Complex sentence: Keeping north over the watershed, he traversed the Claude and Nogoa rivers, then reached the Belyando River an upper reach of the Burdekin River, discovered by Ludwig Leichhardt on his expedition to Port Essington, on 2 April 1845.
Split into simpler sentences: Keeping north over the watershed, he traversed the Claude and Nogoa rivers, then reached the Belyando River an upper reach of the Burdekin River. This had already been discovered by Ludwig Leichhardt on his expedition to Port Essington, 2 April 1845.