Long before surveyors gave the river an English name, this was Kuungkari country, and the language, also written Kungkari or Koonkerri, belonged to the landscape around what are now the Longreach and Blackall-Tambo shires. The river carries the deep-time memory of the people who knew its waterholes as reliable, life-giving places in a country where reliability is everything. Names matter on a river like this, where for much of the year there is no flowing water at all, only a strung-out line of billabongs holding what the last flood left behind. Fifteen of those billabongs are named. To know which holes keep water through a dry year is, here, a kind of survival knowledge older than any map.

The Thomson begins modestly, draining the Alma Range on the western fall of the Great Dividing Range. Its northernmost headwaters start as Torrens Creek, inland from Charters Towers, and only become the Thomson proper near Muttaburra, where three watercourses braid together. From there it gathers strength the outback way, by collecting tributaries: 41 named ones over its 350-kilometre course. It slides past Longreach, where the Landsborough Highway crosses it, then Stonehenge and Jundah, before the famous meeting with the Barcoo. But to call it a river for most of the year flatters it. The country is so flat that when the Thomson does run, it stops behaving like a river and spreads many kilometres wide, a vast shallow flood creeping across the blacksoil plains rather than rushing between banks.

This is semi-arid blacksoil country, the kind that turns to glue in the wet and to a fractured grey crust in the dry, and the life on it follows the water. Sheep and beef cattle are the mainstays, grazing the plains that the river's floods periodically renew. The Thomson is part of the great Lake Eyre Basin, the inward-draining heart of the continent where rivers run not to the sea but toward the lowest dry salt pan in Australia. So much water flows nowhere, and matters enormously, that the river has long fired the imaginations of engineers. The Bradfield Scheme, a grand and never-realised plan to divert inland-flowing rivers like the Thomson toward drier country, still surfaces in Australian debate whenever drought bites, a reminder that the Thomson's wasted floods have tempted dreamers for the better part of a century.