Morena Reservoir: toxic algae advisories
Morena Reservoir, San Diego County. See all San Diego County waters.
What the state's records say
Caution advisory, last posted Sep 21, 2026. No all-clear recorded.
Reporting is voluntary, so the state may not have recorded an end even if conditions changed. Check posted signs and the official map.
What this level asks: Algae that can make toxins may be present. Keep people, children and pets away from algae and scum, and do not let pets drink the water.
Before you go, check the state's official algae page and any signs posted at the water.
Dogs at Morena Reservoir
The state has an advisory on file for Morena Reservoir (Caution advisory), last posted Sep 21, 2026, and no all-clear recorded. Keep your dog out of the water and away from scum on the shore until the state records an end.
Satellite estimate (not an advisory)
No satellite reading on file for Morena Reservoir in recent weeks. Clouds, ice, or a lake shape the satellite's estimate near its center misses can cause this. It is a gap in the data, not a reading.
This is a satellite estimate from the U.S. EPA's Cyanobacteria Assessment Network, not an advisory. It estimates how much cyanobacteria is in the water near the lake's center, not whether toxins are present: a high number does not mean toxins, and a low one does not mean there are none. It covers lakes of about 1 square kilometer and larger, so small ponds, dog parks and most rivers are not covered, and clouds can hide a lake for weeks. It never changes the advisory status above.
Satellite estimates: U.S. EPA Cyanobacteria Assessment Network (CyAN), from Copernicus Sentinel-3 data. Provisional, research-level estimates; EPA does not endorse this site. Checked Oct 22, 2026.
Reported spots
The state records each report at a spot, such as a beach or a boat ramp. Each spot's latest deciding record:
| Spot | Status |
|---|---|
| Lake Morena County Park | Caution advisory, last posted Sep 21, 2026. No all-clear recorded. |
Advisory history
Every advisory record the state has published for Morena Reservoir, newest first. "None" is the state's record that no advisory was recommended on that date. "NA" records do not change a status.
| Date | Spot | State's level | Notes |
|---|---|---|---|
| Sep 21, 2026 | Lake Morena County Park | Caution | satellite based visual observation |
| Sep 14, 2026 | Lake Morena County Park | Caution | satellite based visual observation |
| Mar 30, 2026 | Lake Morena County Park | Caution | satellite based visual observation |
| Jul 30, 2024 | Lake Morena County Park | Caution | Advisory based on visual and toxins |
| Jul 29, 2024 | Lake Morena County Park | Caution | Lake-wide advisory; satellite based visual observation |
| Jan 9, 2024 | Lake Morena County Park | None | Advisory based on visual and toxins; Lake-wide advisory |
| Jan 2, 2024 | Lake Morena County Park | Warning | Advisory based on visual and toxins; Lake-wide advisory |
| Dec 21, 2023 | Lake Morena County Park | Warning | Advisory based on visual and toxins; Lake-wide advisory |
| Dec 21, 2023 | Lake Morena County Park | Warning | Advisory based on visual and toxins; Lake-wide advisory |
| Dec 15, 2023 | Lake Morena County Park | Warning | Advisory based on visual and toxins; Lake-wide advisory |
| Dec 11, 2023 | Lake Morena County Park | Caution | Advisory based on visual and toxins; Lake-wide advisory |
| Dec 4, 2023 | Lake Morena County Park | Danger | Advisory based on visual and toxins; Lake-wide advisory |
| Nov 20, 2023 | Lake Morena County Park | Danger | Advisory based on visual and toxins; Lake-wide advisory |
| Nov 6, 2023 | Lake Morena County Park | Danger | Advisory based on visual and toxins; Lake-wide advisory |
| Oct 31, 2023 | Lake Morena County Park | Danger | Advisory based on visual and toxins; Lake-wide advisory |
| Oct 30, 2023 | Lake Morena County Park | Danger | Advisory based on visual and toxins; Lake-wide advisory |
| Oct 23, 2023 | Lake Morena County Park | Danger | Advisory based on visual and toxins; Lake-wide advisory |
| Oct 16, 2023 | Lake Morena County Park | Danger | Advisory based on visual and toxins; Lake-wide advisory |
| Oct 9, 2023 | Lake Morena County Park | Danger | Advisory based on visual and toxins; Lake-wide advisory |
| Oct 2, 2023 | Lake Morena County Park | Danger | Advisory based on visual and toxins; Lake-wide advisory |
| Sep 25, 2023 | Lake Morena County Park | Danger | Advisory based on visual and toxins; Lake-wide advisory |
| Sep 8, 2023 | Lake Morena County Park | Danger | Advisory based on visual and toxins; Lake-wide advisory |
| Aug 29, 2023 | Lake Morena County Park | Danger | Advisory based on visual and toxins; Lake-wide advisory |
| Aug 25, 2023 | Lake Morena County Park | Danger | Advisory based on visual and toxins; Lake-wide advisory |
| Aug 25, 2023 | Lake Morena County Park | Danger | Advisory based on visual and toxins |
Source
Advisory data: California State Water Resources Control Board, Freshwater Harmful Algal Bloom Program, via data.ca.gov (public domain). Advisories are recommendations; reporting is voluntary and incomplete. The state's data. An advisory ends only when the state records a later "None" (no advisory recommended) at the same spot, or an end date. A blank end date is unknown.