Sarah Ledford


Department of Earth Sciences

316 Heroy GL

Email: shledfor@syr.edu

Sarah's CV




PhD Student Earth Sciences
Advisor: Laura Lautz

Research Interests

Picture of stream in bed


My research focuses on investigating the impacts of urbanization on surface water quality. Urbanization decreases water quality due to increased impervious cover altering the system hydrology.  This results in increased surface runoff, decreased infiltration, a flashier hydrograph, increased flood discharge, decreased groundwater discharge and decreased baseflow, all symptoms of the “urban stream syndrome” that is also evidenced by reduced in-stream habitat.  In the northeastern United States, two surface water contaminants of concern are chloride, from road salt inputs, and nitrate, from anthropogenic nutrient inputs. The growing trend in the U.S. is to restore urban streams and reconnect them to the groundwater to improve surface water quality. However, the degree to which restoration that aims to increase surface water-groundwater interaction has the potential to improve water quality has not been thoroughly evaluated.

For my dissertation I aim to investigate how an urban surface water system responds to reconnection to groundwater. I performed synoptic and experimental fieldwork at my field site, and am working on a heuristic model of the system. I first looked at if groundwater discharge in urban streams buffered seasonal changes in surface water chemistry, resulting in lower winter chloride concentrations and smaller annual ranges of chloride in reaches that receive groundwater discharge. I tested this by conducting a year of synoptic sampling every two weeks along Meadowbrook Creek, a first-order stream in Syracuse, New York, that flows from armored headwaters that are disconnected from the groundwater to a broad riparian floodplain. I also sampled groundwater chemistry in the downstream floodplain and found that my hypothesis was correct.

My second research question is investigating if direct sunlight, warm water temperatures, and large algal communities result in short nitrate uptake lengths in the disconnected, upstream reach of Meadowbrook during non-winter months. Urban reaches with groundwater discharge and riparian vegetation have longer nitrate uptake lengths due to shading, lower water temperatures, and higher nitrate concentrations in non-winter months.  I hypothesize that during the winter the difference between the connected and disconnected reaches will be at a minimum due to limited organic input, lack of algae, cold temperatures, and smaller differences in stream shading.  I am currently testing this by completing nutrient and conservative tracer injection tests during various seasons in each reach to calculate and compare the uptake lengths.

My final question looks at overbank flood events during the winter in the downstream riparian floodplain of Meadowbrook deliver chloride to riparian aquifers adjacent to urban streams, resulting in elevated annual chloride concentrations in the floodplain, which slowly discharge to surface water throughout the year. I will test my conceptual model by creating a three-dimensional computer model of the riparian floodplain in the connected section of the stream to investigate chloride movement and residence time in the groundwater.


Picture of stream floodplain


Peer-Reviewed Publications:

Ledford, S.H. and L.K. Lautz. Available online. Floodplain connection buffers seasonal changes in urban stream water quality. Hydrological Processes. DOI: 10.1002/hyp.10210



Conference Presentations:

Ledford, S.H. and L.K. Lautz. 2014 (accepted). Stream-groundwater interaction mechanisms that promote storage of deicing chemicals in urban floodplains. Geological Society of America Annual Meeting (Oct. 19-22, 2014).

Ledford, S.H. and L.K. Lautz. 2013. Stream-groundwater interaction buffers seasonal changes in urban stream water quality. American Geophysical Union 46th Annual Fall Meeting (Dec. 9-13, 2013).



Conference Posters:

Ledford, S.H. and L.K. Lautz. 2013. Stream-groundwater interaction buffers seasonal changes in urban stream water quality. 13th Annual Syracuse Center of Excellence Symposium (Oct. 21-22, 2013).

Ledford, S.H. and L.K. Lautz. 2013. Seasonal Role of Surface Water-Groundwater Interaction in Regulating Stream Water Chemistry in Urban Streams. Paper No. 59-6. 48th Annual Northeastern Geological Society of America Meeting (March 18-20, 2013).

Ledford, S.H., Lautz, L.K. and M. Holdsworth. 2012. Role of Surface Water-Groundwater Interaction in Regulating Stream Water Chemistry in Urban Streams. Paper H51J-1503. American Geophysical Union 45th Annual Fall Meeting (Dec. 3-Dec. 7, 2012).

Ledford, S.H., and D.P. Gillikin, 2010. The influence of mill dam ponds on the biogeochemistry of small streams. GSA Abstracts with Programs Paper No: 169156. Northeastern Section (45th Annual) and Southeastern Section (59th Annual) Joint Meeting (13-16 March 2010).



Teaching:
TA Coordinator, EAR 111, Climate Change- Fall 2013 (3 sections)
TA, EAR 105, Earth Science- Spring 2012 (5 sections)
TA, EAR 102, Historical Geology- Fall 2012 (3 labs)
TA, EAR 105, Earth Science- Fall 2011 (5 sections)


 




Contact Us

Department of Earth Sciences
204 Heroy GL
Ph: 315-443-2672
Fx: 315-443-3363

Research Area