This annual award is distributed to a distinguished scientist within five years of receiving their highest degree for outstanding achievement in contributing to the hydrogeologic profession through original research and service, and for the demonstrated potential for continued excellence. This award is reflective of Margaret’s work prior to coming to the USGS, but an example of her exceptional research and science leadership.

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Margaret is a watershed hydrologist and current a Supervisory Hydrologist at the USGS Upper Midwest Water Science Center in Madison, WI. Prior to joining USGS, she was an Associate Professor at the University of California, Santa Cruz in the Earth and Planetary Sciences Department. She received her PhD from Duke University, MS from Syracuse University, and BA from Oberlin College. Margaret serves on the Board of the Consortium of Universities for the Advancement of Hydrologic Sciences, Inc. (CUAHSI). She is interested in surface water-groundwater interactions in streams and wetlands, streamflow generation processes, and critical zone science.

Citation from the Kohout Early Career Award

"It is a privilege to prepare this citation for Margaret Zimmer, who is an intellectual and technical leader in hydrogeologic science, having demonstrated exceptional impact and influence at an early career stage. I am fortunate to have been a faculty colleague with Professor Zimmer, and can attest that she is an exemplary mentor, an outstanding classroom instructor, and thought leader in curriculum design and creating an open and welcoming climate for the next generation of hydrology students and scientists.

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Dr. Zimmer explores flows and storage of water and solutes within and below landscapes, and explains and quantifies processes within linked hydrologic and biogeochemical systems. Dr. Zimmer is particularly well known for studies of surface water-groundwater (SW-GW) interactions, and storage of processing of nutrients and carbon below hillslopes and in the critical zone. Several of Dr. Zimmer's first papers focused on SW-GW exhange and chemical responses to changes in channel discharge and transient storage. These early studies highlighted the importance of hydrogeologic "structure" for discharge and geochemical conditions, as shifts in the flow magnitude and drivers impact the nature (length, complexity) of pathways and associated chemical reactions and flows. This work comprised detailed studies of experimental field systems, collecting and analyzing water samples and data, focusing on dynamic responses to transient discharge variations.

More recent papers on "zero-flow" readings at stream gages address a long-standing conundrum: how to interpret streamflow records that include intermittent and/or extended dry periods. From a groundwater perspective, understanding these records is essential for resolving one of the largest, readily measurable inflows to aquifers: stream bed seepage. But to do this effectively, one must understand how to interpret the meaning of a "dry" channel. This topic also has important implications for climate change, shifts in land use, and increased dependance on groundwater resources. Dr. Zimmer is addressing additional topics with big implications for groundwater systems and resource management, including carbon and nutrient transport and fate during SW-GW exchange, tidal influences on nutrient dynamics in coastal wetlands, and the impacts of wildfire on water and solute pathways and flows.

Dr. Zimmer is an accomplished and engaging speaker, amplifying her effectiveness as a scientist and a scientific ambassador to the public at large. She built one of the largest research groups in her department at UCSC, having been primary supervisor for nine graduate students since arriving in 2018. Dr. Zimmer created a new graduate course on the "Hidden Curriculum" in geoscience graduate studies, which was highly beneficial to the current cadre of EPS students at UCSC, and resulted in a student-led publication and a curriculum that has been viewed and downloaded thousands of times.

In summary, Dr. Zimmer is an exceptionally smart, creative and successful hydrologist. It has been humbling to prepare this citation, and I am grateful to the GSA's Hydrogeology Division in recognizing Dr. Zimmer's many achievements. She is an inspiration.

-Andrew T. Fisher, Citationist"