AUSTRALIA has responded to an SOS from the tiny Pacific nation of Tuvalu, which is days away from running out of water.

The federal government has sent officials and 1000 rehydration packs to Tuvalu's hospital as other governments and the Red Cross donate thousands of litres of drinking water.

Water, water everywhere: The lagoon at Tuvalu's capital atoll, Funafuti. Credit:Dean Sewell

''We have less than four or five days' [supply],'' Tuvalu disaster co-ordinator Sumeo Silu told The Age.

''We are rationing water well below the United Nations refugee rate, with just 40 litres per household. An average household here has 10 to 12 people.''