Renovation Aimed at Enhancing Appearance
The Lincoln Memorial Reflecting Pool received a multimillion-dollar renovation. The goal was to add a deeper “American flag blue” finish to the historic landmark. However, an unintended consequence emerged: the water turned green.
Images show algae spreading across the surface just days after the pool’s refilling, raising concerns about whether the redesign favors fast-growing algae blooms. President Donald Trump’s administration ordered this overhaul as part of efforts to revamp the National Mall before the U.S. 250th anniversary. The project involved resurfacing the pool with a dark blue coating to improve its appearance and seal leaks.
Trump estimated the cost to be between $1.5 million and $2 million, but records show that contracts reached approximately $14 million. The work was awarded via a no-bid contract, prompting a lawsuit from preservation group The Cultural Landscape Foundation, which argues changes occurred without required historic review.
Persistent Algae Problems
Stretching over 2,000 feet between the Lincoln Memorial and Washington Monument, the reflecting pool has been a Washington, D.C. feature since 1923. Algae blooms are not new. The shallow, slow-moving water often appears green in summer when heat, sunlight, and stagnant conditions combine.
Even after major upgrades, algae continues to be a problem. In 2012, following a $34 million renovation, algae appeared, causing crews to drain and clean the pool again. This underscores the challenge of eliminating blooms in a shallow outdoor system like the reflecting pool.
Possible Causes of Algae Appearance
Residual Algae from Renovation:
An Interior Department spokesperson indicated that current algae is “residual.” Supply lines sat dormant for eight weeks during construction, suggesting the bloom could be a routine post-renovation effect.
Darker Coating:
The timing, shortly after refilling, sparked debate about the darker coating’s role. Darker surfaces absorb more sunlight and heat than lighter ones, which in shallow water can raise temperatures, enhancing algae growth rates. Expert Alla Silkina noted that darker surfaces increase solar radiation absorption and local water temperatures, possibly favoring algal growth.
Weather Conditions:
Weather plays a role. Warm temperatures, strong sunlight, and relatively still conditions encourage algae growth, especially in shallow water like this pool.
Silkina explained that such conditions boost growth. Light energizes photosynthesis, while temperature affects metabolic and growth rates. Even with favorable conditions, essential nutrients must be available for blooms to develop.
Infrastructure Challenges:
Reports highlight infrastructure challenges beneath the pool, like circulation issues or aging pipe systems. If water movement or filtration decreases, stagnation increases, aiding algae growth.
Silkina stressed that improved circulation reduces bloom development. Continuous water flow prevents algae accumulation, reducing visible blooms.
Understanding the Green Color
Chlorophyll makes the green color visible, as algae use it for photosynthesis. As algae multiply, they dominate light absorption, overshadowing the blue coating and shifting its color to green.
Silkina noted rapid visual changes under the right conditions. Algal populations can double within hours or days. Blooms may appear in one to two weeks, depending on species and conditions.
Speculation and Unverified Claims
Residual algae, heat absorption, weather, and water flow create a perfect storm for rapid blooms. Some social media users speculated—without evidence—that the pool was deliberately interfered with. Figures like radio host and MAGA supporter Grant Stinchfield and author Juanita Broaddrick suggested sabotage by Democrats. Officials have not indicated any foul play, and public evidence does not support these claims.
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