TOLEDO, Ohio - The harmful algal bloom has blossomed across Lake Erie, covering almost the entire western basin of the lake, with shoots as far east Lorain County.

We've had the ideal conditions: calm winds, lots of sun, hot temperatures and plenty of phosphorous - mostly spring fertilizer runoff from farm fields in Northwest Ohio.

"In the last two weeks it's really gone from nothing to something," said Chris Winslow, director of the Ohio Sea Grant program at Ohio State University, which studies the bloom.

The bloom has been an annual problem around Toledo, Sandusky and the Erie Islands, when blue-green algae produces a toxic cyanobaceteria.

The bloom this year isn't so bad; it rates about a 7.5 on a 10-point scale, about the same as in 2013, Winslow said. (In 2015, scientists rated the bloom a 10.5.) That's exactly what scientists expected.

Drinking water is not in danger, unlike in 2014, when 500,000 Toledo-area residents went without water for three days. But green scum covers miles of Lake Erie surface. The Toledo-Lucas County Health Department issued a recreational public health advisory, recommending that children, pregnant women and pets stay out of the Maumee River. And Toledo Mayor Paula Hicks-Hudson changed course this week, announcing her support to federally designate the open waters of Lake Erie "impaired."

"It is about the Clean Water Act but it is also about climate change. It's about us really looking at what has really happened today," Hicks-Hudson told the Toledo Blade. "I am going to do every thing I really can to make a dent in this problem we are facing."

Water near the shoreline and around water intake cribs are already considered federally impaired.

In May, the U.S. Environmental Protection Agency has approved a list of impaired waters in Ohio that did not include Lake Erie's open waters. Michigan's section of the lake is designated impaired, but Ohio disagrees with the status.

"But what we don't disagree on is that the lake has very serious problems," Ohio EPA Director Craig Butler said in a phone interview Wednesday.

So what's the EPA doing?

The EPA has given a grant to researchers at Ohio State and the University of Toledo to sample water quality this year and next, to come up with a measurement to create an impairment threshold in time for the next federal designation in 2019.

"If we were to call the lake impaired, what data would we use to make that declaration?" Winslow said. "It's not a trivial thing."

What about the federal government?

On Wednesday, U.S. Sen. Rob Portman the Senate had reauthorized a program to help states deal with harmful algal blooms.

"It is important that these water bodies are protected, as they supply drinking water to millions of Ohioans and are critical for Ohio's tourism and fishing industries," Portman said in a statement. "I am pleased that this program has provided a toolkit and forecasts that help our communities prepare for and respond to the impact of HABs."

How do you forecast a bloom?

Every year, Winslow and other scientists forecast the size of the bloom, mainly based on rain between March and July. They consider how much rain the farm fields around the Maumee River got, and how hard each rain storm was.

The number of storm runoff events per year was up 67 percent from 1960 to 2010, according to Ohio Sea Grant.

The Maumee River contributes half of all phosphorus in the lake, with about 85 percent of it from fertilizer runoff. So scientists are working with farmers to try to reduce phosphorus runoff by 40 percent by 2025.

What would impairment mean?

Designating Lake Erie as impaired wouldn't necessarily make that goal easier to enforce, though, Butler said. It could instead create litigation that would slow progress.

Officials also question how you could get rid of the designation, when conditions approve. They don't want to scare away swimmers and boaters.

"This designation of federal impairment is not a silver bullet," Butler said. "We share the same concerns. There are serious problems in the lake. We continue to not shy away from it and focus on how to fix it."

For more Lake Erie news, visit www.RocktheLake.com.