If your tap water has an unusually earthy or musty taste and smell, algae living in the Potomac River may be to blame. According to officials with the Washington Suburban Sanitary Commission, residents in parts of Montgomery County and Prince George’s County may notice the change.

However, the water is still perfectly safe to imbibe, officials say, and meets all drinking water standards set by the U.S. Environmental Protection Agency.

The earthy taste comes from a compound called geosmin, which is produced by algae in the river. There’s more aglae right now due to low water levels in the river, after months of dry weather. Earlier this week, the Interstate Commission on the Potomac River Basin began conducting daily drought monitoring — the first step officials take when a drought threatens to cause water shortages.

Over the past six months, there’s been 6.5 inches less rain than normal in the Potomac River basin. Last month was the driest May on record in D.C. since 1999.

Most of the D.C. region gets its drinking water from the Potomac River, though some parts of Prince George’s County are served by the Patuxent River. In the District and Arlington County, drinking water comes from the Potomac, but is treated separately from the water in Maryland.

DC Water has received only a handful of complaints about the water taste, says spokesperson John Lisle in an email to DCist. But, he says, low water levels in the Potomac, and the resulting high algae levels, can affect tap water taste in the District.

WSSC is changing its water treatment process to try to improve the taste, but this will not eliminate the problem. In fact, nothing can really fix the taste, WSSC says, as long as the current drought conditions continue — boiling the water won’t help, nor will flushing water lines.

This post has been updated to clarify that DC Water has received a handful of complaints about the taste of water in the District.