Simplify the following text for a Grade 6 native English-speaking person.
Original: The upper part of the river is sometimes called Valea ObÃ cents rÅ iei River or ObÃ cents rÅ ia IalomiÅ # ei River .
Simplified: The upper reach of the river is sometimes known as Valea ObÃ cents rÅ iei or ObÃ cents rÅ ia IalomiÅ # ei .