When a blaze ignited Ohio’s Cuyahoga River on June 22, 1969, it wasn’t the first—or worst—time the notoriously filthy waterway had caught fire. But national media outlets seized on it as a stark example of the abysmal state of the nation’s waters after decades of unchecked industrial and sewage pollution.

Coming at a time of growing public concern over the environment, the fire was one of many issues that spurred Congress to pass ambitious and bipartisan landmark legislation. In the 50 years since the Clean Water Act (CWA) became law, the health of U.S. rivers, lakes and streams has improved. On the Cuyahoga, insects, fish and birds that are sensitive to pollution have returned, as have kayakers and recreational fishers.

But the CWA is under attack in the court system by people who would weaken it, and there are multiple sources of pollution that the current law doesn’t adequately address. The National Resources Defense Council reports that as of 2019, more than 80 percent of bays and estuaries and around 55 percent of rivers and streams harbored unsafe levels of at least one pollutant. For the sake of our health and economic prosperity, we need stronger protections for our waterways—and we need our courts to uphold the CWA against its current challenges.

A major question in the court debate is what bodies of water the CWA covers. The objective of the law “is to restore and maintain the chemical, physical, and biological integrity of the Nation’s waters” and to eliminate the “discharge of pollutants into the navigable waters.” The Environmental Protection Agency and the Army Corps of Engineers, which administer the CWA, have always interpreted those mandates broadly. But the Trump administration issued rules in 2020 that left out many wetlands and smaller streams under the reasoning that they were not navigable and therefore were not subject to pollution limits.

Although the Biden administration has proposed rules that would restore protections to small streams and wetlands, a Supreme Court case on the docket for this fall could undermine them. In Sackett v. EPA, the petitioners argue that wetlands on their property—and by extension millions of acres of other wetlands—are not covered by the law. But these wetlands connect with other, navigable waters, and as 12 scientific societies have stated in an amicus brief, that argument “rejects hydrological reality.” Water in a river cannot be adequately protected unless we also protect the many sources that feed into it. The Supreme Court therefore must follow the science and rule in favor of the EPA. This ongoing legal wrangling also underscores the need for Congress to strengthen the CWA using the best available science.

Congress also must finally confront a long-standing issue: the CWA addresses point sources of pollution, such as factories and sewage systems, but it does not sufficiently tackle pollution from nonpoint sources—the chemicals from parking lots, roadways, fields and lawns that can be washed into waterways by rain or snowmelt. Agricultural and lawn fertilizers contain nitrogen and phosphorus, which have been shown to feed toxic algal blooms from the Gulf of Mexico to the Chesapeake Bay to Lake Erie. Such blooms have contributed to fish die-offs, and in 2014 one rendered the tap water in Toledo, Ohio, unsafe to drink.

Congress must take stronger action to rein in this pollution, whether by amending the CWA beyond a largely voluntary measure exempting agricultural runoff or through other legislation that targets nonpoint sources. Policy makers should work with farmers, ranchers and scientists to develop strategies tied to clear metrics and provide tangible incentives. One example is a program to pay ranchers in Florida to retain water and nutrients on their lands. In addition, the EPA should set environmental limits for nitrogen and phosphorus so states will have to set standards for them under the CWA, which will help reduce loads of these pollutants from point sources.

We have made notable progress toward Congress’s 1972 goal of eliminating pollution from the nation’s waters so people can once again fish and swim in them and draw their drinking water from them. The Supreme Court and members of Congress now have the chance to uphold existing law and enact bold, visionary legislation—to live up to the legacy of their predecessors and ensure clean water for the generations to come.