Camera footage shows koalas standing on their hind legs for more than 10 minutes to gulp water at drinking stations.
Scientists say rising temperatures and lack of rain are driving the animals to search for new sources of moisture.
It showed the tree-dwelling species no longer relied on eucalyptus leaves alone for nourishment and moisture. They were willing to run the risk of attack from ground predators in their scramble for water.
The researchers placed cameras and water stations around a farm in the rural town of Gunnedah. They captured footage of more than 100 koalas using the water stations over autumn and winter.
Scientists previously believed koalas only needed to consume leaves and did not drink.
The koala is listed as a "vulnerable" species under a 2012 Australian conservation law.
There are fewer than 100,000 of the animals left in the wild, perhaps even as few as 43,000, the Australian Koala Foundation estimates.