Projected Effects of Temperature and Precipitation Variability Change on Streamflow Patterns Using a Functional Flows Approach

Streamflow patterns are shifting with climate change, and these shifts pose increasing risk to freshwater ecosystems. These emerging changes must be linked with ecological functions of river systems to understand how climate change may affect freshwater biota. In this study we used a functional flows approach to analyze the ecological effects of changing streamflow patterns in snowmelt-dominated watersheds of the Sierra Nevada mountains of California. Our climate change modeling method combined ensemble Global Climate Models (GCMs) and decision scaling methods to incorporate the effects of GCM-projected changes in precipitation variability on streamflow patterns. Of climate parameters explored, air temperature causes the most change in functional flows, although precipitation variability compounds changes driven by air temperature. The greatest changes in ecologically-relevant streamflow patterns manifest as longer and drier dry season conditions, earlier snowmelt recession, and higher-magnitude peak flows. Although the directions of changes in functional flow metrics are largely consistent across models and watersheds, the magnitude of change depends strongly on human emissions levels. The analytical approach used in this study can serve as a model for integrating multiple approaches in hydroclimatic assessment of ecological change, and the results can help prioritize specific aspects of the flow regime for restoration efforts.

Automated summary

Streamflow patterns are changing with climate change, posing risks to freshwater ecosystems. This study analyzed the ecological effects of changing streamflow patterns in snowmelt-dominated watersheds using a functional flows approach.