Tap water from Lake Lanier may taste like dirt. Here’s why

Residents across north Georgia who get their drinking water from Lake Lanier or the Chattahoochee River may notice their tap water smelling or tasting like dirt or mildew in the coming weeks. Officials say the water is safe to drink and use, but a seasonal problem is back.

What’s happening: Every fall, as air temperatures drop, cooler water on the surface of Lake Lanier sinks and mixes with deeper water in a process called turnover. That mixing stirs up algae living in the lake that release two compounds, geosmin and MIB, which cause the musty, earthy smell and taste. Because metro Atlanta’s water supply flows from Lake Lanier down the Chattahoochee River, higher concentrations in the lake mean higher concentrations at the tap.

What’s new: The problem was more widespread last year, especially in communities downstream of the lake like Atlanta. This year, Chattahoochee Riverkeeper, which regularly monitors algae levels in Lake Lanier, says it has not seen any unusual spike in total algae in the lake in 2026.

What this means for you: Water officials say your water is safe to drink and wash with even if it smells or tastes off. The compounds causing the problem are not a health risk. Water providers in Gainesville, Cobb County, Gwinnett County, and the City of Atlanta are using activated carbon and ozone treatment to reduce the compounds, and all four are investing in additional treatments to address the issue in future years.

The bigger picture: Chattahoochee Riverkeeper says the taste and odor problems are part of a longer-running concern about Lake Lanier’s water quality and algae levels overall. The group says more investment is needed to cut down on nutrient pollution flowing into the lake, which feeds algae growth. Sources of that pollution include leaking sewer lines, septic tanks, lawn fertilizers, agricultural runoff, and stormwater runoff from developed areas.