Box 1.3 The Chesapeake Bay: Watershed Management Meets Airshed-Scale Problems
The restoration of the Chesapeake Bay has been the focus of intense effort over the last 20 years. The hydrologic watershed covers 64,000 square miles (102,979 sq. km.), encompassing parts of the states of New York, Delaware, Pennsylvania, Mayland, Virginia, and all of Washington, D.C. Three of these states, (VA, MD, PA) and the District of Columbia, together with the USEPA, have joined together in a cooperative effort to clean up the Bay. The have set a goal to reduce the phosphorus and nitrogen entering the Bay by 40 percent. Each state has planned its own approach to meet the goal, using techniques such as a ban on phosphates in detergents; vegetated buffers along streams, wetlands, and bay edges; and more stringent regulations on septic tank placement and operation. But when the Chesapeake Bay Commission modeled the nutrient inputs from the various land and water sources and compared them other amounts found in the Bay, they could not balance the equation. Researchers finally realized that the unaccounted for nitrogen (25-33 percent) was coming from air pollution.
The airshed for the Chesapeake Bay covers 350,000 square miles (563,150 sq. km.) and ranges north to Ontario, to Indiana, and to Tennessee and North Carolina. Atmospheric deposition is also the Bay's leading source of toxic pollutants such as zinc, lead, and mercury. The smallest particles, which are not regulated at this point and which carry the greatest concentration of toxics, are washed out of the air by rain. This enriched rainwater falls directly into the Bay as well as onto the land that drains into the Bay.
This illustrates the difficulty of defining boundaries when dealing with environmental problems. What are the boundaries that we need to be concerned with if we are working to restore the Chesapeake Bay to a healthy aquatic system with an abundance of crab, oysters, and rock fish?