Our third in a series of articles about climate change and water.

Groundwater provides the United States with half of its drinking water. It also waters 40% of American agriculture. But are we using it sustainably? With the changing climate, can we?

Researchers have recently determined how to measure the global groundwater footprint: by combining country-by-country groundwater usage with global hydrology models, scientists and policy-makers are able to measure water use relative to supply in aquifers around the world.

And the footprint is large. According to a recent study in Nature,

… humans are overexploiting groundwater in many large aquifers that are critical to agriculture, especially in Asia and North America. We estimate that the size of the global groundwater footprint is currently about 3.5 times the actual area of aquifers and that about 1.7 billion people live in areas where groundwater resources and/or groundwater-dependent ecosystems are under threat.

Tom Gleeson, a hydrogeologist at McGill University and the lead author of the Nature paper, has some solutions for these threats. He and another groundwater expert, Werner Aeschbach-Hertig, provide guidelines in a new paper this week in Nature Geoscience.

In their abstract, they state,

…a transformation is required in how we value, manage and characterize groundwater systems.

The researchers believe a regional groundwater budget, which would account for both aquifer use and water regeneration, is required.

The authors note that techniques such as improving the efficiency of irrigation and recharging groundwater with sources like waste-water are useful, depending on locale.  However, they argue that regulating the use of water appears to be most effective.

The researchers provide two economic examples that could change the way we use groundwater—water pricing and energy pricing. The current open access model for using groundwater leads to its depletion. In addition, cheap electricity often depends on the availability of water. Raising prices could make users more aware of how truly expensive their energy is.

Gleeson and Aeschbach-Hertig also stress that climate change could only make matters worse, and groundwater modeling is essential to these budgets and policies.

We not only depend on groundwater for food and water, but its depletion has been linked to rising sea levels and earthquakes. The sooner we find a way to sustain groundwater levels, the better for all of us.

For more info on groundwater sustainability, take a look at this recent Scientific American article.

Image: USchick/Wikipedia

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