The Castlereagh from Gilgandra down is a wide river witih low banks, and has many sand benches - often with trees on them - meaning that you can look out a long way across the river, and through trees, giving the feeling of being more encompassed in nature than most western rivers. The sandy shoals also make it very picturesque, as well as fun to pick your way down the numerous channels, often lined with phragmites (common reed), adn containing neat little currents. This paddle is good moving water - not whitewater.
There is no gauge close by; the nearest guage is Lucas Bridge (downstream of Mendooran, well upstream of Gilgandra), and you want this to be above 1.5 m for a day or so before paddling this section (its ok if the gauge has dropped by the day you paddle). Of course this is variable depending on how much water is already in the system - best thing to do is eyeball it and see if there is enough water.
This short and beautiful paddle section is topped off by finishing in time for lunch at the Armatree Hotel! Or you can keep paddling to Gulargambone.