(Chesapeake conservancy)

By Ruth Fox

As the temperature rises and the climate crisis increases in severity, the Potomac River–Washington DC’s principal water source–pays the price. Aquatic ecosystems are extremely delicate- if they are exposed to extreme temperatures or increased pollution from groundwater runoff, the ecosystem and its water quality decline. The Potomac is no exception. In the DCregion, negative impacts from rising temperature and increased runoff are evident, and according to experts, they can be felt by residents. 

The Potomac River plays an essential role in the Washington DC Region. According to the Interstate Commission on the Potomac River Basin, the Potomac supplies 78% of  the DC metropolitan area’s water supply. It also provides important wildlife habitat and recreation resources for area residents with a wide array of interests, including kayakers, runners, and fishers. In evaluating the health of this important resource, scientists must evaluate many  factors. According to the National Oceanic and Atmospheric Administration’s (NOAA)  aquatic food web resource, aquatic ecosystems, like all ecosystems, are made up by a vast food chain of organisms, which depend on each other to function.The density of certain chemicals in the water source, the frequency and intensity of rainfall in comparison to historical patterns, and temperature levels and fluctuation in comparison to normal temperatures are all factors that matter to the health of the river. All of these factors are linked, and if one deviates from the usual pattern, a myriad of issues can occur. According to the Potomac Report Card, all of these elements have been shifting recently because of the heating climate. 

According to Cloud, One of the biggest issues Washington is currently struggling with is algae levels. “Algae has always been a problem in any fresh water system that is affected by pollution and human interactions,” Cloud explained Ms. Cloud. In particular, she’s referring to nitrogen, commonly found in groundwater runoff, especially from wastewater intensive agriculture and overuse of nitrogen-containing fertilizer. “Nitrogen feeds into algae blooms because algae really like nitrates. They feed off of nitrate as a food source. And that [nitrate] comes from lots of different sources, any sort of organic living things, it’s often a waste…Humans are really good at producing a lot of [waste].” The issue with these rising levels of nitrogen is that they feed algae, which hoards all of the resources, creating dead zones. Cloud defines dead zones as “huge sections of water that don’t have anything living in it, and just a swath of algae living on top…it’s not good for the ecosystem, it’s not good for the humans living next to it.” 

Dead zones, according to NOAA,  are classified as areas of water with a reduced amount of oxygen. Dead zones such as these are becoming a larger issue around the word as droughts and unpredictable weather patterns become more common “When an area is in a drought the river that has built up nitrates in it, normally in could potentially handle it that amount by having a lot of water in it diluting the amount, washing it down steam… the organisms in the actual river might be able to absorb the nitrates and process it properly, so it might not be as affected. But in a drought you’re going to have reduced capacity for that.  Effectively, droughts increase the concentration of pollution in water systems; algae thrives because of this, bogarting the oxygen which suffocates the other inhabitants of the ecosystem.

This is not just a possible threat, but the reality of the situation. The Chesapeake Bay has already started to feel the effects of climate change and pollution. 20% of the Chesapeake is fed by the Potomac, according to the Potomac River’s Potomac basin fact sheet, and reflects the health of the Potomac’s own water quality. According to the Chesapeake Bay Foundation, the Chesapeake dead zone spans up to 1.2 cubic miles when the water is at its warmest throughout the summer. On a positive note, the dead zone is decreasing through efforts to reduce the amount of unwanted nutrients entering the water supply. The decrease in size is an important development, but increasing temperatures will simply make these efforts more challenging, as heating waters increases the likelihood of oxygen deficiencies, known as hypoxia, according to the US environmental protection agency. 

How is this affecting Washington DC residents and other communities who surround the Potomac? For years, the Potomac was incredibly polluted by industrial and human waste, but the cleanliness of the river has drastically improved in the past ten years. Though it is still illegal to swim in the Potomac due to water quality concerns, the possibility of it becoming legal in the next two years is being considered. Though this is good news, the Potomac Conservancy notes that the climate crisis is causing challenges in the attempt to clean the river. After large storms, which are becoming more and more frequent, heightened amounts of pollutants are washed into the river straight from the street. These storms also have the possibility of overwhelming the water treatment system. According to DC Water, one third of the Washington DC sewage system is a combined sewage system. This means that both rain water and sanitary waste flow into the same treatment plant. When the combined treatment plant is overflowed, both sanitary waste and rain water is released into the Potomac. In short, the increased rainfall due to climate change is worsening the quality of the Potomac, creating a wider gap between now and when the Potomac could potentially be safe to swim in. These issues though, have been noticed by the DC government. On September 15, 2023, the Northeast Boundary tunnel was put in place. This is a tunnel that was added to the preexisting combined sewage system, in order to reduce flooding during severe weather events. Efforts such as the northeast boundary tunnel can help alleviate the problem of pollution in the potomac in the future. However, climate change is at the same time exacerbating the problem. Only time will tell how this will play out.