Back in 1985, Congress set some erosion control standards for agricultural lands; they were to be put in place over a 10-year period, and many have continued since then. A study just released by the Natural Resources Conservation Service indicates that, for the Great Lakes region, those efforts have had measurable success.
The NRCS study used computer simulations to show that about 50% less sediment now enters the Great Lakes than would have been the case without the changes in cultivation and erosion control practices. It also estimated that about 30% less phosphorus and nitrogen enters the Great Lakes. Excess nutrients—such as the nitrogen and phosphorus in many fertilizers—are responsible for algae blooms, not only in the Great Lakes but also in other parts of the US, including the Gulf of Mexico and Chesapeake Bay, and around the world. Despite the numbers, though, algae blooms are still a serious problem in most of the Great Lakes, and the study did not specifically measure the dissolved phosphorus believed to be mainly responsible for the algae growth.
This study of the Great Lakes Basin follows similar studies of the upper Mississippi River and Chesapeake Bay area; 11 more studies are planned for major US watersheds to assess how changing erosion control practices are affecting water quality. Congress has indicated that it will authorized more money for farm programs that promote erosion control.