Complex computer modeling assesses Delaware River health
Third in a series: dissolved oxygen and the Atlantic sturgeon
A surprise guest at a recent Water Quality Advisory Committee meeting! Serge the Sturgeon wants to make sure the Delaware River is a good place to raise his kids. GRAPHIC ILLUSTRATION BY CELIA HELFRICH
Remember back in August when I started this project on dissolved oxygen and the fate of the Atlantic sturgeon? Story here.
I talked about how the river is much MUCH cleaner than it's been in a long time, like before industrialization and likely before colonial times as well. (Slaughterhouses and tanneries made a mess of the river.)
But there's another question that we need to ask and answer: How healthy is our river?
And that's all about balance.
Tackling the issue of dissolved oxygen in the Delaware is about finding the best balance of many different factors that affect this natural system.
If we went back to before Europeans settled in the Delaware River watershed, we would be looking at a largely hunter/gatherer population that by its very nature never put too much strain on natural balances.
Storms came, but the land was mostly forested, so there wasn't much in the way of sediment to muddy the river. There wasn't farming and no demand for land to produce more and better crops, so no fertilizer to run into streams, and no herds of cows whose manure ran into streams as well.
And remembering the source of our problems right now, there wasn't much human excreta that found its way into the river.
But once Europeans came, that all changed. Farms came, cities grew, and the population in the watershed exploded.
We'll find out a little more about a professor from Tufts University -- Steve Chapra -- a little later but for right now let me introduce you to his novel way of describing how humans have historically decided if water is OK.
Rubbish, stink and death.
Pretty arresting, right?
Chapra explained that rubbish is the aesthetics of a river or water body. Stink is a way we identify the health of an ecosystem. Stink is produced when an ecosystem is out of balance. And death signals that the water can cause immediate or long-term harm.
Until the 1950s, it was still quite common for sewers to gather our untreated sewage and empty it into the river.
We had a rubbish problem and a stink problem. Luckily, thanks to water treatment plants that treated the water they took from the river, we didn't have a death problem.
Then came the Delaware River Basin Commission, the Clean Water Act and the Environmental Protection Agency.
The river got cleaner, largely because wastewater treatment facilities (with significant financial help) started processing the biggest problem -- carbon in the sewage (that's our poop). The other problem we humans quite literally created -- ammonia in the sewage (that's our pee) was given a bye as for the most part, the bacteria in the river processed that for us.
We are in the middle of new ways of thinking about the river. It's always been an economic engine with shipping but now we have businesses that depend on the river, like boating and fishing. We want to spend more time beside, on or even in the river.
Our expectations for the river have moved from those simple judgments of rubbish, stink and death and toward a more sustainable view of the river as it affects our quality of life and its uses for tourism. This thought is also thanks to Chapra, who wrote a paper on this topic which you can find here.
Again, it's all about balance. What can we do to get the river healthier without breaking the bank for hard-pressed municipalities? How do we ensure there's enough water coming from up river to "push back" the ocean's salt front and still have enough water for New Jersey's needs in times of drought? What can we do to minimize the impact of nutrients while recognizing that farms need some help to be economically viable?
OK. Nutrients. Let's take a moment and get underneath the hood of these dang nutrients we hear so much about. There are cycles in nature that are, if you like, energy pathways. The source of all our energy is the sun, and the way we get at the sun's energy is through plants, which have that special magic called photosynthesis.
And many of us get energy from animals that have eaten plants.
Elements like carbon, nitrogen and phosphorus, cycle through the environment -- in water, soil, air or organisms. Organisms include simple cells as well as more complicated, energy-hungry organisms like us.
We derive our energy from internal body processes that break down organic molecules (AKA food) and release energy as they do so.
We are indeed stardust. Every element in our bodies was forged by the explosive energy of stars. But we're (and all the rest of life on earth) also mini-suns, combusting the energy of other organisms to make our living bodies.
Back to the river, the dissolved-oxygen sag we see near the Ben Franklin Bridge in the summer is evidence that the river is a little out of whack, and we need to figure out what exactly whack is before we can figure out how to get back in whack! (Whack=balance)
The river, as I've said, is a natural system, just like the human body. If we have too many cupcakes, we'll get fat. Of course, if we eat one cupcake a month, our bodies can handle that especially if we're not loading up on other sweet stuff, or maybe we balance it out with exercise.
We've essentially fed the river too much of one particular thing -- ammonia --- and we need to figure out the diet that will bring it back to a healthier place.
For that, we have science, with a dose of engineering. The name of this part of the action is modeling.
So that's what the Delaware River Basin Commission has asked its staff to do: model the river south of Trenton where the tidal portion of the river begins.
Forget all notions of models that you have (unless you too are a scientist!) These are not those plastic models that your dad used to make of World War II planes.
And certainly has nothing to do whatsoever with those lovely Victoria Secret models you may have seen.
No, these are models developed to predict what might happen in the future. Not who will win the World Series, but rather what will happen in the river if you change certain variables, with an emphasis on what are called loads (like cupcakes) that negatively affect the river, like treated wastewater, nutrient runoff, stormwater runoff or what gets deposited in the river from the air.
You'll have seen -- when we're expecting snow or other storms -- meteorological models that show one or more possible paths the storm might take. Will it come inland in New Jersey or Long Island? When? How fierce will it be when it makes landfall?
Those models can be accurate. Or not. Depends on whether the meteorologists have all the right data.
The more accurate the data, the better the model, and then we can figure out if this is a good day to visit relatives on the coast. Or maybe it would be better for our relatives to come and visit us inland.
In order to figure out who has to do what to fix the dissolved oxygen problem in the Delaware, the model has to have TONS of data.
"Models are extremely data hungry," explained Vic Bierman, a consultant from LimnoTech hired as part of the DRBC's water quality modeling project.
The Water Quality Advisory Committee met on December 5, 2019. This was a special meeting of that committee. The staff at the DRBC has been working on developing the very complicated model of the river for more than a year. Every six months they review their work with the wise men of modeling: the Model Expert Panel.
The Model Expert Panel (aka the rock stars of modeling) gather to review DRBC's dissolved oxygen model. From left, Carl Cerco, U.S. Army Corps of Engineers (retired); Tim Wool, U.S. Environmental Protection Agency; Bob Chant, Rutgers University; Steve Chapra, Tufts University: and Vic Bierman, LimnoTech - not technically a member of the panel hired by the DRBC as a modeling consultant. PHOTO BY MEG MCGUIRE
These are scientists who have spent their professional lives working on models. Remember Steve Chapra? He's one of them.
The others are: Carl Cerco, U.S. Army Corps of Engineers (retired); Bob Chant, Rutgers University; Tim Wool, U.S. Environmental Protection Agency, Region 4.
Consultants to the DRBC, hired to be the public-facing translator of the panel's findings, are Vic Bierman and Scott Hinz, both from LimnoTech, an environmental engineering firm.
Here's the DRBC staff that have been working on it:
The DRBC is developing not just one model, but two: One is of the way the water moves in the river and bay, hydrodynamic model, and another of water quality with a special focus on what affects dissolved oxygen. And then, figure out how the two models can talk to each other.
As Bierman explained, the hydrodynamic model is a chassis that the water quality model "sits" on. A chassis, if you will, that once developed can be used for other modeling purposes, but it's essential to get the movement of the water right.
Think of it: We have tides that rush in and out. Our estuary is, because of its funnel shape, a high-energy estuary. The tidal push and pull is pretty strong.
We have a great big ocean at our doorstep that creates the salt front coming up the river that can threaten Philadelphia's water draw from the Delaware.
We have fresh water coming down from upriver, from all the way up in New York's reservoirs, and all the way up the Schuylkill. The model has to encompass the effects of all those water sources and 29 other tributaries that empty into the river. That's not all, it has to include the inflow from point-source dischargers like municipal wastewater treatment plants and runoff from all the lands adjacent to the river. Although its focus is on the estuary where the dissolved-oxygen problem is pronounced, the water comes from all over the watershed.
When you look at a map you can see how the bay narrows, but what you can't see is how the bay narrows below the surface. That has to be mapped and understood as well. How deep is it? What's the surface at the bottom? Rocky? Sandy? Muddy?
This slide shows what one possible grid configuration might be -- just to show how complicated this hydrology model is. If the grid were to stay like this not only are there 1,981 cells on the surface, but there are cells stacked up underneath. That stack is also still to be decided and would be anywhere from 3 to 10 cells.
The water quality model is being built to quantify the factors that affect dissolved oxygen, like nitrogen, ammonia-nitrogen and phosphorus.
Here's a slide that will give you some idea of the things being measured, though those "things" can change as the model goes forward.
The "on the ground" data has been collected for 2018 and 2019. The DRBC collects lots of data all the time, but these two years have been the focus of even more intensive gathering in order to get that "whack" point I mentioned.
Unfortunately the river has been unpredictable, as always, and in these two years the flow of water has been stronger than average, so in addition to the 2018-19 data, the modelers are looking back to 2012, which was a dry year to balance their understanding.
This is to produce in 2021 a calibrated model that can be used to ascertain waste load allocations for the primary source of the dissolved oxygen problem: the wastewater treatment plants that dot the river, processing our various excreta.
Remember, these plants have done amazing work over the past 50 years reducing the carbon load and making the river a far cleaner place than it used to be.
In addition to whatever desire we have to make the river more attractive for business and tourism, we also have the responsibility to look after the critters that live in the river, especially when one of them is an endangered species: the Atlantic sturgeon.
Sturgeon were once found in the river by the hundreds of thousands. But the past 100-plus years of industrialization has been tough on them and they mostly disappeared from the Delaware. It's because of our cleaner water that they're back, and now we have to make sure that they can reproduce, and when they do, that their young thrive.
They are most likely to be affected by the dissolved-oxygen problem during the summer when the oxygen sag is typically at it worst.
Different fish -- and different ages of fish -- have different oxygen needs. Remember, fish need oxygen just as we do, they just get it from the water they swim in.
Also, dissolved oxygen is a great indicator of how healthy a water system is. Think of a clear, cool mountain stream bubbling along. It's rich in dissolved oxygen, which is why some fish can only be found there, like trout.
OK. Back to this meeting.
It's an important one. The DRBC scientists have been working away at these models. And today their work is investigated by these modeling gurus, the Model Expert Panel.
They swoop in twice year to see what the DRBC scientists are doing, to make suggestions to improve the work and generally see that the end result does what everyone expects.
Here's the charge from the DRBC:
- Develop a technically sound eutrophication model for the Delaware Estuary and Bay utilizing the current state of the science within a timeframe established by the Commission.
- Identify appropriate levels of source control, especially in relation to dissolved oxygen.
If you remember from the previous stories the timeline established by the commissioners was greeted with some concern, even anger, especially from Maya Van Rossum, the Delaware Riverkeeper, who said that the present parameters for dissolved oxygen should be raised and the wastewater treatment plants should immediately alter and improve the wastewater that empties into the river.
But the largest wastewater treatment plants are public entities, whose funding come from our taxes -- our pockets, and if we just took a guess at what those new regulations should be, and then these plants did a bunch of expensive infrastructure improvements, it may all be less than what is required -- or more. (The second story on dissolved oxygen goes into this here.)
They wanted something provable and specific. So we have this five-year plan.
At this meeting, it was almost as if the wastewater treatment plants were sharing Van Rossum's impatience. Jason Cruz, a scientist with the Philadelphia Water Department asked how soon there might be any results.
Bierman said it was way too soon to say.
Here's the timetable of what's happening when.
It's not surprising that the various wastewater treatment plants want to get some idea of what demand is coming. Changes to their waste treatment systems are likely to be costly, and can't happen in a hurry.
In another meeting later in the week of the New Jersey Sector of the American Water Resources Association, the executive director of the DRBC, Steve Tambini, addressed a similar question from the audience. He expressed sympathy for what cash-strapped municipalities might be facing, but he put the demands of the Clean Water Act and other federal regulations as front and center for the DRBC.
"There's no avoiding it," he said.
There's no interest from the DRBC in telling wastewater treatment plants HOW they get to whatever new allocations might be forthcoming. John Yagecic, manager of Water Quality Assessment for the DRBC, has previously said that its concern is the wastewater at the point where it enters the river,
In addition, DRBC's Director of Science and Water Quality Management Namsoo Suk has explained that it seems likely that some improvements to the amount of ammonia entering the river from the larger plants will improve the water quality of the river. "At least, I hope so!" he said.
That's the point: Model the river as it is, with tons of variables that affect the river in different ways in different places. Define what "whack" is, then work within the model to identify what is the measurable reality now and change that virtually, to a different reality by imagining (via the computers running the model) what different adjustments might mean to the river's quality.
The model will be amazingly complex. First off, decisions have to be made about how to slice and dice the river in order to examine it. There's a grid system that is mentioned above. But then the water quality piece has to be studied. This slide indicates just how complicated that piece is.
And finding out what "whack" is takes time and gets revamped as the model is developed.
For example this grid system laid on the river the last time the Model Expert Panel met extended out into the ocean, recognizing that the ocean plays a big part in the bay. Even though that may be the case, the grid now stops at the mouth of the bay. That line may change again, As Yagacic explains, "Where that boundary line is drawn is important and can affect the whole model."
But the reasoning at the moment is that the dissolved oxygen problem is not in the wide bay but as the estuary narrows near Philadelphia and Camden.
The Model Expert Panel seemed happy with the work that the scientists and engineers at the DRBC have been doing. They have reviewed data and compared actual data with mini-test outs of predictions.
One of the interesting aspects of modeling is that it takes a long time to gather the data, and a long time to actually run the model -- perhaps hundreds of hours. So the expert panel suggested that the DRBC consider running simple tests on a 2D rather than a 3D version, cutting run time down from tens of hours to just hours.
Another suggestion? That the DRBC consider renting "cloud" computing time from Amazon to speed up the process rather than rely on its older, slower computers.
Even as DRBC staff are hard at work developing this model, the Water Quality Advisory Committee is stalking its next project: working to understand other nutrient issues that face the estuary. Some of the issues are masked by the system's water quality. It may be that we need to get the dissolved oxygen problem at least beginning to be resolved so that the other problems can be more easily detected and understood.
There's always more to understand.
There were two other dissolved oxygen stories:
- Clean Water? Mind your pees and carbons!
- Wastewater treatment plants: Problem and solution for a healthier Delaware River
Thanks to many people for their patience with my endless questions! Don't blame them if I didn't get it right! (But let me know!)
These are the people that should be acknowledged for their time for all three of these dissolved oxygen stories.
Steven Chapra of Tufts University; Namsoo Suk, John Yagecic, Steve Tambini and Kate Schmidt from the Delaware River Basin Commission; Maya van Rossum and Erik Silldorff from the Delaware Riverkeeper Network; Angela Padeletti from the Partnership for the Delaware Estuary; John Jackson from Stroud Water Research Center; David Velinsky from Drexel University; David Wolanski from Delaware Department of Natural Resources and Environmental Control; Clair Billett from The William Penn Foundation; Dr. Dewayne Fox from Delaware State University; Andy Kricun, chief engineer for the Camden County Municipal Utilities Authority; Ian Piro, formerly with DELCORA and now with Isles, Inc; Jason Cruz, Philadelphia Water Department.
Special thanks to my Environmental Leadership Program colleague, Christina Catanese, who connected me with Celia Helfrich. Celia patiently created and re-created the delightful graphic illustrations as my understanding of the problem deepened. Thank you!
Week No. 3 →
