Here's why the Lincoln Memorial Reflecting Pool went green so fast
Key takeaways
- The calm, still waters of the Reflecting Pool make it an ideal nursery for algae growth.
- The Potomac also absorbed one of the largest sewage spills in U.S.
- Untreated sewage is high in nitrogen and phosphorus.
A U.S. National Park Service employee uses a vacuum pump to clean algae off the bottom of the newly recoated Lincoln Memorial Reflecting Pool on the National Mall on Tuesday. (Chip Somodevilla / Getty Images) By Mack Baysinger Follow June 19, 2026 5:53 PM PT 4 3 min Click here to listen to this article Share via Close extra sharing options Email Facebook X Linked In Threads Reddit Whats App Copy Link URL Copied! Print 0:00 0:00 1x This is read by an automated voice. Please report any issues or inconsistencies here.
Just days after the Trump administration completed millions of dollars in renovations on the Lincoln Memorial Reflecting Pool to make it American flag-blue, residents and online users noted it had turned a phosphorescent green.
The calm, still waters of the Reflecting Pool make it an ideal nursery for algae growth. Algae need nitrogen and phosphorus to grow, and the Reflecting Pool is primarily fed by the Potomac River, which gets heavy doses of those nutrients from nearby urban and agricultural lands.