Mariposa County: lake and river algae advisories

7 waters in Mariposa County appear in the state's harmful algal bloom records. Waters whose latest record is an advisory come first.

Waters in Mariposa County and what the state's latest record says
Water	Latest record
Lake McSwain	Caution advisory, last posted Jun 12, 2026. No all-clear recorded.
Merced River	Caution advisory, last posted Nov 4, 2022. No all-clear recorded.
North Crane Creek	Algal mat alert sign, last posted Aug 29, 2025. No all-clear recorded.
South Fork Merced River	Algal mat general awareness sign, last posted Nov 4, 2022. No all-clear recorded.
Tenaya Creek	Caution advisory, last posted Sep 17, 2021. No all-clear recorded.
Flyaway Gulch	The state's latest record, from May 17, 2022, recommends no advisory.
Yosemite Creek	The state's latest record, from Aug 29, 2025, recommends no advisory.