With the world's population expected to grow to 9.1 billion by mid-century, already depleted groundwater supplies will continue to be gobbled up by agriculture, industry, power generation and personal use, according to the UN's annual World Water Development Report.
The report, released Friday, says that around 20 percent of groundwater sources are already "overexploited" - a problem that will only grow more dire by 2050, when demand for water is expected to have risen by more than half.
Most alarmingly, the report warns that as early as 2030, the planet could have only 60 percent of the water required to sustain itself if substantial changes are not made to improve management of the resource.
"Unless the balance between demand and finite supplies is restored, the world will face an increasingly severe global water deficit," says the report.
"Unless the balance between demand and finite supplies is restored, the world will face an increasingly severe global water deficit."
Richard Connor, lead author of the UN report and an independent water expert, told VICE News that the crisis could possibly be averted if countries mandate efficient water use and attach a greater price to water itself. He said climate change, which is already beginning to exacerbate variations in weather patterns - some parched climates may become even drier in the future, wetter ones rainier - makes that task even more pressing.
"With respect to climate change, the two major problems have to do with salt water intrusion in aquifers due to sea level rise, as well as the impact in the variability of distribution of rain," Connor said.
Coastal cities like Kolkata, Shanghai, Dhaka and Jakarta already face a rise in salinization of their fresh water supplies in part due to uncontrolled groundwater extraction. As salt water mixes with longstanding aquifers, both licit and illegal wells are dug deeper, furthering the problem.
In Dhaka, the capital of Bangladesh and one of the most vulnerable cities to sea rise, the World Bank predicts salt content in soil could decrease the yields of some rice crops by more than 15 percent. By 2050 researchers say climate change will cause the salinity of rivers in Bangladesh to vary significantly during dry seasons and lead to the disruption of important aquatic habitats for animals like freshwater fish and prawns. Even road construction will cost more, as higher salt levels in soil cause cracking in paved surfaces.
Connor said that inefficient water consumption is irreplaceably draining water supplies in places like the Western US, Middle East and in parts of North Africa, China, and small island states in the Pacific.
"In all of these places people rely on ground water for irrigation and other uses." he said. "And in a lot of cases the ground water isn't used sustainably, they are basically just taking money out of the bank," added Connor.
The report highlighted several localized cases where governments were able to better manage supplies. In Cyprus, subsidies and low-interest loans for farmers helped many switch to more efficient irrigation systems. That efficiency, however, may only "lead to the expansion of irrigated areas instead of increased flows in rivers," it warned.
"In a lot of cases the ground water isn't used sustainably, they are basically just taking money out of the bank."
The report arrives as UN officials are coming to grips with the devastation Cyclone Pam last week inflicted on the Pacific island nation of Vanuatu. Scientists say climate change will only worsen the intensity of storms like Pam and Typhoon Haiyan, which made landfall in the Philippines in 2013 with record strength, leaving more than 6,000 people dead. Such storms already are disrupting delicate water supplies in vulnerable areas.
At the opposite extreme, record droughts are hitting places like the Western United States and Brazil, and imperiling agriculture in those areas.
Although industry, power generation and personal use of water loom large in many parts of the world, agricultural activities account for around 70 percent of water use globally, and as much as 90 percent in poorer countries. The UN predicts the sector will need to produce 60 percent more food to feed the world's population by 2050, and it is not clear where the requisite water for such a surge in food production will come from.
"California is in particular in trouble, which means the US is in trouble, because California is where a lot of the US's food is produced," said Connor, who predicted American food prices will rise in the coming years.
The report, which was unveiled in Delhi, called on countries to raise their water tariffs, claiming they were currently "far too low to actually limit excessive water use by wealthy households or industries."
Governments in developing countries face the daunting goal of decreasing or altering use while at the same time extending proper sanitation systems and clean supplies of fresh water to impoverished communities. In India, where more than half a million people still defecate in the open, some 748 million people also remain without permanent access to an improved drinking water source.
Connor points to UN estimates that put the return on every dollar spent on sanitation at more than five times the initial investment - a payoff seen in decreased healthcare costs due to lessened disease transmission and a subsequent rise in worker productivity. But upfront costs for sanitation systems can be expensive, and in many cases more wells are simply dug.
"If we continue business as usual we are on an unsustainable path," said Connor.
Follow Samuel Oakford on Twitter: @samueloakford