The U.S. Army Corps of Engineers has reported the presence of harmful algae blooms in the Allegheny Reservoir at five monitoring locations.

Satellite images available through the U.S. Environmental Protection Agency’s Cyanobacteria Assessment Network’s mobile app showed high density of bluegreen algae in the reservoir, in the reach of the reservoir on Seneca Nation of Indians territory, on Aug. 5.

Seneca Nation staff collected water samples at reservoir access areas which confirmed that a bloom was occurring.

Rose Reilly, who leads the Corps of Engineers’ water quality unit, said Pittsburgh District HAB Response Plan was implemented at Allegheny Reservoir on Aug. 13. She said Clifford Redeye III of the Seneca Nation collected samples on Aug. 20.

“Cyanobacteria cell counts were at the World Health Organization (WHO) caution level at all sites sampled in the reservoir: near Lowbanks, Bearclaw (Quaker Bay), Highbanks, Moebanks, and Sawmill Bay (Onoville Marina),” Reilly said.

More samples will be collected this week.

The response plan “recommends the use of (WHO’s) guidelines for managing exposure to (bluegreen algae) in recreational waters. These guidelines were developed from direct evidence of acute, non-cumulative health effects associated with primary body contact in recreational surface waters with BGA blooms.”

At the caution level, “there is a high risk for adverse health impacts,” Reilly said. “When a HAB is confirmed, appropriate HAB signs are posted at lake access areas to inform the public of associated risk and algae samples are collected and analyzed weekly. Signs are left in place until algae cell counts remain below action levels for at least two weeks.”

According to the EPA, algal blooms can be toxic. Keep people and pets away from water that is green, scummy or smells bad.

Harmful algae blooms are caused by sunlight, slow-moving water and nutrients — nitrogen and phosphorus, inparticulart — which can be caused by pollution from humans.

Drinking, accidentally swallowing or swimming in water with a bloom can cause serious health problems, including rashes, stomach or liver illness, respiratory problems and neurological effects, according to the EPA.