Part 1 of our climate series starts by confronting the tough realities that we face in an ever-warming planet and explores how the climate crisis is uniquely impacting the Potomac River and our communities.
Published June 28, 2021
A New Climate Reality in the Potomac River Region
This was no ordinary summer shower.
During the morning of July 8, 2019, darkened skies opened up and drenched the greater Washington, DC metro area. Taking the region by surprise, the super storm dumped a month’s worth of rain – a staggering 3.3 inches of precipitation – in just four hours.
Some areas reported even higher rainfall totals with 6.3 inches of rain recorded near Frederick, Maryland.
Inundated by the deluge, the Potomac River and local streams quickly flooded low-lying areas and left some drivers stranded on the roofs of their cars. The severity of the storm prompted the National Weather Service to declare its first-ever flash flood emergency in the Washington, DC region.
Scenes of historic flooding and storm damage often come to mind when we think about the way climate change is impacting the Potomac River region. And that’s for good reason. In the last decade, super storms have left Alexandria, Ellicott City, and other shoreline cities underwater and communities reeling in the wake of costly property and infrastructure damage.
Taking the region by surprise, the super storm dumped a month’s worth of rain – a staggering 3.3 inches of precipitation – in just four hours.
The July 2019 super storm had less than a 1% chance of happening and is considered worse than a 1-in-100-year storm and yet…a year later our region experienced another super storm.
On September 10, 2020, a half foot of rain fell in Washington, DC, causing the levels of local streams to rise eight feet in one hour. Emergency responders in Montgomery County, Maryland received 150 calls of motorists stuck in high water or needing water rescues.
The warming atmosphere is making our region more susceptible to extreme weather and flooding – but is there more to the climate story in our region?
Let’s first look at global climate trends and understand how they compare to patterns we’re experiencing in the Potomac River region.
We’ll confirm what the scientific community (and likely you, the reader) has known with certainty for some time:
Global and regional temperatures are rising at an alarming rate and only bold and immediate actions will save us from the worst-case scenarios.
Driven by cross-sector industrial pollution and exacerbated by mass deforestation, a thickening blanket of carbon dioxide (CO2) and other greenhouse gasses in our atmosphere are trapping heat and causing the planet to warm more than is natural. Global concentrations of CO2 – the main culprit -- are at levels (412 ppm) the planet hasn’t experienced in 3 million years.
In other words, the last time CO2 levels were this high was during the Pliocene epoch, when Mastodons roamed North America.
Average global temperatures have risen by 2.16°F (1.2°C) since the 1880s. The United Nations Paris Agreement commits to keeping Earth’s average temperature from rising above 3.6°F (2°C) this century but current warming trends are not promising. The Intergovernmental Panel on Climate Change (IPCC) 2018 Special Report on Global Warming estimates that average global temperatures will increase 2.7°F (1.5°C) between 2030-2050s, coming dangerously close to the UN limit within a human lifetime.
If greenhouse gas emissions continue to increase throughout the century, the IPCC projects an unthinkable average global temperature increase of 8.8°F (4.9°C) by 2100.
Anne Stoner, co-author of the ATMOS 2015 climate projections study which incorporated the IPCC’s emission scenarios, warns that, “The worst-case scenario is likely if we continue with business-as-usual, without regulating emissions to a greater extent and switching many of our energy sources to renewable energy. Some scientists think it could go even higher if we do not make any changes, because people are becoming more and more dependent on the use of fossil fuels.”
The effects of a warming atmosphere are not uniform across the globe, but climate research helps identify cycles and trends over time. Overall, weather patterns will become more extreme: wet areas will become wetter and dry areas in the mid-high latitudes will become dryer in the coming years and decades.
It may feel like the Potomac River Region is removed from the worst climate crises -- glacial melt, scorching wildfires, prolonged droughts, etc. – but the truth is we are already experiencing the impacts of a warming climate.
Rising heat, warming waters, and extreme weather are taxing the environment and our communities in this region. These hostile conditions are expected to become worse in the coming years and decades if we continue with business as usual.
Washington, DC is coming off its hottest decade on record (2011-2019)* and temperature rises have been observed in every state within the Potomac River watershed. Citation
ATMOS Research and Consulting for Kleinfelder 2015 climate projections based on global emission scenarios and historic temperature data at three District sites: Dalecaria Reservoir, the National Arboretum, and Washington National Airport
In 2015, ATMOS published local climate projections based on a range of future emission scenarios and possible temperature changes in the greater Washington, DC area. The models factored in an urban heat island effect, a phenomenon where dense impervious surfaces (paved areas and rooftops) and sparse vegetation trap heat in cities.
In every ATMOS model – ranging from low to high emission scenarios – local temperatures are projected to increase. Alarmingly, the number of days when the heat index tops 95°F in the nation’s capital may double by mid-century and triple by 2080.
Historically, Washington, DC has experienced an average of 11 extreme heat days per year when the daily temperature exceeds 95°F and 30 days per year when the heat index indicated it felt over 95°F. ATMOS’s research projects that the DC region may experience upwards of 70-80 extreme heat index days annually by 2050 and up to 105 days of extreme heat annually before the end of the century – longer than the length of summer! This drastically increases the potential for heat stroke and other public health crises (Hayhoe & Stoner, 2015).
*Data for Washington, DC represents average temperatures recorded at Washington National Airport from 1947 to 2014.Data from 1901 through 2014 reviewed by the North Carolina Institute for Climate Studies (NCICS) for the National Oceanic and Atmospheric Administration (NOAA) National Centers for Environmental Information (NCEI)
“If you take any group of five years, they are generally warmer than the previous five years,” said Andrew Elmore of the University of Maryland Center for Environmental Science adding, “A consistent warming trend [is] happening over a really large portion of the Bay.”
Following a heat wave in in July 2019, the Potomac River felt like bath water. Scientists from the University of Maryland Center for Environmental Science measured a record water temperature of 94°F at Little Falls, several miles upstream from Washington, DC.
Warmer streams and rivers can adversely impact aquatic life. Warm water holds less dissolved oxygen than cooler water, creating harmful conditions for fish and aquatic species that depend on healthy oxygen levels to survive. Warm waters also promote algal blooms which lower dissolved oxygen levels and foster bacterial growth that can be dangerous to humans, plants, and wildlife.
The science backs up what many in the area have observed personally: The warming climate is affecting local weather patterns. The region’s storms are intensifying and becoming more frequent, and periods of drought are becoming longer.
Annual precipitation in the region has been somewhat stable since the 1940s, but future trends may change. A warming atmosphere can build up and hold more moisture before it precipitates, resulting in more intense rain or snowstorms. This region is particularly vulnerable to increasing rainfall as the IPCC predicts that Eastern North America will see the largest increase in heavy precipitation as Earth warms.
The Washington, DC region saw its wettest year on record in 2018 (66.28 inches of rainfall) and its seventh wettest year on record in 2020 (57.34 inches of rain). Seasonally, we’re receiving more rainfall in the fall and winter months and less in the summer than in years past.
When it does rain, it tends to rain much harder than it used to. November 30, 2020, marked the seventh time that year that Washington, DC accumulated at least two inches of rain in one day – a record for a calendar year. It also marked the second day that month when over two inches of rain fell, making November of 2020, the wettest month in the Washington, DC region’s recorded history. Flash flooding will become more common as heavy downpours increase in intensity and frequency.
The frequency of extreme storms is increasing. Hurricanes, Nor’easters, blizzards, and super storms are all becoming more common in the Potomac River region.
Climate scientists believe that today’s 1-in-100-year storms will become a 1-in-25-year event by the middle of this century, and a 1-in-15-year event by the 2080s.
Download our full report for free and dive into the research to understand more about how these extreme storms will impact your community.
Periods of drought are becoming longer. Not only are storms intensifying, but dryer bouts of weather are also becoming more common, especially during the summer and autumn seasons. Month-long droughts, which occur roughly every 40 years, could happen every 8 years if greenhouse gas emissions continue to rise.
Taking the region by surprise, the super storm dumped a month’s worth of rain – a staggering 3.3 inches of precipitation – in just four hours.
Alternating between hard downpours and longer dry periods is a terrible recipe for achieving clean water and healthy communities.
Drier soils are unable to absorb heavy downpours, forcing excess stormwater to run off the land — carrying sediment, nutrients, and fertilizers into streams. In turn, waterways become polluted with chemicals and turbid waters block sunlight destroying underwater vegetation critical for aquatic life. Strained by heavy rainfall, infrastructure can spill sewage overflows into our waterways, burst pipes, and back up water and sewage flows into residencies. And strong storms leave costly fixes for cities from downed trees and damage to properties, utilities, and roads.
You get the picture – so what can be done?
The urgency of the crisis demands bold action at every level of society. The science is irrefutable: We must change systems to drastically lower greenhouse gas emissions and move away from fossil fuel dependence.
Potomac Conservancy is proud to join other leaders in the region who are taking action to prepare our communities for the future and reduce greenhouse gas emissions through nature-based solutions.
We support critical efforts to capture carbon effectively and naturally through forest protection and restoration, regenerative agriculture, and best management practices – but we must dramatically and immediately scale up these efforts.
Tell your members in Congress to pass the American Jobs Plan with full funding for
nature-based infrastructure, green careers, and environmental justice!
Fun fact: Scientists can identify increases in atmospheric carbon dioxide are, indeed, human-made because carbon created by burning fossil fuels has a different isotopic ratio of heavy-to-light carbon atoms than carbon produced naturally by living plants.
Fun fact: While carbon dioxide is the main culprit, other gasses like methane and nitrous oxide also add to the atmospheric soup of heat-trapping greenhouse gasses. Methane is released from natural gas fracking, the decay of organic waste put in landfills rather than composted, and from livestock and industrial agricultural practices. Nitrous oxide is released during fuel combustion and during the application of fossil-fuel based fertilizers or un-composted manure to fields (U.S. Environmental Protection Agency, 2020a).
In 2015, the ATMOS Research and Consulting for Kleinfelder published local climate projections by studying historic emission and temperature data at three District sites: Dalecaria Reservoir, the National Arboretum, and Washington National Airport.
Andrew Elmore co-authored a study on the warming waters of the Chesapeake Bay for the University of Maryland Center for Environmental Science.
Fun fact: Scientists can use high resolution climate models to tell whether an extreme event was made more likely by climate change – whether it served as a key ingredient in the storm’s formation. This is called “extreme event attribution.”
Fun fact: A rainfall event that is so heavy and unordinary that it only statistically happens once every 100 years
The National Weather Service confirmed an EF0 tornado touched down in Washington, DC and an EF1 tornado touched down Arlington, VA on Thursday, July 1, 2021. The nation’s capital has only experienced three confirmed tornadoes above an EF0 level in the last fifty years (two of which occurred on the same day in 2001).
FACT: According to the U.S. Geological Survey (USGS), glaciers and ice sheets store enough water to raise sea level by about 68 to 70 meters (223 to 230 feet) (Cronin, n.d.).
Thermal expansion is the phenomenon whereby the upper layer of the ocean absorbs heat from the warming atmosphere and expands
Over 400 miles in length, the Potomac River flows with fresh water from the highlands of West Virginia downstream to Washington, DC where it mixes with brackish saltwater and continues on to the Chesapeake Bay, the largest estuary in the world. The Potomac experiences daily low and high tides as far upstream as Washington, DC.
One such effort is underway in Washington, DC where tunnels are being constructed underneath the city’s rivers to divert excess rainwater and reduce sewer overflows into local streams. As part of the $2.7 billion Clean Rivers Project, DC Water has built a 5-mile long tunnel under the Anacostia River with plans to start building another one under the Potomac River in 2023. The plan also includes investments in tree plantings, rain gardens, and other types of nature-based infrastructure.
Living shorelines are a type of nature-based infrastructure that incorporates indigenous vegetation, either alone or in combination with harder materials for structure and stabilization. They restore ecosystems that naturally withstand and recover from the flooding that has become more common because of rising seas, stronger storms and heavier precipitation. Further, living shorelines build habitats that sequester, or store, carbon. According to NOAA, “one square mile of saltwater marsh stores the carbon equivalent of 76,000 gallons of gas annually.
Extreme heat conditions are defined as weather that is much hotter than average for a particular time and place—and sometimes more humid, too.
The heat index is a measure of how hot it feels when relative humidity is factored in with the actual air temperature. Relative humidity is the percentage of moisture in the air compared with the maximum amount of moisture the air can hold. Humidity is an important factor in how hot it feels because when humidity is high, water doesn’t evaporate as easily, so it’s harder for your body to cool off by sweating.
Ozone (O3) is a highly reactive gas composed of three oxygen atoms. It is both a natural and a man-made product that occurs in the Earth's upper atmosphere
(the stratosphere) and lower atmosphere (the troposphere). Depending on where it is in the atmosphere, ozone affects life on Earth in either good or bad ways.
Stratospheric ozone is formed naturally through the interaction of solar ultraviolet (UV) radiation with molecular oxygen (O2). The "ozone layer," approximately 6 through 30 miles above the Earth's surface, reduces the amount of harmful UV radiation reaching the Earth's surface.
Tropospheric or ground-level ozone – what we breathe – is formed primarily from photochemical reactions between two major classes of air pollutants, volatile organic compounds (VOC) and nitrogen oxides (NOx). These reactions have traditionally been viewed as depending upon the presence of heat and sunlight, resulting in higher ambient ozone concentrations in summer months.
Ground level ozone is a secondary byproduct of a chemical relation between human-made nitrogen oxides (NOx) and volatile organic compounds (VOCs) in the presence of sunlight. Humans are producing an extra 24 million tons of NOX annually through combustion processes from vehicles, power plants, cement factories (which are located adjacent to many communities of color in the Potomac River region), and other industry.
Nutrients—primarily nitrogen and phosphorus—are essential for the growth of all living organisms in aquatic ecosystems. However, excessive nitrogen and phosphorus degrade water quality.
Both nitrogen and phosphorus feed algal blooms that block sunlight to underwater grasses and suck up life supporting oxygen when they die and decompose. These resulting "dead zones" of low or no oxygen can stress and even kill fish and shellfish. Algal blooms can also trigger spikes in pH levels, stressing fish, and create conditions that spur the growth of parasites.
The incubation period is the number of days between when you're infected with something and when you might see symptoms. Health care professionals and government officials use this number to decide how long people need to stay away from others during an outbreak.
Coal ash, also referred to as coal combustion residuals or CCRs, is produced primarily from the burning of coal in coal-fired power plants.
Coal ash contains contaminants like mercury, cadmium and arsenic. Without proper management, these contaminants can pollute waterways, ground water, drinking water, and the air.
A Superfund site is an abandoned toxic waste site (usually that once supported an oil refinery or smelting or mining activities). In response to attention on sites like these in the late 1970s, Congress established the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) in 1980.
CERCLA is informally called Superfund. It allows EPA to clean up contaminated sites. It also forces the parties responsible for the contamination to either perform cleanups or reimburse the government for EPA-led cleanup work.
When there is no viable responsible party, Superfund gives EPA the funds and authority to clean up contaminated sites.
Frontline communities are those that experience “first and worst” the consequences of climate change. These are communities of color and low-income, whose neighborhoods will be increasingly vulnerable as our climate deteriorates.
Adaptive capacity is the ability of a habitat to support its species and ecosystem functioning as the climate changes. Plants and animals respond to changing climate by adapting, shifting their range, or fleeing completely.
Species that reproduce quickly are able to adapt or migrate more readily than slower growing, long-lived. species – like Maryland’s bald cypress that regularly lives up to 600 years.
Agriculture, development, and past logging operations played a large role in the large-scale loss of eastern hemlock throughout the Appalachian region.
Indigenous to East Asia, the fast-spreading hemlock woolly adelgid insect attaches to the soft, woody plant tissue and sucks nutrients from the sap of eastern hemlocks. Once the insect establishes a population on a hemlock, it can kill the tree within four years. Click on the link to read more about the pesky adelgid.
Coldwater streams make up approximately 2,750 miles of Maryland’s freshwater streams, spanning across Allegany, Garrett, Frederick, Carroll, Washington, Montgomery, and Prince George’s counties. In West Virginia, coldwater streams are found chiefly in the eastern panhandle. In Virginia, coldwater streams meander through the mountains and valleys of the Interstate 81 corridor, stretching across Augusta, Rockingham, Shenandoah, Warren, and Frederick counties up through Berkeley County in West Virginia.
Rainbow trout from the western U.S. and brown trout from Europe were introduced to the region in the late 1800s. They have slightly higher temperature tolerances and, once temperatures reach 68°F, they can out-compete indigenous brook trout. Elimination by competition is already occurring in some streams.
Fun fact: Salamanders are ectotherms, meaning they regulate their body temperatures through their environment. They sun themselves on rocks to warm up and cool off in streams or shaded areas.
Salamanders prefer temperatures between 33°F and 60°F. Their metabolism and heart rate slows when temperatures reach 50°F to survive more extreme conditions.
The opportunity to roam for resources is an important need for animals’ adaptive capacity in the fight against environmental changes.
NatureServe based its research on data from a weather station in Rock Creek Park and then used an ensemble of global climate models from the IPCC’s 5th Assessment Report to project near-future climate conditions in the Park.
In slightly salty oligohaline marshlands, salinity ranges from 0.5- 5 parts per thousand (ppt).
Visit Dyke Marsh or Mattawoman Creek to venture through two of our region’s freshwater marshes, areas of the Potomac River with salinity ranging from 0-0.5 parts per thousand (ppt).
According to a 2016 study in PLoS One, this edge might only be pushed up as far as Indian Head by the end of the century due to the region’s topography and the potential for water to spill out cross-sectionally (widening the river), rather than being pushed far upstream (Cadol et al., 2016).
Visit The American Scientist’s “Spring Budburst in a Changing Climate” for more information on how a warming climate is throwing off the timing of spring. The authors use Henry David Thoreau’s 160-year-old field notes to compare the timing of spring activities between then and now.
Roosevelt Island was transformed back into a “real forest” in the 1930s to mimic the natural ecosystems that covered the landscape before settler-colonial interference. Learn how this island has been transformed time and again – including how it was used as a place of refuge by people who were enslaved.
Source: University of Maryland Center for Environmental Science, 2015; Ding & Elmore, 2015.
www.umces.edu
The Maryland Commission on Climate Change, the Department of the Environment’s Scientific and Technical Working Group (STWG).
Source: “Understanding Virginia’s Vulnerability,” 2015
Every community produces polluted runoff – a type of pollution caused when excess rainwater carries toxins, debris, and litter into nearby streams – but the issue is particularly problematic on farmland. In fact, agricultural runoff is the greatest source of pollution to our region’s waterways. Poor land-use practices on farmland pollute streams with excess nutrients from fertilizers, pest treatments, and animal feces.
In 2018, the United States’ agricultural activity alone emitted approximately 698 million metric tons of greenhouse gasses into the atmosphere: 12.3% as carbon dioxide, 36.2% as methane, and 51% as nitrous oxide (U.S. Department of Agriculture, 2020).
Nitrous oxide is 298 times more potent than carbon dioxide over one hundred years, and is produced as microbes in the soil break down fossil-fuel based synthetic fertilizers and manure that hasn’t been aged or composted before being applied to fields.
Best management practices (BMPs) are conservation measures that improve land health and prevent or mitigate pollution through natural means. BMPs are critically important to restoring water quality in the Potomac River region. Potomac Conservancy helps connect area landowners to available resources to implement BMPs on residential properties with a focus on family-owned farms in the headwaters region.
Learn more at www.potomac.org/lands.
TEK refers to the ever-evolving wisdom gained by indigenous and locally rooted peoples over hundreds of years by means of direct contact with their environment. The U.S. Fish and Wildlife Service explains that, “this knowledge is specific to a location and includes the relationships between plants, animals, natural phenomena, landscapes, human beings, and timing of events that are used for lifeways,” like agriculture or hunting and trapping (Rinkevich et al., 2011).
Source (Aman & Pratt, 2014).
Industrial farming that relies on growing expansive fields of one crop – corn, wheat, soy, as examples – planted year after year, drain the soil of essential nutrients and lack the genetic diversity to fight diseases and pests. Consequently, they require the help of artificial additives.
The Lacandon are the last of the Mayans who escaped the Conquistadors’ forced Christianity by hiding in the heart of the jungle. For the last five hundred years, the Lacandon lived very simply and have kept their borders closed to outsiders. Their population consists of about six or seven hundred people now.
Earthaven Ecovillage is a permaculture community outside of Black Mountain, North Carolina that applies Traditional Ecological Knowledge.
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