Castlereagh River
The Castlereagh rises 20 km west of Coonabarabran in the heart of the Warrumbungle mountains at an elevation of about 850 metres. From its commencement upstream in the mountains the river initially flows east through the town of Coonabarabran. It then arcs round south and southwesterly to the village of Ulamambri, then south to Binnaway, and SSW to the small town of Mendooran which lies at the eastern side of the river's hook-shape. From here the Castlereagh flows in a westerly direction at the flattened bottom of the hook and then turns north-westerly towards the town of Gilgandra. From Gilgandra it continues to run northwesterly across the plains through Gulargambone and Coonamble, then continuing across expansive plains, with no urban centres, where elevations are less than 200m, until it joins the Macquarie River at its uppermost reaches beyond the Macquarie Marshes. Its confluence with the Macquarie is about 65 km SW of Walgett. Not far from the Castlereagh/Macquarie confluence the Macquarie itself joins the Barwon River at a place about halfway between Walgett and Brewarrina.
George Evans (explorer)
Once Evans' scouting party had returned, (17 July) the whole expedition departed on 19 July 1818 in the same north-easterly direction George Evans had taken. On 27 July they reached the Castlereagh, but it was now flooded since Evans' first crossing two weeks earlier. Only on 2 August did Evans again cross the Castlereagh near Combara, once there was a sufficient drop in the river level. This time on reaching the Warrumbungles south-east of their crossing, the party continued easterly through the Goorianawa Gap and eventually reached the coast near Port Macquarie. John Oxley named the river that year in honour of the British Foreign Secretary, Lord Castlereagh, who had held the position since 1812.