What is the source of the Swan river?

The Swan River is fed by the Avon River, which has a catchment area of over 120 000 sq km. Another source of the Swan is the Mounts Bay Drain, part of a system which connects Lake Monger to the Swan River at Mounts Bay, near Perth. The Mounts Bay Drain was constructed in 1909 to allow regulation of water levels in Lake Monger.