The Niobrara is a relatively undammed river for most of it's 535 miles. The only dam that currently exists on the Scenic River stretch is Cornell Dam. Cornell Dam is located on the Ft. Niobrara National Wildlife Refuge and has a significant historical context for the Niobrara River Valley and the nearby town of Valentine. The dam was built in the early 1900's, but has not been operational since 1984. It now exists as a "run-of-the-river" dam, however it still serves as an impediment to upstream migration of aquatic species. It also continues to alter the hydrology of the upper portion of the Scenic River stretch.
Another important environmental factor affecting the Niobrara National Scenic River valley are several exotic plant species including purple loosestrife, leafy spurge, Canada thistle, and spotted knapweed. Currently, The Nature Conservancy has integrated a biological control program on the Niobrara Valley Preserve (TNC owns approximately 25 miles of riverfront property in the Scenic River corridor) by releasing Galerucella spp. beetles to control loosestrife. Additionally, the University of Nebraska-Lincoln has an experimental plot on the Preserve where researchers are examining the effects of different tilling and mowing regimes on purple loosestrife.
Water quality is also another environmental factor that is of major concern to resource management staff at Niobrara National Scenic River. We have recently implemented a long-term water quality monitoring program that monitors dissolved oxygen, pH, turbidity, conductivity, and a variety of other chemical factors specifically targeting tributaries with major waterfall attractions and various points along the mainstem of the Niobrara. In the future, resource management staff will also implement an aquatic invertebrate sampling program that will complement the chemical component of the water quality monitoring program, and will give a more comprehensive evaluation of the ecological impacts to the Niobrara National Scenic River watershed.