flooded fields in the Phillipines, photo: Sir Mervs
We’ve all heard by now that global warming will bring about changes in precipitation patterns, with some areas seeing increases with other areas drying out. A new piece of research from MIT delves into this area and finds that the changes in groundwater levels could be much greater than the changes in precipitation itself.
While the researchers acknowledge that a wide array of factors will influence the effect at a given location, this the broad stroke:
20% Change in Rainfall = Double or More Change in Groundwater
In areas where rainfall increases 20% groundwater levels might actually rise 40%; while in areas seeing a similar decrease in rainfall there could be as much as a 70% decrease in groundwater.
But It’s Not That Simple
In describing the types of variables which could influence the effect at a given location, Science Codex summed it up:
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.
If most of the rain falls while plants are growing, much of the water may be absorbed by the vegetation and released back into the atmosphere through transpiration, so very little percolates down to the aquifer. Similarly, it makes a big difference whether an overall increase in rainfall comes in the form of harder rainfalls, or more frequent small rainfalls. More frequent small rainstorms may be mostly soaked up by plants, whereas a few more intense events may be more likely to saturate the soil and increase the recharging effect.