Heat Flux Processes in Streams and Their Impact on Coldwater and Coolwater Fishes
The deluge of rain that soaked the lower Susquehanna watershed during last week is now just a memory. Streams to the west of the river, where the flooding courtesy of the remnants of Hurricane Debby was most severe, have reached their crest and receded. Sliding away toward the Chesapeake and Atlantic is all that runoff, laden with a brew of pollutants including but not limited to: agricultural nutrients, sediment, petroleum products, sewage, lawn chemicals, tires, dog poop, and all that litter—paper, plastics, glass, Styrofoam, and more. For aquatic organisms including our freshwater fish, these floods, particularly when they occur in summer, can compound the effects of the numerous stressors that already limit their ability to live, thrive, and reproduce.
One of those preexisting stressors, high water temperature, can be either intensified or relieved by summertime precipitation. Runoff from forested or other densely vegetated ground normally has little impact on stream temperature. But segments of waterways receiving significant volumes of runoff from areas of sun-exposed impervious ground will usually see increases during at least the early stages of a rain event. Fortunately, projects implemented to address the negative impacts of stormwater flow and stream impairment can often have the additional benefit of helping to attenuate sudden rises in stream temperature.
Of the fishes inhabiting the Lower Susquehanna River Watershed’s temperate streams, the least tolerant of summer warming are the trouts and sculpins—species often described as “coldwater fishes”. Coldwater fishes require water temperatures below 70° Fahrenheit to thrive and reproduce. The optimal temperature range is 50° to 65° F. In the lower Susquehanna valley, few streams are able to sustain trouts and sculpins through the summer months—largely due to the effects of warm stormwater runoff and other forms of impairment.
Coldwater fishes are generally found in small spring-fed creeks and headwaters runs. Where stream gradient, substrate, dissolved oxygen, and other parameters are favorable, some species may be tolerant of water warmer than the optimal values. In other words, these temperature classifications are not set in stone and nobody ever explained ichthyology to a fish, so there are exceptions. The Brown Trout for example is sometimes listed as a “coldwater transition fish”, able to survive and reproduce in waters where stream quality is exceptionally good but the temperature may periodically reach the mid-seventies.
More tolerant of summer heat than the trouts, sculpins, and daces are the “coolwater fishes”—species able to feed, grow, and reproduce in streams with a temperature of less than 80° F, but higher than 60° F. Coolwater fishes thrive in creeks and rivers that hover in the 65° to 70° F range during summer.
What are the causes of modern-day reductions in coldwater and coolwater fish habitats in the lower Susquehanna River and its hundreds of miles of tributaries? To answer that, let’s take a look at the atmospheric, cosmic, and hydrologic processes that impact water temperature. Technically, these processes could be measured as heat flux—the rate of heat energy transfer per unit area per unit time, frequently expressed as watts per meter squared (W/m²). Without getting too technical, we’ll just take a look at the practical impact these processes have on stream temperatures.
HEAT FLUX PROCESSES IN A SEGMENT OF STREAM
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- INCOMING TEMPERATURE AND FLOW—The baseline temperature of stream water entering a given segment of waterway is obviously the chief factor determining its temperature when exiting that segment. Incoming temperature and flow also determine the water’s susceptibility to heat absorption or loss while transiting the segment. Lower flows may subject the given volume of water to a greater loss or gain of heat energy during the time needed to pass through the segment than the same volume at a higher flow. Lower flows may also reduce stream velocity and extend a given volume of water’s exposure time to the exchange of heat energy while moving through the segment. Generally speaking…
- …the higher the stream flow, the less a given volume of that stream’s water may be impacted by the effects of the heat flux processes within the segment.
- …the lower the stream flow, the more a given volume of that stream’s water may be impacted by the effects of the heat flux processes within that segment.
- …the temperature and flow rate of precipitation entering the segment are factors that determine the impact of its heat energy transfer to or from a given volume of the stream’s waters.
- …the temperature and flow rate of runoff and point-source discharges entering the segment are factors that determine the impact of their heat energy transfer to or from a given volume of the stream’s waters.
- INCOMING TEMPERATURE AND FLOW—The baseline temperature of stream water entering a given segment of waterway is obviously the chief factor determining its temperature when exiting that segment. Incoming temperature and flow also determine the water’s susceptibility to heat absorption or loss while transiting the segment. Lower flows may subject the given volume of water to a greater loss or gain of heat energy during the time needed to pass through the segment than the same volume at a higher flow. Lower flows may also reduce stream velocity and extend a given volume of water’s exposure time to the exchange of heat energy while moving through the segment. Generally speaking…
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- GROUNDWATER INPUT—In streams connected to the aquifer, the temperature in a flowing segment can be impacted by the influx of cold groundwater. With temperatures ranging from about 52° to 60° Fahrenheit, groundwater will absorb heat from the stream in summer, and warm it in the winter. In warmwater streams, coldwater and coolwater fishes will often seek areas of the substrate where groundwater is entering for use as refugium from the summer heat. Yellow Perch in the lower Susquehanna are known to exhibit this behavior.
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- HYPORHEIC EXCHANGE—Related to groundwater input, hyporheic exchange is the slow movement of water through the rock, sand, gravel, and soils composing the streambed, saturated shoreline, shallow aquifer, and connected floodplain of a creek or river. As a heat flux process, hyporheic exchange helps moderate extremes in seasonal water temperatures by conducting energy between the solid materials in the zone and the flowing water. Hyporheic zones are important habitats for many species of aquatic invertebrates and spawning fish. Natural chemical processes within these zones convert ammonia-producing wastes into nitrite, then nitrate, allowing it to be absorbed as food by plants growing in the stream or in the alluvium within the zone. Vegetation removal, channelization, legacy sediments, silt deposits, and man-made walls and dams can negate the benefits of hyporheic exchange.
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- ATMOSPHERIC EXCHANGE (CONVECTION, EVAPORATION)—Primarily a process by which a stream loses heat energy and cools its waters, atmospheric exchange is also a means by which a warm air mass can relinquish heat to cooler waters and thus increase their temperature. This phenomenon can be dramatically enhanced when a stream passes through a so-called urban heat island where air temperatures remain warm through the night. Convection, the movement of heat energy through a fluid (liquid or gas), causes warmer, less-dense water to rise to the surface of a stream, particularly where there is minimal turbulence. When the air above is cooler than the water’s surface layer, the stream will conduct heat energy across the water/atmosphere interface causing the warmed air molecules to rise in a convection column. If the atmospheric relative humidity is less than 100%, some surface water will vaporize—a process that expends more of the stream’s heat energy. The rate of convective and evaporative cooling in a given stream segment is directly related to the degree of difference between the water temperature and air temperature, and to the relative humidity in the air mass above the lake, creek, or river. The mechanical action of stream turbulence including rapids, riffles, and falls increases the contact area between air and water to maximize the atmospheric exchange of heat energy. The convective air current we call surface wind has a turbulent wave-producing effect on water that can also maximize atmospheric exchange; think of a cold autumn wind robbing heat energy from a warm lake or river or a hot summer wind imparting its heat to a cooler creek. These exchanges are both conductive in nature (air-to-water/water-to-air) and evaporative, the latter being expedited by the movement of dry air over warm water.
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- STREAMBED CONDUCTIVE EXCHANGE—In the lower Susquehanna watershed, there may be no better natural example of streambed conductive exchange than the Triassic-Jurassic diabase pothole bedrocks of Conewago Falls on the river at the south end of Three Mile Island.
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- SOLAR (SHORTWAVE) RADIATION—The sun provides the energy that fuels the earth’s complex climate. The primary heat flux process that heats our planet is the absorption of solar radiation in the shortwave spectrum, which includes ultraviolet, visible, and infrared frequencies at the upper end of the longwave spectrum. Streams and other bodies of water absorb the greatest amounts of solar (shortwave) radiation during the weeks around summer solstice when the sun at mid-day is closer to zenith than at any other time of the year. However, the heating impact of the radiation may be greatest when the volume of water in the creek, river, or lake is at its minimum for the year—often during early fall.
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- INCIDENT SHORTWAVE RADIATION—Also known as insolation (incoming solar radiation), incident shortwave radiation is the sum total energy of both the direct solar radiation that travels to the earth’s surface unaffected by the atmosphere and the diffuse radiation, waves that have been weakened and scattered by constituents of the atmosphere before reaching the planet’s surface. On a cloudy day, the warming of terrestrial surfaces including streams and other bodies of water is the result of diffuse radiation. On days with any amount of sunshine at all, both direct and diffuse radiation heat our waters and lands.
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- REFLECTED SHORTWAVE RADIATION—known as albedo, reflected solar (shortwave) radiation is energy directed away from the earth’s surface before being absorbed. A surface’s albedo value is basically determined by its color, black having little reflective value, white and silvery surfaces reflecting nearly all solar (shortwave) radiation away. A surface with no reflective properties has an albedo value of 0, while a totally reflective surface has a value of 1. Clean snow with a value of about 0.85 to 0.9 (85% to 90%) is a highly reflective surface; yellow snow isn’t as good. A stream, river, or lake blanketed with ice and snow will absorb very little solar energy and will rely upon other heat flux processes to trigger a melt and thaw. The surface of open water has a varying albedo value determined mostly by the angle of the sun. Solar radiation striking the water’s surface at a low angle is mostly reflected away, while that originating at an angle closer to zenith is more readily absorbed.
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- LONGWAVE RADIATION—Radiation in the longwave spectrum is composed of infrared waves at frequencies lower than those of the shortwave spectrum. Longwave radiation, sometimes just called infrared radiation, is produced by the earth and its atmosphere and is propagated in all directions, day and night. It warms mostly the lower atmosphere which in turn warms the earth’s surface including its waters. Some longwave energy can even be radiated into the waterway from its own streambed—and the stream can return the favor. Other forms of mass surrounding a stream such as a rocky shoreline or a man-made structure such as bridge pier can trade longwave radiation with a waterway. The effect of these latter exchanges is largely trivial and never rivals the heat flux transfer of warm to cold provided by conduction.
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- CANOPY RADIATION—Trees emit longwave radiation that may have a limited heat flux impact on waterway temperature. This radiation is diffuse, of scattered effect, and scarcely detectable, particularly beneath multilayered dense canopies. Some of the infrared energy transmitted by the tree canopy is radiated skyward as well.
- WATER RADIATION—Water, like all earthly matter composed of vibrating molecules, emits longwave radiation. This heat flux process provides an ongoing cooling effect to streams, rivers, lakes, and oceans—warmer ones shedding infrared energy at a faster rate than those that are cold.
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Now that we have a basic understanding of the heat flux processes responsible for determining the water temperatures of our creeks and rivers, let’s venture a look at a few graphics from gauge stations on some of the lower Susquehanna’s tributaries equipped with appropriate United States Geological Survey monitoring devices. While the data from each of these stations is clearly noted to be provisional, it can still be used to generate comparative graphics showing basic trends in easy-to-monitor parameters like temperature and stream flow.
Each image is self-labeled and plots stream temperature in degrees Fahrenheit (bold blue) and stream discharge in cubic feet per second (thin blue).
The daily oscillations in temperature reflect the influence of several heat flux processes. During the day, solar (shortwave) radiation and convection from summer air, especially those hot south winds, are largely responsible for the daily rises of about 5° F. Longwave radiation has a round-the-clock influence—adding heat to the stream during the day and mostly shedding it at night. Atmospheric exchange including evaporative cooling may help moderate the rise in stream temperatures during the day, and certainly plays a role in bringing them back down after sunset. Along its course this summer, the West Conewago Creek absorbed enough heat to render it a warmwater fishery in the area of the gauging station. The West Conewago is a shallow, low gradient stream over almost its entire course. Its waters move very slowly, thus extending their exposure time to radiated heat flux and reducing the benefit of cooling by atmospheric exchange. Fortunately for bass, catfish, and sunfish, these temperatures are in the ideal range for warmwater fishes to feed, grow, and reproduce—generally over 80° F, and ideally in the 70° to 85° F range. Coolwater fishes though, would not find this stream segment favorable. It was consistently above the 80° F maximum and the 60° to 70° F range preferred by these species. And coldwater fishes, well, they wouldn’t be caught dead in this stream segment. Wait, scratch that—the only way they would be caught in this segment is dead. No trouts or sculpins here.
Look closely and you’ll notice that although the temperature pattern on this chart closely resembles that of the West Conewago’s, the readings average about 5 degrees cooler. This may seem surprising when one realizes that the Codorus follows a channelized path through the heart of York City and its urbanized suburbs—a heat island of significance to a stream this size. Before that it passes through numerous impoundments where its waters are exposed to the full energy of the sun. The tempering factor for the Codorus is its baseflow. Despite draining a smaller watershed than its neighbor to the north, the Codorus’s baseflow (low flow between periods of rain) was 96 cubic feet per second on August 5th, nearly twice that of the West Conewago (51.1 cubic feet per second on August 5th). Thus, the incoming heat energy was distributed over a greater mass in the Codorus and had a reduced impact on its temperature. Though the Codorus is certainly a warmwater fishery in its lower reaches, coolwater and transitional fishes could probably inhabit its tributaries in segments located closer to groundwater sources without stress. Several streams in its upper reaches are in fact classified as trout-stocked fisheries.
The Kreutz Creek gauge shows temperature patterns similar to those in the West Conewago and Codorus data sets, but notice the lower overall temperature trend and the flow. Kreutz Creek is a much smaller stream than the other two, with a flow averaging less than one tenth that of the West Conewago and about one twentieth of that in the Codorus. And most of the watershed is cropland or urban/suburban space. Yet, the stream remains below 80° F through most of the summer. The saving graces in Kreutz Creek are reduced exposure time and gradient. The waters of Kreutz Creek tumble their way through a small watershed to enter the Susquehanna within twenty-four hours, barely time to go through a single daily heating and cooling cycle. As a result, their is no chance for water to accumulate radiant and convective heat over multiple summer days. The daily oscillations in temperature are less amplified than we find in the previous streams—a swing of about three degrees compared to five. This indicates a better balance between heat flux processes that raise temperature and those that reduce it. Atmospheric exchange in the stream’s riffles, forest cover, and good hyporheic exchange along its course could all be tempering factors in Kreutz Creek. From a temperature perspective, Kreutz Creek provides suitable waters for coolwater fishes.
Muddy Creek is a trout-stocked fishery, but it cannot sustain coldwater species through the summer heat. Though temperatures in Muddy Creek may be suitable for coolwater fishes, silt, nutrients, low dissolved oxygen, and other factors could easily render it strictly a warmwater fishery, inhabited by species tolerant of significant stream impairment.
A significant number of stream segments in the Chiques watershed have been rehabilitated to eliminate intrusion by grazing livestock, cropland runoff, and other sources of impairment. Through partnerships between a local group of watershed volunteers and landowners, one tributary, Donegal Creek, has seen riparian buffers, exclusion fencing, and other water quality and habitat improvements installed along nearly ever inch of its run from Donegal Springs through high-intensity farmland to its mouth on the main stem of the Chiques just above its confluence with the Susquehanna. The improved water quality parameters in the Donegal support native coldwater sculpins and an introduced population of reproducing Brown Trout. While coldwater habitat is limited to the Donegal, the main stem of the Chiques and its largest tributary, the Little Chiques Creek, both provide suitable temperatures for coolwater fishes.
Despite its meander through and receipt of water from high-intensity farmland, the temperature of the lower Conewago (East) maxes out at about 85° F, making it ideal for warmwater fishes and even those species that are often considered coolwater transition fishes like introduced Smallmouth Bass, Rock Bass, Walleye, and native Margined Madtom. This survivable temperature is a testament to the naturally occurring and planted forest buffers along much of the stream’s course, particularly on its main stem. But the Conewago suffers serious baseflow problems compared to other streams we’ve looked at so far. Just prior to the early August storms, flow was well below 10 cubic feet per second for a drainage area of more than fifty square miles. While some of this reduced flow is the result of evaporation, much of it is anthropogenic in origin as the rate of groundwater removal continues to increase and a recent surge in stream withdraws for irrigation reaches its peak during the hottest days of summer.
A little side note—the flow rate on the Conewago at the Falmouth gauge climbed to about 160 cubic feet per second as a result of the remnants of Hurricane Debby while the gauge on the West Conewago at Manchester skyrocketed to about 20,000 cubic feet per second. Although the West Conewago’s watershed (drainage area) is larger than that of the Conewago on the east shore, it’s larger only by a multiple of two or three, not 125. That’s a dramatic difference in rainfall!
The temperatures at the Bellaire monitoring station, which is located upstream of the Conewago’s halfway point between its headwaters in Mount Gretna and its mouth, are quite comparable to those at the Falmouth gauge. Although a comparison between these two sets of data indicate a low net increase in heat absorption along the stream’s course between the two points, it also suggests sources of significant warming upstream in the areas between the Bellaire gauge and the headwaters.
The waters of the Little Conewago are protected within planted riparian buffers and mature woodland along much of their course to the confluence with the Conewago’s main stem just upstream of Bellaire. This tributary certainly isn’t responsible for raising the temperature of the creek, but is instead probably helping to cool it with what little flow it has.
Though mostly passing through natural and planted forest buffers above its confluence with the Little Conewago, the main stem’s critically low baseflow makes it particularly susceptible to heat flux processes that raise stream temperatures in segments within the two or three large agricultural properties where owners have opted not to participate in partnerships to rehabilitate the waterway. The headwaters area, while largely within Pennsylvania State Game Lands, is interspersed with growing residential communities where potable water is sourced from hundreds of private and community wells—every one of them removing groundwater and contributing to the diminishing baseflow of the creek. Some of that water is discharged into the stream after treatment at the two municipal sewer plants in the upper Conewago. This effluent can become quite warm during processing and may have significant thermal impact when the stream is at a reduced rate of flow. A sizeable headwaters lake is seasonally flooded for recreation in Mount Gretna. Such lakes can function as effective mid-day collectors of solar (shortwave) radiation that both warms the water and expedites atmospheric exchange.
Though Conewago Creek (East) is classified as a trout-stocked fishery in its upper reaches in Lebanon County, its low baseflow and susceptibility to warming render it inhospitable to these coldwater fishes by late-spring/early summer.
The removal of two water supply dams on the headwaters of Hammer Creek at Rexmont eliminated a large source of temperature fluctuation on the waterway, but did little to address the stream’s exposure to radiant and convective heat flux processes as it meanders largely unprotected out of the forest cover of Pennsylvania State Game Lands and through high-intensity farmlands in the Lebanon Valley. Moderating the temperature to a large degree is the influx of karst water from Buffalo Springs, located about two miles upstream from this gauging station, and other limestone springs that feed tributaries which enter the Hammer from the east and north. Despite the cold water, the impact of the stream’s nearly total exposure to radiative and other warming heat flux processes can readily be seen in the graphic. Though still a coldwater fishery by temperature standards, it is rather obvious that rapid heating and other forms of impairment await these waters as they continue flowing through segments with few best management practices in place for mitigating pollutants. By the time Hammer Creek passes back through the Furnace Hills and Pennsylvania State Game Lands, it is leaning toward classification as a coolwater fishery with significant accumulations of sediment and nutrients. But this creek has a lot going for it—mainly, sources of cold water. A core group of enthusiastic landowners could begin implementing the best management practices and undertaking the necessary water quality improvement projects that could turn this stream around and make it a coldwater treasure. An organized effort is currently underway to do just that. Visit Trout Unlimited’s Don Fritchey Chapter and Donegal Chapter to learn more. Better yet, join them as a volunteer or cooperating landowner!
For coldwater fishes, the thousands of years since the most recent glacial maximum have seen their range slowly contract from nearly the entirety of the once much larger Susquehanna watershed to the headwaters of only our most pristine streams. Through no fault of their own, they had the misfortune of bad timing—humans arrived and found coldwater streams and the groundwater that feeds them to their liking. Some of the later arrivals even built their houses right on top of the best-flowing springs. Today, populations of these fishes in the region we presently call the Lower Susquehanna River Watershed are seriously disconnected and the prospect for survival of these species here is not good. Stream rehabilitation, groundwater management, and better civil planning and land/water stewardship are the only way coldwater fishes, and very possibly coolwater fishes as well, will survive. For some streams like Hammer Creek, it’s not too late to make spectacular things happen. It mostly requires a cadre of citizens, local government, project specialists, and especially stakeholders to step up and be willing to remain focused upon project goals so that the many years of work required to turn a failing stream around can lead to success.
You’re probably glad this look at heat flux processes in streams has at last come to an end. That’s good, because we’ve got a lot of work to do.
Birds Along the River’s Edge
Just as bare ground along a plowed road attracts birds in an otherwise snow-covered landscape, a receding river or large stream can provide the same benefit to hungry avians looking for food following a winter storm.
Here is a small sample of some of the species seen during a brief stop along the Susquehanna earlier this week.
Piscivorous Waterfowl Visiting Lakes and Ponds
Heavy rains and snow melt have turned the main stem of the Susquehanna and its larger tributaries into a muddy torrent. For fish-eating (piscivorous) ducks, the poor visibility in fast-flowing turbid waters forces them to seek better places to dive for food. With man-made lakes and ponds throughout most of the region still ice-free, waterfowl are taking to these sources of open water until the rivers and streams recede and clear.
With a hard freeze on the way, the fight for life will get even more desperate in the coming weeks. Lakes will ice over and the struggle for food will intensify. Fortunately for mergansers and other piscivorous waterfowl, high water on the Susquehanna is expected to recede and clarify, allowing them to return to their traditional environs. Those with the most suitable skills and adaptations to survive until spring will have a chance to breed and pass their vigor on to a new generation of these amazing birds.
Photo of the Day
Four Common Grasshoppers
Grasshoppers are perhaps best known for the occasions throughout history when an enormous congregation of these insects—a “plague of locusts”—would assemble and rove a region to feed. These swarms, which sometimes covered tens of thousands of square miles or more, often decimated crops, darkened the sky, and, on occasion, resulted in catastrophic famine among human settlements in various parts of the world.
The largest “plague of locusts” in the United States occurred during the mid-1870s in the Great Plains. The Rocky Mountain Locust (Melanoplus spretus), a grasshopper of prairies in the American west, had a range that extended east into New England, possibly settling there on lands cleared for farming. Rocky Mountain Locusts, aside from their native habitat on grasslands, apparently thrived on fields planted with warm-season crops. Like most grasshoppers, they fed and developed most vigorously during periods of dry, hot weather. With plenty of vegetative matter to consume during periods of scorching temperatures, the stage was set for populations of these insects to explode in agricultural areas, then take wing in search of more forage. Plagues struck parts of northern New England as early as the mid-1700s and were numerous in various states in the Great Plains through the middle of the 1800s. The big ones hit between 1873 and 1877 when swarms numbering as many as trillions of grasshoppers did $200 million in crop damage and caused a famine so severe that many farmers abandoned the westward migration. To prevent recurrent outbreaks of locust plagues and famine, experts suggested planting more cool-season grains like winter wheat, a crop which could mature and be harvested before the grasshoppers had a chance to cause any significant damage. In the years that followed, and as prairies gave way to the expansive agricultural lands that presently cover most of the Rocky Mountain Locust’s former range, the grasshopper began to disappear. By the early years of the twentieth century, the species was extinct. No one was quite certain why, and the precise cause is still a topic of debate to this day. Conversion of nearly all of its native habitat to cropland and grazing acreage seems to be the most likely culprit.
In the Mid-Atlantic States, the mosaic of the landscape—farmland interspersed with a mix of forest and disturbed urban/suburban lots—prevents grasshoppers from reaching the densities from which swarms arise. In the years since the implementation of “Green Revolution” farming practices, numbers of grasshoppers in our region have declined. Systemic insecticides including neonicotinoids keep grasshoppers and other insects from munching on warm-season crops like corn and soybeans. And herbicides including 2,4-D (2,4-Dichlorophenoxyacetic acid) have, in effect, become the equivalent of insecticides, eliminating broadleaf food plants from the pasturelands and hayfields where grasshoppers once fed and reproduced in abundance. As a result, few of the approximately three dozen species of grasshoppers with ranges that include the Lower Susquehanna River Watershed are common here. Those that still thrive are largely adapted to roadsides, waste ground, and small clearings where native and some non-native plants make up their diet.
Here’s a look at four species of grasshoppers you’re likely to find in disturbed habitats throughout our region. Each remains common in relatively pesticide-free spaces with stands of dense grasses and broadleaf plants nearby.
CAROLINA GRASSHOPPER
Dissosteira carolina
DIFFERENTIAL GRASSHOPPER
Melanoplus differentialis
TWO-STRIPED GRASSHOPPER
Melanoplus bivittatus
RED-LEGGED GRASSHOPPER
Melanoplus femurrubrum
Protein-rich grasshoppers are an important late-summer, early-fall food source for birds. The absence of these insects has forced many species of breeding birds to abandon farmland or, in some cases, disappear altogether.
Take a Deep Breath This Independence Day Weekend
The gasoline and gunpowder gang’s biggest holiday of the year has arrived yet again. Where does all the time go?
In observance of this festive occasion, we’ve decided to take a look at all the stuff that’s floating around in the atmosphere before all the motor travel, celebratory fires, and exciting explosions get underway.
We’ll start with the smoke from wildfires in Canada…
If you think that smoke accounts for all the particulate matter now obscuring skies in the northern half of the western hemisphere, then have a gander at this…
As you can see, natural processes are currently providing a plentiful load of particulates in our skies. There’s no real need to aggravate yourself and the situation by sitting in traffic or burning your groceries on the barbecue. And you can let those cult-like homeowner chores for later. After all, running the mower, whacker, and blower will only add to the airborne pollutants. While celebrating this Fourth of July, why risk mangling fingers on your throwing hand or catching the neighbor’s house on fire when you could just relax and quietly eat ice cream or watermelon? Yeah, that’s more like it.
The Value of Water
Are you worried about your well running dry this summer? Are you wondering if your public water supply is going to implement use restrictions in coming months? If we do suddenly enter a wet spell again, are you concerned about losing valuable rainfall to flooding? A sensible person should be curious about these issues, but here in the Lower Susquehanna River Watershed, we tend to take for granted the water we use on a daily basis.
This Wednesday, June 7, you can learn more about the numerous measures we can take, both individually and as a community, to recharge our aquifers while at the same time improving water quality and wildlife habitat in and around our streams and rivers. From 5:30 to 8:00 P.M., the Chiques Creek Watershed Alliance will be hosting its annual Watershed Expo at the Manheim Farm Show grounds adjacent to the Manheim Central High School in Lancaster County. According to the organization’s web page, more than twenty organizations will be there with displays featuring conservation, aquatic wildlife, stream restoration, Honey Bees, and much more. There will be games and custom-made fish-print t-shirts for the youngsters, plus music to relax by for those a little older. Look for rain barrel painting and a rain barrel giveaway. And you’ll like this—admission and ice cream are free. Vendors including food trucks will be onsite preparing fare for sale.
And there’s much more.
To help recharge groundwater supplies, you can learn how to infiltrate stormwater from your downspouts, parking area, or driveway…
…there will be a tour of a comprehensive stream and floodplain rehabilitation project in Manheim Memorial Park adjacent to the fair grounds…
…and a highlight of the evening will be using an electrofishing apparatus to collect a sample of the fish now populating the rehabilitated segment of stream…
…so don’t miss it. We can hardly wait to see you there!
The 2023 Watershed Expo is part of Lancaster Conservancy Water Week.
Forty Years Ago in the Lower Rio Grande Valley: Day Eight
Back in late May of 1983, four members of the Lancaster County Bird Club—Russ Markert, Harold Morrrin, Steve Santner, and your editor—embarked on an energetic trip to find, observe, and photograph birds in the Lower Rio Grande Valley of Texas. What follows is a daily account of that two-week-long expedition. Notes logged by Markert some four decades ago are quoted in italics. The images are scans of 35 mm color slide photographs taken along the way by your editor.
DAY EIGHT—May 28, 1983
“Bentsen State Park, Texas”
“Alarm at 6:00 A.M. After breakfast we traveled to Falcon State Park and toured the whole camp area, stopping many places to observe birds. We ran up a good list.”
And so we left what had been our home for the last several days and headed west. In the forty years since our departure that morning, Bentsen-Rio Grande State Park has experienced a number of operational changes. Today, it is a World Birding Center site. For conducting the seasonal hawk census, a tower has been erected to provide counters and observes with an unrestricted view above the treetops. If you wanted to camp in the park now, you would need reservations and would have to hike your gear in to one of only a few primitive campsites. Trailer and motor home accommodations no longer exist. A tram service is now available for touring the park by motor vehicle.
Falcon State Park is located along the east shore of Falcon Reservoir. There are no shade trees beneath which one can escape the scorching rays of the sun on a hot day. This is the easternmost section of the scrubland’s Tamaulipan Saline Thornscrub, a xeric plant community of head-high brush found only on clay soils with a particularly high salinity. Many of the plants look similar to other varieties of shrubs and small trees with which one may be familiar, except nearly all of them are covered with nasty thorns and prickles. And yes, there are cactus. You can’t make your way bushwhacking cross country without obtaining cuts, gashes, and scars to show for it. The Falcon State Recreation Area bird checklist published in 1977 has a nice description of the plants found there—mesquite, ebano, guaycan, blackbrush and catclaw acacia, granjeno, coyotillo, huisache, tasajillo, prickly pear, allthorn, cenizo, colima, and yucca. In the margins between the thornscrub growth, there is an abundance of grasses and wildflowers. On nearby ridges, Tamaulipan Calcareous Thornscrub, a similar xeric plant community, occupies soils with a higher content of calcium carbonate. Together, these communities comprise much of the Tamaulipan Mezquital ecoregion of scrublands in Starr County and western Hidalgo County in the Rio Grande valley of Texas.
After being greeted by a Greater Roadrunner at the campsite, we took a walk to the nearby shoreline of the reservoir. We spotted Olivaceous Cormorants perched on some dead limbs in the water nearby. Known today as Neotropic Cormorant (Phalacrocorax brasilianus), it is yet another specialty of the Rio Grande Valley. Elsewhere on or near the water—Cattle Egret, Great Egret, Black-bellied Whistling Duck, Osprey, Common Gallinule, Killdeer, Laughing Gull, Forster’s Tern (Sterna forsteri), Least Tern, and Caspian Tern were seen.
In the thornscrub around the campground, which, like Bentsen-Rio Grande State Park, we had pretty much to ourselves, we saw Scissor-tailed Flycatcher, Curve-billed Thrasher, White-winged Dove, Mourning Dove, Ground Dove, Inca Dove, and White-tipped Dove. A single Chihuahuan Raven was a fly by. We saw and smelled several road-killed Nine-banded Armadillos (Dasypus novemcinctus), but never found one alive.
Then, it started to rain. Not just a shower, but a soaker that persisted through much of the day. Rainy days can make for great birding, so we kept at it. Unfortunately, such days aren’t too ideal for photography, so we did only what we could without ruining our equipment.
“Finally we drove to the spillway of the dam and parked.”
Falcon Dam was another of the numerous flood-control projects built on the Rio Grande during the middle of the twentieth century. Behind it, Falcon Reservoir stores water for irrigation and operation of a hydroelectric generating station located within the dam complex. Construction of the dam and power plant was a joint venture shared by Mexico and the United States. The project was dedicated by Presidents Adolfo Ruiz Cortines and Dwight D. Eisenhower in 1953.
Rainy days aside, the route precipitation takes to reach the Falcon Reservoir and the Lower Rio Grande Valley includes hundreds of miles through arid grasslands and scrublands. Along the way, much of that water is lost to natural processes including evaporation and aquifer recharge, but an increasing percentage of the volume is being removed by man for civil, industrial, and agricultural uses. Can the Rio Grande and its tributaries continue to meet demand?
“On the way in we saw and photographed an apparent sick or injured Swainson’s Hawk. We approached it very close.”
“At the spillway we sat in the camper, except when the rain slackened, then we stood out and watched in vain for the Green or Ringed Kingfisher, which we never did see.”
At the spillway House Sparrows, Rough-winged Swallows, and Cliff Swallows were nesting on the dam, the latter two species grabbing flying insects above the waters of the Rio Grande.
“I made dinner here at this spillway and we continued to watch. The rain almost stopped, so we walked down the road about 1 1/2 miles, during which time we saw a lifer for Harold — Hook-billed Kite. We followed Father Tom’s directions to a spot for the Ferruginous Owl — no luck.”
“Back at the spillway we had supper and then repeated the hike — no Ferruginous Owl, but a Barn Owl and Great Horned Owl. Back to our #201 campsite and wrote up the day’s log.”
Trees along the river provided habitat for orioles and other species. Since the rain had subsided, we decided to see what might come out and begin feeding. Soon, we not only saw an Altamira Oriole, but found Hooded Oriole (Icterus cucullatus) and the yellow and black tropical species, Audubon’s Oriole (Icterus graduacauda), formerly known as Black-headed Oriole. Three species of orioles on a backdrop of lush green subtropical foliage, it was magnificent.
Along the dirt road below the dam, the mix of scrubland and subtropical riparian forest made for excellent birding. We not only found a soaring Hook-billed Kite, one of the target birds for the trip, but we had good looks at both a Great Horned Owl, then a Barn Owl (Tyto alba) that we flushed from the bare ground in openings among the vegetation as we walked the through. Both had probably pounced on some sort of small prey species prior to our arrival. Because there are seldom crows or ravens to bother them, owls here are more active during than day than they are elsewhere. The subject of this afternoon’s intensive search, the elusive and diminutive Ferruginous Pygmy Owl (Glaucidium brasilianum), is routinely diurnal. Other sightings on our two walks included Turkey Vulture, Black Vulture, White-tailed Kite, Northern Bobwhite, Yellow-billed Cuckoo, Golden-fronted Woodpecker, Ladder-backed Woodpecker, Couch’s Kingbird, Brown-crested Flycatcher, Green Jay, Black-crested Titmouse, Mockingbird, Long-billed Thrasher, Great-tailed Grackle, Bronzed Cowbird, Northern Cardinal, and Painted Bunting.
The day finished as so many others had earlier during the trip—with insect-hunting Common Nighthawks calling from the skies around our campsite.
How Much Rainwater Runs Off Your Roof During a Storm?
During the spare time you have on a rainy day like today, you may have asked yourself, “Just how much water do people collect with those rain barrels they have attached to their downspouts?” That’s a good question. Let’s do a little math to figure it out.
First, we need to determine the area of the roof in square feet. There’s no need to climb up there and measure angles, etc. After all, we’re not ordering shingles—we’re trying to figure out the surface area upon which rain will fall vertically and be collected. For our estimate, knowing the footprint of the building under roof will suffice. We’ll use a very common footprint as an example—1,200 square feet.
40′ x 30′ = 1,200 sq. ft.
By dividing the area of the roof by 12, we can calculate the volume of water in cubic feet that is drained by the spouting for each inch of rainfall…
1,200 ÷ 12 = 100 cu. ft. per inch of rainfall
Next, we multiply the volume of water in cubic feet by 7.48 to convert it to gallons per inch of rainfall…
100 x 7.48 = 748 gallons per inch of rainfall
That’s a lot of water. Just one inch of rain could easily fill more than a single rain barrel on a downspout. Many homemade rain barrels are fabricated using recycled 55-gallon drums. Commercially manufactured ones are usually smaller. Therefore, we can safely say that in the case of a building with a footprint of 1,200 square feet, an array of at least 14 rain barrels is required to collect and save just one inch of rainfall. Wow!
Why send that roof water down the street, down the drain, down the creek, or into the neighbors property? Wouldn’t it be better to catch it for use around the garden? At the very least, shouldn’t we be infiltrating all the water we can into the ground to recharge the aquifer? Why contribute to flooding when you and I are gonna need that water some day? Remember, the ocean doesn’t need the excess runoff—it’s already full.
Three Mile Island and Agnes: Fifty Years Later
Fifty years ago this week, the remnants of Hurricane Agnes drifted north through the Susquehanna River basin as a tropical storm and saturated the entire watershed with wave after wave of torrential rains. The storm caused catastrophic flooding along the river’s main stem and along many major tributaries. The nuclear power station at Three Mile Island, then under construction, received its first major flood. Here are some photos taken during the climax of that flood on June 24, 1972. The river stage as measured just upstream of Three Mile Island at the Harrisburg gauge crested at 33.27 feet, more than 10 feet above flood stage and almost 30 feet higher than the stage at present. At Three Mile Island and Conewago Falls, the river was receiving additional flow from the raging Swatara Creek, which drains much of the anthracite coal region of eastern Schuylkill County—where rainfall from Agnes may have been the heaviest.
Pictures capture just a portion of the experience of witnessing a massive flood. Sometimes the sounds and smells of the muddy torrents tell us more than photographs can show.
Aside from the booming noise of the fuel tank banging along the rails of the south bridge, there was the persistent roar of floodwaters, at the rate of hundreds of thousands of cubic feet per second, tumbling through Conewago Falls on the downstream side of the island. The sound of the rapids during a flood can at times carry for more than two miles. It’s a sound that has accompanied the thousands of floods that have shaped the falls and its unique diabase “pothole rocks” using abrasives that are suspended in silty waters after being eroded from rock formations in the hundreds of square miles of drainage basin upstream. This natural process, the weathering of rock and the deposition of the material closer to the coast, has been the prevailing geologic cycle in what we now call the Lower Susquehanna River Watershed since the end of the Triassic Period, more than two hundred million years ago.
More than the sights and sounds, it was the smell of the Agnes flood that warned witnesses of the dangers of the non-natural, man-made contamination—the pollution—in the waters then flowing down the Susquehanna.
Because they float, gasoline and other fuels leaked from flooded vehicles, storage tanks, and containers were most apparent. The odor of their vapors was widespread along not only along the main stem of the river, but along most of the tributaries that at any point along their course passed through human habitations.
Blended with the strong smell of petroleum was the stink of untreated excrement. Flooded treatment plants, collection systems overwhelmed by stormwater, and inundated septic systems all discharged raw sewage into the river and many of its tributaries. This untreated wastewater, combined with ammoniated manure and other farm runoff, gave a damaging nutrient shock to the river and Chesapeake Bay.
Adding to the repugnant aroma of the flood was a mix of chemicals, some percolated from storage sites along watercourses, and yet others leaking from steel drums seen floating in the river. During the decades following World War II, stacks and stacks of drums, some empty, some containing material that is very dangerous, were routinely stored in floodplains at businesses and industrial sites throughout the Susquehanna basin. Many were lifted up and washed away during the record-breaking Agnes flood. Still others were “allowed” to be carried away by the malicious pigs who see a flooding stream as an opportunity to “get rid of stuff”. Few of these drums were ever recovered, and hundreds were stranded along the shoreline and in the woods and wetlands of the floodplain below Conewago Falls. There, they rusted away during the next three decades, some leaking their contents into the surrounding soils and waters. Today, there is little visible trace of any.
During the summer of ’72, the waters surrounding Three Mile Island were probably viler and more polluted than at any other time during the existence of the nuclear generating station there. And little, if any of that pollution originated at the facility itself.
The Susquehanna’s floodplain and water quality issues that had been stashed in the corner, hidden out back, and swept under the rug for years were flushed out by Agnes, and she left them stuck in the stinking mud.
Photo of the Day
Pick Up and Get Out of the Floodplain
The remnants of Hurricane Ida are on their way to the Lower Susquehanna River Watershed. After making landfall in Louisiana as a category 4 storm, Ida is on track to bring heavy rain to the Mid-Atlantic States beginning tonight.
Rainfall totals are anticipated to be sufficient to cause flooding in the lower Susquehanna basin. As much as six to ten inches of precipitation could fall in parts of the area on Wednesday.
Now would be a good time to get all your valuables and junk out of the floodways and floodplains. Move your cars, trucks, S.U.V.s, trailers, and boats to higher ground. Clear out the trash cans, playground equipment, picnic tables, and lawn furniture too. Get it all to higher ground. Don’t be the slob who uses a flood as a chance to get rid of tires and other rubbish by letting it just wash away.
Flooding not only has economic and public safety impacts, it is a source of enormous amounts of pollution. Chemical spills from inundated homes, businesses, and vehicles combine with nutrient and sediment runoff from eroding fields to create a filthy brown torrent that rushes down stream courses and into the Susquehanna. Failed and flooded sewage facilities, both municipal and private, not only pollute the water, but give it that foul odor familiar to those who visit the shores of the river after a major storm. And of course there is the garbage. The tons and tons of waste that people discard carelessly that, during a flood event, finds its way ever closer to the Susquehanna, then the Chesapeake, and finally the Atlantic. It’s a disgraceful legacy.
Now is your chance to do something about it. Go out right now and pick up the trash along the curb, in the street, and on the sidewalk and lawn—before it gets swept into your nearby stormwater inlet or stream. It’s easy to do, just bend and stoop. While you’re at it, clean up the driveway and parking lot too.
We’ll be checking to see how you did.
And remember, flood plains are for flooding, so get out of the floodplain and stay out.
Smoke from a Distant Fire
Have a look at these images of the smoke plume being generated by fires in forests and other wildlands in the western United States.
While viewing these amazing images, consider for a moment the plight of migrating birds. Each one struggles to survive the energy-depleting effects of wind, distance, storm, cold, drought, dust, and sometimes even smoke as it strives to reach its breeding grounds each spring and its wintering grounds each fall. Natural and man-made effects can cause migrating birds to become disoriented. Songbirds are known to become lost at sea. Others strike objects including buildings and radio towers, particularly when visibility is impaired. The dangers seem endless.
For migrating birds, places of refuge where they can stop to feed and rest during their long journeys are essential to their survival. For species attempting flights through conditions as extreme as those seen in these images, there is the potential for significant loss of life, particularly among the birds with less than optimal stores of energy.
Get Out of the Floodplain…And Get Your Stuff Out Too!
After threading its way through waves of Saharan dust plumes, Tropical Storm Isaias, or the remnants thereof, is making a run up the eastern seaboard toward the lower Susquehanna watershed.
Heavy rain and flooding appears likely, particularly east of the Susquehanna. Now might be a good time to clean up the trash and garbage that could clog nearby storm drains or otherwise find its way into your local waterway. NOW is the time to get all your stuff out of the floodplain! The car, the camper, the picnic table, the lawn furniture, the kid’s toys, the soda bottles, the gas cans, the lawn chemicals, the Styrofoam, and all that other junk you’ve piled up. Get that stuff cleaned up and out of the floodway. And of course, get you and your pets out of the there too!
Saharan Dust Cloud: A Tale of Two Tropical Storms
Have a look at the effect of the Saharan dust event of 2020 on tropical storm and hurricane development…
Sunset Over the Gettysburg Basin
This evening over the eastern Gettysburg Basin in the lower Susquehanna valley…
Tropical Storm Fay
Saharan Dust Cloud: Out of the Loop
Dust continues to be carried aloft on dry updrafts over the Sahara Desert. The plume is presently stretching for thousands of miles due west across the tropical Atlantic into the Pacific, leaving the United States out of the loop—at least for now.
With no dry air to spoil the fun, the warm waters of the Gulf Stream off the coast of North Carolina are spawning some convective clouds in a low pressure system that could become tropical within the next day or so.
Now that the heat and humidity is upon us, why not get out and take a look at the damselflies and dragonflies that inhabit the ponds, wetlands, and waterways of the lower Susquehanna watershed? These flying insects thrive in sultry weather and some species will breed in a body of water as small as a garden pond—as long as it is free of large fish. Check out some of the species found locally by clicking on the “Damselflies and Dragonflies” tab at the top of this page. We’ll be adding more photos and species soon.
Saharan Dust: Atlantic to Pacific
The overcast of Saharan dust that was as close to the Susquehanna valley as the Appalachians of Virginia and West Virginia has, for now, dissipated. This week, the plume of particulates followed a hairpin route originating with the Saharan updrafts, then flowing across the Atlantic and Caribbean only to make a 180-degree turn along the coastal areas of the Gulf of Mexico to return to the Atlantic via Florida, where it then drifted northeast—loosely following the path of the Gulf Stream.
During the last several days, portions of the dust layer have been carried due west across Mexico into the Pacific.
For the Susquehanna region, a low pressure system is in place for Independence Day. In the image below, the cloud of hazy humid air seen blanketing the northeast coast consists of air pollution, pollen, mold spores, “domestic particulates”, condensing water vapor—and little if any red-brown Saharan dust. For the gasoline and gunpowder gang, it’ll be a sticky-hot summer weekend for the celebration of their favorite holiday. Kaboom!
Saharan Dust Plume Approaching the Mid-Atlantic States
The latest satellite image shows the Saharan dust cloud now covering much of the southern United States including most of West Virginia and the Appalachians of North Carolina and Virginia. Due to the density of the particulate matter, air quality warnings have been issued by the National Weather Service for South Carolina, western North Carolina, and the Atlanta metro area.
As the plume of dust drifts east from the southern United States into the Atlantic…
…yet more can be seen coming west from the African Sahara into the Caribbean Sea. It ain’t over til’ it’s over.
Saharan Dust Cloud Arrives on Gulf Coast
The Saharan dust cloud made its way across the Caribbean Sea and the Gulf of Mexico to reach the skies above the shores of the United States by mid-day yesterday. There, as seen in the image below, the dusty air mass encountered a storm that caused heavy rains and flooding in Louisiana.
By this morning, the leading edge of the dust cloud encircled the gulf coastline and had spread east across northern Florida into the Atlantic. The latest satellite image (below) shows a dense dry core of the system covering the western Caribbean, the central gulf, and the Yucatan Peninsula.
For the eastern Caribbean, there is a break in the action. But a second wave is on the way.
Start watching the skies. Look for any increase in haze during the coming days. Then too, it might be interesting to compare the sunsets for one evening to the next. Over successive nights, take note of the stars and planets in the night sky. If the Saharan dust reaches the lower Susquehanna region with sufficient density, you may find that only the brightest celestial objects are discernible.
Saharan Dust Cloud Update
Dust carried aloft by hot dry air over the Sahara Desert continues to stream west into the Caribbean Sea. In this image, a dense band of the airborne particles can be seen passing over the Dominican Republic, Puerto Rico, and the Leeward Islands. North of these islands, note the development of puffy white clouds outside the border of the dust storm. The Saharan air mass appears to be effectively limiting convective cloud development within much of its course. No hurricanes for now.
What is the impact of the Saharan dust cloud on the affected islands? In Puerto Rico, the National Weather Service is forecasting visibility of four to eight miles in widespread haze through at least the next twenty-four hours. For the coming several days, the forecast daily high temperatures are expected to be in the low eighties—several degrees cooler than the normal high eighties and low nineties.
Stay tuned, we’ll keep an eye on the plume as it moves into the Gulf of Mexico.
Dirty Summer 2020?
Summer is nigh upon us. With the solstice just hours away, it might be fun to have a look at a satellite view of the earth while the south pole lies plunged into days of endless night, and the north pole suffers none.
In the image above, darkness can be seen engulfing the southern Atlantic Ocean and southernmost Chile. The latter is the longitudinal equivalent of the lower Susquehanna valley. Today, it experiences nightfall more than five hours earlier than we, heralding the first day of our summer, and of their winter.
Just to the north of the South American continent, note the enormous tan-colored cloud over the Atlantic. What is that? From whence doth that cloud come?
Closer inspection reveals an enormous plume of dust rising from the Sahara Desert in Africa and drifting west approaching the Leeward Islands of the Caribbean. (In the image above, Africa can be seen outlined in the darkness along the east horizon) Look closely and you’ll notice that the dust is obscuring the white clouds below it, indicating that it has reached altitudes high in the atmosphere. Particle fallout from Saharan dust clouds is known to fertilize tropical forests—including the Amazon (bottom center of image). Because they are composed of wind blown particles and not water vapor, Saharan dust clouds carry aloft not only minerals and nutrients, but microscopic and macroscopic life too.
Is this particular Saharan dust cloud going to impact the Amazon? What might the meteorological and biological effects of this cloud be if it continues into the Caribbean and even into the United States? Might we be showered by little pieces of the Sahara this summer? Will we see spectacular sunrises and sunsets? Time will tell.
The Colorful Birds Are Here
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!
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.
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.
Tornado: Close Call
Severe thunderstorms with hail, torrential rain, and flooding passed through the lower Susquehanna valley this evening. The National Weather Service in State College issued a warning for a radar-indicated tornado shown crossing the Susquehanna River downstream of Conewago Falls at 6:55 P.M. E.D.T. The rascal revealed itself about ten minutes later.
The staff at a retirement community west of Elizabethtown was on the alert and had the fortitude to quickly sound a warning siren. It was howling away as this image was taken. What could have been a disaster was instead a spectacular close call.
2018 Migration Count Summary: Rainout
If you were a regular visitor to this website during the autumn of 2017, you will recall the proliferation of posts detailing the bird migration at Conewago Falls during the season. The lookout site among the Pothole Rocks remained high and dry for most of the count’s duration.
In the fall of 2018, those lookout rocks were never to be seen. There was to be no safe perch for a would-be observer. There was no attempt to conduct a tally of passing migrants. If you live in the lower Susquehanna River drainage basin, you know why—rain—record setting rain.
Put Up the White Flag
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.
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.
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.
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.
They Call Me the Wanderer
It’s been an atypical summer. The lower Susquehanna River valley has been in a cycle of heavy rains for over a month and stream flooding has been a recurring event. At Conewago Falls, the Pothole Rocks have been inundated for weeks. The location used as a lookout for the Autumn Migration Count last fall is at the moment submerged in ten feet of roaring water. Any attempt to tally the migrants which are passing thru in 2018 will thus be delayed indefinitely. Of greater import, the flooding at Conewago Falls is impacting many of the animals and plants there at a critical time in their annual life cycle. Having been displaced from its usual breeding sites on the river, one insect species in particular seems to be omnipresent in upland areas right now, and few people have ever heard of it.
So, you take a cruise in the motorcar to your favorite store and arrive at the sprawling parking lot. Not wishing to have your doors dented or paint chipped because you settled for a space tightly packed among other shopper’s conveyances, you park out there in the “boondocks”. You know the place, the lightly-used portion of the lot where sometimes brush grows from cracks in the asphalt and you must be on alert for impatient consumers who throttle-up to high speeds and dash diagonally across the carefully painted grids on the pavement to reach their favorite parking destination in the front row. Coming to a stop, you take the car out of gear, set the brake, disengage the safety belt, and gather your shopping list. You grasp the door handle and, not wanting to be flattened by one of the aforementioned motorists, you have a look around before exiting.
It was then that you saw the thing, hovering above your shiny bright hood. For a brief moment, it seemed to be peering right through the windshield at you with big reddish-brown eyes. In just a second or two, it turned its whole bronze body ninety degrees to the left and darted away on its cellophane wings. Maybe you didn’t really get a good look at it. It was so fast. But it certainly was odd. Oh well, time to walk inside a grab a few provisions. Away you go.
Upon completion of your shopping, you’re taking the long stroll back to your car and you notice more of these peculiar creatures. Two are coupled together and are hovering above someone’s automobile hood, then they drop down, and the lower of the two taps its abdomen on the paint. You ask yourself, “What are these bizarre things?”
Meet the Wandering Glider (Pantala flavescens), also known as the Globe Wanderer or Globe Skimmer, a wide-ranging dragonfly known to occur on every continent with the exception of Antarctica.
Wandering Gliders travel the globe, and as such are accomplished fliers. Adults spend most of the day on the wing, feeding upon a variety of flying insects. Days ago, I watched several intercepting a swarm of flying ants. As fast as ants left the ground they were grabbed and devoured by the gliders. Wandering Gliders are adept at taking day-flying mosquitos, often zipping stealthily past a person’s head or shoulders to grab one of the little pests—the would-be skeeter victim usually unaware of the whole affair.
Due to their nomadic life history, Wandering Gliders are opportunists when breeding and will lay eggs in most any body of freshwater. Their larvae do not overwinter prior to maturity; adults can be expected in a little more than one to two months. Repetitive flooding in the Lower Susquehanna River Watershed this summer may be reducing the availability of the best local breeding sites for this species—riverine, stream, and floodplain pools of standing water with prey. This may explain why thousands of Wandering Gliders are patrolling parking lots, farmlands, and urban areas this summer. And it’s the likely reason for their use of puddles on asphalt pavement, on rubber roofs, and in fields as places to try to deposit eggs. Unfortunately, they may be as likely to succeed there as they are on your motor vehicle hood.
At this time a year ago, the airspace above the Diabase Pothole Rocks at Conewago Falls was jammed with territorial male Wandering Gliders. Each male hovered at various locations around his breeding territory consisting of pools and water-filled potholes. Intruders would quickly be dispatched from the area, then the male would resume his patrols from a set of repetitively-used hovering positions about six feet above the rocks. Mating and egg-laying continued into late September. The larvae, also called nymphs or naiads, were readily observed in many pools and potholes in early October and the emergence of juveniles was noted in mid-October. The absence of flooding, the mild autumn weather, and the moderation of water temperatures in the pools and potholes courtesy of the sun-drenched diabase boulders helped to extend the 2017 breeding season for Wandering Gliders in Conewago Falls. They aren’t likely to experience the same favor this year, but their great ability to travel and adapt should overcome this momentary misfortune.
Shocking Fish Photos!
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.
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.
Essential Ice
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.
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.
Eighteen, and I Like It
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.
Strangers In The Night
We all know that birds (and many other animals) migrate. It’s a survival phenomenon which, above all, allows them to utilize their mobility to translocate to a climate which provides an advantage for obtaining food, enduring seasonal weather, and raising offspring.
In the northern hemisphere, most migratory birds fly north in the spring to latitudes with progressively greater hours of daylight to breed, nest, and provide for their young. In the southern hemisphere there are similar movements, these to the south during their spring (our autumn). The goal is the same, procreation, though the landmass offering sustenance for species other than seabirds is limited “down under”. Interestingly, there are some seabirds that breed in the southern hemisphere during our winter and spend our summer (their winter) feeding on the abundant food sources of the northern oceans.
Each autumn, migratory breeding birds leave their nesting grounds as the hours of sunlight slowly recede with each passing day. They fly to lower latitudes where the nights aren’t so long and the climate is less brutal. There, they pass their winter season.
Food supply, weather, the start/finish of the nesting cycle, and other factors motivate some birds to begin their spring and autumn journeys. But overall, the hours of daylight and the angle of the sun prompt most species to get going.
But what happens after birds begin their trips to favorable habitats? Do they follow true north and south routes? Do they fly continuously, day and night? Do they ease their way from point to point, stopping to feed along the way? Do they all migrate in flocks? Well, the tactics of migration differ widely from bird species to species, from population to population, and sometimes from individual to individual. The variables encountered when examining the dynamics of bird migration are seemingly endless, but fascinatingly so. Bird migration is well-studied, but most of its intricacies and details remain a mystery.
Consider for a moment that just 10,000 years ago, an Ice Age was coming to an end, with the southernmost edge of the most recent glaciers already withdrawn into present-day Canada from points as near as the upper Susquehanna River watershed. Back then, the birds migrating to the lower portion of the drainage basin each spring probably weren’t forest-dwelling tropical warblers, orioles, and other songbirds. The migratory birds that nested in the lower Susquehanna River valley tens of millennia ago were probably those species found nesting today in taiga and tundra much closer to the Arctic Circle. And the ancestors of most of the tropical migrants that nest here now surely spent their entire lives much closer to the Equator, finding no advantage by journeying to the frigid Susquehanna valley to nest. It’s safe to say that since those times, and probably prior to them, migration patterns have been in a state of flux.
During the intervening years since the great ice sheets, birds have been able to adapt to the shifts in their environment on a gradual basis, often using their unmatched mobility to exploit new opportunities. Migration patterns change slowly, but continuously, resulting in differences that can be substantial over time. If the natural transformations of habitat and climate have kept bird migration evolving, then man’s impact on the planet shows great potential to expedite future changes, for better or worse.
Now, let’s look at two different bird migration strategies, that of day-fliers or diurnal migrants, and that of night-fliers, the nocturnal migrants.
Diurnal migrants are the most familiar to people who notice birds on the move. The majority of these species have one thing in common, some form of defense to lessen the threat of becoming the victim of a predator while flying in daylight. Of course the vultures, hawks, and eagles fly during the day. Swallows and swifts employ speed and agility on the wing to avoid becoming prey, as do hummingbirds. Finches have an undulating flight, never flying on a horizontal plane, which makes their capture more difficult. Other songbirds seen migrating by day, Red-winged Blackbirds for example, congregate into flocks soon after breeding season to avoid being alone. Defense flocks change shape constantly as birds position themselves toward the center and away from the vulnerable fringes of the swarm. The larger the flock, the safer the individual. For a lone bird, large size can be a form of protection against all but the biggest of predators. Among the more unusual defenses is that of birds like Indigo Buntings and other tropical migrants that fly across the Gulf of Mexico each autumn (often completing a portion of the flight during the day), risking exhaustion at sea to avoid the daylight hazards, including numerous predators, found in the coastal and arid lands of south Texas. Above all, diurnal migrants capture our attention and provide a spectacle which fascinates us. Perhaps diurnal migrants attract our favor because we can just stand or sit somewhere and watch them go by. We can see, identify, and even count them. It’s fantastic.
What about a bird like the Canada Goose (Branta canadensis)? It is often seen migrating in flocks during the day (the truly migratory ones flying much higher than the local year-round resident “transplants”), but then, during the big peak movements of spring and fall, they can be heard overhead all through the night. Perhaps the Canada Goose and related waterfowl bridge the gap between day and night, introducing us to the secretive starlight and moonshine commuters, the nocturnal migrants.
The skies are sometimes filled with thousands of them, mostly small perching birds and waders. These strangers in the night fly inconspicuously in small groups or individually, and most can be detected when passing above us only when heard making short calls to remain in contact with their travel partners. They need not worry about predators, but instead must have a method of finding their way. Many, like the Indigo Bunting, can navigate by the stars, a capability which certainly required many generations to refine. The nocturnal migrants begin moving just after darkness falls and ascend without delay to establish a safe flight path void of obstacles (though lights and tall structures can create a deadly counter to this tactic). Often, the only clue we have that a big overnight flight has occurred is the sudden appearance of new bird species or individuals, on occasion in great numbers, in a place where we observe regularly. Just days ago, the arrival of various warbler species at Conewago Falls indicated that there was at least a small to moderate movement of these birds during previous nights.
In recent years, the availability of National Weather Service radar has brought the capability to observe nocturnal migrants into easy reach. Through the night, you can log on to your local National Oceanic and Atmospheric Administration’s National Weather Service radar page (State College for the Conewago Falls area) and watch on the map as the masses of migrating bird pass through the sweep of the radar beam. As they lift off just after nightfall, rising birds will create an echo as they enter the sweeping beam close to the radar site. Then, due to the incline of the transmitted signal and the curvature of the earth, migrants will be displayed as an expanding donut-like ring around the radar’s map location as returns from climbing birds are received from progressively higher altitudes at increasing distances from the center of the site’s coverage area. On a night with a local or regional flight, several radar locations may show signs of birds in the air. On nights with a widespread flight, an exodus of sorts, the entire eastern half of the United States may display birds around the sites. You’ll find the terrain in the east allows it to be well-covered while radars in the west are less effective due to the large mountains. At daybreak, the donut-shaped displays around each radar site location on the map contract as birds descend out of the transmitted beam and are no longer detected.
Weather systems sometimes seem to motivate some flights and stifle others. The first example seen below is a northbound spring exodus, the majority of which is probably migrants from the tropics, the Neotropical migrants, including our two dozen species of warblers. A cold front passing into the northeastern United States appears to have stifled any flight behind it, while favorable winds from the southwest are motivating a heavy concentration ahead of the front.
The second and third examples seen below are an autumn nocturnal migration movement, probably composed of many of the same tropics-bound species which were on the way north in the previous example. Note that during autumn, the cold front seems to motivate the flight following its passage. Ahead of the front, there is a reduced and, in places, undetectable volume of birds. The two images below are separated by about 42 hours.
You can easily learn much more about birds (and insects and bats) on radar, including both diurnal and nocturnal migrants, by visiting the Clemson University Radar Ornithology Laboratory (CUROL) website. There you’ll find information on using the various mode settings on NEXRAD (Next-Generation Radar) to differentiate between birds, other flying animals, and inanimate airborne or grounded objects. It’s superbly done and you’ll be glad you gave it a try.
SOURCES
Clemson University Radar Ornithology Laboratory (CUROL) website: http://virtual.clemson.edu/groups/birdrad/ as accessed September 6, 2017.