The Niobrara River (/ˌnaɪ.əˈbrærə/; Omaha–Ponca: Ní Ubthátha khe, pronounced[nĩꜜubɫᶞaꜜɫᶞakʰe], literally "water spread-out horizontal-the" or "The Wide-Spreading Water") is a tributary of the Missouri River, approximately 568 miles (914 km) long,[2] running through the U.S. states of Wyoming and Nebraska.[3] The river drains one of the most arid sections of the Great Plains, and has a low flow for a river of its length. The Niobrara's watershed includes the northern tier of Nebraska Sandhills, a small south-central section of South Dakota, as well as a small area of eastern Wyoming.
^U.S. Geological Survey. Many early settlers, such as Mari Sandoz, referred to the river as Running Water. National Hydrography Dataset high-resolution flowline data. The National Map, accessed March 30, 2011