Overpumping is depleting US groundwater

The United States is overpumping groundwater so fast that some damaged aquifers will never recover, and the reduced supply of groundwater reportedly is threatening agricultural production and the availability of drinking water.

Those findings come from a monthslong investigation by The New York Times using a database it assembled of more than 80,000 wells nationwide despite the data of US aquifers being sketchy. The Times also spoke to more than 100 experts and professionals in the field.

It found that about 45 percent of examined wells showed significant declines in water levels since 1980. Four in 10 sites reached record-low water levels during the past decade, and last year was the worst yet, the Times reported.

Consequences of the groundwater shortage have manifested in many ways, the investigation found.

Last year, the US produced 39 percent of global sorghum exports, 32 percent of soybean exports, and 23 percent of corn exports, according to federal data. That success couldn't have been achieved without pumping groundwater to grow the crops.

As a result, groundwater is nearly exhausted in some farm areas, the Times reported, threatening the US' status as an agricultural giant.

In Wichita County, Kansas, farmers used to produce 165 to 175 bushels of corn per acre, above the national average. But it came at a cost of draining the aquifer to irrigate the crops.

As groundwater ran out, Wichita farmers have had to rely on rainwater alone to grow their crops. With an average of only 20 inches of rain each year, their corn yield was a meager 70.6 bushels last year, about 40 percent of peak yield.

"We overpumped it," Farrin Watt, a Wichita County for 23 years, told the Times. "We didn't know it was going to run out."

Arkansas, one of the largest rice producers in the country, is another state that consumes a large amount of groundwater. The state is pumping twice as much water each year as can be naturally replenished, state data show, and some aquifers have fallen below 10 percent of their capacities.

Kansas has no mechanism in place to stop its groundwater decline, nor do Texas and Colorado, where groundwater is allowed to be drained completely, the Times reported.

In Colorado, farming, residential development and reduced precipitation have increasingly strained the state's groundwater.

In Texas, around the Houston-Galveston area, overpumping has caused the ground to sink more than a foot in the past century, with some areas subsiding as much as 12 to 13 feet.

Aquifers in the area have lost between 300 and 400 feet of water since groundwater was drawn, leaving some of the land to collapse, according to Texas Living Waters.

California is another agricultural giant and a major groundwater user. Aquifers in at least 76 basins there last year were being pumped out faster than they could be replenished by precipitation, according to state data.

In the US, more than one-third of drinking water comes from aquifers. Depleting groundwater could end the drinking water supply for some areas, the study warns.

In one example, Arizona has determined that there is insufficient groundwater for housing projects already approved, and the government has stopped granting new permits to builders of new subdivisions around the fast-growing metropolitan area of Phoenix.

In Maryland, close to three-quarters of monitoring wells have seen their water levels drop over the past 40 years, some by more than 100 feet. Charles County, which contains the fast-growing suburbs of Washington DC, has used most of its groundwater for houses and agriculture. And the water isn't coming back anytime soon.

"Most of the water we're pulling out of the ground is thousands of years old," Jason Groth, the county's deputy director of planning and growth management, told the Times. "It's not like it rains on Monday, and by Saturday it's in the aquifer."

Groth said the county, which gets most of its water from its own aquifers, will hit a point within a decade where it doesn't have enough water.

Overpumping could contaminate aquifers and make the remaining water unsafe or undrinkable. For example, in coastal areas, overpumping can accelerate "saltwater intrusion", drawing ocean water into the freshwater aquifer. The Times discovered that such saltwater intrusion is already happening in the Northeast, the mid-Atlantic states, Florida, the Gulf Coast and California.

It happened in the past, too. Some wells in Brooklyn and Queens in New York City began to show signs of saltwater intrusion at the beginning of the last century. By the middle of the 20th century, some of those wells had to be shut down.

Depletion of groundwater also can poison aquifers and render groundwater undrinkable. The cancer-causing heavy metal arsenic is commonly present in clay, and it can be released into drinking water supplies when aquifers are overpumped. Such a case has been documented in San Joaquin Valley in California, and similar changes in the San Luis Valley in Colorado are being evaluated.

Contamination of aquifers also can come from industrial activities. A Times reader named Mark, a former gas engineer and manager, said that there are 800,000 abandoned wells in the US. "Each one, as the casings deteriorate, puts a possible conduit into groundwater," he wrote.

Another reader who also worked in the oil gas industry wrote that many old wells contain high quantities of naturally occurring toxic and corrosive materials such as sulphur, waxes, salts, radioactive materials, condensates, brine and freshwater that eat through steel casing over time, "producing a time bomb that's only going to add to the toxic contents of the shrinking aquifers over time".

Climate change is exacerbating the problem, the Times report said. Rising temperatures are reducing snowpack, which in turn led to less water flowing through rivers. The higher temperatures also mean plants and lawns require more water. The situation makes people depend even more on the disappearing groundwater.

Water stress is a worldwide problem facing humans. A recent study released by the World Resources Institute shows that one-quarter of the world's population in 25 countries are already facing extremely high water stress. Those countries are concentrated in the Middle East and North Africa.

The study said that by 2050, another 1 billion people will live with extremely high water stress, as global water demand is projected to increase by 20 to 25 percent by 2050.

Currently, the water stress in the US is rated as medium high at 20-40 percent level.