In their own words: Joanna Blaszczak

We are always excited to see publication of research coming out of the Duke Forest. In June, Duke Forest staff were excited to see the announcement of publication for important water quality research from the Bernhardt lab at Duke Biology. From the June edition of the academic journal Biogeochemistry the study Watershed urban development controls on urban streamwater chemistry variability examines urban water runoff in our region and how different urban development designs affect the water quality in surrounding streams. Joanna Blasczcak (primary author), Jo Delesantro, and Ying Zhong under advisement of Professors Emily Bernhardt and Dean Urban used data collected in Mud Creek in the Durham Division of the Duke Forest to complete the study. We asked Joanna if she could summarize this study for us:  

What motivated this study?

Over the past two to three decades of work in urban streams, we’ve come to realize that there is a lot of variability in the water quality of streams draining areas that are moderately developed (think suburban areas such as those surrounding the urban cores of Durham, Raleigh, and Chapel Hill) and we wanted to understand why some streams had better water quality than others. In order to understand the water quality of a stream, you need to understand the land use in a watershed, which is the area of land that drains to a particular stream (think a valley). So we asked, what characteristics of urban development determine water quality in the streams that drain them?

What did you study?

From the fall of 2013 to the fall of 2015 (and to the fall of 2016 for a subset), we monitored the water quality of twenty-four streams draining watersheds in the municipal boundaries of Durham, Raleigh, and Chapel Hill. What makes this study unique is that we tried to select watersheds that had approximately the same percentage of developed land in a watershed, but spanned the widest possible gradient we could find in the density of roads, stormwater pipes, and sewer pipes. Something that people might not realize, is that there is a lot of variability in the ways that urban areas are developed even if it all feels the same when you’re driving around. This gives us an opportunity to try and understand how we can design new development in a way that reduces our impact on the environment.

What did your study find and why is it important?

We found that the chemistry in these streams is highly variable, and that the variability is most strongly driven by the signal of road salts that are washed off of roads directly into streams during the winter which cause spikes in salinity. And something that I found particularly interesting was that in streams draining watersheds with less stormwater piping, we saw a decrease in storm spikes, but instead observed elevated salinity between storms in comparison to other watersheds. These results suggest that the extent to which pavement is drained by stormwater pipes creates a tradeoff between routing urban salts directly to streams via pipes versus indirectly to streams via loading to groundwater when salt leaches through the soil. Road salting is important for human safety while driving in the winter, but this work suggests that when designing future development, we should try to limit the extent of roads that we will need to salt.

Joanna Blasczcak earned her Ph.D. from the Nicholas School of the Environment at Duke University in 2018, advised by Professors Emily Bernhardt and Dean Urban. She has been engaged in postdoctoral work at the University of Montana’s Flathead Lake Biological Station. This month, Joanna will be joining the faculty of the University of Nevada Reno Natural Resources and Environmental Science Department.

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