Groundwater, the world’s greatest hidden treasure

The most precious resource beneath the earth’s surface isn’t oil or diamonds, it’s groundwater.

This year, groundwater is the focus of World Water Day, observed March 22. Although we can’t see it, there is more than 1,000 times more water in the ground than all the world’s lakes and rivers combined. In the United States, groundwater provides 40 percent of public-use water and 39 percent of water used for agriculture. In desert regions, where this treasure might be hidden hundreds of meters beneath the earth’s surface, it’s often the only source of water.

In Delaware, where water is abundant, many of us tend to take groundwater for granted. We get much of our drinking water, especially in the southern part of the state, from aquifers, geological formations of rocks and sand that can hold underground water for hundreds and thousands of years. Groundwater irrigates our fields and helps run our industries. Groundwater discharge into our streams and estuaries nurtures healthy aquatic ecosystems.

That’s why we must safeguard this priceless resource, which is being squeezed from both sides in our small state. In our coastal community, preserving groundwater is a see-saw, a competition between land and sea.

On the land, the fertilizer, treated wastewater and industrial contaminants pollute our groundwater. On the sea side, there is an infinite source of pollution, seawater, that increasingly threatens groundwater due to sea-level rise and storm surges caused by climate change. As a measure of how serious that threat is, a level of just 1 percent seawater renders fresh water undrinkable.

As our populations grow denser and we use more and more groundwater, we draw these pollutants from the surface of the land and from the sea. This risk is unseen as it creeps in from below the earth’s surface due to increasing pressures from sea level and decreasing pressures from pumping on land. And once groundwater is polluted, especially over large areas, it’s very difficult to clean up.

World Water Day reminds us that clean water is a global issue. An estimated 2 billion people do not have access to safe water. Climate change has brought more droughts and longer droughts. In the deltas of Asia, naturally occurring arsenic is poisoning groundwater. The Nubian Sandstone Aquifer, a huge fossil aquifer beneath the Sahara Desert, is a critical source of water that is not being sufficiently recharged. Aquifers in California, the Great Plains and the Middle East also are being drawn from faster than they can be replenished by rain. And as climate change depletes reservoirs and other sources of surface water, groundwater becomes an even more essential resource.

We must be good stewards if we are to preserve and protect groundwater for generations to come. What we put on the ground will percolate into the earth and our water. It’s up to us to be mindful. Use de-icing salt and pesticides sparingly. Never dump chemicals down drains or onto the ground. Ask yourself: Do we need to fertilize our lawn?

We can’t see groundwater in its natural state, but the benefits of clean and abundant groundwater are visible every day.