The Rock River watershed covers 1,075,032 acres in Rock, Nobles, Pipestone and Murray counties in southwestern Minnesota. It is the largest of the four watersheds in Minnesota that are part of the Missouri River Basin, extending south into Iowa.
Land use in this watershed is primarily agriculture, with most land in row crop production. Pastureland is also prevalent throughout the watershed. There are no natural lakes in this watershed. Some of the larger communities in the watershed are Luverne, Adrian, Edgerton and Wilmont.