Scientists fear that global climate change can negatively impact water supplies around the world, and that too in huge proportions. The alarm was sounded after a new analysis by researchers at MIT (Massachusetts Institute of Technology).
The research was conducted by Gene-Hua Crystal Ng, King Bhumipol, Professor Dennis McLaughlin, Professor Dara Entekhabi, from MIT, and Bridget Scanlon, a senior researcher at the University of Texas.
The analysis has found that the changes in groundwater may actually be much greater than the precipitation changes themselves.
For example, in places where annual rainfall may increase by 20 percent as a result of climate change, the groundwater might increase as much as 40 percent.
Conversely, the analysis showed in some cases just a 20 percent decrease in rainfall could lead to a 70 percent decrease in the recharging of local aquifers - a potentially devastating blow in semi-arid and arid regions.
The study found that the exact effects depend on a complex mix of factors, including soil type, vegetation, and the exact timing and duration of rainfall events.
So, detailed studies will be required for each local region in order to predict the possible range of outcomes.
The analysis combines computer modeling and natural chloride tracer data to determine how precipitation, soil properties, and vegetation affect the transport of water from the surface to the aquifers below.
This analysis focused on a specific semi-arid region near Lubbock, Texas, in the southern High Plains.
Predictions of the kinds and magnitudes of precipitation changes that may occur as the planet warms are included in the reports by the Intergovernmental Panel on Climate Change (IPCC), and are expressed as ranges of possible outcomes.
"Because there is so much uncertainty, we wanted to be able to bracket the expected impact on water supplies under the diverse climate projections," Ng said.
"What we found was very interesting. It looks like the changes in recharge could be even greater than the changes in climate. For a given percentage change in precipitation, we're getting even greater changes in recharge rates," she added.
Among the most important factors, the team found, is the timing and duration of the precipitation.
For example, it makes a big difference whether it comes in a few large rainstorms or many smaller ones, and whether most of the rainfall occurs in winter or summer.
"Changes in precipitation are often reported as annual changes, but what affects recharge is when the precipitation happens, and how it compares to the growing season," said Ng.