Chief tributary of the Murrumbidgee River , central New South Wales , Australia.
Rising in the Great Dividing Range , it flows northwest and turns southwest, joining the Murrumbidgee after a course of 930 mi (1,500 km). Though usually perennial, it may run dry in severe drought years. It was explored in 1815 by George W. Evans and was named after Lachlan Macquarie, governor of New South Wales.