The Big Hole is Impaired. Will it Hinder the Jefferson?

Montana's Department of Environmental Quality declared the Big Hole River environmentally impaired early this month, which may be problematic for swimmers and anglers planning to enjoy the county's namesake waterway.

Brian Wheeler, a program director at the water monitoring nonprofit Save Wild Trout, said the issue in the Big Hole, a key Jefferson River tributary, is eutrophication, meaning that it's over-enriched with nutrients like nitrogen and phosphorus, causing large algal blooms.

When they decompose, these blooms cause a drop in dissolved oxygen, potentially creating "dead zones" that su...