The Snowy is, hydrologically, a rarity on the driest inhabited continent. Most Australian rivers are wildly unreliable, running hard one season and bone-dry the next, because the continent's ancient soils swallow water greedily. The Snowy is different. Fed by melting alpine snow, its headwaters, the Eucumbene, the Gungarlin, the Thredbo, and a web of smaller streams, gather in Kosciuszko National Park and meet near Jindabyne, and from there the river has never once been recorded running dry in its lower reaches. Its flow peaks in October as the snowpack releases, surging just when the inland rivers are failing. That dependable mountain pulse shaped everything downstream: the cold-water insects, the fish, the clean cobbled riverbed scoured bright by each spring flood.

Paterson's verse drew on a real landscape, the high, broken alpine country where stockmen mustered cattle across terrain that punished horse and rider alike. The poem's hero chases a colt down a mountainside so steep that the other riders pull up and refuse to follow, and Paterson's galloping rhythm made the scene immortal. It spawned a whole lineage of works: a 1920 silent film, the famous 1982 Fox film and its 1988 Disney sequel, a television series, and an arena spectacular. The Snowy became a place in the national imagination before most Australians could place it on a map, a symbol of nerve, wildness, and a vanishing frontier. The river earned its legend honestly. It would soon pay a price the balladeers never foresaw.

In the 1950s and 1960s, the Snowy Mountains Scheme rose as one of the largest engineering projects in Australian history, a vast network of dams, tunnels, and power stations built largely by post-war migrants. Four major dams, Guthega, Island Bend, Eucumbene, and Jindabyne, plus countless diversions, captured the Snowy's alpine flow and turned it inland, through the mountains, to feed the Murray and Murrumbidgee for irrigation while generating hydroelectricity for two states. As measured at Jindabyne, 99 percent of the river's water was diverted away. The nation got farms, power, and jobs; the Snowy got a fraction of itself. There was public protest in those decades, but it was brushed aside. The needs of agriculture spoke louder than a starved river that few people lived beside.

Cut to one percent of its strength, the Snowy below Jindabyne sickened in ways that took decades to fully register. Without its scouring spring floods, the channel could no longer keep itself clear; vegetation crept in, and sediment, much of it washed down after the devastating 2002-03 bushfires, smothered the once-clean cobble bed under fine silt. Salt water from the sea pushed seven to ten kilometres up the estuary. The insects and fish adapted to a cold, fast, snow-fed river found themselves in something sluggish and choked. The riverbed became "armoured," its particles locked in place, and only a genuine flood could break it loose. By the 1990s the Snowy's plight had become a national environmental cause, a symbol of what large-scale water engineering had cost.

The fight to revive the river had a face. Craig Ingram, an independent from East Gippsland, won a seat in the Victorian parliament in 1999 on a single burning promise: restore the Snowy's flow. He became pivotal in pushing the three governments that controlled the scheme to agree to return environmental water, with staged targets aiming as high as 28 percent of natural flow. The first releases came in 2002, doubling the discharge at Dalgety; by 2010 and 2011, with the drought breaking, larger spring releases of up to 12,000 megalitres a day were sent down deliberately to scour the armoured bed and mimic the floods the river had lost. When the same governments moved to privatise Snowy Hydro in 2005, public outcry stopped the sale within months. The Snowy is not what it was. But the legend, it turns out, has defenders still.