Impacts of Climate and Human-induced Changes on Stream Temperature in Large River Systems: An Earth System Modeling Perspective

Abstract:

Stream temperature plays an important role in closing the energy balance at local, regional and global scales, and exerts significant impacts on aquatic biodiversity, power plant operation and energy production. It is therefore a critical component for representing the energy-water nexus in earth system models. The stream temperature particularly in large river systems is very often regulated by human activities such as reservoir and power plant operations. This study is a first attempt to develop a physically based stream temperature model within the Community Earth System Model (CESM) framework. The Model for Scale Adaptive River Transport (MOSART) has been developed to represent riverine water dynamics and incorporated into CESM by coupling with the Community Land Model (CLM). Here we build upon CLM-MOSART to represent the riverine transport of heat along with water flux and the energy exchanges between river water and the atmosphere. More importantly, the impacts of reservoir and power plant operations are also explicitly parameterized within this new stream temperature model. This new stream temperature model will first be driven by historical forcing and validated against the observed stream temperature at a number of USGS gauges across the US. Then, driven by dynamically downscaled climate change scenarios, the relative contributions of climate change and reservoir and power-plant operation on the projected spatiotemporal changes in stream temperature will be systematically analyzed. Lastly the current limitations and future directions will be discussed.