A small stream in southwestern Indiana has become a striking example of how long-term watershed restoration can reverse ecological damage. In 2016, monitoring of a 1.27-mile section of Big Branch in Sullivan County revealed a severely degraded fish community. The stream’s Index of Biotic Integrity (IBI) score was just 18, a level classified as very poor. Seven years later, follow-up monitoring produced a dramatically different result: the fish IBI had climbed to 48, rated good, while habitat quality also improved substantially. The recovery has prompted Indiana environmental officials to recommend removing the segment from the state’s impaired-waters list for 2026.
Big Branch is part of the Mud Creek–Big Branch watershed within the larger Busseron Creek watershed. The approximately four-mile stream passes through a landscape dominated by forests, farmland, hay and pasture. Indiana Department of Environmental Management monitoring had identified ecological concerns, particularly elevated turbidity and total suspended solids. Agricultural runoff and historical pollution sources contributed to the biological degradation. Although the habitat assessment in 2016 was considered good, the fish community told a different story, demonstrating why water-quality restoration cannot rely on habitat appearance alone.
