A Watershed Moment
The Academy of Natural Sciences of Drexel University is leading a massive, $35 million conservation initiative to ensure that the Delaware River remains a vibrant natural habitat and safe source of drinking water for millions.

When fish biologist Richard Horwitz talks about streams in the Delaware River Basin, people listen.

Horwitz, a senior scientist at the Academy of Natural Sciences of Drexel University who has worked in the region for nearly 40 years, isn’t your typical fish expert — he’s also a student of environmental history and a keen observer of all living things. When he walks a stream, he is not only studying what’s in the water, he is also looking all around, ahead and behind.

With this perspective, he understands how the land and the streams it drains into, together forming a watershed, are connected. He and his colleagues in the Academy’s Patrick Center for Environmental Research know that everything we do on land has implications for the health of streams, the species that live in them and the people who depend on them. Since 1947, the Patrick Center has been devoted to studying the health of watersheds through its embodiment of this holistic view. The center is named for its founder, Ruth Patrick, who developed the fundamental “Patrick Principle” on which much of environmental science and management is based: that biological diversity holds the key to understanding the environmental problems affecting an ecosystem. Patrick helped to write the Clean Water Act, and over the past half century Academy scientists have continued to influence river science, policy and management.

So when the William Penn Foundation looked for an institution to help guide a massive new collaboration of conservation groups to improve water quality in the Delaware Watershed, the Academy was an obvious choice.

The foundation had honed its vision for clean water in the Delaware through early conversations with experts like Horwitz; Roland Wall, the Academy’s senior director for environmental initiatives; and Carol Collier, the former executive director of the Delaware River Basin Commission who later joined the Academy.

The William Penn team concluded from these discussions that only a sizeable investment could make a measureable difference for the Delaware’s water quality. On April 1, 2014, the foundation pledged $35 million to protect the watershed’s healthiest streams and restore impaired ones to good condition.

The foundation awarded the Academy oversight of the multi-year effort, christened the Delaware River Watershed Initiative (DRWI).

The Academy and one of its partners, the Open Space Institute, kicked off the project by identifying the highest-priority “clusters” of smaller watersheds throughout Pennsylvania, New York, New Jersey and Delaware that feed into the Delaware River Basin. Academy researchers are now guiding more than 40 grantee conservation groups as they establish baseline conditions for water quality and begin restoring areas where the foundation’s investment in conservation has the potential to do the most good.


Delaware River Watershed Initiative conservation and monitoring activities are underway throughout the 6,575 square miles of the Delaware River Basin in clusters of smaller watersheds that are targeted for agricultural restoration, suburban restoration, protection of intact forests, or a combination.


From its fountainhead in the Catskill Mountains in New York, the Delaware River courses over 300 miles of urban and rural landscape and four different states on its path to the Atlantic Ocean, crossing all kinds of terrain and feeding into nearly 1,000 community water systems.

There’s a direct line from the Delaware Watershed to the health and well-being of more than 15 million people who rely on it for drinking water.

Almost half of those people live outside the basin in the greater New York City area, underscoring the importance of the Delaware for the larger region.

The health of streams in the watershed varies from place to place and is tied to surrounding land use, with water quality being more impaired in downstream agricultural, suburban and urban areas. Excess nutrients and sediment loads from increased development, agriculture and urban runoff impair some streams. Toxic pollutants — including some “legacy” contaminants like DDT and PCBs from historic activities — affect others. In some places, streams suffer from drainage from long-abandoned mines.

Nonetheless, most people in the region have access to all the clean water they need. So why invest in protecting and restoring the watershed?

“It’s true that clean, abundant water is available in the Delaware River watershed now, but we shouldn’t plan on that always being the case,” Stefanie Kroll, the Academy’s project science director for the DRWI, explains. “Recent news headlines highlight the fragility of our water supply, with hundreds of thousands losing access to clean water as a result of pollution and poor management. Paying attention to the Delaware today is essential for having the same resource quality in the future.”



It’s nearly impossible to describe the Delaware River Watershed Initiative without illustrating the scale of effort.

The eight clusters where the project will focus together cover around 6,575 square miles, or an area larger than the size of Connecticut and Rhode Island combined.

To compare data across sites and obtain reliable results, scientists and partners must execute activities and collect data similarly from site to site. Coordination and standardization, which are baked into the initiative’s design, are rare in a project involving so many actors.

And the cast is literally in the hundreds. The coordinating group members — the William Penn Foundation, the Academy, the Open Space Institute, the National Fish and Wildlife Foundation and the Institute for Conservation Leadership — each have their own expert teams.

There are also dozens of local organizations working within individual clusters to put protection and restoration strategies into practice.

“You won’t find other watershed projects that engage so many organizations,” observes Collier, now the Academy’s senior advisor for watershed management and policy. “The DRWI is a wonderful example of how to build support from the ground up. After all, it takes all the citizens of a watershed to make a clean, healthy river system.”


Good water quality is essential not only to people, but also to the species that rely on the Delaware’s aquatic systems.

From the tiniest algae to the majestic bald eagle, degraded water affects the flora and fauna living in and around it.

“If you put a garbage dump next to your house, everyone who lives in the neighborhood is going to move,” says Kroll. “Animals and plants are the same way. They don’t want to live in horrible conditions, so their presence or absence tells us if something has happened in the past year.”

The disappearance from degraded sites of species that need high-quality habitat, and the proliferation of more tolerant species, is at the core of biological monitoring, she says.

At dozens of sites, Academy scientists sample algae, macroinvertebrates, crayfish, fish, salamanders and water chemistry (the Academy’s current monitoring projects on the Delaware River are described on the following pages). Together these indicators, along with measures of water flow, temperature and streamside conditions, illustrate ecosystem health.

For instance, salamanders often disappear or show abnormalities when exposed to pollutants, but the types of pollutants may be unknown. Different kinds of algae can help fill in the picture by indicating whether heavy metals or excess nutrients have been in the water.


Local organizations are adopting Academy protocols and undertaking their own monitoring programs at individual sites, often for the first time. Academy scientists are providing guidance, to ensure consistency of methods so that all the data can ultimately be used together.

The data from more than 300 sampling sites will help scientists understand whether the initiative’s stream restoration and protection activities are improving water quality. If they are, then there is a good argument to replicate them elsewhere in the Delaware and beyond. If they aren’t, then it’s important to figure out why and consider changing course.

Evaluating what works may seem like common sense. Yet a landmark 2005 study of thousands of stream restoration projects in the United States found that the vast majority lacked rigorous scientific evaluation of whether the projects were successful.

The DRWI built in evaluation from the start.

“The William Penn Foundation emphasized the importance of scientific credibility from our earliest discussions with them,” says Wall, the Academy’s team leader on the DRWI. “They made sure that monitoring and assessing ecological quality were going to play a central role in the project.”

As the monitoring program gets fully underway this year, it will begin generating scores of datasets for integration into a single database accessible to all project partners.

This standardized dataset, which Kroll happily refers to as a “luxury,” will be an accomplishment in and of itself. But the real achievement will be using it to understand what it takes to move the needle on water quality at a scale that will make a difference to the millions of people who live, work and play in the Delaware River Watershed.

This story first appeared in Academy Frontiers, the magazine of the Academy of Natural Sciences of Drexel University.

_An Index for the Delaware

One way to assess impacts to an ecosystem and express it to the public is to compile biological indicators, like fish and algae, into an index called the Index of Biotic Integrity (IBI).

One simple way to assess impacts to an ecosystem and express it to practitioners and the public is to compile biological indicators, like fish and algae, into a summary index called the Index of Biotic Integrity (IBI).

However, no such index exists for the Delaware River watershed as a whole, because the basin runs through four states with their own individual approaches.

Academy scientists are working to change that. Stefanie Kroll, project science director for the Delaware River Watershed Initiative, and a team of Academy scientists in collaboration with the Stroud Water Research Center in Avondale, Pennsylvania, are visiting streams and sites to investigate how certain bioindicators relate to degradation and conservation efforts.


Scientists are compiling an “Index of Biotic Integrity” that summarizes the biological well-being of the Delaware River watershed as a whole.

“This work is generating information on the Delaware River Basin and using local waterways to answer questions about watersheds on both regional and local scales, like ‘Which areas should be prioritized for conservation?’ or ‘Where can we target conservation actions so they have a cumulative effect on improving or maintaining water quality?’” she says.

To further their knowledge of the effect of conservation efforts, Kroll and other scientists are also looking into how water quality is affected by stream connectivity and tributaries that flow into larger streams. They will target certain places along the river where tributaries connect to larger streams or to pollution “hotspots.”

Altogether, the work will measure the effects of restoration and protection on water quality, and help target where these practices can have the greatest positive impact, according to Kroll. The next step is to understand how researchers can best use these approaches to determine the biggest stressors to regional streams.

_Still-Water Dwellers

The old proverb says that “still waters run deep,” but Academy scientist Meghan O’Donnell is going one step further and asking “run deep with what?”

_Meghan O’Donnell

O’Donnell is a staff scientist at the Academy of Natural Sciences of Drexel University.

The old proverb says that “still waters run deep,” but Academy scientist Meghan O’Donnell is going one step further and asking “run deep with what?”


are key bioindicators used to assess stream health. To get a full picture, scientists are sampling the critters in often-overlooked slow-moving currents.

To find answers, she’s looking at the parts of the Schuylkill and Brandywine-Christina watersheds that are lentic, or slow-moving and without any current. There, she’ll search for macroinvertebrates (think: insects, small crustaceans, crayfish and mollusks) that can act as bioindicators to reflect the environmental conditions of the area. Typically, samples are taken from lotic, or areas where the current is strong in the center of the water column, because that’s where the area is teeming with diversity.

“There aren’t metrics for indicators of biological integrity for lentic areas,” she says. “In lentic areas, there is lower dissolved oxygen and increased sedimentation; you will find different kinds of macroinvertebrates that tend to have a high population of predators and air breathers.”

Since the organisms she’s looking at are as slow-moving as their watery habitat, O’Donnell says that the tolerance level of the macroinvertebrates sampled tells a lot about the long-term conditions of the aquatic environment. The various bioindicators give insight into the water conditions, but that’s not enough for O’Donnell. She’s still taking water samples and measuring pH, water temperature, conductivity, stream depth and width, and soil and vegetation cover at the sample sites to learn even more about the macroinveterbrates’ habitat and impact from land use.

In the future, O’Donnell hopes to compare her specimens’ tolerance level to pollutants to those sampled in the lotic areas, and potentially establish a lentic Index of Biotic Integrity, or IBI, to gauge the health based on what families of organisms are found.

_Scanning Streams, Remotely

How do Academy scientists know where to observe water quality or test sediment conditions throughout the Delaware River Basin? By “hiking” the streams using any laptop.

_Alex Waldman

Waldman is the GIS manager and watershed modeler for the Academy of Natural Sciences of Drexel University.

How do Academy scientists know exactly where to observe water quality or test sediment conditions near riverbanks throughout the entirety of the Delaware River Basin? By “hiking” the streams from the comfort of their offices, using any laptop.


The Academy developed a computer model called StreamHiker for evaluating environmental conditions along a stream from a laptop.

StreamHiker, an Academy-developed watershed analysis tool, evaluates environmental conditions along and near a stream or river at the “reach” scale, or where monitoring efforts are conducted. So far, DRWI researchers have used StreamHiker to choose sites for sampling and examine environmental conditions at project sites and potential sampling sites. In the future, StreamHiker will offer statistical models to predict stream temperature at unmonitored reaches and simulate changes due to land development and climate change scenarios.

“Our goals are for watershed scientists, modelers and managers to incorporate the accessibility of data and analytical processes that StreamHiker facilitates into their work, while also leveraging StreamHiker’s flexibility of data scaling to make innovative watershed models and tools,” says Alex Waldman, StreamHiker’s lead programmer, GIS manager and watershed modeler.

StreamHiker isn’t limited to one geographic location or institution. The project is open-sourced, meaning it is accessible to anyone, anywhere, no matter what body of water or environment they want to investigate.

StreamHiker is managed by Waldman and Jerry Mead, section leader of watershed and systems ecology and assistant research professor in the College of Arts and Sciences, with contributions from Scott Haag, database administrator. Mead developed the algorithim as a post-doc in 2006, but StreamHiker has since evolved into a complete software package after Waldman became involved with the project in 2013. The team has applied for NSF funding to grow StreamHiker’s reach and capacity even further.

_Sediment and Small Habitats

Sediment by erosion or runoff from farm fields can cause a “domino effect” on the ecosystem, according to David Keller, project coordinator within the Fisheries Department at the Academy.

_David Keller

Keller is the project coordinator for fisheries at the Academy of Natural Sciences of Drexel University.

The biggest threat to water quality isn’t what’s inside the stream, it’s what’s next to it. Sediment created by erosion or runoff from farm fields can cause a horrible “domino effect” on the ecosystem, according to David Keller, project coordinator within the Fisheries Department at the Academy.

Not only does the sediment affect the light penetration and water quality, but it can also change the substrate composition already in the river. Runoff sediment can fill in pore spaces, or spaces in between the substrate, which can transform the stream bottom from something more coarse to something more fine.
“Some animals use that substrate and pore space for habitat. So when you introduce sediment into a stream, it fills in the pore space and alters the habitat for the animals that live in the stream, like fish, salamanders and macroinvertebrates,” says Keller.

Though sediment runoff is a common problem throughout the area, special circumstances have caused Keller and other Academy scientists to focus on a very specific part of land along Barrett’s Run, in the Cohansey River watershed in New Jersey. There, the American Littorial Society, an environmental nonprofit, is currently restoring a seven-acre tract of farmland to a grassy meadow in hopes that their efforts will reduce sediment and improve water quality.

Currently, Academy scientists are assessing the impact of the new meadow by installing traps up and down the slope of the field that will measure the amount of fine sediment running off during storms. If successful, the meadow vegetation will hold onto the soil, slowing water flow and increasing infiltration into the ground.


Academy scientists are looking for reductions in sediment runoff in a seven-acre tract of farmland that is being restored to a meadow of grasses.

_Invasion of the Knotweed

Japanese knotweed (Fallopia japonica), a non-native invasive species, has been covering a lot of ground, and water, and wreaking havoc on its environment.

_Kathryn Christopher

Christopher is a staff scientist at the Academy of Natural Sciences of Drexel University.

The Delaware River Basin is under attack from a foreign enemy: Japanese knotweed (Fallopia japonica), a non-native invasive species, has been covering a lot of ground, and water, and wreaking havoc on its environment.

Though the bamboo-like plant seems harmless with its heart-shaped leaves and small white flowers, Japanese knotweed is known as the “Attila the Hun” of the plant world because once it invades, it’s capable of much damage. The plant grows quickly and densely, crowding out native streamside vegetation and worsening erosion and sedimentation. It’s incredibly hard for humans to limit its growth, let alone get rid of the plant altogether.

“A lot of money is spent on stream bank restoration, which often includes removal of invasive plant species, but Japanese knotweed is very difficult to eradicate. It reproduces quickly from seeds or roots, and only a small root fragment is enough to regrow a population or travel downstream and colonize a new area,” says Kathryn Christopher, a staff scientist researching the invasive plant.


Researchers release mesh bags stuffed with leaves into streams to study the kinds of insects that colonize them.

Christopher and her research partner, Derron LaBrake of Wetlands & Ecology Inc., have created a pilot study to research the effect the plant has on insects in the water, and how insects interact with it versus native plant species. She hopes to start a framework for other, more intricate questions regarding knotweed and stream conditions.

In January, the team deployed leaf packs, or mesh bags stuffed with leaves, into several area streams. The packs were collected over several weeks through February and early March for the researchers to examine the insect communities that have colonized the leaves.

“We are looking to see if the insects show a difference in preference between native leaves and knotweed,” she says. “We are trying to better understand the effects of knotweed on stream ecosystems so that management plans can be better tailored for specific sites, with hopefully better results.”

_Canaries of the Stream

Many salamanders need water to breathe through their moist skin, so salamanders typically found by water can serve as indicators of water quality.

_David Keller

Keller is the project coordinator for fisheries at the Academy of Natural Sciences of Drexel University.

Many salamanders need water to breathe through their moist skin, so salamanders typically found by water can serve as indicators of water quality. While most states lack monitoring programs for stream salamanders, Academy scientists hope to change that by using their assessments of salamanders in the Delaware River watershed to create an index of stream health, much like how researchers use fish.

“We’re trying to understand what habitat features are important to salamanders in the Delaware and which ones are not; and for the features that are important, we’re trying to quantify them,” says fisheries coordinator David Keller.

The researchers visit different clusters of the Delaware River watershed to develop methods to assess salamander abundance. Sometimes, the work can be as backbreaking as repeatedly lifting rocks to find hiding salamanders.

“By the method we’re using, we’re not able to catch all of the salamanders in a given area. What we are able to do is to get an estimate of the relative density of animals in a given area by using CPUE, or catch per unit effort,” Keller says.

Each grouping of the sites will, in theory, show how salamanders are responding to anthropogenic stress, which can vary by site. Stormwater runoff is prevalent in Philadelphia, whereas agriculture is the main stressor to the environment in the Brandywine-Christina area. It’s a lot of ground (and rocks!) to cover, but Keller hopes that the work will give scientists another tool for monitoring water quality.


Salamanders are sensitive to habitat loss and stream impairment, and existing protocols for their study are inadequate.