The Blue River field site, Harrison Spring, is named for the largest spring in Indiana. Harrison Spring is quite unusual because it captures a portion of it's water from Indian Creek downstream from Corydon. This water then percolates through the karst, surfacing as Harrison Spring near the study site. The site is located off of Highway 62 on Harrison Springs Road at a point 12.48 river miles from the Ohio River. The actual sample site is located in Harrison County, and is the first sizeable rifle upstream from where the spring itself empties into the Blue River. The site was accessed by walking up the stream bed. Harrison Spring was evaluated at 1:10 PM EDT on October 7, 1999. The weather was pleasant with sunshine, and an air temperature of 70 degrees.
The general area around this portion of the river is second growth forest. The riparian area was moderately steep with a road on the northern side, and some agriculture nearby. The immediate area around Harrison Springs proper is open field. Along the banks there are extant root wads providing habitat. Bank vegetation and streamside cover were rated as excellent and the large amount of understory vegetation provided substantial bank stability.
Upstream from the riffle there are large rocks along the banks. Immediately behind these are stands of sycamore and beech trees. Facing downstream to the left there are again large rocks. There are also stands of water willow and sycamore and beech trees. Also along the left bank slightly farther downstream was a newly forming gravel bar. Downstream on the right is a complex gravel outwash community. This area has a large fringe of water willow and small sycamore trees. Next to the right bank there was a dry race.
The physiographic region is characterized by mesophytic forest and is part of the Eastern Deciduous Forest Biome, Highland Rim Natural Region, Mitchell Karst Plain Section. The bankside soils are classified as Crider Silt Loam.
The study riffle site was approximately 18 feet wide with an average depth of 5.7 inches. The average velocity in the riffle was 5.5 feet per second and the discharge was 37 cubic feet per second. Upstream from the riffle there is a wide expanse of pool that is naturally channeled on the left side and had a maximum depth of 10 feet. Nearing the riffle, this pool shallowed to be ankle deep. Downstream, the riffle gives way to another pool. This pool constitutes the entire width of the river at this point and goes downstream for several hundred yards. This pool is not quite as deep as the upstream one. On average downstream is 3 feet deep. Once again the left side is channelized and gives the greatest depth.
The substrate of the riffle was sand and gravel. The bottom of the riffle ended in sand, rock and silt. The pools at this point in the river were mainly covered by rocks, cobbles and sand. In several areas the rocks were covered with a layer of algal growth. Fallen leaves were also noted on the river bottom.
There were no disturbances noted at this site.
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