The Paradox of More Rain and Drier Land
Another strange phenomenon in the world of science has been uncovered. New research reveals that while the planet is experiencing more rain overall, it’s also becoming drier at the same time. This apparent contradiction can be explained by the fact that rainfall is increasingly concentrated into larger storms with longer dry spells in between. When a lot of rain falls all at once, it overwhelms the soil, leading to problems for ecosystems and water resources.
The study found that even if total precipitation increases, the way the rain falls affects how much water is available for aquifers, plants, and people. Soil can only absorb so much water at once, so any excess runs off the surface, where it is more likely to evaporate. This means that even with more rain, less water is actually retained in the land.
Understanding the Impact of Rainfall Patterns
Corey Lesk, the lead author of the study, who conducted the research while a fellow at Dartmouth College, explained this concept in an email to USA TODAY: “Regardless of how much precipitation falls, when rain and snow come in stronger bursts separated by longer dry spells, less water tends to remain on the land (in soils, lakes, and groundwater) for use by people and nature.”
Justin Mankin, the senior author of the study and an associate professor of geography at Dartmouth, described the situation as “asking the land to drink from a firehose.” He added that when rainfall is intense, there are more consecutive dry days, but more importantly, heavier rains lead to surface ponding that is more easily evaporated by the atmosphere.
Climate Change and Rainfall Concentration
Researchers believe that climate change is likely to blame for this shift in rainfall patterns. While they did not specifically test the extent to which recent trends in precipitation concentration are caused by climate change, they noted that the findings align with what would be expected from the theory of how warming affects rainfall distribution.
Lesk told USA TODAY: “We show that warming weighs the dice for drying, regardless of whether total precipitation increases or decreases in the future.” The study projects that as global temperatures rise due to climate change, rainfall will become more consolidated, potentially leading to abnormally dry conditions for 27% of the world’s population if temperatures increase by 3.6 degrees.
“This is not a good effect we’ve uncovered,” said Lesk, who is now a professor of Earth and atmospheric sciences at the University of Quebec in Montreal. “It really exposes the mechanics of how climate change will affect water resources for everyone.”
Challenges for Water Resource Management
The erratic boom-bust cycle of heavy rainfall and long droughts presents a significant challenge for managing public water supplies, especially in arid regions where water storage is critical. Mankin said that this new pattern complicates the management of water resources.
Lesk added that understanding the concentration effect could help improve water management and drought forecasting. “Rainfall concentration is not typically included in those assessments, largely because its importance wasn’t understood until now,” he said.
The study offers a new perspective on water resources, showing that the timing and frequency of rainfall are as important as the total amount of rain received throughout the year. Climate scientists have projected that a warmer climate will result in more rain, but it remains uncertain whether this will translate to more water for the land.
The Western US and Rain Consolidation
According to the study, the western United States, particularly the area west of the Mississippi River, has experienced some of the highest levels of rainfall consolidation. Yearly rainfall in the Rocky Mountains has become 20% more compacted into heavier downpours.
California has faced similar issues during long-term droughts, where atmospheric rivers have brought heavy rainfall to the state. Water managers must decide whether to release reservoirs of water to capture freshly fallen rainwater, without knowing how long the new supply will last.
This article originally appeared on USA TODAY: Something weird and worrying is happening with rain, study finds
