National Park Service Drains Lincoln Memorial Reflecting Pool to Combat Algae Growth

The National Park Service (NPS) has initiated a scheduled draining of the Lincoln Memorial Reflecting Pool in Washington, D.C., to manage persistent algae blooms and perform essential maintenance on the basin’s water filtration system. According to the National Park Service, the process began on Saturday and is a recurring operational requirement to maintain water quality and aesthetic standards for the landmark site.

Why is the Reflecting Pool being drained?

The primary driver for the maintenance is the accumulation of algae, which thrives in the shallow, sunlit environment of the pool. The NPS reports that the water system, which was significantly upgraded in 2012, requires periodic clearing to prevent the buildup of organic matter that can discolor the water and affect the structural integrity of the pool’s lining. By draining the basin, crews can manually remove debris and inspect the filtration intake valves, ensuring the circulation system remains functional for the peak tourism season.

How does the current maintenance compare to past efforts?

The current operation reflects a continued effort by the NPS to address the pool’s unique environmental challenges. Before the 2012 renovation, which introduced a more robust filtration system, the pool was frequently drained due to severe water quality issues that often left the basin stagnant. Recent data from the National Park Service confirms that while the modern system has reduced the frequency of full drainings, the shallow depth of the pool—averaging only 18 to 30 inches—means that seasonal temperature spikes inevitably lead to rapid algae growth that filtration alone cannot fully mitigate.

What happens to the water during the process?

The water is not simply dumped into the Potomac River; it undergoes a filtration and treatment process. According to agency protocols, the water is pumped into the city’s storm sewer system, which is designed to handle large volumes of discharge. The NPS coordinates with the D.C. Department of Energy and Environment to ensure that the water quality meets local safety standards before it is released. Once the pool is empty, maintenance crews spend several days pressure-washing the bottom and sides of the structure to remove stubborn algae films before refilling the basin with fresh, treated water.

Key Facts Regarding the Reflecting Pool

• Dimensions: The pool is approximately 2,029 feet long and 167 feet wide.
• Water Capacity: The basin holds roughly 6.75 million gallons of water when full.
• Maintenance Frequency: Full drainings typically occur once or twice a year, depending on weather conditions and algae accumulation.
• Primary Purpose: The pool serves as a central feature of the National Mall, reflecting the Lincoln Memorial and the Washington Monument.

When will the pool reopen to the public?

While the NPS has not provided a specific date for the refilling, similar maintenance cycles typically span one to two weeks, depending on the severity of the cleaning required. Visitors to the National Mall can expect the pool to remain empty through the maintenance window, though the surrounding walkways and the Lincoln Memorial itself remain fully accessible to the public. The NPS advises that updates regarding the status of the pool are posted on their official current conditions page.