The Clean Water Act made history when it passed in 1972, and, in the 50 years since, has gone far to clean up U.S. waterways and restore them as havens for recreation, wildlife and drinking. But experts say some provisions are outdated, and legal challenges threaten to undermine the reach of the landmark policy.

"After 50 years, we have made significant improvements to many of our water bodies. And that's something to absolutely celebrate," said Oday Salim, director of the University of Michigan's Environmental Law and Sustainability Clinic, which offers students real world experience in environmental law. "But we don't have enough improvement to enough of our water bodies." 

In June 1969, a blaze on the infamously-polluted Cuyahoga River near Cleveland, Ohio, ignited a wave of outrage and activism across the U.S. That fire, a symbol of other environmental calamities occurring at the time, was credited with inspiring the Clean Water Act of 1972. The bill made it illegal to dump waste from a "point source" into waterways unless specific permitting was obtained. 

"The main goals of the Clean Water Act are super simple, but they're also pretty audacious, you know, they're to make sure that our waters are fishable and swimmable, that we can recreate in them," Salim said. "And that [the fish] are thriving in them."

In many ways, the CWA has succeeded. The Cuyahoga River, for example, may not be perfect, but it is home to more than 70 species of fish and is a popular spot for boaters. 

"I have folks come into my office routinely from other states and around the world, wanting to see the Cuyahoga River," Kurt Princic, a district chief at the Ohio Environmental Protection Agency, told the Associated Press. "They want to know how we got from where it was in the '60s to where it is today. It starts with the Clean Water Act, partnerships and hard work."

The permitting process went far to address "point source" pollution, meaning sources of pollution that are visible or identifiable like facilities with sewage pipes or ditches. What the bill does not adequately address, Salim said, are indirect sources of pollution like agricultural runoff.

"I think most people would agree that the biggest shortcoming of the Clean Water Act is that it divided things into point sources and nonpoint sources," he said. "It didn't have to set up the same kind of permitting scheme for nonpoint sources, but it could have done more and it didn't." 

In addition to addressing past loopholes, lawmakers hoping to meaningfully impact water quality in the years ahead for the Clean Water Act must factor in new challenges like climate change and newly detected pollutants.

Because of climate change, waterways are growing shallower and warmer. Limitations on pollutants should be adjusted accordingly, Salim said. 

Furthermore, regulators are just getting around to addressing classes of chemicals like per- and polyfluoroalkyl substances or PFAS. These chemicals have been linked to an array of conditions like cancer, birth defects, decreased fertility and obesity, according to the Environmental Protection Agency. And researchers and industry leaders have known since the 1950s that these so-called "forever chemicals" build up in blood. Even so, it's estimated that 83 percent of U.S. waterways contain these chemicals, according to a report from Waterkeeper Alliance. 

"There are some kind of unregulated pollutants out there like PFAS, and the Clean Water Act needs to step up with new standards for those pollutants," Salim said.

One more area that could be improved, Salim said, is how the Clean Water Act's revolving fund for clean water infrastructure is allocated. As federal investment overall in clean water infrastructure has fallen, those funds increasingly go to well-resourced cities, but communities of color and lower income communities need clean water too. 

"The Clean Water Act as a legal tool -- how can it achieve environmental justice more effectively? How can it make life better for black and brown communities and low income communities, Indigenous communities?" Salim said.

These are big questions on the anniversary of the Clean Water Act, at a time its scope is under threat. 

The Supreme Court heard opening arguments on Sackett vs. EPA in early October, which concerns a couple looking to build atop wetlands on their property near Priest Lake in Idaho. The EPA argued the property is subject to the Clean Water Act. If the agency loses, half of the wetlands and 60 percent of streams could lose protections from the CWA , according to the Washington Post. 

The conservative makeup of the Supreme Court raises concerns among environmentalists about the possible toll on the environment, and a recent decision did curb the EPA's regulatory powers over power plant emissions. 

But environmentalists did clock a victory in the County of Maui v. Hawaii Wildlife Fund case, in which the Supreme Court determined permitting also applied to groundwater discharge should it make its way to jurisdictional waters.

"I'm naïve enough to think that we can still get some things done in bipartisan fashion," Salim said.