Tuesday’s collision of the container ship Dali into Baltimore’s Francis Scott Key Bridge and the nearly immediate collapse of the span into the chilly waters below reminds us just how unforgiving and deadly maritime accidents can be. Upon termination of rescue and recovery operations, salvage and cleanup will be prioritized as the next steps in the long-term process of reopening the navigable waters to ship traffic and construction of a new bridge. Part of the effort will include monitoring for leaks of fuels and other hazardous materials from the ship, its damaged cargo containers, and vehicles and equipment that were on the bridge when it failed.
Damage to the hull of the Dali and to the cargo containers on her deck could lead to leaks of hazardous liquids or other materials into Chesapeake Bay. (United States Army Corps of Engineers Baltimore image)
On the waters and shores of today’s Chesapeake, numerous county, state, and federal agencies, including the United States Coast Guard, monitor and inspect looking for conditions and situations that could lead to point-source or accidental discharges of petroleum products and other hazardous materials into the bay. Many are trained, equipped, and organized for emergency response to contain and mitigate spills upon detection. But this was not always the case.
Through much of the twentieth century, maritime spills of oil and other chemicals magnified the effects of routine discharges of hazardous materials and sanitary sewer effluent into the Chesapeake and its tributaries. The cumulative effect of these pollutants progressively impaired fisheries and bay ecosystems leading to noticeable declines in numbers of many aquatic species. Rather frequently, spills or discharges resulted in conspicuous fish and/or bird kills.
One of the worst spills occurred near the mouth of the Potomac River on February 2, 1976, when a barge carrying 250,000 gallons of number 6 oil sank in a storm and lost its cargo into the bay. During a month-long cleanup, the United States Coast Guard recovered approximately 167,000 gallons of the spilled oil, the remainder dispersed into the environment. A survey counted 8,469 “sea ducks” killed. Of the total number, the great majority were Horned Grebes (4,347 or 51.3%) and Long-tailed Ducks (2,959 or 34.9%). Other species included Surf Scoter (Melanitta perspicillata) (405 or 4.8%), Common Loon (195 or 2.3%), Bufflehead (166 or 2.0%), Ruddy Duck (107 or 1.3%), Common Goldeneye (78 or 0.9%), Tundra Swan (46 or 0.5%), Greater Scaup (19 or 0.2%), American Black Duck (12 or 0.2%), Common Merganser (11 or 0.1%), Canvasback (10 or 0.1%), Double-crested Cormorant (10 or 0.1%), Canada Goose (8 or 0.1%), White-winged Scoter (Melanitta deglandi) (7 or 0.1%), Redhead (5 or 0.1%), gull species (10 or 0.1%), miscellaneous ducks and herons (13 or 0.2%) and unidentified (61 or 0.7%). During the spring migration, a majority of these birds would have made their way north and passed through the lower Susquehanna valley. The accident certainly impacted the occurrence of the listed species during that spring in 1976, and possibly for a number of years after.
Of the 8,469 birds killed by the February 2, 1976, oil spill on the Chesapeake, 51.3% (4,347) were Horned Grebes. Many of them would have migrated north through the Lower Susquehanna River Watershed during the coming spring.
The Federal Water Pollution Control Act Amendments of 1972, commonly known as the Clean Water Act, put teeth into the original FWCPCA of 1948 and began reversing the accumulation of pollutants in the bay and other bodies of water around the nation. Additional amendments in 1977 and 1987 have strengthened protections and changed the culture of “dump-and-run” disposal and “dilution-is-the-solution” treatment of hazardous wastes. During the late nineteen-seventies and early nineteen-eighties, emergency response teams and agencies began organizing to control and mitigate spill events. The result has been a greater awareness and competency for handling accidental discharges of fuels and other chemicals into Chesapeake Bay and other waterways. These improvements can help minimize the environmental impact of the Dali’s collision with the Francis Scott Key Bridge in Baltimore.
Oil spills and other pollution in the Chesapeake can impact populations of migratory fish including the anadromous Hickory Shad which are presently transiting the bay on their way to the waters of the Susquehanna below Conowingo Dam.
SOURCES
Roland, John V., Moore, Glenn E., and Bellanca, Michael A. 1977. “The Chesapeake Bay Oil Spill—February 2, 1976: A Case History”. International Oil Spill Conference Proceedings (1977). 1977 (1): 523-527.
As week-old snow and ice slowly disappears from the Lower Susquehanna River Watershed landscape, we ventured out to see what might be lurking in the dense clouds of fog that for more than two days now have accompanied a mid-winter warm spell.
After freezing to a slushy consistency earlier this week, the Susquehanna is already beginning to thaw. Below the York Haven Dam at Conewago Falls, the water is open and ice-free.On frozen man-made lakes and ponds, geese and ducks like these Mallards and American Wigeon are presently concentrated around small pockets of open water.During the past ten days, American Robin numbers have exploded throughout the lower Susquehanna valley. The majority of these birds may be a mix of both those coming south to escape the late onset of wintry conditions to our north and those inching north into our region as early spring migrants.The January thaw has melted the snow from lawns and fields to provide thousands of visiting robins with a chance to forage for earthworms.A visit by this young Cooper’s Hawk to the susquehannnawildlife.net headquarters garden sent songbirds scrambling……but did nothing to unnerve our resident Eastern Gray Squirrels,……which promptly went into tail-waving mode to advertise their presence.But earlier in the week, when heavy snow cover in the rural areas surrounding our urbanized neighborhood made it difficult for rodent-eating raptors to find food, we received brief visits from both a Red-tailed Hawk……and this young Red-shouldered Hawk, an uncommon bird of prey most often found in wet woods and other lowlands.To escape notice during visits by these larger raptors, our squirrels remained motionless and commenced performance of their best bump-on-a-log impressions.Unimpressed, each of our visiting buteos remained for just a few minutes before moving on in search of more favorable hunting grounds and prey.As snow melted and exposed bare ground in fields of early successional growth, we encountered……a flock of White-crowned Sparrows, most in first-winter plumage……and at least a dozen American Tree Sparrows. During the twentieth century, these handsome songbirds were regular winter visitors to the lower Susquehanna region. During recent decades, they’ve become increasingly more difficult to find. Currently, moderate numbers appear to be arriving to escape harsher weather to our north.What could be more appropriate on a foggy, gray evening than finding a “gray ghost” (adult male Northern Harrier) patrolling the fields in search of mice and voles.
If scenes of a January thaw begin to awaken your hopes and aspirations for all things spring, then you’ll appreciate this pair of closing photographs…
The maroon-red flower buds of Silver Maples are beginning to swell. And woodpeckers including Pileated Woodpeckers are beginning to drum, a timber-pounding behavior they use to establish breeding territories in habitats with suitable sites for cavity nesting.In wet soil surrounding spring seeps and streams, Skunk Cabbage is rising through the leaf litter to herald the coming of a new season. Spring must surely be just around the corner.
The last of the year’s migrating Bald Eagles are streaming down the ridges of the mid-Atlantic region and many of them will be stopping for at least a part of the winter season along the lower Susquehanna River. If you want to see them, now is the best time. Taking a walk along a riverside recreation trail is a relaxing way to spend some time checking them out. To see the greatest concentrations of these majestic birds, plan a visit to one of the lower river’s hydroelectric dams. Conowingo Dam, located where U.S. Route 1 crosses the river at Rising Sun, Maryland, is currently hosting dozens of visiting eagles. If you’ve never been there, we can assure you that it’s certainly worth the trip.
Mid-summer can be a less than exciting time for those who like to observe wild birds. The songs of spring gradually grow silent as young birds leave the nest and preoccupy their parents with the chore of gathering enough food to satisfy their ballooning appetites. To avoid predators, roving families of many species remain hidden and as inconspicuous as possible while the young birds learn how to find food and handle the dangers of the world.
But all is not lost. There are two opportunities for seeing unique birds during the hot and humid days of July.
First, many shorebirds such as sandpipers, plovers, dowitchers, and godwits begin moving south from breeding grounds in Canada. That’s right, fall migration starts during the first days of summer, right where spring migration left off. The earliest arrivals are primarily birds that for one reason on another (age, weather, food availability) did not nest this year. These individuals will be followed by birds that completed their breeding cycles early or experienced nest failures. Finally, adults and juveniles from successful nests are on their way to the wintering grounds, extending the movement into the months we more traditionally start to associate with fall migration—late August into October.
For those of you who find identifying shorebirds more of a labor than a pleasure, I get it. For you, July can bring a special treat—post-breeding wanderers. Post-breeding wanderers are birds we find roaming in directions other than south during the summer months, after the nesting cycle is complete. This behavior is known as “post-breeding dispersal”. Even though we often have no way of telling for sure that a wandering bird did indeed begin its roving journey after either being a parent or a fledgling during the preceding nesting season, the term post-breeding wanderer still applies. It’s a title based more on a bird sighting and it’s time and place than upon the life cycle of the bird(s) being observed. Post-breeding wanderers are often southern species that show up hundreds of miles outside there usual range, sometimes traveling in groups and lingering in an adopted area until the cooler weather of fall finally prompts them to go back home. Many are birds associated with aquatic habitats such as shores, marshes, and rivers, so water levels and their impact on the birds’ food supplies within their home range may be the motivation for some of these movements. What makes post-breeding wanderers a favorite among many birders is their pop. They are often some of our largest, most colorful, or most sought-after species. Birds such as herons, egrets, ibises, spoonbills, stilts, avocets, terns, and raptors are showy and attract a crowd.
While it’s often impossible to predict exactly which species, if any, will disperse from their typical breeding range in a significant way during a given year, some seem to roam with regularity. Perhaps the most consistent and certainly the earliest post-breeding wanderer to visit our region is the “Florida Bald Eagle”. Bald Eagles nest in “The Sunshine State” beginning in the fall, so by early spring, many of their young are on their own. By mid-spring, many of these eagles begin cruising north, some passing into the lower Susquehanna valley and beyond. Gatherings of dozens of adult Bald Eagles at Conowingo Dam during April and May, while our local adults are nesting and after the wintering birds have gone north, probably include numerous post-breeding wanderers from Florida and other Gulf Coast States.
So this week, what exactly was it that prompted hundreds of birders to travel to Middle Creek Wildlife Management Area from all over the Mid-Atlantic States and from as far away as Colorado?
Birders observing something special at Middle Creek Wildlife Management Area on July 10, 2023.
Was it the majestic Great Blue Herons and playful Killdeer?
Great Blue Heron and a Killdeer.
Was it the colorful Green Herons?
Green Heron
Was it the Great Egrets snapping small fish from the shallows?
Great Egret
Was it the small flocks of shorebirds like these Least Sandpipers beginning to trickle south from Canada?
Least Sandpipers
All very nice, but not the inspiration for traveling hundreds or even thousands of miles to see a bird.
It was the appearance of this very rare post-breeding wanderer…
A Limpkin at Middle Creek Wildlife Management Area in Lancaster County. The Limpkin (Aramus guarauna) is the only surviving member of the family Aramidae.
…Pennsylvania’s first record of a Limpkin, a tropical wading bird native to Florida, the Caribbean Islands, and South America. Many observers visiting Middle Creek Wildlife Management Area had never seen one before, so if they happen to be a “lister”, a birder who keeps a tally of the wild bird species they’ve seen, this Limpkin was a “lifer”.
The Limpkin is an inhabitant of vegetated marshlands where it feeds almost exclusively upon large snails of the family Ampullariidae, including the Florida Applesnail (Pomacea paludosa), the largest native freshwater snail in the United States.
In the United States, the native range of the Limpkin lies within the native range of the Florida Applesnail, shown here in gold. Introduced populations of the snail are shown in brown. (United States Geological Survey Nonindigenous Aquatic Species image)A spectacular nineteenth-century rendition of the Florida Applesnail, including an egg mass, illustrated by Helen E. Lawson in Samuel S. Haldeman’s “Monograph of the Freshwater Univalve Mollusca of the United States”.
Observations of the Limpkin lingering at Middle Creek Wildlife Management Area have revealed a pair of interesting facts. First, in the absence of Florida Applesnails, this particular Limpkin has found a substitute food source, the non-native Chinese Mystery Snail (Cipangopaludina chinensis). And second, Chinese Mystery Snails have recently become established in the lakes, pools, and ponds at the refuge, very likely arriving as stowaways on Spatterdock (Nupharadvena) and/or American Lotus (Nelumbo lutea), native transplants brought in during recent years to improve wetland habitat and process the abundance of nutrients (including waterfowl waste) in the water.
The Chinese Mystery Snail is the largest freshwater snail in the Lower Susquehanna River Watershed. (Vintage 35 mm image)By hitching a ride on aquatic transplants like this Spatterdock, non-native freshwater snails are easily vectored into new areas outside their previous range.Spatterdock, a native species also known as Yellow Pond Lily or Cow Lily, flowering in August.Blooming American Lotus transplants in a pool at Middle Creek Wildlife Management Area during August.The Limpkin at Middle Creek W.M.A. capturing a Chinese Mystery Snail.The Limpkin at Middle Creek carrying a Chinese Mystery Snail.The Limpkin is seen here maneuvering the the snail in its bill, a set of mandibles specially adapted for extracting the bodies of large freshwater snails from their shells.The tweezers-like tip of the bill is used to grasp the shell by the rim of the opening or by the “trapdoor” (operculum) that protects the snail inside.A posed Chinese Mystery Snail showing its “trapdoor”, the operculum protecting the soft body tissue when the animal withdraws inside. The tips of the Limpkin’s bill close tightly like the end of a tweezers to grasp the operculum and remove it and the snail’s body from the shell. (Vintage 35 mm image)The tweezers-tipped bill, which is curved slightly to the right in some Limpkins, is slid into the shell to grasp the snails body and remove it for consumption. The entire extraction process takes 10 to 30 seconds.
The Middle Creek Limpkin’s affinity for Chinese Mystery Snails may help explain how it was able to find its way to Pennsylvania in apparent good health. Look again at the map showing the range of the Limpkin’s primary native food source, the Florida Applesnail. Note that there are established populations (shown in brown) where these snails were introduced along the northern coast of Georgia and southern coast of South Carolina…
Native (gold) and non-native (brown) ranges of the Florida Applesnail. (United States Geological Survey Nonindigenous Aquatic Species image)
…now look at the latest U.S.G.S. Nonindigenous Aquatic Species map showing the ranges (in brown) of established populations of non-native Chinese Mystery Snails…
Range (in brown) of established populations of non-native Chinese Mystery Snails. (United States Geological Survey Nonindigenous Aquatic Species image)
…and now imagine that you’re a happy-go-lucky Limpkin working your way up the Atlantic Coastal Plain toward Pennsylvania and taking advantage of the abundance of food and sunshine that summer brings to the northern latitudes. It’s a new frontier. Introduced populations of Chinese Mystery Snails are like having a Waffle House serving escargot at every exit along the way!
Be sure to click the “Freshwater Snails” tab at the top of this page to learn more about the Chinese Mystery Snail and its arrival in the Lower Susquehanna River Watershed. Once there, you’ll find some additional commentary about the Limpkin and the likelihood of Everglade Snail Kites taking advantage of the presence of Chinese Mystery Snails to wander north. Be certain to check it out.
The endangered Everglade Snail Kite (Rostrhamus sociabilis plumbeus), a Florida Applesnail specialist, has survived in part due to its ability to adapt to eating the non-native Pomacea maculata applesnails which have become widespread in Florida following releases from aquaria. The adaptation?…a larger body and bill for eating larger snails. (National Park Service image)
A juvenile Ring-billed Gull with a freshly caught Gizzard Shad is pursued by a hungry adult Great Black-backed Gull on the Susquehanna at Conowingo Dam.
First there was the Nautilus. Then there was the Seaview. And who can forget the Yellow Submarine? Well, now there’s the S. S. Haldeman, and today we celebrated her shakedown cruise and maiden voyage. The Haldeman is powered by spent fuel that first saw light of day near Conewago Falls at a dismantled site that presently amounts to nothing more than an electrical substation. Though antique in appearance, the vessel discharges few emissions, provided there aren’t any burps or hiccups while underway. So, climb aboard as we take a cruise up the Susquehanna at periscope depth to have a quick look around!
Brunner Island as seen from the east channel.Close-in approach to emergent Water Willow growing on an alluvial Island.The approach to York Haven Dam and Conewago Falls from the west channel.A pair of Powdered Dancers on a midriver log.
Watertight and working fine. Let’s flood the tanks and have a peek at the benthos. Dive, all dive!
American Eelgrass, also known as Tapegrass, looks to be growing well in the channels. Historically, vast mats of this plant were the primary food source for the thousands of Canvasback ducks that once visited the lower Susquehanna each autumn.As is Water Stargrass (Heteranthera dubia). When mature, both of these native plants provide excellent cover for young fish. Note the abundance of shells from deceased Asiatic Clams (Corbicula fluminea) covering the substrate.A three-tailed mayfly (Ephemeroptera) nymph and a several exoskeletons cling to the downstream side of a rock.This hollowed-out stick may be a portable protective shelter belonging to a Comb-lipped Casemaker Caddisfly larva (Calamoceratidae). The larva itself appears to be extending from the end of the “case” in the upper right of the image. Heteroplectron americanum, a species known for such behavior, is a possibility. In the Susquehanna and its tributaries, the Rusty Crayfish (Faxonius rusticus) is an introduced invasive species. It has little difficulty displacing native species due to its size and aggressiveness.A Rusty Crayfish.Summers with conditions that promote eelgrass and stargrass growth tend to be big years for Virginian River Horn Snails (Elimia virginica). 2022 appears to be one of those years. They’re abundant and they’re everywhere on the rocks and gravel substrate in midriver. Feeding almost incessantly on algae and detritus, these snails are an essential component of the riverine ecosystem, breaking down organic matter for final decomposition by bacteria and fungi.Bits of debris suspended in the flowing water streak by this Virginian River Horn Snail. The spire-shaped shell is a streamlining adaptation for maneuvering and holding fast in the strong current.A young Virginian River Horn Snail following a mature adult. Note the green algae growing among the decaying plant and animal remains that blanket the river bottom.Two of a population that may presently include millions of Virginian River Horn Snails living downstream of Conewago Falls.Virginian River Horn Snails with Lesser Mystery Snails (Campeloma decisum), another native species commonly encountered at Conewago Falls and in surrounding waters.A River Snail (Leptoxis carinata), also known as a Crested Mudalia, hitching a ride on a Virginian River Horn Snail. The two species are frequently found together.A River Snail cleaning the shell of a native freshwater Unionidae mussel, Lampsilis cariosa, commonly called the Yellow Lampmussel or Carried Lampmussel. Because of their general decline in abundance and range, all Unionidae mussels are protected in Pennsylvania.The Banded Darter (Etheostoma zonale) is a member of the perch family (Percidae).A Smallmouth Bass in strong current.Along the edge of an alluvial island at midriver, Cyprinella (Spotfin or Satinfin) Shiners gather in the cover of an emergent stand of Water Willow. The closely related Spotfin Shiner (Cyprinella spiloptera) and Satinfin Shiner (Cyprinella analostanus) are nearly impossible to differentiate in the field.A breeding condition male Cyprinella (Spotfin or Satinfin) Shiner.A juvenile Channel Catfish.
We’re finding that a sonar “pinger” isn’t very useful while running in shallow water. Instead, we should consider bringing along a set of Pings—for the more than a dozen golf balls seen on the river bottom. It appears they’ve been here for a while, having rolled in from the links upstream during the floods. Interestingly, several aquatic species were making use of them.
River Snail cleaning a golf ball.A golf ball used as an anchor point for silk cases woven by Net-spinning Caddisfly (Hydropsychidae) larvae to snare food from the water column.A Creeping Ancylid (Ferrissia species), a tiny gastropod also known as a Coolie Hat Snail, River Limpet, or Brook Freshwater Limpet, inhabits the dimple on a “Top Flight”.A closeup view of the Creeping Ancylid. The shell sits atop the snail’s body like a helmet.We now know why your golf balls always end up in the drink, it’s where they go to have their young.
Well, it looks like the skipper’s tired and grumpy, so that’s all for now. Until next time, bon voyage!
Why are there dozens of people with enormous lenses on complicated cameras atop sturdy tripods gathered at Fisherman’s Park below the Conowingo Dam on the lower Susquehanna River in Maryland? It’s Bald Eagle time, that’s why. Here are some photos from the scene, taken just two days ago.
Dozens of observers and photographers line up along the Harford County shoreline of the Susquehanna downstream of the powerhouse at the Conowingo Hydroelectric Station, the majority awaiting the opportunity to catch a shot of a Bald Eagle grabbing a fish from the river just in front of them. Visitors travel to Conowingo from all over the continental United States to see and photograph eagles in concentrations that are often rivaled only in less accessible areas of Alaska and Canada.Bald Eagles migrate to the lower Susquehanna near Conowingo and the upper Chesapeake Bay to spend the early winter in congregations that can, in good years, number in the hundreds of birds. There are presently at least 60 to 80 Bald Eagles present, and numbers are increasing.If you visit, you’ll have a chance to see Bald Eagles in the various stages of plumage transition experienced during the six years needed to acquire the familiar all-white head and tail of adulthood. This particular immature eagle is in its third year. Birds at this age are sometimes known as “Osprey face” Bald Eagles due to the dark stripe through the eye. Be certain to click the “Hawkwatchers Helper: Identifying Bald Eagles and other Diurnal Raptors” tab at the top of this page to see a photographic guide to aging the eagles and other birds of prey you observe.An adult Bald Eagle snags a fish from the Susquehanna in front of photographers and gets the cameras clicking and other eagles in the area cackling and chattering.The majority of the Bald Eagles at Conowingo are there for the early winter only; they’ll disperse to their nesting grounds later in the season. An exception is this mated pair that is already at their nest site adjacent to the Fisherman’s Park car lot. They can often be seen perched in the treetops directly above visitor’s vehicles.
To reach Exelon Energy’s Conowingo Fisherman’s Park from Rising Sun, Maryland, follow U.S. Route 1 south across the Conowingo Dam, then turn left onto Shuresville Road, then make a sharp left onto Shureslanding Road. Drive down the hill to the parking area along the river. The park’s address is 2569 Shureslanding Road, Darlington, Maryland.
Do make an excursion to the lower Susquehanna at Conowingo soon. To avoid crowds and parking congestion, plan to visit on a weekday. You’ll want warm clothing, binoculars, and a camera too.
The Fisherman’s Park Bald Eagles copulating. If you don’t know what that is, ask your mother…no, wait, on second thought, look it up on the internet.
Meet the Double-crested Cormorant, a strangely handsome bird with a special talent for catching fish. You see, cormorants are superb swimmers when under water—using their webbed feet to propel and maneuver themselves with exceptional speed in pursuit of prey.
Like many species of birds that dive for their food, Double-crested Cormorants run across the surface of the water to gain speed for a takeoff. Smaller wings may make it more difficult to get airborne, but when folded, they provide improved streamlining for submerged swimming.
Double-crested Cormorants, hundreds of them, are presently gathered along with several other species of piscivorous (fish-eating) birds on the lower Susquehanna River below Conowingo Dam near Rising Sun, Maryland. Fish are coming up the river and these birds are taking advantage of their concentrations on the downstream side of the impoundment to provide food to fuel their migration or, in some cases, to feed their young.
Double-crested Cormorants, mostly adult birds migrating toward breeding grounds to the north, are gathered on the rocks on the east side of the river channel below Conowingo Dam. A Great Blue Heron from a nearby rookery can be seen at the center of the image.Bald Eagles normally gather in large numbers at Conowingo Dam in the late fall and early winter. Presently there are more than 50 there, and the majority of them are breeding age adults. Presumably they are still on their way north to nest. Meanwhile, local pairs are already feeding young, so it seems these transient birds are running a bit late. Many of them can be seen on the rocks along the east side of the river channel,……on the powerline trestles on the island below the dam……in the trees along the east shore,……and in the trees surrounding Fisherman’s Park on the west shore.
In addition to the birds, the movements of fish attract larger fish, and even larger fishermen.
Anglers gather to fish the placid waters below the dam’s hydroelectric powerhouse . Only a few of the generating turbines are operating, so the flow through the dam is minimal.Some water is being released along the west shoreline to attract migratory river herring to the west fish lift for sorting and retention as breeding stock for a propagation program. The east lift, the passage that hoists American Shad (Alosa sapidissima) to a trough that allows them to swim over the top of the dam to waters upriver, will begin operating as soon as these larger migratory fish begin arriving.
The excitement starts when the sirens start to wail and the red lights begin flashing. Yes friends, it’s showtime.
Red lights and sirens are a warning that additional flow is about to be released from the dam. Boaters should anticipate rough water and persons in and along the river need to seek higher ground immediately.Gates are opened at mid-river to release a surge of water through the dam.The wake from the release quickly reaches the shoreline, raising the water level in moments.Experienced anglers know that the flow through the dam gets fish moving and can improve the catch significantly, especially in spring when many species are ascending the river.
Within minutes of the renewed flow, birds are catching fish.
A Double-crested Cormorant with a young Channel Catfish (Ictalurus punctatus).A Double-crested Cormorant fleeing others trying to steal its Channel Catfish.Another Double-crested Cormorant eating a Channel Catfish. Did you realize that Channel Catfish were an introduced species in the Susquehanna River system?An Osprey with a stick, it’s too busy building a nest right now to fish.Great Blue Herons swallow their prey at the spot of capture, then fly back to the nest to regurgitate a sort of “minced congealed fish product” to their young.
Then the anglers along the wave-washed shoreline began catching fish too.
This young man led off a flurry of catches that would last for the remainder of the afternoon.Though Gizzard Shad are filter feeders that don’t readily take baits and lures, they are regularly foul-hooked and reeled in from the large schools that ascend the river in spring.Gizzard Shad are very abundant in the lower Susquehanna, providing year-round forage for many species of predatory animals including Bald Eagles.A Double-crested Cormorant swallowing a Gizzard Shad.This angler soon helped another fisherman by landing his large catch, a Northern Snakehead (Channa argus).The teeth of a Northern Snakehead are razor sharp. It is an aggressive non-native invasive species currently overtaking much of the Lower Susquehanna River Watershed. Anglers are encouraged to fish for them, catch them, keep them, and kill them at the site of capture. Never transport a live Northern Snakehead anywhere at any time. It is illegal in both Maryland and Pennsylvania to possess a live snakehead. Northern Snakehead advisory sign posted at Exelon Energy’s Conowingo Fishermen’s Park.A stringer of Northern Snakeheads. This species was imported from Asia as a food fish, so it has excellent culinary possibilities. It’s better suited for a broiler or frying pan than a river or stream.Another stringer of Northern Snakeheads. It’s pretty safe to say that they have quickly become one of the most abundant predatory fish in the river. Their impact on native species won’t be good, so catch and eat as many as you can. Remember, snakeheads swim better in butter and garlic than in waters with native fish.This foul-hooked Shorthead Redhorse (Moxostoma macrolepidotum), a native species of sucker, was promptly released.Striped Bass are anadromous fish that leave the sea in spring to spawn in fresh water. They ascend the Susquehanna in small numbers, relying upon the operation of the fish passages at the Conowingo, Holtwood, Safe Harbor, and York Haven Dams to continue their journey upstream. During spring spawning, Striped Bass in the Susquehanna River and on the Susquehanna Flats portion of the upper Chesapeake Bay are not in season and may not be targeted, even for catch-and-release. This accidental catch was immediately turned loose.After removal from the hook, this hefty Smallmouth Bass was returned to the river. Many anglers are surprised to learn that Smallmouth Bass are not native to the Susquehanna basin.This angler’s creel contains a Northern Snakehead (left) and a Walleye (right). Did you know that the Walleye (Sander vitreus) is an introduced species in the Susquehanna watershed?By late afternoon, anglers using shad darts began hooking into migrating Hickory Shad (Alosa mediocris), a catch-and-release species in Maryland.Hickory Shad are recognized by their lengthy lower jaw. They are anadromous herring that leave the sea to spawn in freshwater streams. Hickory Shad ascend the Susquehanna as far as Conowingo Dam each year, but shy away from the fish lifts. Downriver from the dam, they do ascend Deer Creek along the river’s west shore and Octoraro Creek on the east side. In Pennsylvania, the Hickory Shad is an endangered species.A Hickory Shad angled on a dual shad dart rig. During the spring spawning run, they feed mostly on small fish, and are the most likely of the Susquehanna’s herring to take the hook.Simultaneous hook-ups became common after fours hours worth of release water from the dam worked its way toward the mouth of the river and got the schools moving. Water temperatures in the mid-to-upper-fifties trigger the ascent of Hickory Shad. On the Susquehanna, those temperatures were slow to materialize in the spring of 2021, so the Hickory Shad migration is a bit late.Catch-and-release fishing for Hickory Shad appears to be in full swing not only at the dam, but along the downstream shoreline to at least the mouth of Deer Creek at Susquehanna State Park too.Many Hickory Shad could be seen feeding on some of the millions of caddisflies (Trichoptera) swarming on the river. These insects, along with earlier hatches of Winter Stoneflies (Taeniopterygidae), not only provide forage for many species of fish, but are a vital source of natural food for birds that migrate up the river in March and April each year. Swallows, Ring-billed Gulls, and Bonaparte’s Gulls are particularly fond of snatching them from the surface of the water.A Winter Stonefly (Taeniopterygidae) from an early-season hatch on the Susquehanna River at the Veteran’s Memorial Bridge at Columbia/Wrightsville, Pennsylvania. (March 3, 2021)Just below Conowingo Dam, a lone fly fisherman was doing a good job mimicking the late-April caddisfly hatch, successfully reeling in numerous surface-feeding Hickory Shad.You may have noticed the extraordinary number of introduced fish species listed in this account of a visit to Conowingo Dam. Sorry to say that there are two more: the Flathead Catfish (Pylodictis olivaris) and the Blue Catfish (Ictalurus furcatus). Like the Northern Snakehead, each has become a plentiful invasive species during recent years. Unlike the Northern Snakehead, these catfish are “native transplants”, species introduced from populations in the Mississippi River and Gulf Slope drainages of the United States. So if you visit the area, consider getting a fishing license and catching a few. Like the snakeheads, they too are quite palatable.
The arrival of migrating Hickory Shad heralds the start of a movement that will soon include White Perch, anadromous American Shad, and dozens of other fish species that swim upstream during the springtime. Do visit Fisherman’s Park at Conowingo Dam to see this spectacle before it’s gone. The fish and birds have no time to waste, they’ll soon be moving on.
To reach Exelon’s Conowingo Fisherman’s Park from Rising Sun, Maryland, follow U.S. Route 1 south across the Conowingo Dam, then turn left onto Shuresville Road, then make a sharp left onto Shureslanding Road. Drive down the hill to the parking area along the river. The park’s address is 2569 Shureslanding Road, Darlington, Maryland.
A water release schedule for the Conowingo Dam can be obtained by calling Exelon Energy’s Conowingo Generation Hotline at 888-457-4076. The recording is updated daily at 5 P.M. to provide information for the following day.
And remember, the park can get crowded during the weekends, so consider a weekday visit.
You need to see this to believe it—dozens, sometimes hundreds, of Bald Eagles doing their thing and you can stand or sit in just one place to take it all in.
Conowingo Dam on the Susquehanna River near Darlington, Maryland, attracts piscivores galore. Young Gizzard Shad (Dorosoma cepedianum) and other small fishes are temporarily stunned as they pass through the turbines and gated discharges at the hydroelectric facility’s power house. Waiting for them in the rapids below are predatory fishes including Striped Bass (Moronesaxatilis), White Perch (Moroneamericana), several species of catfishes, and more. From above, fish-eating birds are on the alert for a disoriented turbine-traveler they can easily seize for a quick meal.
U.S. Route 1 crosses the Susquehanna River atop the Conowingo Dam. Conowingo Fisherman’s Park, the observation site for the dam’s Bald Eagles and other birds, is located downstream of the turbine building along the river’s west (south) shore. As the name implies, the park is a superb location for angling.Heed this warning. Close your windows and sunroof or the vultures will subject your vehicle’s contents to a thorough search for food. Then they’ll deposit a little consolation prize on your paint.Scavenging Black Vultures congregate by the hundreds at Conowingo Dam to clean up the scraps left behind by people and predators. They’ll greet you right in the parking lot.Photographers line up downstream of the turbine building for an opportunity to get the perfect shot of a Bald Eagle.The operator of the Conowingo Hydroelectric Generating Station, Exelon Energy, provides clean comfortable facilities for fishing, sightseeing, and wildlife observation.There’s almost always a Peregrine Falcon zooming around the dam to keep the pigeons on their toes.Double-crested Cormorants on the boulders that line the channel below the dam. Hundreds are there right now.Double-crested Cormorants dive for fish near the power house discharge, which, while just one small generator is operating, seems nearly placid. The feeding frenzy really gets going when Conowingo begins generating with multiple large turbines and these gently flowing waters become torrential rapids filled with disoriented fishes.Ring-billed Gulls seek to snag a small fish from the water’s surface.After successfully nabbing shad or perch, these Double-crested Cormorants need to swallow their catch fast or risk losing it. Stealing food is a common means of survival for the gulls, eagles, and other birds found here.Where do migrating eagles go? There are, right now, at least 50 Bald Eagles at Conowingo Dam, with more arriving daily. Numbers are likely to peak during the coming weeks.Eagles can be seen perched in the woods along both river shorelines, even in the trees adjacent to the Conowingo Fisherman’s Park car lot. Others take stand-by positions on the boulders below the dam.To remind visiting eagles that they are merely guests at Conowingo, a resident Bald Eagle maintains a presence at its nest on the wooded slope above Fisherman’s Park. Along the lower Susquehanna, female Bald Eagles lay eggs and begin incubation in January.When an eagle decides to venture out and attempt a dive at a fish, that’s when the photographers rush to their cameras for a chance at a perfect shot.The extraordinary concentrations of Bald Eagles at Conowingo make it an excellent place to study the plumage differences between birds of various ages.Here’s a first-year Bald Eagle, also known as a hatch-year or juvenile bird.A second-year or Basic I immature Bald Eagle. Note the long juvenile secondaries giving the wings a ragged-looking trailing edge.A third-year or Basic II immature Bald Eagle.A second-year/Basic I immature Bald Eagle (top) and a third-year/Basic II immature Bald Eagle (bottom).A second-year/Basic I immature Bald Eagle (bottom) and a third-year/Basic II immature Bald Eagle (top). Note the white feathers on the backs of eagles in these age classes.A third-year/Basic II immature Bald Eagle perched in a tree alongside the parking area. Note the Osprey-like head plumage.A sixth-year or older adult Bald Eagle in definitive plumage (left) and a fourth-year or Basic III immature Bald Eagle (right).If you want to see the Bald Eagles at Conowingo Dam, don’t wait. While many birds are usually present throughout the winter, the large concentrations may start dispersing as early as December when eagles begin wandering in search of other food sources, particularly if the river freezes.A pair of Bald Eagles is already working on a nest atop this powerline trestle downstream of Conowingo Dam. By late December, most adult eagles will depart Conowingo to begin spending their days establishing and defending breeding territories elsewhere. Any non-adult eagles still loitering around the dam will certainly begin receiving encouragement from the local nesting pair(s) to move along as well.
To reach Exelon’s Conowingo Fisherman’s Park from Rising Sun, Maryland, follow U.S. Route 1 south across the Conowingo Dam, then turn left onto Shuresville Road, then make a sharp left onto Shureslanding Road. Drive down the hill to the parking area along the river. The park’s address is 2569 Shureslanding Road, Darlington, Maryland.
As Bald Eagle numbers continue to increase, expect the parking lot to become full during weekends and over the Thanksgiving holiday. To avoid the crowds, plan to visit during a weekday.
You can get the generating schedule for the Conowingo Dam by calling the Conowingo Generation Hotline at 888-457-4076. The recording is updated daily at 5 P.M. to provide information for the following day.
You need to get outside and go for a walk. You’ll be sorry if you don’t. It’s prime time to see wildlife in all its glory. The songs and colors of spring are upon us!
Flooding that resulted from mid-week rains is subsiding. The muddy torrents of Conewago Falls are seen here racing by the powerhouse at the York Haven Dam.Receding waters will soon leave the parking area at Falmouth and other access points along the river high and dry.Migrating Yellow-rumped Warblers are currently very common in the riparian woodlands near Conewago Falls. They and all the Neotropical warblers, thrushes, vireos, flycatchers are moving through the Susquehanna watershed right now.A Baltimore Oriole feeds in a riverside maple tree.Ruby-crowned Kinglets are migrating through the Susquehanna valley. These tiny birds may be encountered among the foliage of trees and shrubs as they feed upon insects .Gray Catbirds are arriving. Many will stay to nest in shrubby thickets and in suburban gardens.American Robins and other birds take advantage of rising flood waters to feed upon earthworms and other invertebrates that are forced to the soil’s surface along the inundated river shoreline.Spotted Sandpipers are a familiar sight as they feed along water’s edge.The Yellow Warbler (Setophaga petechia) is a Neotropical migrant that nests locally in wet shrubby thickets. Let your streamside vegetation grow and in a few years you just might have these “wild canaries” singing their chorus of “sweet-sweet-sweet-I’m-so-sweet” on your property.
If you’re not up to a walk and you just want to go for a slow drive, why not take a trip to Middle Creek Wildlife Management Area and visit the managed grasslands on the north side of the refuge. To those of us over fifty, it’s a reminder of how Susquehanna valley farmlands were before the advent of high-intensity agriculture. Take a look at the birds found there right now.
Red-winged Blackbirds commonly nest in cattail marshes, but are very fond of untreated hayfields, lightly-grazed pastures, and fallow ground too. These habitats are becoming increasingly rare in the lower Susquehanna region. Farmers have little choice, they either engage in intensive agriculture or go broke.Nest boxes are provided for Tree Swallows at the refuge.Numbers of American Kestrels have tumbled with the loss of grassy agricultural habitats that provide large insects and small rodents for them to feed upon.White-crowned Sparrows (Zonotrichia leucophrys) are a migrant and winter resident species that favors small clumps of shrubby cover in pastures and fallow land.When was the last time you saw an Eastern Meadowlark (Sturnella magna) singing “spring-of-the-year” in a pasture near your home?And yes, the grasslands at Middle Creek do support nesting Ring-necked Pheasants (Phasianus colcichus). If you stop for a while and listen, you’ll hear the calls of “kowk-kuk” and a whir of wings. Go check it out.
And remember, if you happen to own land and aren’t growing crops on it, put it to good use. Mow less, live more. Mow less, more lives.
Within the last few years, the early-summer emergence of vast waves of mayflies has caused great consternation among residents of riverside towns and motorists who cross the bridges over the lower Susquehanna. Fishermen and others who frequent the river are familiar with the phenomenon. Mayflies rise from their benthic environs where they live for a year or more as an aquatic larval stage (nymph) to take flight as a short-lived adult (imago), having just one night to complete the business of mating before perishing by the following afternoon.
In 2015, an emergence on a massive scale prompted the temporary closure of the mile-long Columbia-Wrightsville bridge while a blizzard-like flight of huge mayflies reduced visibility and caused road conditions to deteriorate to the point of causing accidents. The slimy smelly bodies of dead mayflies, probably millions of them, were removed like snow from the normally busy Lincoln Highway. Since then, to prevent attraction of the breeding insects, lights on the bridge have been shut down from about mid-June through mid-July to cover the ten to fourteen day peak of the flight period of Hexagenia bilineata, sometimes known as the Great Brown Drake, the species that swarms the bridge.
An adult (imago) male Great Brown Drake (Hexagenia bilineata) burrowing mayfly. Adult mayflies are also known as spinners.A sub-adult (based on the translucence of the wings) female burrowing mayfly (Hexagenia species). The sub-adult (subimago or dun) stage lasts less than a day. Normally within 18 hours of leaving the water and beginning flight, it will molt into an adult, ready to breed during its final night of life.
After so many years, why did the swarms of these mayflies suddenly produce the enormous concentrations seen on this particular bridge across the lower Susquehanna? Let’s have a look.
Following the 2015 flight, conservation organizations were quick to point out that the enormous numbers of mayflies were a positive thing—an indicator that the waters of the river were getting cleaner. Generally, assessments of aquatic invertebrate populations are considered to be among the more reliable gauges of stream health. But some caution is in order in this case.
Prior to the occurrence of large flights several years ago, Hexagenia bilineata was not well known among the species in the mayfly communities of the lower Susquehanna and its tributaries. The native range of the species includes the southeastern United States and the Mississippi River watershed. Along segments of the Mississippi, swarms such as occurred at Columbia-Wrightsville in 2015 are an annual event, sometimes showing up on local weather radar images. These flights have been determined to be heaviest along sections of the river with muddy bottoms—the favored habitat of the burrowing Hexagenia bilineata nymph. This preferred substrate can be found widely in the Susquehanna due to siltation, particularly behind dams, and is the exclusive bottom habitat in Lake Clarke just downstream of the Columbia-Wrightsville bridge.
Native mayflies in the Susquehanna and its tributaries generally favor clean water in cobble-bottomed streams. Hexagenia bilineata, on the other hand, appears to have colonized the river (presumably by air) and has found a niche in segments with accumulated silt, the benthic habitats too impaired to support the native taxa formerly found there. Large flights of burrowing mayflies do indicate that the substrate didn’t become severely polluted or eutrophic during the preceding year. And big flights tell us that the Susquehanna ecosystem is, at least in areas with silt bottoms, favorable for colonization by the Great Brown Drake. But large flights of Hexagenia bilineata mayflies don’t necessarily give us an indication of how well the Susquehanna ecosystem is supporting indigenous mayflies and other species of native aquatic life. Only sustained recoveries by populations of the actual native species can tell us that. So, it’s probably prudent to hold off on the celebrations. We’re a long way from cleaning up this river.
In the absence of man-made lighting, male Great Brown Drakes congregate over waterways lit often by moonlight alone. The males hover in position within a swarm, often downwind of an object in the water. As females begin flight and pass through the swarm, they are pursued by the males in the vicinity. The male response is apparently sight motivated—anything moving through their field of view in a straight line will trigger a pursuit. That’s why they’re so pesky, landing on your face whenever you approach them. Mating takes place as males rendezvous with airborne females. The female then drops to the water surface to deposit eggs and later die—if not eaten by a fish first. Males return to the swarm and may mate again and again. They die by the following afternoon. After hatching, the larvae (nymphs) burrow in the silt where they’ll grow for the coming year. Feathery gills allow them to absorb oxygen from water passing through the U-shaped refuge they’ve excavated.
Several factors increase the likelihood of large swarms of Great Brown Drakes at bridges. Location is, of course, a primary factor. Bridges spanning suitable habitat will, as a minimum, experience incidental occurrences of the flying forms of the mayflies that live in the waters below. Any extraordinarily large emergence will certainly envelop the bridge in mayflies. Lights, both fixed and those on motor vehicles, enhance the appearance of movement on a bridge deck, thus attracting hovering swarms of male Hexagenia bilineata and other species from a greater distance, leading to larger concentrations. Concrete walls along the road atop the bridge lure the males to try to hover in a position of refuge behind them, despite the vehicles that disturb the still air each time they pass. The walls also function as the ultimate visual attraction as headlamp beams and shadows cast by moving vehicles are projected onto them over the length of the bridge. Vast numbers of dead, dying, and maimed mayflies tend to accumulate along these walls for this reason.
The absence of illumination from fixed lighting on the deck of the bridge reduces the density of Great Brown Drake swarms. Some communities take mayfly countermeasures one step further. Along the Mississippi, some bridges are fitted with lights on the underside of the deck to attract the mayflies to the area directly over the water, concentrating the breeding mayflies and fishermen alike. The illumination below the bridge is intended to draw mayflies away from light created by headlamps on motor vehicles passing by on the otherwise dark deck above. Lights beneath the bridge also help prevent large numbers of mayflies from being drawn away from the water toward lights around businesses and homes in neighborhoods along the shoreline—where they can become a nuisance.
Lights out on the Columbia-Wrightsville bridge. Dousing the lights to eliminate fixed illumination on bridges is an effective method of reducing the density of Hexagenia bilineata swarms.With the bridge lights darkened, male Great Brown Drakes, their cellophane-like wings illuminated by headlamps to appear as white spots on the road, number in the hundreds instead of hundreds of thousands in swarms on the bridge near the east and west shorelines.Swarms of Great Brown Drake mayflies are still present at the Columbia-Wrightsville bridge, they’re just not concentrated there in enormous numbers. Evidence includes their bodies found in cobwebs along the entire length of the span.The aptly-named Bridge Orb Weaver (Larinioides sclopetarius) constructs webs along the entire length of the Columbia-Wrightsville bridge, and on many of the buildings at both ends. The abundance of victims tangled in silk must overwhelm their appetite, or maybe they actually consume only the smaller insects. They have their choice. Of the Bridge Orb Weaver, Uncle Ty Dyer says, “When you live along the river, it’s your friendly neighborhood spider, man.”The native Eastern Dobsonfly (Corydalus cornutus) is among the reliable indicators of stream quality in the Susquehanna at the Columbia-Wrightsville bridge. Winged adults, which live for about a week, are clumsy fliers attracted to lights. The aquatic larvae are known as hellgrammites, which require clean flowing water over rocky or pebbly substrate to thrive. Two adults were found on the bridge last evening. It would be encouraging to find more. Maybe we’ll stop back to have another look when the lights are back on.
SOURCES
Edsall, Thomas A. 2001. “Burrowing Mayflies (Hexagenia) as Indicators of Ecosystem Health.” Aquatic Ecosystem Health and Management. 43:283-292.
Fremling, Calvin R. 1960. Biology of a Large Mayfly, Hexagenia bilineata (Say), of the Upper Mississippi River. Research Bulletin 482. Agricultural and Home Economics Experiment Station, Iowa State University. Ames, Iowa.
McCafferty, W. P. 1994. “Distributional and Classificatory Supplement to the Burrowing Mayflies (Ephemeroptera: Ephimeroidea) of the United States.” Entomological News. 105:1-13.
It was a routine occurrence in many communities along tributaries of the lower Susquehanna River during the most recent two months. The rain falls like it’s never going to stop—inches an hour. Soon there is flash flooding along creeks and streams. Roads are quickly inundated. Inevitably, there are motorists caught in the rising waters and emergency crews are summoned to retrieve the victims. When the action settles, sets of saw horses are brought to the scene to barricade the road until waters recede. At certain flood-prone locations, these events are repeated time and again. The police, fire, and Emergency Medical Services crews seem to visit them during every torrential storm—rain, rescue, rinse, and repeat.
We treat our local streams and creeks like open sewers. Think about it. We don’t want rainwater accumulating on our properties. We pipe it away and grade the field, lawn, and pavement to roll it into the neighbor’s lot or into the street—or directly into the waterway. It drops upon us as pure water and we instantly pollute it. It’s a method of diluting all the junk we’ve spread out in its path since the last time it rained. A thunderstorm is the big flush. We don’t seem too concerned about the litter, fertilizer, pesticides, motor fluids, and other consumer waste it takes along with it. Out of sight, out of mind.
Failure to retain and infiltrate stormwater to recharge aquifers can later result in well failures and reduced base flow in streams. (Conoy Creek’s dry streambed in June, 2007)
Perhaps our lack of respect for streams and creeks is the source of our complete ignorance of the function of floodplains.
Floodplains are formed over time as hydraulic forces erode bedrock and soils surrounding a stream to create adequate space to pass flood waters. As floodplains mature they become large enough to reduce flood water velocity and erosion energy. They then function to retain, infiltrate, and evaporate the surplus water from flood events. Microorganisms, plants, and other life forms found in floodplain wetlands, forests, and grasslands purify the water and break down naturally-occurring organic matter. Floodplains are the shock-absorber between us and our waterways. And they’re our largest water treatment facilities.
Why is it then, that whenever a floodplain floods, we seem motivated to do something to fix this error of nature? Man can’t help himself. He has a compulsion to fill the floodplain with any contrivance he can come up with. We dump, pile, fill, pave, pour, form, and build, then build some more. At some point, someone notices a stream in the midst of our new creation. Now it’s polluted and whenever it storms, the darn thing floods into our stuff—worse than ever before. So the project is crowned by another round of dumping, forming, pouring, and building to channelize the stream. Done! Now let’s move all our stuff into our new habitable space.
Natural Floodplain- Over a period of hundreds or thousands of years, the stream (dark blue) has established a natural floodplain including wetlands and forest. In this example, buildings and infrastructure are located outside the zone inundated by high water (light blue) allowing the floodplain to function as an effective water-absorbing buffer.Impaired Floodplain- Here the natural floodplain has been filled for building (left) and paved for recreation area parking (right). The stream has been channelized. Flood water (light blue) displaced by these alterations is likely to inundate areas not previously impacted by similar events. Additionally, the interference with natural flow will create new erosion points that could seriously damage older infrastructure and properties.
The majority of the towns in the lower Susquehanna valley with streams passing through them have impaired floodplains. In many, the older sections of the town are built on filled floodplain. Some new subdivisions highlight streamside lawns as a sales feature—plenty of room for stockpiling your accoutrements of suburban life. And yes, some new homes are still being built in floodplains.
When high water comes, it drags tons of debris with it. The limbs, leaves, twigs, and trees are broken down by natural processes over time. Nature has mechanisms to quickly cope with these organics. Man’s consumer rubbish is another matter. As the plant material decays, the embedded man-made items, particularly metals, treated lumber, plastics, Styrofoam, and glass, become more evident as an ever-accumulating “garbage soil” in the natural floodplains downstream of these impaired areas. With each storm, some of this mess floats away again to move ever closer to Chesapeake Bay and the Atlantic. Are you following me? That’s our junk from the curb, lawn, highway, or parking lot bobbing around in the world’s oceans.
A shed, mobile home, or house can be inundated or swept away during a flood. Everything inside (household chemicals, gasoline, fuel oil, pesticides, insulation, all those plastics, etc.) instantly pollutes the water. Many communities that rely on the Susquehanna River for drinking water are immediately impacted, including Lancaster, PA and Baltimore, MD. This dumpster was swept away from a parking lot in a floodplain. It rolled in the current, chipping away at the bridge before spilling the rubbish into the muddy water. After the flood receded, the dumpster was found a mile downstream. Its contents are still out there somewhere.Floodplains along the lower Susquehanna River are blanketed with a layer of flotsam that settles in place as high water recedes. These fresh piles can be several feet deep and stretch for miles. Nature decomposes the organic twigs and driftwood to build soil-enriching humus. However, the plastics and other man-made materials that do not readily decay or do not float away toward the sea during the next flood are incorporated into the alluvium and humus creating a “garbage soil”. Over time, the action of abrasives in the soil will grind small particles of plastics from the larger pieces. These tiny plastics can become suspended in the water column each time the river floods. What will be the long-term impact of this type of pollution?Anything can be swept away by the powerful hydraulic forces of flowing water. Large objects like this utility trailer can block passages through bridges and escalate flooding problems.The cost of removing debris often falls upon local government and is shared by taxpayers.Here, a junked boat dock is snagged on the crest of the York Haven Dam at Conewago Falls. Rising water eventually carried it over the dam and into the falls where it broke up. This and tons of other junk are often removed downstream at the Safe Harbor Dam to prevent damage to turbine equipment. During periods of high water, the utility hauls debris by the truck-load to the local waste authority for disposal. For the owners of garbage like this dock, it’s gone and it’s somebody else’s problem now.Motor vehicles found after floating away from parking areas in floodplains can create a dangerous dilemma for police, fire, and E.M.S. personnel, particularly when no one witnesses the event. Was someone driving this car or was it vacant when it was swept downstream? Should crews be put at risk to locate possible victims?
Beginning in 1968, participating municipalities, in exchange for having coverage provided to their qualified residents under the National Flood Insurance Program, were required to adopt and enforce a floodplain management ordinance. The program was intended to reduce flood damage and provide flood assistance funded with premiums paid by potential victims. The program now operates with a debt incurred during severe hurricanes. Occurrences of repetitive damage claims and accusations that the program provides an incentive for rebuilding in floodplains have made the National Flood Insurance Program controversial.
In the Lower Susquehanna River Watershed there are municipalities that still permit new construction in floodplains. Others are quite proactive at eliminating new construction in flood-prone zones, and some are working to have buildings removed that are subjected to repeated flooding.
Another Wall— Here’s an example of greed by the owner, engineer, and municipality… placing their financial interests first. The entire floodplain on the north side of this stream was filled, then the wall was erected to contain the material. A financial institution’s office and parking lot was constructed atop the mound. This project has channelized the stream and completely displaced half of the floodplain to a height of 15 to 20 feet. Constructed less than five years ago, the wall failed already and has just been totally reconstructed. The photo reveals how recent flooding has begun a new erosion regime where energy is focused along the base of the wall. Impairment of a floodplain to this degree can lead to flooding upstream of the site and erosion damage to neighboring infrastructure including roads and bridges.The floodplain along this segment of the lower Swatara Creek in Londonderry Township, Dauphin County is free to flood. Ordinances prohibit new construction here and 14 older houses that repeatedly flooded were purchased, dismantled, and removed using funding from the Federal Emergency Management Agency (F.E.M.A). A riparian buffer was planted and some wetland restorations were incorporated into stormwater management installations along the local highways. When the waters of the Swatara rise, the local municipality closes the roads into the floodplain. Nobody lives or works there anymore, so no one has any reason to enter. There’s no need to rescue stubborn residents who refused advice to evacuate. Sightseers can park and stand on the hill behind the barricades and take all the photographs they like.A new Pennsylvania Turnpike bridge across Swatara Creek features wide passage for the stream below. Water flowing in the floodplain can pass under the bridge without being channelized toward the path where the stream normally flows in the center. The black asterisk-shaped floats spin on the poles to help deflect debris away from the bridge piers. (flood crest on July 26, 2018)People are curious when a waterway floods and they want to see it for themselves. Wouldn’t it be wise to anticipate this demand for access by being ready to accommodate these citizens safely? Isn’t a parking lot, picnic area, or manicured park safer and more usable when overlooking the floodplain as opposed to being located in it? Wouldn’t it be a more prudent long-term investment, both financially and ecologically, to develop these improvements on higher ground outside of flood zones?Now would be a good time to stop the new construction and the rebuilding in floodplains. Aren’t the risks posed to human life, water quality, essential infrastructure, private property, and ecosystems too great to continue?Isn’t it time to put up the white flag and surrender the floodplains to the floods? That’s why they’re there. Floodplains are for flooding.
There are two Conewago Creek systems in the Lower Susquehanna River Watershed. One drains the Gettysburg Basin west of the river, mostly in Adams and York Counties, then flows into the Susquehanna at the base of Conewago Falls. The other drains the Gettysburg Basin east of the river, flowing through Triassic redbeds of the Gettysburg Formation and York Haven Diabase before entering Conewago Falls near the south tip of Three Mile Island. Both Conewago Creeks flow through suburbia, farm, and forest. Both have their capacity to support aquatic life impaired and diminished by nutrient and sediment pollution.
This week, some of the many partners engaged in a long-term collaboration to restore the east shore’s Conewago Creek met to have a look at one of the prime indicators of overall stream habitat health—the fishes. Kristen Kyler of the Lower Susquehanna Initiative organized the effort. Portable backpack-mounted electrofishing units and nets were used by crews to capture, identify, and count the native and non-native fishes at sampling locations which have remained constant since prior to the numerous stream improvement projects which began more than ten years ago. Some of the present-day sample sites were first used following Hurricane Agnes in 1972 by Stambaugh and Denoncourt and pre-date any implementation of sediment and nutrient mitigation practices like cover crops, no-till farming, field terracing, stormwater control, nutrient management, wetland restoration, streambank fencing, renewed forested stream buffers, or modernized wastewater treatment plants. By comparing more recent surveys with this baseline data, it may be possible to discern trends in fish populations resulting not only from conservation practices, but from many other variables which may impact the Conewago Creek Warmwater Stream ecosystem in Dauphin, Lancaster, and Lebanon Counties.
So here they are. Enjoy these shocking fish photos.
Matt Kofroth, Watershed Specialist with the Lancaster County Conservation District, operates the electrofishing wand in Conewago Creek while his team members prepare to net and collect momentarily-stunned fish. Three other electrofishing units operated by staff from the Susquehanna River Basin Commission and aided by teams of netters were in action at other sample locations along the Conewago on this day.Really big fish, such as this Common Carp (Cyprinus carpio), were identified, counted, and immediately returned to the water downstream of the advancing electrofishing team. Koi of the garden pond are a familiar variety of Common Carp, a native of Asia.Other fish, such as the Swallowtail Shiner, Redbreast Sunfish (Lepomis auritus), Fallfish, and suckers seen here, were placed in a sorting tank.Fallfish (Semotilus corporalis) are very active and require plenty of dissolved oxygen in the water to survive. Fallfish, Rainbow Trout (Oncorhynchus mykiss), and Smallmouth Bass (Micropterus dolomieu) were quickly identified and removed from the sorting tank for release back into the stream. Other larger, but less active fish, including suckers, quickly followed.Small fish like minnows were removed from the sorting tank for a closer look in a hand-held viewing tank. This Fathead Minnow (Pimephales promelas) was identified, added to the tally sheet, and released back into the Conewago. The Fathead Minnow is not native to the Susquehanna drainage. It is the minnow most frequently sold as bait by vendors.A breeding condition male Bluntnose Minnow (Pimephales notatus).The Cutlips Minnow (Exoglossum maxillingua) is a resident of clear rocky streams. Of the more than 30 species collected during the day, two native species which are classified as intolerant of persisting stream impairment were found: Cutlips Minnow and Swallowtail Shiner.This young River Chub (Nocomis micropogon) is losing its side stripe. It will be at least twice as large at adulthood.The Eastern Blacknose Dace (Rhinichthys atratulus) is found in clear water over pebble and stone substrate..The Longnose Dace (Rhinichthys cataractae) is another species of pebbly rocky streams.A juvenile Golden Shiner (Notemigonus crysoleucas). Adults lack the side stripe and grow to the size of a sunfish.A Swallowtail Shiner (Notropis procne) and a very young White Sucker (Catostomus commersonii) in the upper left of the tank.A Spotfin Shiner (Cyprinella spiloptera).A breeding male Spotfin Shiner. Show-off!The Margined Madtom (Noturus insignis) is a small native catfish of pebbly streams.The Banded Killifish (Fundulus diaphanus) is adept at feeding upon insects, including mosquitos.A young Rock Bass (Ambloplites rupestris). This species was introduced to the Susquehanna and its tributaries.The Greenside Darter (Etheostoma blennioides) is not native to the Susquehanna basin. The species colonized the Conewago Creek (east) from introduced local populations within the last five years.The Tessellated Darter (Etheostoma olmstedi) is a native inhabitant of the Susquehanna and its tributaries.The stars of the day were the American Eels (Anguilla rostrata).After collection, each eel was measured and weighed using a scale and dry bucket. This specimen checked in at 20 inches and one pound before being released.Prior to the construction of large dams, American Eels were plentiful in the Susquehanna and its tributaries, including the Conewago. They’ve since been rarities for more than half a century. Now they’re getting a lift.American Eels serve as an intermediate host for the microscopic parasitic glochidia (larvae) of the Eastern Elliptio (Elliptio complanata), a declining native freshwater mussel of the Lower Susquehanna River Watershed. While feeding on their host (usually in its gills), the glochidia cause little injury and soon drop off to continue growth, often having assured distribution of their species by accepting the free ride. Freshwater mussels are filter feeders and improve water quality. They grow slowly and can live for decades.American Eels are a catadromous species, starting life as tiny glass eels in the saltwater of the Atlantic Ocean, then migrating to tidal brackish marshes and streams (males) or freshwater streams (females) to mature. This 20-incher probably attempted to ascend the Susquehanna as an elver in 2016 or 2017. After hitching a ride with some friendly folks, she bypassed the three largest dams on the lower Susquehanna (Conowingo, Holtwood, and Safe Harbor) and arrived in the Conewago where she may remain and grow for ten years or more. To spawn, a perilous and terminally fatal journey to the Sargasso Sea awaits her. (You may better know the area of the Sargasso Sea as The Bermuda Triangle…a perilous place to travel indeed!)
SOURCES
Normandeau Associates, Inc. and Gomez and Sullivan. 2018. Muddy Run Pumped Storage Project Conowingo Eel Collection Facility FERC Project 2355. Prepared for Exelon.
Stambaugh, Jr., John W., and Robert P. Denoncourt. 1974. A Preliminary Report on the Conewago Creek Faunal Survey, Lancaster County, Pennsylvania. Proceedings of the Pennsylvania Academy of Sciences. 48: 55-60.
One can get a stiff neck looking up at the flurry of bird activity in the treetops at this time of year. Many of the Neotropical migrants favor rich forests as daytime resting sites after flying through the night. For others, these forests are a destination where they will nest and raise their young.
The Veery (Catharus fuscescens) is a Neotropical thrush that breeds in extensive mature forest on the dampest slopes of the Diabase ridges in the Gettysburg Basin. Their rolling flute-like songs echo through the understory as newly arrived birds establish nesting territories.The whistled song of the Baltimore Oriole is often heard long before this colorful Neotropical is seen among the foliage of a treetop. Some dead branches allow us a glimpse of this curious beauty.The “Pee-a-wee……..Pee-urr” song of the Eastern Wood-Pewee (Contopus virens), a small flycatcher, is presently heard in the Riparian Woodlands at Conewago Falls. It breeds in forested tracts throughout the lower Susquehanna valley. The vocalizations often continue through the summer, ending only when the birds depart to return to the tropics for the winter.While constructing a nest beneath a tree canopy, an Eastern Wood-Pewee form-fits the cup where eggs will soon be laid.The Yellow-billed Cuckoo (Coccyzus americana) nests in the treetops of Riparian Woodlands along the Susquehanna and its tributaries. Most arrive during the second half of May for their summer stay. It is a renowned consumer of caterpillars.The Cedar Waxwing is a notorious wanderer. Though not a Neotropical migrant, it is a very late nester. Flocks may continue moving for another month before pairs settle on a place to raise young.Of the more than twenty species of warblers which regularly migrate through the lower Susquehanna Valley, the Common Yellowthroat (Geothlypis trichas) is among those which breeds here. It is particularly fond of streamside thickets.
For the birds that arrive earlier in spring than the Neotropical migrants, the breeding season is well underway. The wet weather may be impacting the success of the early nests.
Northern Rough-winged Swallows arrived back in April. At traditional nest sites, including the York Haven Dam and local creek bridges, small groups of adults were seen actively feeding and at times perching in dead treetops during recent days. There was an absence of visits to the actual nest cavities where they should be feeding and fledging young by now. It’s very possible that these nests failed due to the wet weather and flooding. Another nest attempt may follow if drier conditions allow stream levels to subside and there is an increase in the mass of flying insects available for the adults to feed to their young..A Carolina Chickadee, a resident species, is seen atop a hollow stump where it and a mate are constructing a new nest for a second brood. Did the first brood fail? Not sure.Common Mergansers are an uncommon but regular nesting species of waterfowl on the lower Susquehanna River. They nest in cavities, requiring very large trees to accommodate their needs. It was therefore encouraging to see this pair on a forested stream in northern Lancaster County during the weekend. However, a little while after this photograph was taken the pair flew away, indicating that they are not caring for young which by now should be out of the nest and on the move under the watchful care of the female.
So long for now, if you’ll excuse me please, I have a sore neck to tend to.
Two days ago, widespread rain fell intermittently through the day and steadily into the night in the Susquehanna drainage basin. The temperature was sixty degrees, climbing out of a three-week-long spell of sub-freezing cold in a dramatic way. Above the ice-covered river, a very localized fog swirled in the southerly breezes.
By yesterday, the rain had ended as light snow and a stiff wind from the northwest brought sub-freezing air back to the region. Though less than an inch of rain fell during this event, much of it drained to waterways from frozen or saturated ground. Streams throughout the watershed are being pushed clear of ice as minor flooding lifts and breaks the solid sheets into floating chunks.
Today, as their high flows recede, the smaller creeks and runs are beginning to freeze once again. On larger streams, ice is still exiting with the cresting flows and entering the rising river.
Ice chunks on Swatara Creek merge into a dense flow of ice on the river in the distance. Swatara Creek is the largest tributary to enter the Susquehanna in the Gettysburg Basin. The risk of an ice jam impounding the Swatara here at its mouth is lessened because rising water on the river has lifted and broken the ice pack to keep it moving without serious impingement by submerged obstacles. Immovable ice jams on the river can easily block the outflow from tributaries, resulting in catastrophic flooding along these streams.Fast-moving flows of jagged ice race toward Three Mile Island and Conewago Falls. The rising water began relieving the compression of ice along the shoreline during the mid-morning. Here on the river just downstream of the mouth of Swatara Creek, ice-free openings allowed near-shore piles to separate and begin floating away after 10:30 A.M. E.S.T. Moving masses of ice created loud rumbles, sounding like a distant thunderstorm.Ice being pushed and heaved over the crest of the York Haven Dam at Conewago Falls due to compression and rising water levels.Enormous chunks of ice being forced up and over the York Haven Dam into Conewago Falls and the Pothole Rocks below.Ice scours Conewago Falls, as it has for thousands of years.The action of ice and suspended abrasives has carved the York Haven Diabase boulders and bedrock of Conewago Falls into the amazing Pothole Rocks.The roaring torrents of ice-choked water will clear some of the woody growth from the Riverine Grasslands of Conewago Falls.To the right of center in this image, a motorcar-sized chunk of ice tumbles over the dam and crashes into the Pothole Rocks. It was one of thousands of similar tree-and-shrub-clearing projectiles to go through the falls today.
The events of today provide a superb snapshot of how Conewago Falls, particularly the Diabase Pothole Rocks, became such a unique place, thousands of years in the making. Ice and flood events of varying intensity, duration, and composition have sculpted these geomorphologic features and contributed to the creation of the specialized plant and animal communities we find there. Their periodic occurrence is essential to maintaining the uncommon habitats in which these communities thrive.
Fish Crows (Corvus ossifragus) gather along the flooding river shoreline. Soon there’ll be plenty of rubbish to pick through, some carrion maybe, or even a displaced aquatic creature or two to snack upon.
Is this the same Conewago Falls I visited a week ago? Could it really be? Where are all the gulls, the herons, the tiny critters swimming in the potholes, and the leaping fish? Except for a Bald Eagle on a nearby perch, the falls seems inanimate.
Yes, a week of deep freeze has stifled the Susquehanna and much of Conewago Falls. A hike up into the area where the falls churns with great turbulence provided a view of some open water. And a flow of open water is found downstream of the York Haven Dam powerhouse discharge. All else is icing over and freezing solid. The flow of the river pinned beneath is already beginning to heave the flat sheets into piles of jagged ice which accumulate behind obstacles and shallows.
Ice and snow surround a small zone of open water in a high-gradient area of Conewago Falls.Ice chunks and sheets accumulate atop the York Haven Dam. The weight of miles of ice backed up behind the dam eventually forces the accumulation over the top and into the Pothole Rocks below. The popping and cracking sounds of ice both above and below the dam could be heard throughout the day as hydraulic forces continuously break and move ice sheets.Steam from the Unit 1 cooling towers at the Three Mile Island Nuclear Generating Station rises above the frozen Riverine Grasslands at Conewago Falls. The scouring action of winter ice keeps the grasslands clear of substantial woody growth and prevents succession into forest.Despite a lack of activity on the river, mixed flocks of resident and wintering birds, including this White-breasted Nuthatch (Sitta carolinensis), were busy feeding in the Riparian Woodlands. The White-breasted Nuthatch is a cavity nester and year-round denizen of hardwoods, often finding shelter during harsh winter nights in small tree holes.The White-breasted Nuthatch is often seen working its way head-first down a tree trunk as it probes with its well-adapted bill for insects among the bark.Jackpot!Looking upstream from the river’s east shore at ice and snow cover on the Susquehanna above Conewago Falls and the York Haven Dam. The impoundment, known as Lake Frederic, and its numerous islands of the Gettysburg Basin Archipelago were locked in winter’s frosty grip today. Hill Island (Left) and Poplar Island (Center) consist of erosion-resistant York Haven Diabase, as does the ridge on the far shoreline seen rising in the distance between them. To the right of Poplar Island in this image, the river passes by the Harrisburg International Airport. At the weather station there, the high temperature was eighteen degrees Fahrenheit on this first day of 2018.
It was one of the very first of my memories. From the lawn of our home I could look across the road and down the hill through a gap in the woodlands. There I could see water, sometimes still with numerous boulders exposed, other times rushing, muddy, and roaring. Behind these waters was a great stone wall and beyond that a wooded hillside. I recall my dad asking me if I could see the dam down there. I couldn’t see a dam, just fascinating water and the gray wall behind it. I looked and searched but not a trace of a structure spanning the near to far shore was to be seen. Finally, at some point, I answered in the affirmative to his query; I could see the dam…but I couldn’t.
We lived in a small house in the village of Falmouth along the Susquehanna River in the northwest corner of Lancaster County over fifty years ago. A few years after we had left our riverside domicile and moved to a larger town, the little house was relocated to make way for an electric distribution sub-station and a second set of electric transmission wires in the gap in the woodlands. The Brunner Island coal-fired electric generating station was being upgraded downstream and, just upstream, a new nuclear-powered generating station was being constructed on Three Mile Island. To make way for the expanding energy grid, our former residence was trucked to a nearby boat landing where there were numerous other river shacks and cabins. Because it was placed in the floodplain, the building was raised onto a set of wooden stilts to escape high water. It didn’t help. The record-breaking floods of Hurricane Agnes in June of 1972 swept the house away.
The view through the cut in the woodland, a little wider than in the early 1960s with the addition of the newer electric transmission wire towers. The “Wall” is the same.
During the time we lived along the Susquehanna, the river experienced record-low flow rates, particularly in the autumn of 1963 and again in 1964. My dad was a dedicated 8mm home-movie photographer. Among his reels was film of buses parked haphazardly along the road (PA Route 441 today) near our home. Sightseers were coming to explore the widely publicized dry riverbed and a curious moon-like landscape of cratered rocks and boulders. It’s hard to fathom, but people did things like that during their weekends before Sunday-afternoon football was invented. Scores of visitors climbed through the rocks and truck-size boulders inspecting this peculiar scene. My dad, his friends, and so many others with camera in hand were experiencing the amazing geological feature known as the Pothole Rocks of Conewago Falls.
Conewago Falls on the Susquehanna River and several exposed York Haven Diabase Pothole Rocks. Lancaster (foreground) and Dauphin (center) Counties meet along a southwest to northeast borderline through the rapids. Lands on the west shoreline in the background are in York County. Three Mile Island is seen in the upper right.
The river here meets serious resistance as it pushes its way through the complex geology of south-central Pennsylvania. These hard dark-gray rocks, York Haven Diabase, are igneous in origin. Diabase sheets and sills intruded the Triassic sediments of the Gettysburg Formation here over 190 million years ago. It may be difficult to visualize, but these sediments were eroded from surrounding mountains into the opening rift valley we call the Gettysburg Basin. This rift and others in a line from Nova Scotia to Georgia formed as the supercontinent Pangaea began dividing into the continents we know today. Eventually the Atlantic Ocean rift would dominate as the active dynamic force and open to separate Africa from North America. The inactive Gettysburg Basin, filled with sediments and intruded by igneous diabase, would henceforth, like the mountainous highlands surrounding it, be subjected to millions of years of erosion. Of the regional rocks, the formations of Triassic redbeds, sandstones, and particularly diabase in the Gettysburg Basin are among the more resistant to the forces of erosion. Many less resistant older rocks, particularly those of surrounding mountains, are gone. Today, the remains of the Gettysburg Basin’s rock formations stand as rolling highlands in the Piedmont Province.
Flooded from the heavy rains of Tropical Storm Lee, the sediment-laden Susquehanna River flows through the Gettysburg Basin just south of Harrisburg, PA, September 10, 2011. The “Wall” as seen from space. (NASA Earth Observatory Image)
The weekend visitors in 1963 and 1964 marveled at evidence of the river’s fight to break down the hard York Haven Diabase. Scoured bedrock traced the water’s turbulent flow patterns through the topography of the falls. Meltwater from the receding glaciers of the Pleistocene Ice Ages thousands to tens of thousands of years ago raged in high-volume, abrasive-loaded torrents to sculpt the Pothole Rocks into the forms we see today. Our modern floodwaters with ice and fine suspended sediments continue to wear at the smooth rocks and boulders, yet few are broken or crumbled to be swept away. It’s a very slow process. The river elevation here drops approximately 19 feet in a quarter of a mile, a testament to the bedrock’s persisting resistance to erosion. Conewago Falls stands as a natural anomaly on a predominantly uniform gradient along the lower Susquehanna’s downhill path from the Appalachian Mountains to the Chesapeake Bay.
Normally the scene of dangerous tumbling rapids, the drought and low water of 1963 and 1964 had left the falls to resemble a placid scene—a moonscape during a time when people were obsessed with mankind’s effort to visit earth’s satellite. Visitors saw the falls as few others had during the twentieth century. Dr. Herbert Beck of Franklin and Marshall College described an earlier period of exposure, “…pot holes…were uncovered during the third week in October, 1947, for the first time in the memory of man, when the drought parched Susquehanna River retreated far below its normal low stage”. Then, as in 1963 and on occasions more recent, much of it was due to the presence of the wall. I had to be a bit older than four years old to grasp it. You see the wall and the dam are one and the same. The wall is the York Haven Dam. And it is responsible for channeling away the low flow of the Susquehanna during periods of drought so that we might have the opportunity to visit and explore the Pothole Rocks of Conewago Falls along the river’s east shore.
The initial segment of the dam, a crib structure built in 1885 by the York Haven Paper Company to supply water power to their mill, took advantage of the geomorphic features of the diabase bedrock of Conewago Falls to divert additional river flow into the abandoned Conewago Canal. The former canal, opened in 1797 to allow passage around the rapids along the west shore, was being used as a headrace to channel water into the grinding mill’s turbines. Strategic placement of this first wall directed as much water as possible toward the mill with the smallest dam practicable. The York Haven Power Company incorporated the paper mill’s crib dam into the “run-of-the-river” dam built through the falls from the electric turbine powerhouse they constructed on the west shore to the southern portion of Three Mile Island more than a mile away. The facility began electric generation in 1904. The construction of the “Red Hill Dam” from the east shore of Three Mile Island to the river’s east shore made York Haven Dam a complete impoundment on the Susquehanna. The pool, “Lake Frederic”, thus floods that portion of the Pothole Rocks of Conewago Falls located behind the dam. On the downstream side, water spilling over or through the dam often inundates the rocks or renders them inaccessible.
During the droughts of the early 1960s, diversion of nearly all river flow to the York Haven Dam powerhouse cleared the way for weekend explorers to see the Pothole Rocks in detail. Void of water, the intriguing bedrock of Conewago Falls below the dam greeted the curious with its ripples, cavities, and oddity. It was an opportunity nature alone would not provide. It was all because of the wall.
York Haven Dam and powerhouse. The “Wall” traverses Conewago Falls upstream to Three Mile Island to direct water to the powerhouse on the west shore of the Susquehanna River.
SOURCES
Beck, Herbert H. 1948. “The Pot Holes of Conewago Falls”. Proceedings of the Pennsylvania Academy of Science. Penn State University Press. 22: pp. 127-130.
Smith, Stephen H. 2015. #6 York Haven Paper Company; on the Site of One of the Earliest Canals in America. York Past website www.yorkblog.com/yorkpast/2015/02/17/6-york-haven-paper-company-on-the-site-of-one-of-the-earliest-canals-in-america/ as accessed July 17, 2017.
Stranahan, Susan Q. 1993. Susquehanna, River of Dreams. The Johns Hopkins University Press. Baltimore, Maryland.
Van Diver, Bradford B. 1990. Roadside Geology of Pennsylvania. Mountain Press Publishing Company. Missoula, Montana.
