This is a famous river in Serbia, the 2nd largest after the Donau.
Anyways, this tone poem, with Spring in mind, flowers blooming, animals coming to life, water flowing, then gushing, all to end very peacefully when the river quietly joins the Donau river in Belgrade at the Kalimegdan Park.
Note: Bedrich Smatana of "the Moldau" fame inspired me to name this music after another river in another country...