Groundwater systems can take decades to millennia to respond to the present impact of climate change, scientists warned Monday. Researchers found that groundwater reserves in arid regions take much longer to respond to climate variability than those in wetter regions. More than two billion people rely on groundwater to drink and irrigate crops.
Groundwater is the largest usable source of freshwater on the planet. Groundwater reserves are already under pressure, in some areas groundwater extraction has lowered entire cities.
Our heating planet, accompanied by escalating drought, will have a long lasting impact on how quickly water reserves replenish, according to a study published in Nature Climate Change. Computer modelling developed by an international team of researchers used groundwater datasets to put a timescale on how reserves will respond to climate change. Researchers found that only half of the planet’s groundwater will be able to naturally fully replenish within the next 100 years and there will be groundwater shortages in drier regions.
The process of groundwater reserves being replenished through bedrock can take centuries and varies by region. The team found that reserves in arid areas can take several thousand years longer to respond to changes in climate than reserves in more humid parts.
Groundwater underneath the Sahara is presently responding to climate change from 10,000 years ago when the region was much more moist. There are massive lags in the response time for groundwater rebalancing.