Losing Ground 

Houston, Texas, isn’t just one of the most populous cities in the United States. It’s also the fastest-sinking one. A recent study found that the land beneath Houston and 27 other major U.S. cities is dropping 2 to 10 millimeters (0.08 to 0.4 inches) per year. In all but three of the cities, more than 65 percent of the land is sinking.

A few millimeters might not seem like much. But over time, the sinking can increase the risk of floods and damage to buildings, roads, and other infrastructure, warns Leonard Ohenhen, the study’s lead author.

Why is this happening? Water beneath Earth’s surface supports the land above it. Scientists say humans are extracting that water—for everything from drinking to farming—faster than it can be replenished by rainfall, streams, and rivers. That leads to the sinking.

But there’s good news, Ohenhen points out. Using the data, city officials can pinpoint the areas most at risk and devise plans to strengthen infrastructure in those spots. They can also encourage residents to reduce their water use. In Houston, the city fines businesses for removing too much groundwater.

Those changes can help, Ohenhen says. “Whatever we do now can prevent further damage and losses in the future."

—Lisa M. Herrington