New research has found climate change and urbanisation are threatening drinking water quality.

More than half of the world’s population faces a looming threat to the quality and availability of their drinking water due to an increase in groundwater organic carbon, according to a study by the University of NSW.

The research examined the largest global dataset of 9,404 published and unpublished groundwater dissolved organic carbon (DOC) concentrations from aquifers in 32 countries across six continents.

DOC is a naturally occurring component of groundwater, but the higher its concentration, the more difficult and expensive it is to make groundwater drinkable. In Australia, groundwater is widely used as the main source of drinking water for many cities and towns.

Lead author Dr Liza McDonough said the study forecasted elevated DOC concentrations because of projected changes in temperature and rainfall due to climate change, as well as increased urbanisation.

“We identified groundwater DOC concentration increases of up to 45 per cent, largely because of increased temperatures in the wettest quarter of the year – for example, in a number of south-eastern states in the United States. We predict increases in DOC in these locations could increase water costs for a family of four by US$134 per year,” Dr McDonough said.

“Other areas such as eastern China, India and parts of Africa already experience severe groundwater contamination issues. These may be further compounded, particularly in south-eastern China, by groundwater DOC increases associated with large predicted increases in temperature in the wettest quarter of the year by 2050.

“Generally, we expect urbanisation to increase groundwater DOC concentrations by up to 19 per cent, compared to agricultural or natural land use, likely as the result of contamination – for example, through leaking septic and sewer systems.”

She said future studies would determine the best water treatment options for areas where groundwater DOC concentrations are anticipated to increase.

“Our next step is to investigate how the character of DOC changes when you have different aquifer minerals, because some types of organic matter can stick to certain mineral surfaces and ultimately reduce this type of organic matter remaining in the water,” Dr McDonough said.

“This will help provide guidance on the most suitable water treatment options in areas where DOC concentrations are expected to increase.”