Blue River has been described as the best remaining example of a natural and scenic river in Indiana. In 1975, it was designated a State Scenic River for the over 45 miles of the river that courses through Washington, Harrison and Crawford Counties. This designation helps government regulators to terminate or modify any projects, public or private that would harm the river's natural features. The Nature Conservancy has also designated the Blue River one of Indiana's Last Great Places. Based in part on the research done here at Indiana University Southeast by ecology students and Professors Forsyth and Baker, The Nature Conservancy of Indiana has established a Field Office in Corydon.This office was purchasing and preserving ecologically sensitive property along the river and is conducting research in the area. IUS provided student interns for three of their projects.
Blue River of southern Indiana, a fourth order tributary of the Ohio River, has the reputation of being a high quality, scenic stream with an ample population of game fishes and an unmatched population of rare swift-water, darters. The spotted darter may occur only in this stream in Indiana. The range of the bluebreast darter and the variegate darter in Indiana is very limited. Blue River is also known worldwide for its large population of hellbender salamanders, Cryptobranchus allegheniensis.
The river’s watershed has the large number of cave systems with springs emptying into the mainstream of the river. The largest spring in Indiana, Harrison Spring, and one of the largest cave systems in Indiana, Wyandotte Cave, are located in the watershed. Both areas support populations of northern blindfish, Amblyopsis spelaea and many poorly known subterranean species.
Blue River is located in the Escarpment Section of the Shawnee Hills Natural Region and in the Mitchell Plain Section of the Highland Rim Natural Region. The upper forks of the Blue River are located almost wholly in the Mitchell Karst Plain, a region known for its extensive sinkhole plains and cavern systems.
The stream’s headwaters are well to the Northeast in Clark, Scott and Washington Counties, Indiana. In Washington County, various creeks and smaller branches combine to form the South, Middle and North Forks of the river. The Middle Fork and North Fork join south of Salem while the South Fork flows southwest joining Blue River just North of Fredericksburg, Indiana. Below Fredericksburg, the only significant tributary is Whiskey Run joining the stream North of Milltown. An accompanying map illustrates the location of Blue River as well as the locations of all study sites (Figure 1).
The river’s mainstream serves as the border between Harrison and Crawford Counties along a major portion of its 45-mile length. Years of erosion and cave formation have produced a watershed with sloping hillsides covered by deciduous trees. Large leaning sycamore trees with huge rootwads are characteristic shoreline features. In some areas, the river has a sufficient floodplain to provide flat farmland. The major soil along the river is the Haymond silt loam, a deep, nearly level, well-drained soil with a moderate amount of organic matter.
The river has a fairly typical set of instream features including alternating fast water riffles and slower moving pools. Some very swift high velocity riffles provide the preferred habitat for the endangered spotted, bluebreast and variegate darters. The banded darter, uncommon in other southern Indiana streams frequents Blue River's swift, high discharge riffles, and it inhabits the slower riffles and pools as well.
Most riffle areas have boulder, cobble and gravel substrates that offer shelter and attachment areas for fishes and macroinvertebrates. Dissolved oxygen levels are near saturation in these riffles. Near the riffles, one often finds a gravel outwash community consisting of smartweed, small sycamores and waterwillow growing on the rocks and sand. Relict mussel shells are often washed into these areas during flooding.
This area of southern Indiana has four well-defined seasons. The weather is continental by nature and is variable because of its position in the mid-latitudes. We are in a belt where southwesterly winds bring us storms when moisture is pumped up from the Gulf of Mexico ahead of the fronts. As winter storms move from west to east, the area is subject to substantial rainfall. During the spring and summer, point source thunderstorms and fronts can dump considerable precipitation. Runoff causes the river to rise dramatically. At these times, the river will run muddy for several days. The month with the lowest rainfall is usually October. During this month, the river is often low and clear.Collection of specimens during this time is usually advisable.During 1999, we had a severe summer drought that significantly reduced Blue River's discharge and concentrated the fish populations.Many pools in the Blue River are long, deep and have a variety of shoreline fish habitats including rootwads, logs, brush, and rock outcrops. Some areas with mud banks have undercuts that provide additional shelter for game fishes like spotted bass and longear sunfish.