Join us in congratulating Water Institute postdoctoral associate Dr. Nathan Reaver, recipient of the Universities Council on Water Resources UCOWR 2019 Ph.D. Dissertation Award in the category of Natural Science and Engineering. The award will be presented at the 2019 Annual Water Resources Conference on June 12.

Nathan’s dissertation investigated drivers of change in the primary producer communities of Florida’s spring-fed rivers, which is key information for the development of ecologically relevant flow regulations  and restoration goals.

While much research has focused on the role of nutrients in driving shifts in the vegetation community of springs ecosystems, less work has focused on how water flow within a river controls plant and algal abundances and their interactions. Nathan’s dissertation tested flow controls on vegetation using a multi-scale observational, experimental, and modeling approach. He first investigated landscape-scale drivers of spring flow creation using a water and energy balance method.  Next, using water tracer experiments to link landscape-scale processes to spring-scale flow processes he was able to understand the relationships between the volume of spring flow and the spring flow velocity. Then he linked spring-scale flow processes to the plant and algae community structure using observational and experimental tests that looked for critical flow speed thresholds above which algae abundance is reduced. Finally, he combined results from all three scales into a modeling framework and applied it to a single spring run, the Silver River. The results from his combined model suggest that the vegetation community shifts in the Silver River can be associated with flow declines driven by declines in aquifer recharge at the landscape-scale.  Thus restoration of flow may reverse algal proliferation in Silver Springs, and other springs where flow control is a dominant driver.

As a postdoctoral researcher Nathan’s is continuing this research to determine the major causes of declining flow:

“They are many proposed mechanisms for the observed flow declines, such as decreased rainfall, groundwater pumping, land use changes, etc.  We are developing a model that integrates all the potential processes to predict their relative impacts on spring flow. We will use this model to test which of the processes are most likely occurring in Silver Springs.”

Learn more about Nathan’s research in is recently published paper: Reaver N. G. F., D. A. Kaplan. R. A. Mattson, E. Carter, P. V. Sucsy & T. K. Frazer. 2019. Hydrodynamic Controls on Primary Producer Communities in Spring‐Fed Rivers. Geophysical Research Letters