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Water from snow and rain seeps deep into the ground between layers of soil and accumulates in sponge-like underground bathtubs, called aquifers. Farmers rely heavily on this groundwater to irrigate their crops when they can't get enough water from surface water sources.
Roughly 85 percent of Californians also rely on groundwater for some portion of their water supply. Worldwide, an estimated two billion people depend on it. However, excessive groundwater use combined with droughts has caused land surface to sink, damaging critical infrastructure including roads, buildings, and sewage and water pipes.
New UC Riverside research shows groundwater takes an average of three years to recover from drought -- if it ever recovers at all. In the largest study of its kind, scientists found that this recovery time only applies to aquifers that aren't touched by human activity, and the recovery time might be even longer in regions with excessive pumping.
For groundwater levels to recover after a drought, new precipitation requires time to percolate through the soil and recharge the depleted aquifer. The researchers show that this process can take several years longer in areas with deeper groundwater levels.
"If people pump groundwater without first letting it recharge, groundwater levels keep going down, the cost of pumping goes up, and the land sinks," explained Hoori Ajami, UCR groundwater hydrologist and study co-author and principal investigator on this project.
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