Passage of the Clean Water Act of 1972 brought many improvements to surface waters by curbing much of the toxic and organic pollution going into waterways. But 42 years later, we have yet to make significant reductions in two major pollutants in our rivers, lakes, and coastal sounds—the nutrients nitrogen and phosphorus. Although nitrogen pollution overall has gone down in U.S. streams and rivers since 2004, it remains a serious problem in many waterways, and phosphorus pollution has gone up significantly. The problem is especially challenging in that the deleterious effects of nitrogen and phosphorus often occur hundreds or thousands of miles from where the nutrients originate.