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urban watersheds

CUAHSI Cyberseminar on Watershed Sensitivity to Climate and Land Use Change

From an email to CUAHSI members today:

A quick reminder that we invite you to join us for a special CUAHSI Cyberseminar this Thursday at a special time hosted by Roy Haggerty,  Tom Meixner, and Patrick Belmont, members of the Water, Sustainability and Climate  (WSC) community.

Thursday, January 23rd, 2 -3 PM ET

Dr. Thomas Johnson

EPA Office of Research and Development

Watershed Modeling to Assess  the Sensitivity of Streamflow, Nutrient, and Sediment Loads to  Potential Climate Change and Urban Development in 20 U.S. Watersheds

Join the seminar at: http://cuahsi.adobeconnect.com/cyberseminar/

Dr. Johnson will discuss the release of the final report released by EPA this fall. From the release:

“There is growing concern about the potential effects of climate change on water resources. To develop this report, watershed modeling was conducted in 20 large U.S. watersheds to characterize the sensitivity of streamflow, nutrient (nitrogen and phosphorus), and sediment loading to a range of plausible mid-21st century climate change and urban development scenarios. The report also provides an improved understanding of methodological challenges associated with integrating existing tools (e.g., climate models, downscaling approaches, and watershed models) and data sets to address these scientific questions. To view the study and related links, visit: http://cfpub.epa.gov/ncea/global/recordisplay.cfm?deid=256912.”

Please join us on January 23rd. Dr. Johnson will present on the results of the report, and there will be a Q&A following the presentation.

Our regular Cyberseminar series will have a spring theme of “Snow Hydrology,” and is being hosted/organized by Dr. Jessica Lundquist (Washington). The spring series begins February 7th. See http://www.cuahsi.org/Cyberseminars.aspx for more info.

Reflecting on Teaching Urban Hydrology – Spring 2013 edition

I was hired as part of a cluster hire focused on urban ecosystems at Kent State University, and while my research has a significant urban component to it, I had not taught an urban-focused class… until this past semester, when I created a new class in Urban Hydrology. Urban hydrology is a fascinating and relevant topic, but its not part of the standard curriculum for geology students in the US. Where urban hydrology is typically taught is at the graduate level to civil engineering students, and follows on courses on hydraulics, fluid mechanics, etc. Thus, the content and approach taken in civil engineering Urban Hydro classes was not quite what I wanted for the senior geology majors and graduate students in my class, most of whom had no experience with hydrology before arriving in my classroom. This class was my first full course taught at Kent State, so it was a big semester of learning about the students here and how to effectively teach to them. While I think my students learned a lot in my class, I can say with some confidence that I learned just as much from the experience of teaching a new topic to a new audience.

At the beginning of my course planning, I set four learning objectives for the students:

  1. Understand the natural and human factors that regulate hydrologic processes in urban areas
  2. Evaluate watershed land use changes and associated hydrologic impacts
  3. Describe methods to mitigate the effects of urbanization on aquatic systems
  4. Analyze the scientific literature on urban aquatic systems and discuss the approaches and main conclusions with fellow scientists and the public

Upon reflection, the first two objectives have some significant overlap, though “evaluation” requires a different set of skills than “understanding.” These two objectives were the primary focus of the first half of the semester, in which I introduced students to the concepts of watersheds, water budgets, and hydrographs, and had them work through the USDA NRCS handbook TR-55 “Urban Hydrology for Small Watersheds” (pdf link) with a real example from the Cleveland metropolitan area. Overall I’m very happy with how this part of the course went, because I took students from not knowing how to define a watershed given a topographic map to being able to solve an applied hydrologic problem in an urban setting.

The first half of the course could also be summed up as “how we got to where we are today in urban watersheds,” and my goal for the second half was to help students understand “where do we go from here.” This is where objectives 3 and 4 came into greater play. We talked about principles and practices of stormwater control and low impact development, stream restoration, solving the legacy problem of combined sewer overflows, and attempts at watershed-scale approaches to reducing stormwater inputs to streams. I organized two optional field trips – one to look at stream restoration and dam removal sites in Kent (with help from the Ohio EPA) and surrounding towns and one lead by Cleveland Metroparks to look at stormwater BMPs and stream restoration in the West Creek watershed in Parma. The culminating project for this half of the class was the design of rain garden. While I’m reasonably happy with how this half of the class went, there are some tweaks I’d like to make for the future. I need to tie the topics covered in the second half of the semester into a more cohesive unit, and I need to rethink my fourth learning objective (re: scientific literature), because I didn’t do as a good of a job as I would like with implementing it. We certainly read quite a number of papers, and they wrote reflective essays about them, but the discussion with the public part didn’t happen.

I’m quite pleased with the final project though. In many neighborhoods, this rainfall that lands on a rooftop is delivered to driveways, streets, or pipes that lead to the storm sewer network and straight to streams. The goal of rain gardens is to “disconnect” the rooftop and treat the water on-site, returning the hydrology to a more natural state. The class worked in teams of three as competing consulting firms angling for a design-build contract on the rain garden. They had to survey the site to quantify impervious surface, soil characteristics, and lot and topographic limitations. Then using a variety of resources that they’d identified for rain garden design and construction, the teams developed plans that detailed size, position, soil characteristics, and planting for the rain garden. On the last day of class they presented their designs to each other. I didn’t actually ask the students to construct the rain garden (that’s something Chris and I have taken on over the summer, since it is in our front yard), but several have asked how the process is going. (I may post some pre-, syn- and post-project pictures later.)

I also had students participate in water quality data collection and analysis for the Cuyahoga River in Kent. I think this was a very valuable way for the students to gain a small amount of experience with hydrologic data from hypothesis generation and testing, to quality control of field measurements, to putting their results in the context of the literature. I’d like to keep a version of this project in future iterations of the course, but I want to tie it more explicitly into the course objectives.

I’m not likely to teach the course again for at least two years, but I’m hopeful that I can build off of what I did last spring to create an even better Urban Hydrology class at Kent State. In the meantime, almost all course materials can be found on my website, which I hope will be a resource for other people interesting in learning more about this fascinating and important field of hydrology.

Mackenzie Osypian defends her thesis on stream restoration and transient storage

Woman in stream with PVC pipes (piezometers)

Mackenzie tending to piezometers in one of her streams.

Mackenzie Osypian is defending her MS research in Civil Engineering at UNC Charlotte, April 22nd at 4:00 pm in McEniry Hall 441 on the UNC Charlotte campus. Mackenzie is advised by Anne Jefferson and Sandra Clinton. John Daniels and Jim Bowen are on her committee.

Mackenzie’s research is titled: “Evaluating restoration effects on transient storage and hyporheic exchange in urban and forested streams.”  Her abstract is below:

Millions of dollars are spent each year on restoration projects designed to improve stream habitat, but few studies have investigated effects of restoration on groundwater- surface water interactions. Hyporheic exchange and transient storage in four second-order streams (urban/forest; restored/unrestored) were studied by measuring geomorphology, streambed vertical head gradients and water fluxes, and by using conservative, impulse-loaded tracer studies along with the OTIS model. Total storage exchange and percent hyporheic exchange were found by utilizing the OTIS P parameters and the sum of downwelling fluxes calculated in SURFER. The upwelling and downwelling varied between -1.783 m/m to 3.760 m/m in the restored urban stream, which contains large step structures, while the unrestored urban stream had no measured upwelling or downwelling (0 m/m) along the reach, which is incised to bedrock.  The forested restored stream had a smaller range of hydraulic gradients (-0.012 m/m to 1.99 m/m) compared to the forested unrestored stream, which ranged from -0.725 m/m to 0.610 m/m. The forested unrestored reach had the highest percent of hyporheic exchange, reaching 22% during the winter season. The urban restored has the smallest percent of hyporheic exchange of 0% across all seasons due to the exposure of bedrock in the streambed. The restored reaches were found to have between 0% and 6% of total transient storage exchange occurring in the hyporheic zones, with some seasonal variability.

The results indicate that restoration increases the hyporheic storage when the stream has incised to bedrock, but that large in-channel storage is also created. When the stream has an alluvial bed (as in the forested streams), the percent of hyporheic flow compared to total storage is reduced. The forested unrestored stream had the largest average hydraulic conductivity of 0.006 cm/s compared to the forested restored, 0.001 cm/s, and the urban restored, 0.001 cm/s.  The restored forested site had a maximum area to storage area ratio of 247 m2/m2 in the spring, which was higher than the forested unrestored site. That site had a maximum of 16.4 m2/m2, which occurred during the fall season.

We are currently preparing her thesis for publication.

Lost Rivers documentary showing in Kent!

I’m super-excited! Super super excited. I’ve just found out about a new documentary on Lost Urban Rivers! The trailer looks great (see below). And it’s showing in Kent! This week!

Lost Rivers is a new documentary by Montreal-based Catbird Films, and it tells the story of how cities built around water, then built over it “losing” the rivers, and how today we are starting to uncover those rivers again. The film was released earlier this year, and there’s only been two other screenings of it in the US so far. And totally unbeknownst to me, the third US screening is here in Kent, Ohio on Friday (April 19th) as part of the Who’s Your Mama? Environmental Film Festival. The film festival runs from 5 to 9 pm, with lots of great shorts, and Lost Rivers is the featured documentary, which will show at 7:30 pm. The film festival is in the Kiva on the Kent State Campus, and admission is $7, $5 for students and seniors, or free for kids under 12. There will also be local food tastings and booths by local environmental organizations, including Kent State’s student group CRICK.

Lost Rivers – OFFICIAL TRAILER from Catbird Productions on Vimeo.

Doesn’t it look great? I’ll definitely be at the screening on Friday, and I hope I’ll see some of my students there as well (though I know many will be on a field trip). In any case, I’ll report back, but I’m hopeful that by the next time I teach Urban Hydrology, I’ll have a copy on DVD and be able to show it to my class. Whee!

Rain garden resources

A compilation of some of the better resources available on line for rain garden design. If you find other good resources, please contact me or leave a comment.

In my mind, an adequate resource should help you figure out how to do the following things:

  1. Determine the needed size, depth, and location.
  2. Understand your soils and figure out how to build a soil for infiltration
  3. Provide recommendations for planting the garden (e.g., species lists, things to consider) that are appropriate for your climate, soil, and shade conditions.
A good resource will help you do those things and understand how and why the size, depth, soils, and plants work together to reduce runoff.

Urban Hydrology students: Please search the web for one good rain garden design resource to be added to the list above. When you have found one, leave a comment or email me with the link. I’ll update the list as we go along.

 

Combined sewer overflows: Solving a 19th century problem in the 21st century

Combined sewers are pipes that catch both sewage and stormwater and route it to a waste water treatment plant. In dry weather, it’s all sewage in the pipes. In small rain storms, the pipes carry sewage mixed with stormwater and it all goes to the wastewater treatment plant to get cleaned up and returned to a stream or lake. The origins of combined sewers predate waste water treatment, when there was little distinction between stormwater and sewage and stream and city dwellers just wanted the foul-smelling, disease-festering stuff out of their way as soon as possible. Later, engineers and public health folks added the crucial waste water treatment plant step to the system but the sewers remained combined. Combined sewers were common until the early 20th century, so over 772 communities in the US, mostly in the Northeast and Great Lakes regions have combined sewers, as shown on this map from the US EPA:

Pink US with black dots stretching from Iowa to Maine

US EPA map of Combined Sewers. Click for source.

Most of the time, combined sewers route all of the water to the waste water treatment plant, and all is relatively well. But in large storms, the volume of stormwater and sewage can overwhelm the waste water treatment capacity. If the volume of water was too much to treat, you can imagine the pipes starting to fill up with sewage. If there were no “pressure release valve” on the system, urban dwellers in combined sewer cities would see the sewage/stormwater cocktail start to back up into their basements, sinks, … and, you get the picture. Fortunately for those city residents, there is a “pressure release valve in the system,” but it’s a solution that creates more problems downstream, literally. When flows in the combined sewers are too great to be treated, the sewage/stormwater cocktail overflows out of the pipe network and into local streams. Then you’ve got raw sewage in your stream and that’s not pretty, or healthy, or environmentally friendly. This is the infamous combined sewer overflow or “CSO.”

Dry weather all water in pipe is sewage and goes away from the stream. Wet weather sewage and stormwater overflow in the stream

US EPA diagram of a combined sewer in dry and wet weather. From U.S. Environmental Protection Agency, Washington, D.C. “Report to Congress: Impacts and Control of CSOs and SSOs.” Document No. EPA 833-R-04-001 found on Wikimedia commons. Click for source.

Here’s a Northeast Ohio Regional Sewer District video explaining combined sewers and touting their treatment system:

Under the Clean Water Act, cities and sewer districts can be required to bring their raw sewage discharges down to acceptable levels by reducing the frequency and magnitude of combined sewer overflows (CSOs). Right now, Cleveland, the District of Columbia, Philadelphia, and other cities are under mandate to reduce their CSO discharges. This is a big, expensive undertaking because we’re talking about billions of gallons of overflows each year and thousands of miles of combined pipe network underneath the city. Big problems require big solutions, so how are the cities dealing with their CSO problem? It turns out that they are taking a range of different approaches.

In Cleveland, waste water treatment and stormwater are managed by the Northeast Ohio Regional Sewer District (NEORSD). Their “consent decree” with the EPA was filed in July 2011, and according to that decree, they have 25 years to reduce CSO volumes by 90%. That’s taking the CSOs from 4.5 billion gallons per year to the still non-trivial 494 million gallons per year. If they meet that goal, 98% of all wet weather flows will be treated before being released to a stream. The price tag for this ambitious project is $3 billion, and it has been termed “Project Clean Lake” in homage to Cleveland’s Lake Erie shoreline. a source of regional pride.

How is NEORSD planning to reduce CSOs? With a lot of digging. Most of the money and effort is being spent on “gray infrastructure” – big engineering projects. BIG engineering projects. NEORSD is boring 7 tunnels, each 2-5 miles long, up to 24 feet in diameter, and up to 300 feet below the ground or lake bottom. These tunnels will intercept the combine sewers before they overflow and store the water until the treatment plants have capacity to treat it.

Sewer pipes with human to scale.

The 7 future storage tunnels of Cleveland’s combined sewers. Image courtesy NEORSD. Click for larger.

This is a massive undertaking, and it’s just getting started. The videos below show the first tunnel boring machine arriving in Cleveland and a tour of the tunnel first tunnel to begin construction. You can follow the progress of the tunnel boring on the NEORSD blog.

But it’s not just tunnels, NEORSD is also enhancing their wastewater treatment capacity and spending $42 million on green infrastructure. Green infrastructure is defined as “a range of stormwater control measures that use plant/soil systems, permeable pavement, or stormwater harvest and reuse, to store, infiltrate, or evapotranspirate stormwater.” These can include things like green roofs, green streets, bioretention swales, and other projects. The goal is control 44 million gallons of would-be stormwater using green infrastructure, with projects completed in the next 8 years. Those numbers are nothing to sneer at it, but it’s 1% of the current combined sewer overflow volume and 1.5% of the budget. The fact that the budget % is bigger than the volume percent may hint at why green infrastructure isn’t being used more broadly in Cleveland.

Washington DC is taking a somewhat different approach than Cleveland. One-third of DC is served by combined sewers, and they are spending $2.6 billion over 25 years to reduce their overflow problem, which is currently about 2.5 billion gallons per year. DC Water has nicknamed their CSO program the “Clean Rivers Project.” Like Cleveland, they are also building large storage tunnels, improving their waste water treatment plants, and rehabilitating pumping stations. Unlike Cleveland, DC will actually be separating the sewers in some areas, sending sewage and stormwater down different pipes from each other. In DC, green infrastructure seems to get only a rhetorical nod, rather than a significant component of the budget. Their plan says they will “advocate implementation of Low Impact Development,” but they’ve only budgeted $3 million for it, a mere 0.1% of their overall project cost. However, they do have the world’s best explainer video.

Philadelphia is taking a radically different approach. Like Cleveland and DC, their price tag comes out to about $3 billion over 25 years. However, in Philadelphia it’s a “Green City, Clean Waters” program and green infrastructure steals the show. Philadelphia’s goal is to “reduce reliance on construction of additional underground infrastructure” by pushing extensive green infrastructure throughout the city. In other words, they don’t want to dig tunnels. Instead, they want to green acres:

Each Greened Acre represents an acre of impervious cover within the combined sewer service area that has at least the first inch of runoff managed by stormwater infrastructure. This includes the area of the stormwater management feature itself and the area that drains to it. One acre receives one million gallons of rainfall each year. Today, if the land is impervious, it all runs off into the sewer and becomes polluted. A Greened Acre will stop 80–90% of this pollution from occurring.

Philadelphia’s rationale for making green infrastructure their big push centers around social and economic benefits to come and their historic heritage as a park city. Their video is all about people, not all about pipes:

Philadelphia’s vision is the most radical departure from a traditional “grey infrastructure” approach like that pursued in Cleveland, DC and other cities. There’s certainly an aesthetic and emotional appeal behind greening a city and its stormwater. This is the way many people want to move urban hydrology in the 21st century, integrating the built and natural environment more closely than we’ve done in the past. But it will be interesting to watch where Philadelphia succeeds and if and where it fails, as the fully green infrastructure approach could be seen as much riskier than a traditional engineering-driven approach. Fortunately, EPA is devoting some funding to research on the effectiveness of Philadelphia’s project. I won’t be doing that work directly, but I will be following it closely and think it would be fascinating to put together a more rigorous multi-city analysis of approaches and outcomes.

More broadly, the combined sewer overflow problem is a fantastic example of how our environmental and societal choices are constrained by decisions made in the past. No one today would build a combined sewer, but yet millions of people live in cities served by them, thousands of engineers, scientists, and sewer district workers work with them, and billions of dollars are being spent trying to mitigate the problems they cause. We can’t just rebuild cities from the underground up, so we have to work with what we’ve inherited and try to make decisions that won’t cause consternation for future generations.

Note: This blog post is adapted from the lecture I gave today in Urban Hydrology. If I’ve gotten anything wrong or missed an important point, please let me know and I’ll try to make it better for current and future students.

Collecting Data on the Cuyahoga River in Kent

Next week my Urban Hydrology class embarks on their first project: exploring the potential water quality changes in the Cuyahoga River as it flows through the City of Kent, which is really the first good-sized town on its path to Lake Erie.

Here’s a summary of what we’ll be doing, and you can click through to the attached document to get more details.

Beginning February 5th, we’ll be collecting near-daily water quality measurements of Cuyahoga River water as it flows through Kent. Using the data we collect, we’ll attempt to answer the following questions:
• How does water quality change as the river flows through an urban area?
• How does water quality vary with respect to discharge in the Cuyahoga River?

Each student will sign up for one weekday on the class calendar. On the assigned day, that student will be responsible for taking a suite of measurements at 2-4 locations. The measurements we will take are (1) turbidity, (2) specific conductance, and (3) temperature and we will also collect water samples for later analysis on the Picarro water isotope analyzer. Each student will be required to take one set of measurements at the base of the steps just upstream of Main Street and one set of measurements at the beach just downstream of Summit Street. Students with access to cars are also encouraged to take measurements at the River Bend Road boat launch (at Kent’s upstream end) and at the Middlebury Road boat launch (at Kent’s downstream end). Details of each measurement technique and each site are [in the linked document].

Trail and stairs going down to river. Patches of snow and ice in the scene.

River access just upstream of the Main Street bridge in Kent. This is one of the spots we’ll be using to sample the river.