Brazil's armed forces are preparing to take water, food and medical supplies to communities isolated by the worst drought in the Amazon for decades.
The move comes after Amazonas state Governor Eduardo Braga requested military help from the president.
Low river levels are preventing boats - for many the only means of transport - from using the Amazon safely.
Mr Braga declared a state of emergency on Monday and ordered workers to start digging wells for drinking water.
Many towns along the world's second longest river have declared alerts amid fears they could become isolated as the region's worst drought in more than 30-years continues.
The dry spell is also affecting Peru, where the Amazon River at the river port of Iquitos has seen a record low.
Experts say water levels are expected to continue dropping until November.
They are blaming climate cycles, not global warming, for the drought, which has also led to enormous fires.
Brazilian meteorologists think the weather in the Amazon is affected by sunspots and water temperatures in the Pacific Ocean - factors which vary in regular patterns.