Lake Pepin, located roughly 60 miles downstream from St. Paul, is the largest lake on the Mississippi River. It is approximately 21 miles long, covers about 29,295 acres, and has a maximum depth around 60 feet. The lake formed when sedimentary deposits of the Chippewa River's delta restricted the flow of the Mississippi River, causing water to backup. Several tributaries enter into Lake Pepin, such as the cold water Bullard, Gilbert, Miller, and Wells Creeks. Lake Pepin has slower flows as the river widens into a lake, so it is susceptible to the pressures of pollution from upstream areas such as excess nutrients and sediment. Lake Pepin is part of the USACE's 9-Foot Channel Navigation Project and is in navigation Pool 4. Several natural areas and parks lie along Lake Pepin, such as Espen Island State Wildlife Management Area, Pierce County Islands State Public Hunting Grounds, Frontenac State Park, Rush River Delta State Natural Area, and Maiden Rock Bluff State Natural Area. Lake Pepin is a popular recreational destination for activities such as boating and fishing.Lake Pepin was routinely sampled by Metropolitan Council in the late 1970s and early 1980s at several locations as part of the Large Rivers Monitoring Program. Additionally, several locations on Lake Pepin and Rush River were monitored as part of a special phosphorus study in 1996. The last sample collected by Metropolitan Council in Lake Pepin occurred in 2006.The Mississippi River is one of the world's largest rivers, flowing over 2,300 miles through the center of the United States. It begins at Lake Itasca in northern Minnesota and ends at the Gulf of Mexico, where pollutants carried by the river contribute to the Gulf's Dead Zone. Millions of people rely on the Mississippi River as a source of drinking water, and the river is also an important waterway for shipment of commodities. The Mississippi River watershed is the 4th largest in the world at about 1.2 million square miles. The section of the watershed in and upstream of the Twin Cities Metropolitan Area has a mix of several types of land including forests, wetlands, agriculture, and developed areas.