The algal blooms have returned in force to Lake Erie, in a matter of a few warm, sunny weeks. They range from the western basin near Toledo to the north near Canada and east along the shoreline to Lorain County. The thickish, fetid green slime is evidence of an ailing body of water. This isn’t the lake that one generation responsibly hands to the next.

Lake watchers report that this blanket of algae isn’t the largest or the most toxic of late. Recall the blooms stretching as far as Cleveland two years ago and in 2014 infiltrating the Toledo city water supply, resulting in 500,000 people without drinking water for three days.

Those episodes were alarms, and so are the current algal blooms, the risk there for something worse. Millions depend on Lake Erie for their drinking water. For others, the lake supports their livelihood, or serves as recreation. Along with the rest of the Great Lakes and their one-fifth of the world’s fresh surface water, Erie is a natural treasure to protect and preserve.

Practically everyone agrees on the need to act. Ohio, Michigan and the Canadian province of Ontario have set an objective — reduce the algae-fueling phosphorous pollution flowing into the lake 40 percent by 2025.

That goal reflects the analysis and recommendations of scientists. An Ohio task force came to the same conclusion in 2013. The International Joint Commission, a U.S.-Canadian panel with the job of overseeing the Great Lakes, reinforced the thinking a year later.

The argument involves how to get there. Ideally, the federal Environmental Protection Agency would declare the open waters of Lake Erie to be “impaired.” That would trigger the development of an action plan, with requirements and deadlines. Unfortunately, that isn’t likely, some even warning that an “impaired” designation merely would bring lawsuits.

Or prove hard to define, or the label difficult to shake, ultimately.

Clear enough is the consensus: To get rid of the algal bloom problem, phosphorous pollution, the largest share coming from farming operations in the Maumee River Valley, must be reduced by the necessary amount. Get there, and the lake no longer would be “impaired.”

The state Environmental Protection Agency recently released the draft of its latest plan to fight the algal blooms. The plan contains many helpful steps, including the restoration of wetlands (natural pollution controllers) and heightened monitoring of septic systems. It calls for more aggressive steps to limit manure runoff into streams and rivers.

The approach builds on advances already made by Gov. John Kasich and state lawmakers, plus Congress, for instance, limiting the use of fertilizer on frozen and rain-drenched fields and providing funds for the larger Great Lakes Restoration Initiative. Yet the concern remains that all of this falls short of the need.

Past experience reveals that success requires regulation with enforcement. It isn’t sufficient to rely on good intentions or voluntary programs. If continued study makes sense, the problem is plain, large farming and livestock operations contributing heavily to phosphorous runoff.

The federal EPA calculates that a reduction of 1.25 million pounds of phosphorous would bring a 20 percent reduction. To reach 40 percent? The agency says it will take an additional decrease of 7.3 million pounds. That won’t get done without strong rules and a firm regulatory hand. Until then, the algal blooms will keep coming.