The effect of antecedent soil moisture conditions on green roof runoff water quality and quantity

Lab alumna and 2015 REU student Jillian Sarazen is presenting her work this week at the 59th Annual Conference on Great Lakes Research, affectionately known as IAGLR. Jillian graduated from Oberlin College in May. Congratulations on both fronts, Jillian!

The effect of antecedent soil moisture conditions on green roof runoff water quality and quantity.


1. Oberlin College Department of Biology, Oberlin, OH, 44074, USA;
2. Kent State University Department of Biological Sciences, Kent, OH, 44240, USA;
3. Kent State University Department of Geology, Kent, OH, 44240, USA;
4. Kent State University Department of Geography, Kent, OH, 44240, USA.

One of the many benefits of green roofs is that they reduce the amount of stormwater runoff as compared to normal roofs, however they can negatively impact water quality. This study was conducted at the three year-old green roof on Cleveland Metropark’s Watershed Stewardship Center in Parma, Ohio. The objectives were to (1) measure green roof runoff quantity and quality of phosphate (PO43-), nitrate (NO3-) and ammonium (NH4+) concentrations during rain events and (2) relate antecedent soil moisture conditions to water quality and quantity. We sampled sequential water samples (Teledyne, ISCO) during four summer 2015 rain events that varied in size and intensity. We measured soil moisture at high temporal resolution using four logging sensors and two to three times per week at 33 sampling locations using a handheld probe. Soil moisture increased immediately upon commencement of rainfall. Spatial data show a response in the soil to rain events with high variability, but no clear patterns. Phosphate export increased linearly with total outflow, while ammonium and nitrate export did not show clear relationships with outflow quantity. Results of our study show that there is a trade off between ecohydrologic function and water quality, as indicated by leaching of excess nutrients in the green roof outflow.

Keywords: Water quality, Green Roof, Urban watersheds, Green Infrastructure, Lake Erie.

Simulation of the cumulative hydrological response of green infrastructure

As a first product of post-doc Pedro Avellaneda’s work at Kent State, we were pleased to submit the following abstract to the 2016 Low Impact Development Conference. A short version of the work will be published as a conference paper in August, and we are preparing a more detailed version for journal submission this summer.

Simulation of the cumulative hydrological response of green infrastructure

P.M. Avellaneda, A.J. Jefferson, and J.M. Grieser

The performance variability of green infrastructure is connected to the changing dynamics in rainfall-runoff processes. Because of these dynamics, a green infrastructure facility experiences a range of rainfall-runoff events that are difficult to fully capture during a monitoring program. In this study, we evaluated the cumulative hydrologic performance of green infrastructure in two residential areas of the city of Parma, Ohio, both draining to a tributary of the Cuyahoga River. Green infrastructure involved the following spatially distributed devices: 19 street side biorententions, with surface area ranging from 26 to 44 m2; 5 rain gardens, with surface area less than 25 m2; and 43 rain barrels. The engineered soils for the bioretentions and rain gardens consisted of sand (~72%), organic matter (5-28%), and clay (~10%). Data consisted of rainfall and outfall flow records for a wide range of storm events, from 0.5 mm to 89 mm of measurable precipitation, monitored over three years, including pre-treatment (~1 year) and post-treatment periods (~2 years). The Stormwater Management Model (SWMM) was calibrated and validated to predict the hydrologic response of green infrastructure. Optimized parameters, in the form of Posterior Probability Distributions (PPDs), were used to estimate flow attenuation over multiple years of precipitation data in order to capture the complex rainfall-runoff dynamics. The hydrologic performance of green infrastructure was evaluated by statistically comparing the non-exceedence probability plot for pre-treatment and post-treatment outfall flow rate scenarios. In addition, the following probability plots were estimated: (1) ratio of pre-control and post-control total runoff volume, and (2) ratio of pre-treatment and post-treatment maximum peak flow rate. Parameter and predictive uncertainties were inspected by implementing a Bayesian statistical approach. Overall, the cumulative hydrological response of green infrastructure was positive: reductions of up to 33% of peak discharge and 40% of total run-off volume were estimated.

CUAHSI cyberseminars on Urban Streams

Green infrastructure, groundwater and the sustainable city
Larry Band, Institute for the Environment at University of North Carolina

Watershed context and the evolution of urban streams
Derek Booth, Bren School of Environmental Management at UC Santa Barbara

The Little Stringybark Creek project
Tim Fletcher, University of Melbourne

Contaminants of emerging concern as agents of ecological change in urban streams
Emma Rosi-Marshall, Cary Institute of Ecosystem Studies and Baltimore Ecosystem Study

Stormwater-Stream Connectivity: Process, Context, and Tradeoffs
Anne Jefferson, Kent State University

Mammals March Madness – Friends of the Watershed Hydrology Lab pool

Come one, come all to the internet phenom, the most nerdy fun alternative march madness event ever:

Mammals March Madness 2016!

Will the snow leopard be upset by the Siberian chipmunk in the first round?* Unlikely. But what happens when the #8 seed Schoolcraft College Ocelots face the #9 seed Quinnipiac Bobcats in the Mascot Mammals division? Who will make the final four? Only science, and a bit of luck, can tell.

If you are on twitter, you can follow the action starting March 7th using the hashtag #2016MMM as the matches are announced live, or you can check back with the post above for updates as the tournament goes on. But the key thing is to go the web page above, print out a bracket and fill it out with your picks for the win. Before the 7th! If you send me a picture/copy of your completed bracket, I’ll track your progress and get a tasty item from Brimfield Bread Oven for the winner of our Kent State pool.

Do we know anything about mammals? Not really. Does that matter? Probably, but Wikipedia, ARKive, and gut instinct let us place our bets anyway.

If this all sounds insane, (it is), ask people like Stuart and Eric who played the last few years and who will vouch for how much fun it is. Or listen to the story that NPR did last year: Or check out the Wikipedia page:

Pass the link to the tournament along to your friends.

Can the biologists beat the geologists? Will lab alumni beat the current lab members? Can we get the paleontologists on board this year? Will anyone be able to unseat Elisabeth as the champion of long shot (cute) animals that make good?

Check back here for updates as the month progresses.

* No actual animals are harmed in the course of Mammals March Madness. All battles are simulated based on biology and an element of chance.

Stuart Baker won the pool for overall points, while Lauren Kinsman-Costello and I at least got a mammal into the championship. Verdict: Bread for everyone!

Eric Traub Thesis Defense!

You are invited to attend Eric Traub’s  public MS thesis defense in Geology.

“The Effects of Biogeochemical Sinks on the Mobility of Contaminants in an Area Affected By Acid Mine Drainage, Huff Run, Ohio.”

(Co-Advisors: David Singer and Anne Jefferson)

Monday, Feb. 22, 12:30 pm in McGilvrey Hall, room 339, Kent State University

2015 in review (with pictures)

2015 was an incredible year of scientific adventures for the Watershed Hydrology lab. Here are some of our highlights:

Figure 3 from Reilly, D., Singer, D., Jefferson, A., and Eckstein, Y., 2015. Identification of Local Groundwater Pollution in Northeastern Pennsylvania: Marcellus Flow-back or Not?, Environmental Earth Sciences, 73(12): 8097-8109. doi:10.1007/s12665-014-3968-0.


These Piper diagrams show the geochemistry of flowback water from fracking operations in the Marcellus shale of Pennsylvania, relative to literature values of groundwater contaminated with road salt, septic waste, and animal manure. The information on these Piper diagrams, along with other geochemical analyses, were used to assess whether alleged contamination of rural, residential well water in northeastern Pennslyvania was likely to be due to the extensive shale gas development occurring in the area. Based on major and trace ion water chemistry, Anne and her coauthors found no evidence of flowback fluid in the tested residential wells. While this work was not definitive proof that flowback contamination is entirely absent, it was a good reminder that contamination of rural, residential wellwater is much more likely to come from leaky septic systems and other less exotic sources.

Figure 3 from Reilly, D., Singer, D., Jefferson, A., and Eckstein, Y., 2015. Identification of Local Groundwater Pollution in Northeastern Pennsylvania: Marcellus Flow-back or Not?, Environmental Earth Sciences, 73(12): 8097-8109. doi:10.1007/s12665-014-3968-0

Figure 7a from Jefferson, A., Bell, C., Clinton, S., and McMillan, S. 2015. Application of isotope hydrograph separation to understand urban stormwater dynamics, Hydrological Processes, 29(25): 5290-5306. doi: 10.1002/hyp.10680.


This year I was pleased to find a way to merge her interests in urban hydrology and using water stable isotopes as tools in hydrology. We published a paper that shows that stormwater detention ponds produce distinctive isotopic signatures that can be used to trace the influence of stormwater on the receiving urban streams. Using a two end-member mixing model, my team showed that a stormwater pond in suburban Charlotte, North Carolina had an outsized contribution to streamflow during hydrograph recession periods, thanks to the temporary storage and slow release of water from the pond. For more on this project, you can read the paper or take a look at slides from the talk I gave at the Geological Society of America meeting in November.

Figure 4 from Jarden, K.M., Jefferson, A., and Grieser, J.M. 2015. Assessing the effects of catchment-scale green infrastructure retrofits on hydrograph characteristics. Hydrological Processes, online ahead of print. doi: 10.1002/hyp.10736.


Rain gardens and their fancier cousins, bioretention cells, are popping up all over the urban landscape. But how well do they work? Engineers have done an excellent job designing and testing them at the site scale, but few studies have been able to test their effectiveness at larger scales. What happens when a bunch of rain gardens and bioretention cells are added to a neighborhood? Do they make a significant difference in the stormwater runoff entering the local stream? Thanks to a brilliant study design by Cleveland Metroparks, Anne and graduate student Kimm Jarden were able to answer this question with a resounding “Yes, but…” Their paired watershed study showed that the green infrastructure retrofits can very effective at reducing peak and total stormflow, but that seemingly small differences in design and construction can have big ramifications for performance at the neighborhood scale.

This research was highlighted in a press release issued by Kent State in mid-November and was featured in several local news articles.

A bioretention cell from our study. Photo by A. Jefferson, August 2015.

A bioretention cell from our study. Photo by A. Jefferson, August 2015.


Bioretention cells, like the one pictured, are designed to capture stormwater runoff and infiltrate it into the ground. Plants use and evapotranspire some of the infiltrated water. In some designs, the infiltrated water moves deeper and recharges groundwater, while in other designs, a perforated underdrain at the bottom of the bioretention cell eventually delivers the water to the storm sewer system – ideally, after the storm has passed.

The picture above is one of the bioretention cells Anne and her collaborators studied in the project above. This bioretention cell has an underdrain, so it probably wasn’t super-helpful at reducing total runoff volumes, but did delay water entering the storm sewer system and receiving stream.


Freeze core skillfully collected by graduate student Stuart Baker from a restored stream. Photo by S. Baker.


On Thursday at the American Geophysical Union meeting,  graduate student Stuart Baker gave a talk presenting results of his in-progress M.S. thesis research. Stuart’s research examines how subsurface properties of streambeds change in the months and years following stream restoration. Stuart employed a high density array of piezometers to make repeated hydraulic conductivity and head measurements in two streams. At the end of his field work, he extracted freeze cores (“gravel popsicles”) to see if areas near the head of constructed riffles had measurable differences in sediment size and geochemistry relative to riffle tails or pool positions.

The experimental set up from: Griffith, E., Ortiz, J. and Jefferson, A. 2015. HANDS-ON OCEANOGRAPHY. Mimicking the Rayleigh Isotope Effect in the Ocean. Oceanography. 28 (4).


As part of an NSF-funded project aiming to devise and test methods for improving stable isotope content understanding amongst geoscience undergraduates, my collaborators (with a little help from me) developed a lab module on Rayleigh distillation. This module can be used in an environmental geochemistry class or oceanography class, and is adaptable into a variety of formats (with or without isotope instrumentation, or even just as a data analysis exercise). We’ve written it up so that others can adopt or adapt the technique, and our paper is appeared in the December 2015 issue of Oceanography. The paper and affiliated files (which are open access) have everything you need to use the exercise in your classroom.

West Creek, October 2015. Photo by A. Jefferson


The West Creek watershed has been a major focus of our research for the past 3 years, because it is (a) emblematic of the problems facing urban streams; (b) a place where a lot of effort is being put into managing stormwater; and (c) one of the most beautiful urban streams I have ever seen.  This shot of West Creek in Parma, Ohio, was taken on October 24th, when the Watershed Hydrology class field trip visited the stream and nearby Cleveland Metroparks Watershed Stewardship Center.

An innovative cleanup effort in Baltimore’s urban waterways. Photo by A. Jefferson, November 2015.


At the Geological Society of America annual meeting in Baltimore, I sought out a fantastic example of an innovative and successful approach to improving urban water quality. The Inner Harbor Water Wheel, affectionately known as Mr. Trash Wheel, is moored at the mouth of Jones Falls, an ultra-urban stream that drains much of the City of Baltimore. Floating rubbish is diverted to Mr. Trash Wheel by booms that span the stream, and the stream’s current powers rakes and a conveyor belt that lift the trash out of the water and deposit it into a dumpster barge. Solar panels power the operation when the stream’s velocity is insufficient to power the water wheel. Thousands of pounds of trash can be removed from the stream per day. As an added bonus, Mr. Trash Wheel has a charismatic Twitter account. Read more about the water wheel at Southern Fried Science and help fund a second one.

Anne on a roof, covered with brown vegetation, dramatic sky

On the (dormant) green roof at Cleveland Metroparks’ Watershed Stewardship Center, April 2015


I can’t resist the terrible pun about my work taking me to new heights in 2015. I have a new project monitoring five pieces of green infrastructure at Cleveland Metroparks’ Watershed Stewardship Center, and I’m having a blast learning the ins and outs of this particular site’s green roof, bioretention cells, enhanced swale, and constructed wetland. I have two new graduate students and two fantastic collaborators working with me on the project, and I’m anticipating the arrival of a postdoctoral scholar soon. I think it’s safe to say that my urban hydrology research looks set to soar in 2016.

Research on street-scale bioretention featured in the news

A bioretention cell from our study. Photo by A. Jefferson, August 2015.

A bioretention cell from our study. Photo by A. Jefferson, August 2015.

Our work with Cleveland Metroparks on assessing the effects of retrofitting bioretention cells, rain gardens, and rain barrels into residential neighborhoods in Parma, Ohio has been been featured in several news stories thanks to a nice press release issued by Kent State.

On November 20th, ran the story: “Kent State University, Cleveland Metroparks project reduces storm water, pollution in Parma neighborhoods

The study was also featured in’s “best of the beat” roundup on November 22.

The local Record-Courier ran a fantastic feature on the work (unfortunately behind a paywall) on November 30th. They called the article “Kent State professor studies rain gardens’ effect on storm water runoff.

To read the full scientific story of the work, check out our recent publication:
Jarden, K.M., Jefferson, A., and Grieser, J.M. 2015. Assessing the effects of catchment-scale green infrastructure retrofits on hydrograph characteristics. Hydrological Processes, online ahead of print. doi: 10.1002/hyp.10736.