Relatively mild drought conditions may have been enough to cause the collapse of the Classic Maya civilisation, which flourished until about AD950 in what is now southern Mexico and Guatemala.
Scientists have long thought that severe drought caused its collapse.
But Mexican and British researchers now think that a sustained drop in rainfall of only 25-40% was enough to exhaust seasonal water supplies in the region.
The findings were published in the journal Science.
The research was conducted by the Yucatan Centre for Scientific Research in southern Mexico and the University of Southampton in the UK.
Scientists used advanced modelling techniques to estimate rainfall and evaporation rates between AD800 and 950, when the classic Maya civilisation went into sharp decline.
They found that a relatively modest decline in rainfall was enough to deplete freshwater storage systems in the Yucatan lowlands, where there are no rivers.
"These reductions amount to only 25 to 40% in annual rainfall, but they were large enough for evaporation to become dominant over rainfall, and open water was rapidly reduced," Professor Eelco Rohling of Southampton University told the Press Association.
"Societal disruptions and abandonment of cities are likely consequences of critical water shortages, especially because there seems to have been a rapid repetition of multi-year droughts," he added.
The reconstructed droughts are similar in extent to some predictions for the near future of the same region as a result of climate change.
"There are differences too, but the warning is clear - what seems like a minor reduction in water availability may lead to important, long-lasting problems," Professor Martin Medina-Elizalde said.
"The problem is not unique to the Yucatan Peninsula, but applies to all regions in similar settings where evaporation is high," he added.
Archaeologists have long been intrigued by the collapse of the Classic Maya civilisation, which flourished for around six centuries and developed sophisticated architecture, mathematics and culture.
Other studies have variously blamed social unrest, disease and deforestation for its demise.