The Nodaway River originates near the town of Fontanelle in southwestern Iowa as the Middle Nodaway River. The Middle Nodaway flows southwest to join the West Nodaway just below Villisca, Iowa. The East and West Nodaway join to form the mainstem Nodaway River four miles north of the Iowa-Missouri border and the river enters Missouri near Clearmont, Missouri. The mainstem river flows in a southerly direction about 60 miles to its confluence with the Missouri River near the town of Nodaway, Missouri (Figure Lo01). Major tributaries of the Nodaway River include Seven Mile Creek, Middle Nodaway River, East Nodaway River, and West Nodaway River in Iowa and Clear Creek, Mill Creek, Elkhorn Creek, and Arapahoe Creek in Missouri. The Nodaway River peak elevation is 1,400 feet mean sea level (M.S.L.) at its headwaters and 800 feet M.S.L. at the mouth.
The Nodaway River basin encompasses parts of 10 counties in southwestern Iowa and northwestern Missouri. Iowa's portion of the basin is located in Adair, Adams, Cass, Montgomery, Page, Taylor, and Union counties while in Missouri the basin covers portions of Andrew, Holt, and Nodaway counties. The population in the Nodaway basin has declined slowly and steadily since the 1950's. In 1970 there were approximately 35,000 people living in the basin. Clarinda, Iowa was the largest city with a population of about 5,500 people (USCOE 1973). Population in the basin as of the 1990 U.S. population census was 28,779 with the largest city in the basin still being Clarinda, Iowa (population 5,104).