The United States made good progress in cleaning up its lakes and rivers in the years immediately following the passage of the 1972 Clean Water Act. Then that progress slowed nearly to a stop.

Tuesday night, Hedrick Smith, producer of the Frontline program “Poisoned Waters,” explained what went wrong. Kris Sigford, MCEA’s water quality program director, participated on a panel with Smith and others that took audience questions for an hour.(That' s Kris, left, next to Minnesota Pollution Control Agency watershed section manager Glenn Skuta in a photo provided by Patrick Sweeney of Freshwater Society)

In the 1970s and 1980s, government officials went hard after point sources, that is, pipes from factories, sewage treatment plants, and other facilities that dumped pollution directly into a river or lake. The owners of those facilities received permits which required them to dramatically cut the pollution that came out of the pipe.

Now, however, much of the pollution comes from non-point sources, things such as water washed off of streets and parking lots and water runoff from farms.

“It used to be that 85 percent of the problem was point sources,” Smith said. “Now, 85 percent of the problem is non-point sources.”

Smith showed dramatic footage of a healthy body of water with fish and aquatic plants growing on the bottom. Then he showed a dead zone in the Chesapeake Bay that looked like the surface of the moon, with nothing growing and a dead crab lying on the bottom.

Sigford, in her opening remarks, told the crowd of about 125 people at the University of Minnesota’s St. Paul Student Center, that the dead zone in the Gulf of Mexico is the second largest in the world. It’s caused by too much phosphorus and nitrogen being washed into the Mississippi River and ending up in the Gulf and eventually causing the oxygen in the water to disappear.

Eighty percent of that nitrogen and 60 percent of the phosphorus is from agriculture run-off, Sigford said.

Smith concluded his talk by stressing two points.

 “We need to understand that we are all polluters,” and we need to find better, non-technical ways to communicate the causes of  polluted rivers and lakes to the general public, Smith said.

The talk was sponsored by the Freshwater Society, whose president, Gene Merriam, is a member of MCEA’s board of directors, and the University of Minnesota’s College of Biological Sciences.