The Platte Rivers
The Platte Rivers drainage system is the largest and longest in the state. I say “rivers” because this drainage comprises the North Platte, South Platte, and from the confluence of these two to the Missouri River, the Platte River. The combined rivers in Nebraska run from the Panhandle at Henry, Nebraska (North Platte) and near Big Springs, Nebraska (South Platte) to the confluence with the Missouri River north of Plattsmouth, Nebraska.
Both the North and South Platte Rivers have their headwaters in Colorado. The headwaters of the North Platte River are near Walden, Colorado, in the north-central Rocky Mountains. The headwaters of the South Platte River are near Hartsel, Colorado, in the east-central Rocky Mountains.
The complete article can be found on Cropwatch at https://cropwatch.unl.edu/2023/major-nebraska-rivers-and-their-drainages-part-5.