The Juruena originates in the Parecis plateau.[2] Within Mato Grosso the river defines the eastern boundary of the 227,817 hectares (562,950 acres) Igarapés do Juruena State Park, created in 2002.[3] For the last 190 km (120 mi) of its lower part the river becomes the border between the states Mato Grosso and Amazonas.[2] In this section the river forms the boundary between the Sucunduri State Park to the west in Amazonas and the Juruena National Park to the east in Mato Grosso.[4] In the north of this section it forms the boundary between the Bararati Sustainable Development Reserve in Amazonas and the Apiacás Ecological Reserve in Mato Grosso.[5]