Climate Fact: The Fate of Groundwater
Globally, humans draw nearly one-third of our fresh water from underground sources, supplying 36 percent of domestic water, 42 percent of agricultural water and 27 percent of industrial water. However, our water demands are beginning to alter this critical resource in profound ways. Until now, scientists have struggled to understand how increased demand coupled with and a changing climate impacts ground water supplies, but a new team of international water wizards has begun to unlock some of our planet’s subterranean secrets. Here’s what they’ve found so far:
- Some of our most important groundwater storage areas, called aquifers, haven’t received substantial deposits of water for thousands of years. This is mostly because the rate of new soil water accumulation only represents a small fraction of Earth’s total ground water storage. However, we’re extracting this “fossil water” from the earth much more quickly than nature can restore it, essentially making these aquifers non-renewable resources.
- Even though the speed of ground water restoration is complicated by many factors like land cover and local geology, its “recharge” rate generally varies with the global distribution of precipitation – a principle component of any location’s climate.
- Current research points to less snow accumulation, earlier snow melts, more winter rainfall events, and more rain-on-snow events in a warmer world. Preliminary ground water research shows that changing snowmelt patterns usually reduce the seasonal variation and amount of ground water deposits.
- Droughts cause irrigation systems to shift from using renewable surface waters to non-renewable fossil water. California’s 2006-2009 Central Valley drought forced farmers to pump enough groundwater to fill Lake Mead, the largest surface reservoir in the United States.
Aquifers of the United States – Courtesy of USGS. Click map for a larger view.
(Source: Taylor, Richard G. et al., 2012. “Ground water and climate change.” Nature Climate Change, doi:10.1038/nclimate1744)