The Columbus Dispatch recently reported, citing a study by two environmental groups, that at least half the manure in the Maumee River’s watershed comes from often sizable livestock farms that aren’t big enough to be required to obtain state permits.

The Maumee is the largest watershed in the Great Lakes basin, and it sluices phosphorus-laden manure from these poorly regulated livestock farms directly into Lake Erie. There, the phosphorus feeds toxic algal blooms that threaten drinking water for millions.

Most of the Maumee watershed is in Ohio — where only 14 percent of livestock operations have state permits, The Dispatch reported. Without an Ohio permit, there are no routine state inspections.

The study by the Environmental Working Group and Environmental Law & Policy Center used satellite and aerial photos and state permit figures to track unregulated livestock farms.

Among other findings was a 40 percent jump overall over the last 13 years in the number of hog, cattle and chicken farms in the Maumee watershed, which also reaches into Indiana and Michigan.

Ohio’s shamefully lax regulation of factory farms is something the state can and must change if it’s serious about preserving Lake Erie.

The Dispatch reported, for instance, that Ohio requires permits for farms with 700 or more mature dairy cows — but not for a farm with 699 cows.

But 699 dairy cows are capable of producing more than 52 tons of manure every day (based on a New York Times report from 2009 that a single, lactating Holstein cow on average produces 150 pounds of waste daily).

The phosphorus from manure that gets into the Maumee River and thence into Lake Erie promotes the growth of algae, which in turn can produce a toxin that poisons drinking water supplies. In 2014, an algal bloom in western Lake Erie contaminated public drinking water for hundreds of thousands in the Toledo area. That threat remains.

A solution is possible. Some of the $900 million that Gov. Mike DeWine, very much to his credit, wants to earmark for freshwater protection for Lake Erie and Ohio’s other freshwater sources should be used to bulk up Ohio regulation of farm runoff. It could also be used to provide aid to smaller farmers who want to limit — or better yet, prevent — runoff.

Many of Ohio’s farmers are dedicated stewards of land and water. Factory farms don’t necessarily share those values. That’s why — absent tougher state policing — Ohio faces a critical challenge in keeping Lake Erie from becoming a farm-waste cesspool.

Last summer, due to agribusiness griping, legislative Republicans stymied a bid by then-Gov. John Kasich, a fellow Republican, to clean up parts of the Maumee basin. That must not happen again: The public interest in protecting Lake Erie must outweigh the demands of a special interest seemingly more inclined to exploit rather than conserve a resource that belongs to every Ohioan.

— The Plain Dealer, April 21; Online: https://bit.ly/2KWmmU1