BUTTE FALLS — Bob Jones hopes a good new fence will make good neighbors out of cattle grazing around Willow Lake.

BUTTE FALLS — Bob Jones hopes a good new fence will make good neighbors out of cattle grazing around Willow Lake.

Jones, a Medford Water Commission geologist, is overseeing a project to encircle Willow Lake with barbed-wire fencing to keep free-ranging cattle and their nitrogen-rich cowpies out of the lake.

The cattle are believed to be a significant contributor of nutrients that can trigger massive blue-green algae blooms, which have tainted the lake's water quality at times and kept anglers away.

The nearly three miles of barbed-wire fencing will stretch around the lake from one edge of Willow Lake County Park to the other, keeping cattle from entering the lake bed and wandering into the park's campgrounds.

"It's one way to help minimize nutrient loading into the lake," Jones says. "It's a big factor, but it's not the sole source by any means."

The 927-acre lake is not used for drinking water. The impounded water is diverted by the Eagle Point Irrigation District in exchange for EPID water rights to Big Butte Springs, the main water source for the city of Medford.

The $30,000 fence, built by commission employees, is about two-thirds done and contains several entry points so anglers can gain access to the shoreline outside the county park.

"We're actually trying to be fishermen-friendly," Jones says. "They won't have to climb over the fence to fish."

"Keeping cows out of the lake has to be a good idea," says Richard Spink of Klamath Falls, who was driving past two commission employees as they extended the fence Friday along Forest Service Road 3050, which is directly across the lake from the park. "Just think about it."

Oregon has been thinking a lot about blooms of blue-green algae over the past decade. The potentially toxic blooms appear routinely across the state, mainly in the summer during warm spells.

The algae are actually cyanobacteria that can bloom quickly and release toxins when they die.

When algae levels rise above Oregon Public Health Department standards, the agency issues an advisory asking people and pets to avoid all water contact, but compliance is voluntary. Anglers are encouraged to practice catch-and-release fishing during advisories.

Toxins cannot be filtered by standard camp filters or by boiling the water. In-home filtering systems cannot cleanse the water, though public treatment plants can reduce algae toxins through filtration and disinfection.

People who eat fish from algae-tainted waters should remove all fat, skin and organs before cooking, because toxins can collect there. People should not eat crayfish or freshwater shellfish taken from infested lakes during an advisory.

Not all blue-green algae strains produce toxins dangerous to people or pets, and not all blooms release toxins.

No confirmed human illnesses have been tied directly to an algae outbreak in Oregon. However, at least four dogs have died in recent years from toxins in water near the Umpqua River near Elkton.

Willow Lake last suffered a blue-green algae infestation in 2010, when two different blooms rendered the lake a health risk for 165 days. Angler visits dwindled to nearly nothing, forcing the park's concessionaire to relinquish his contract to operate there.

Tests showed the second bloom, which lasted 64 days, actually produced toxins, Kann says.

The reasons for algae outbreaks can be different from one body of water to another. Jones hopes that study will shed some light on how to keep Willow Lake from developing the neon glow from algae.

"Not that we can get a concrete answer, but we want to see if there are some management practices we can have in place to minimize algae," Jones says.

Reach reporter Mark Freeman at 541-776-4470 or mfreeman@mailtribune.com.