title: Castlereagh River
context: Estimates of the length of the course of the Castlereagh River from its commencement to its mouth vary from 541 kilometres (336mi),[2] 549km,[3] and 566km.[1]  Over its course it drops over 600m.
question: How long is the Castlereagh River in New South Wales?
answers: 541 kilometres (336mi)