CEE Seminar Series: Laura Lautz

Impacts of channel degradation on stream health and water quality in urban watersheds

Abstract: Urbanization degrades stream health and water quality due to multiple interacting physical and chemical impacts. Sources of salinity and nutrients are elevated in urban streams due to winter deicing, fertilizer use, and discharge of wastewater effluent. At the same time, degradation of stream corridors due to channelization, armoring and straightening reduces the potential for natural attenuation. Here, Lautz investigates the degree to which undisturbed stream corridors in urban watersheds attenuate concentrations and loads of urban contaminants. Degraded urban stream reaches deliver chloride loads comparable in magnitude to chloride application rates in the surrounding watershed, indicating rapid and conservative transport of road salt. In contrast, stream–groundwater interactions in undisturbed reaches reduced stream chloride loads by 50%. Degraded urban stream reaches were also a net source of nitrate year-round, regardless of season. In contrast, stream-groundwater exchange in undisturbed reaches reduced annual nitrate loads overall and served as both a source and sink for nitrate, depending on time of year. Attenuation of chloride and nitrate loads in undisturbed reaches in urban areas were driven by temporary solute storage in riparian groundwater, as well as dynamic stream-groundwater interactions that promote nutrient cycling. A unique feature at the study site is a large cemetery that comprises 9% of the total watershed area. Although cemeteries provide ecosystem services, they also pose a unique threat to groundwater quality. Lautz's observations suggest cemeteries may be an overlooked source of nutrient loading in urban watersheds.

Biography: Laura Lautz is a program director in the Hydrologic Sciences Program in the Directorate of Geosciences’ Earth Science Division at the National Science Foundation (NSF). Her research addresses how hydrologic processes influence water quality and movement through watersheds, with particular emphasis on how water and solutes move through paired surface and groundwater systems. Prior to her arrival at NSF, she was the Jessie Page Heroy Professor and Department Chair of Earth Sciences at Syracuse University, where she served as principal investigator on one of the inaugural NSF Research Traineeship (NRT) awards. Lautz has received the Chancellor's Citation for Faculty Excellence and Scholarly Distinction from Syracuse University, a CAREER award from the NSF, and is a Fellow of the Geological Society of America. She lives in northern Virginia with her husband, twin twelve-year-olds, dog, and cat.

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