Water-condition and advisory sources
A conditions link is not an endorsement of the data's completeness. Read its sampling date, place, scope, and agency disclaimer. An empty map or an unlisted lake may mean no test was reported.
Lake Tahoe
The Tahoe Nearshore Human Health program samples E. coli at popular beaches during its operating season. California also publishes a recreational bacteria map and harmful-algal-bloom reports. Nevada publishes its HAB program.
Lake Chelan
Washington's Toxic Algae database is the state starting point. Washington Ecology says there is no statewide monitoring program, and Chelan-Douglas testing is complaint-driven. Absence from the list does not establish a condition.
Lake Lanier and Lake Norman
For Lanier, use Georgia EPD harmful-algal-bloom information plus the named park manager. For Norman, use North Carolina DEQ bloom reports and Mecklenburg County notices where applicable.
Lake Havasu, Lake Mead, Lake Powell, and Lake Las Vegas
For Havasu, start with the named city, state-park, or BLM manager. For Mead, use the NPS conditions and alerts page. For Powell, use the Glen Canyon conditions page. Lake Las Vegas access is operator- or property-controlled, so the resort, club, or booked marina remains the first contact.
Lake George and Flathead Lake
New York publishes harmful-algal-bloom bathing-beach guidance for Lake George visitors. At Flathead Lake, use each Montana State Parks unit page for alerts and operating information; a park listing does not represent a current water-quality finding.
Lake Ouachita, Lake Jocassee, Lake Wappapello, and Lake Nockamixon
Arkansas maintains a state swim-beach monitoring program. At Jocassee, consult Devils Fork State Park for access and posted notices. At Wappapello, beach opening depends on lake level; use the Army Corps lake gage and posted rules. Lake swimming is prohibited at Nockamixon, so its manager page—not a water-condition inference—answers the access question.
At the water
Posted closures and manager instructions control. Do not enter near active marinas or launch ramps where prohibited. Leave the water when visibility, weather, a suspected bloom, debris, current, or another condition is outside your ability—even when a web page has not been updated.