The Potomac, which runs through the heart of the United States Capital, has suffered centuries of environmental degradation. Water quality has declined steadily as more humans have populated its watershed. However, according to new research, the river is beginning to benefit from restoration efforts that have improved water clarity and reduced nutrient overload. The result has been a ten-fold increase in native submerged aquatic vegetation (SAV). This SAV consists of plant life below the water surface which is an important habitat for fish and other marine life.