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LOOKING AT THE Susquehanna River AS A Circuit
LOOKING AT THE Susquehanna River AS A Circuit
This is a systems-based analogy—not a literal electrical model—but it helps illustrate how connectivity drives ecological function
Stand along the banks of the Susquehanna River in Sunbury and you’ll see water moving, fish swimming, life continuing.
At a glance, everything seems fine.
But beneath the surface, something essential is missing.
The river still flows—but the system is impeded.
The River as a Circuit
The River as a Circuit
Think of the Susquehanna not just as water, but as a living electrical circuit.
The Chesapeake Bay is the power source
The river channels are the wires
Migratory fish are the current
Nutrients are the energy being transferred
When everything is connected, energy flows freely. Life moves. Systems build on systems.
For thousands of years, that current pulsed upstream each spring.
Species like American shad, River herring, and even Atlantic sturgeon carried ocean energy deep into Pennsylvania—past Sunbury, into the branches, feeding the entire watershed.
This wasn’t just a migration.
It was a transfer of life.
For millennia, the Chesapeake Bay acted as the primary power source, sending a biological 'current' of migratory fish upstream to power the entire inland network. Today, we are looking at a system suffering from high resistance. To restore the river, we have to think like engineers: we need to repair the connections.
Where the Circuit Broke
Where the Circuit Broke
Now imagine that same circuit—but with breaks in the wire.
Major interruptions sit downstream:
Conowingo Dam
Holtwood Dam
Safe Harbor Dam
Each one acts like a resistor—or in some cases, a full disconnect.
Fish lifts and ladders try to bridge the gap, but it’s not the same as an open path. The current weakens with every obstacle.
By the time migratory fish would reach Sunbury, most of that energy has already been lost.
Finding the Harmonic Balance: In any complex circuit, resistors serve a purpose—they manage flow. Our dams provide flood control, energy, and recreation, making them a permanent part of our social landscape. But when a resistor becomes a disconnect, the whole system suffers. We have to learn to live with the river, not just on top of it. True balance means optimizing our infrastructure so that human progress and migratory life can occupy the same 'wire' at the same time.
Smallmouth bass like this are incredibly resilient! A testament to the strength and adaptability of our river systems, thriving predators like this one show us that even through ecological changes, the river’s heart still beats strong. What an incredible catch!
What Happens When the Current Stops
What Happens When the Current Stops
When the circuit breaks, the effects ripple outward:
Fewer migratory fish means less food for predators like Smallmouth bass and Walleye
Fewer nutrients reach upstream ecosystems
Biodiversity declines—not always visibly, but steadily
The river shifts from a dynamic system to a more isolated one
The river still functions—but at a fraction of its potential.
What a Reconnected River Could Look Like
What a Reconnected River Could Look Like
Now imagine repairing that circuit.
Not perfectly—but better.
Stronger fish passage at dams
Restored spawning habitat
Improved water quality and flow timing
What returns?
Larger runs of American shad pushing upstream
Schools of river herring feeding everything around them
The possible return of species like American eel in greater numbers
A measurable boost in predator growth, bird activity, and overall biodiversity
The current starts flowing again.
And when it does, the system doesn’t just improve—it amplifies.
Why This Matters Beyond the Water
Why This Matters Beyond the Water
A healthy river doesn’t stay in the river.
It shows up in:
Stronger recreational fishing
Increased tourism and local business activity
Cleaner water for communities
More resilient ecosystems
In other words, repairing the river’s “circuit” doesn’t just restore fish—it strengthens the entire region.
Standing at the Break
Standing at the Break
Right here in Sunbury, near structures like the Fabri Dam, you are standing at one of those connection points.
Places like this matter.
They are where awareness turns into action.
Where small improvements can reconnect larger systems.
The Question Moving Forward
The Question Moving Forward
The river isn’t gone.
The current isn’t gone.
It’s just interrupted.
And that leaves us with a choice:
Do we leave the circuit broken…
or do we start reconnecting it, piece by piece?
When we step back and look at the Susquehanna River as a connected system rather than a collection of separate issues, a different picture emerges. Flow, resistance, and connection begin to explain patterns we often describe in isolation—fish movement, water quality, sediment shifts, and ecosystem health. This perspective doesn’t point to a single cause or a single solution. Instead, it highlights where the system has become fragmented and where restoring connections may allow it to function more effectively again. In the end, understanding the river this way is less about assigning blame and more about recognizing how interconnected systems respond when their pathways are altered—and how they respond when those pathways are restored.
What the Science Shows (Reality Check)
📌 Dams have fundamentally altered the river’s ecology
📌 Dams have fundamentally altered the river’s ecology
Large dams on the lower Susquehanna River—including Holtwood, Safe Harbor, and Conowingo—have blocked or severely restricted migration for species such as American shad, river herring, and American eel. These barriers have eliminated access to historical upstream spawning habitat and contributed to long-term population declines.
Source:https://www.hec.usace.army.mil/sustainablerivers/publications/docs/Susquehanna%20-%20Ecological%20flow%20watershed%20assessment.pdf
📌 Migratory fish populations are at historically reduced levels
📌 Migratory fish populations are at historically reduced levels
Species like American shad have experienced major declines due to dam blockage, habitat loss, and historical overfishing. Studies show that many migrating fish are still unable to pass key lower-river dams effectively, limiting recovery upstream.
Source:https://www.fws.gov/testimony/oversight-hearing-conowingo-dam
📌 Dams change flow, temperature, and habitat
📌 Dams change flow, temperature, and habitat
Reservoirs created by dams slow water velocity, trap sediment, alter seasonal flow timing, and increase water temperatures. These changes reduce the quality of spawning and nursery habitat for native species that evolved in free-flowing river conditions.
Source:https://www.lowersusquehannariverkeeper.org/about-us/watershed-information
📌 Water quality and land use have long impacted the watershed
📌 Water quality and land use have long impacted the watershed
Since industrialization, the Susquehanna watershed has been affected by agricultural runoff, sewage inputs, and legacy pollution. While conditions have improved compared to historical peaks of pollution, nutrient loading and sediment issues continue to affect ecosystem health.
Source:https://www.lowersusquehannariverkeeper.org/about-us/watershed-information
📌 Connectivity is essential for recovery
📌 Connectivity is essential for recovery
Restoration science emphasizes that reconnecting migratory pathways—through improved fish passage or dam modification/removal—is critical for restoring populations of diadromous fish such as American shad and American eel, and for improving overall river health.
Source:https://www.usgs.gov/centers/pennsylvania-water-science-center/science/susquehanna-river-and-basin
Author’s Note
Author’s Note
This article was written by Douglas E. Fessler. The ideas and reflections are my own, drawing on decades of experience in IT, environmental monitoring, STEM education, and community initiatives. AI-assisted tools were used to structure and clarify complex concepts — a reflection, in itself, of the subject explored.
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