The Niobrara River (; Omaha-Ponca: Ní Ubthátha khe, pronounced [nĩꜜ ubɫᶞaꜜɫᶞa kʰe], literally "water spread-out horizontal-the" or "The Wide-Spreading Water") is a tributary of the Missouri River, approximately 568 miles (914 km) long, running through the U.S. states of Wyoming and Nebraska. 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. Source: Wikipedia