson Valley issues to citizens, scientists, and decision makers.

Contributions to Education

  • Data from this project was incorporated into the Changing Hudson Project. The Changing Hudson Project is a web-based environmental education curriculum for inquiry-based learning developed by scientists and educators at the Cary Institute of Ecosystem Studies. It is used in classrooms throughout the Hudson River Valley. Click here to access the lesson plans and materials that include our data.

Policy Documents Citing this Project

Selected Media Reports

Press Releases


. Rising stream and river temperatures in the United States. Frontiers in Ecology and the Environment, 2010.

PDF Project Supplemental Information

. The Hudson River is Warming. Currents: The Newsletter of the Hudson River Environmental Society, 2009.

PDF Dataset Project