The Australian river that can simply vanish for an entire year

Countries & Cities · Published 30 September 2026 Swipe more like this →

In short: While most major rivers flow steadily, the Lachlan River is defined by its unpredictability. It is an intermittent system that can experience zero flow for over twelve months, occasionally disconnecting from the Murray–Darling basin entirely until the next great flood arrives.

Rising on the western slopes of the Great Dividing Range, the Lachlan River travels a 1,440-kilometre course through New South Wales. Unlike the Murray or Murrumbidgee, which have maintained continuous flow since European settlement, the Lachlan is famously erratic. In extreme droughts, the river can cease to flow for more than a year, such as the period between April 1944 and April 1945. Its annual volume fluctuates wildly, ranging from less than 1,000 megalitres in 1944 to as much as 10,900 megalitres in 1950.

The river's landscape is defined by significant wetlands that stretch along its length, including Lake Cowal-Wilbertroy, Lake Cargelligo, and Lake Brewster. It is the only river in New South Wales to feature such extensive wetlands throughout its course rather than just at its terminus. The system eventually reaches the 500-square-kilometre Great Cumbung swamp, where it joins the Murrumbidgee River. This connection to the wider Murray–Darling basin only occurs when both the Lachlan and Murrumbidgee are in flood.

Human history and ecology are deeply intertwined with these cycles. The river flows through the traditional homelands of the Wiradjuri people, who lived in the 'land of the three rivers.' Colonial exploration by George William Evans in 1815 led to the river being named after Governor Lachlan Macquarie. Today, the catchment supports over 100,000 people and roughly 12% of the state's agricultural businesses. However, the river's volatility brings danger; in June 1952, a peak of 10.8 metres at the Forbes Iron Bridge forced the evacuation of over 900 families.

General information, not professional advice. Spotted an error? Flag the card or see corrections and complaints.

Intellect Plus is a visual educational discovery platform for exploring fascinating facts and ideas. Brain Food, Not Brain Rot. What is Intellect Plus?

Related

• Australia's longest river system is a fragile lifeline struggling against drought and human management
• Why Australia's 'Big Water' River Is Only Half the Stream It Once Was
• Australia’s longest river is entirely New South Wales water
• The Australian river that rarely reaches the sea and flows only when it chooses
• The Nile of New South Wales: How a river shaped the history of Sydney
• Lafourche Parish: A Louisiana landscape shaped by sugar, racial violence, and rising waters
• Why a Canadian town was named after the gnawing habits of local beavers
• Lahaul and Spiti is a high-altitude mountain desert spanning two distinct, ancient cultural regions
• The narrow waterway where international diplomacy meets a hidden maritime graveyard
• The ambitious Australian reservoir that failed its original mission
• The L train's evolution from a numbered route to New York's first automated line
• Africa's lowest point is a shimmering, hypersaline crater lake of white gold.

More in Bodies of water · More in Countries & Cities · Latest · A–Z · All topics