PNNL

The new model can simulate stream temperature to explicitly account for the impacts of climate change and human activities, such as using freshwater for power plant steam generation and cooling. The ability to simulate stream temperature over complex river systems is important to support decisions on management and policy related to the water-energy-land nexus.

In the United States, 90 percent of electrical power comes from generating electricity using heat-conversion (thermoelectric) systems, fueled by coal, gas, oil, and nuclear generators. These power plants require fresh water to generate steam and for cooling purposes.

To better understand how stream temperature is influenced by climate change and human activities, scientists at PNNL developed a new modeling tool.

First they applied the new module in a river transport model and coupling it with a generic water management model within an Earth system model framework. From that, they were able to closely mimic the observed stream temperature variations from over 320 river gauges across the contiguous United States.

Their additional analysis focused on reservoir operations. They found that by altering the timing of streamflow to boost throughput in the low-flow summer season—from August to October—downstream temperatures could cool by as much as 1 to ~2°C.

"Our new capability lays a solid foundation for future studies on the water-energy-land nexus," said Dr. Hong-Yi Li, a PNNL hydrologist who led the study. "It opens exciting opportunities to evaluate our options for managing resources in an evolving environment."

For more information, read the research highlight.