New studies analyze the watershed’s past climate and refine predictions of what’s to come
Image Credit: Edwin Remsberg
Like the entire mid-Atlantic region in which it’s nestled, the Chesapeake Bay watershed is facing a future filled with hotter summer nights, more tropical temperatures, fewer frosts in winter and more severe and variable rainfall. But a high resolution assessment of just how those changes could play out across the watershed—a 64,0000 square mile swath of land and water that cuts through six states and the District of Columbia—have been unavailable, until now.
In a recent study, Puneet Srivastava, Associate Dean for the College of Agriculture and Natural Resources, and Ritesh Kairki, Senior Faculty Specialist with the Maryland Agricultural Experiment Station, performed a comprehensive assessment of the potential changes in future climate extremes for the Chesapeake Bay watershed. Their results offer critical insight for mitigating and adapting to the changing climate in one of the most ecologically important and economically productive regions in the northeastern U.S.
“This region is particularly vulnerable to changing climate, but it poses unique challenges for assessing and developing management plans for climate mitigation,” Srivastava said. “With these studies, we are filling a gap in knowledge that helps us understand what’s happening at finer scales relevant to industries such as recreation, tourism, agriculture and fisheries.”
The Chesapeake Bay watershed is home to more than 18 million people and more than 36,000 species of plants and animals. It supports more than $100 billion in economic goods and services. Previous estimates suggest that summertime water temperatures in the Bay are rising nearly twice as fast as global ocean temperatures, and overall, the northeast region has seen a 53% increase in extreme precipitation events. These changes are expected to intensify, but generating scientific models for the watershed is challenging because it encompasses so many varied geographic regions with different climates and land use from Delaware to West Virginia, and New York all the way down to Virginia.
The new study provides a fine-scale assessment of expected changes across 20 extreme climate indices such as temperature maximums, number of tropical nights, duration of warm spells, consecutive dry days, icing days, extreme precipitation days, etc.
To evaluate future changes in climate, the researchers used 13 models from the most up to date Coupled Model Intercomparison Project (CMIP6), which is an international climate modeling project that serves as the basis for the Intergovernmental Panel on Climate Change (IPCC) Assessment Reports. They scaled their model outputs to a gridded map of the watershed to provide high-resolution data for individual locations across the region. Then they ran their models for four potential scenarios in which the global human population either reduces, maintains or increases greenhouse gas emissions. Although the amount of change varies depending on specific location and emissions scenario, across the watershed, the study found that the future will bring:
Rising temperatures: Both daily maximum and minimum temperatures are projected to increase across all scenarios until mid-century, with more pronounced warming under higher emissions scenarios and continued warming beyond mid-century in high emissions scenarios.
Hotter summers: Summer months will see the most substantial temperature increases, leading to more frequent heatwaves and tropical nights under all scenarios.
More rainfall variability, more frequent extreme rain events: Annual precipitation is expected to rise, though with significant year-to-year variability, and heavy rainfall events will be more frequent.
Reduced Cold Extremes: A decline in frost and icing days.
The researchers also pointed to the potential impacts of these changes, such as stress to aquatic species throughout the watershed as warmer waters exacerbate algal growth and increase low-oxygen zones that threaten fish like brook trout and striped bass. Higher temperatures and precipitation extremes could intensify competition for water among agricultural, municipal, and industrial sectors. Meanwhile, rainfall variability will complicate water resource management. Agricultural productivity could decline due to heat stress and altered growing seasons, and a decline in frost and icing days may hurt crops requiring winter chill periods, such as certain fruits. An uptick in heavy rainfall events could lead to increased nutrient runoff, degrading water quality, and overwhelming infrastructure.
This study underscore the urgency for both mitigation and adaptation strategies to address impending challenges. While even the low-emission scenario indicated some of these adverse climate effects, it also suggested that proactive measures can stabilize climate conditions by mid-century.
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The study, Fine-scale assessment of projected future changes in weather and climate extremes in the Chesapeake Bay watershed of the Mid-Atlantic United States was published May 24, 2025 in the journal Theoretical and Appliece Climatology.
Additional authors from the University of Maryland College of Agriculture and Natural Resources include Majid Mirzaei and Adel Shirmohammadi.
