06/21/2026
🟢 The Reflecting Pool Turned Green in D.C. — and Why Lake Hickory Does the Same Almost Every Summer
Sunday, June 21, 2026 — 10 A.M.
Catawba Valley, N.C. — If you've seen the photos of the Lincoln Memorial Reflecting Pool turning bright green this week, here's something that probably doesn’t surprise anyone in our area: the same thing happens right here in the foothills nearly every summer — and a lot of us can taste it.
Lake Hickory, which supplies drinking water across much of the region, goes through algae blooms during the hot, dry stretches of summer. When it does, that faint earthy, musty flavor shows up in a plain glass of tap water — and if a restaurant's filtration isn't up to par, it can even sneak into the brewed tea, no matter how much sugar the sweet southern lady in the kitchen stirred in.
The good news: that taste is an aesthetic issue, not a safety one, and treated tap water stays safe to drink. The science behind it, though, is the same story now playing out 350 miles away in Washington.
WHAT HAPPENED IN D.C.
The Reflecting Pool on the National Mall was drained earlier this year, resurfaced with a dark "American flag blue" coating ordered by President Donald Trump ahead of the nation's 250th anniversary, and refilled this month. Within days, the water bloomed green.
A Washington Post analysis of satellite data found more algae in the pool than at any recorded point in June for at least five years. The renovation cost more than $14 million, according to multiple national outlets.
THE SCIENCE BEHIND THE BLOOM
Algae are simple, plant-like organisms that turn sunlight, carbon dioxide and water into energy through photosynthesis. They live in nearly every body of water on Earth — lakes, rivers, ponds, even a pet's water bowl left near a sunny window.
A bloom happens when conditions line up: shallow water, warm temperatures, strong sunlight, plenty of nutrients and little movement. The Reflecting Pool checks every box. It is broad and shallow, sits in full sun with no shade, and its water moves slowly.
Rosalina Stancheva Christova, a professor of aquatic ecology at the College of Science at George Mason University, sampled the water and identified the algae as the genus Desmodesmus — a common green algae she described as not toxic or harmful, NPR reported. She noted this kind of growth is widespread across the region in summer and could return year after year.
The pool's new dark surface may be speeding things along. Scientists interviewed by NPR and Newsweek explained that a darker bottom absorbs more sunlight, which warms the water and creates friendlier conditions for algae. Researchers added that the renovation may also have shifted the balance of nutrients in the water, and that recent extreme heat in Washington likely accelerated the bloom. As any meteorologist will tell you, heat and sunshine are the engine here — and this summer has delivered plenty of both.
WHAT THE TWO SIDES SAY
Several scientists view the renovation as one of several factors that accelerated the bloom.
The Trump administration and the U.S. Department of the Interior say algae has plagued the Reflecting Pool since it opened in 1922, and that the National Park Service is now actively maintaining it. Officials said the recent bloom stemmed from residual material that sat in supply lines for weeks and was worsened by the heat.
Crews have treated the water with hydrogen peroxide — which the Interior Department called a milder alternative to chlorine, with no harmful effects on wildlife or the environment — along with "nanobubble" ozone technology. Workers have also been vacuuming dead algae from the bottom of the pool.
ALGAE ISN'T ALL BAD
While a green pool makes for unflattering photos, algae are essential to life. They form the base of the aquatic food web, feed countless species and produce a large share of the oxygen in our water and atmosphere.
They also have growing commercial value. The U.S. Department of Energy is researching algae as a source of renewable fuel, because the oils they produce can be converted into gasoline, diesel and jet fuel. In simple terms, petroleum itself is ancient algae transformed by heat and pressure over millions of years.
Certain algae are even marketed as "superfoods." Spirulina and chlorella show up in supplements, while algae-derived ingredients appear in skin care and cosmetics.
Dr. Marshall Shepherd, a University of Georgia professor and former president of the American Meteorological Society, laid out the science of algae in a Forbes essay this weekend, noting the organisms are among the oldest life forms on Earth — cyanobacteria fossils date back more than 3.5 billion years.
BACK HOME: WHY YOU CAN TASTE IT
That earthy, musty flavor in Lake Hickory water has a name — actually two. The blue-green algae that thrive in warm, slow water release compounds called geosmin and 2-methylisoborneol, or MIB. The human palate can detect them at extraordinarily low concentrations, which is why a bloom announces itself in your glass before you ever read about it.
The pattern is well documented. In a 2005 bloom, blue-green algae in Lakes Hickory and Rhodhiss caused taste-and-odor complaints across public water systems serving Hickory, Longview, Lenoir, Valdese and Granite Falls — plus communities that buy water from them, including Conover, Claremont, Maiden, Catawba, Hudson, Sawmills, and parts of Alexander and Caldwell counties, state officials reported at the time. Utilities treated the water with activated carbon to cut the taste and odor, and state lab testing found no microcystin, a common algal toxin, in samples from Hickory and Lenoir.
State environmental crews still monitor these Catawba River reservoirs through the warm months. The conditions that drive blooms — heat, strong sun, calm water and nutrient runoff — line up most reliably from late spring into early fall.
Most of what you will see on local water is harmless green algae, but not all blooms are equal. Blue-green algae, or cyanobacteria, can sometimes produce toxins that are dangerous to people, pets and livestock. A few simple precautions: keep children and pets away from water that looks like spilled green paint, a thick scum or a pea-soup surface; do not let dogs drink from or swim in it; and rinse off after contact with lake water. Dogs are especially vulnerable because they swallow water while swimming and lick it from their fur. If you spot a suspicious bloom on a public lake, you can report it to the NC Dept of Environmental Quality.
Bottom line: the green water in Washington is a national talking point, but the science behind it is something foothills residents quite literally taste every summer.
🍵 Have you noticed the summer change in your tap water — or even in your sweet tea? Tell us about it in the comments.
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📸 Graphic: CCNW
