Lake Okeechobee is the "liquid heart" of South Florida.  It is a large, shallow lake located in south-central Florida.  The lake has a surface area of 730 square miles and is relatively shallow, with an average depth of 9 feet (2.7 meters). It is the second-largest freshwater lake in the continental United States, second only to Lake Michigan.  Lake Okeechobee's drainage basin covers more than 4,600 square miles (11,913 km2).  An extensive network of monitoring sites provide data about flood control, water supply, and water quality. By monitoring Lake Okeechobee's waters, the South Florida Water Management District is gaining a better understanding of this essential part of South Florida's heritage, and can make more accurate predictions and plans for the continuing protection of this great resource.