With Groundwater Losses, Many Cities are Sinking

As I’ve mentioned in previous articles, water seems to be becoming scarcer. To accommodate increasing populations and agriculture, the pumping of groundwater is reducing water tables across the globe. As a result, many cities around the world are slowly sinking, a process known as land subsidence. One of the most famous cities that has been sinking is Venice, Italy. However, there are others that are subsiding at a much faster rate.

Natural geological processes can cause the ground to sink over time. In recent times, human activities such as excessive groundwater pumping, rapid urban development, and climate change leading to increasing droughts have greatly accelerated the problem. Sinking cities certainly face major risks, including drought and flooding, damage to infrastructure, and economic losses.

One of the fastest-sinking cities in the world is Jakarta in Indonesia. Large parts of the city have sunk by at least 6 feet over the past few decades. This has been largely due to millions of residents relying on underground water wells. Since piped drinking water is limited, groundwater extraction has emptied underground aquifers, causing the land above them to collapse. In addition to the depletion of groundwater, coastal flooding has become increasingly severe, especially during high tides and heavy rainstorms. The Indonesian government has even begun moving the nation’s capital to a new city called Nusantara because Jakarta’s long-term future is uncertain.

Another fast-sinking city is Mexico City. The region is also experiencing severe subsidence as it was built on the site of an ancient lakebed once occupied by Lake Texcoco. As groundwater is continuously pumped out to support the growing population of around 20 million people, the soft clay beneath the city compresses. In some areas, the city sinks by several inches each year. Roads, buildings, pipelines, and historic structures have been damaged as the uneven ground shifts and cracks. The subsidence was first reported in the 1920s, but within the last 60 years, it’s estimated that parts of the city have dropped close to 32 feet.

Another major sinking city, and likely the most famous, is Venice. The city was built on wooden foundations over soft sediment in a lagoon. As a result, Venice has been gradually sinking for centuries. Rising sea levels in the Adriatic Sea have worsened the problem, leading to more frequent flooding events known as “acqua alta.” Although engineering projects such as the MOSE flood barrier system have helped reduce flooding in recent years, Venice remains highly vulnerable to erosion and other related factors.

In the United States, New Orleans is one of the most well-known sinking cities. Much of the city lies below sea level and was built on soft delta soils near the Mississippi River. Levees and drainage systems prevent natural sediment from rebuilding the land, causing the ground to compact and sink over time. The danger became clear during Hurricane Katrina, when catastrophic flooding caused widespread destruction. Scientists warn that continued subsidence and potential sea-level rise will make future storms even more dangerous.

Bangkok is also threatened by subsidence. Located on low-lying land near the Gulf of Thailand, Bangkok faces sinking caused by groundwater extraction and the weight of heavy urban construction. Seasonal flooding already affects many neighborhoods, and experts predict that potentially rising sea levels could place much of the city at risk in the future. Thailand has attempted to slow the sinking by regulating groundwater use, but the city remains vulnerable.

Shanghai is another example of a rapidly growing city facing land subsidence. Rapid construction, combined with groundwater removal, caused significant sinking during the twentieth century. Chinese authorities have reduced the rate of subsidence through stricter groundwater controls and monitoring systems, but parts of Shanghai still remain at risk due to flooding and typhoons.

Land sinking in Idaho is generally localized. There have been instances of sudden landslides or geological subsidence rather than widespread regional sinking. Key incidents include devastating landslides in the Boise foothills damaging luxury homes, and a historical, ongoing sinking farm near Buhl caused by unstable, ancient volcanic clay deposits and moisture.

In terms of our local weather, May is starting off to be a dry month across the Inland Northwest. Through the first 11 days, no measurable rainfall occurred. The normal May precipitation for Coeur d’Alene is 2.37 inches. The long-range forecast models are pointing to an increased chance for showers, and perhaps a few thunderstorms beginning late in the week and continuing off-and-on through the end of the month. However, May is shaping up to be drier than normal.

Scattered showers and thunderstorms are possible into early June, but high pressure is expected to rebuild across the northwestern portion of the country. Despite the expected shower activity later this month, the spring season is likely to be drier than normal. The upcoming summer across the Inland Northwest is also expected to be drier and warmer than average. Wildfire predictions for the northwestern U.S. is for “above normal potential” to develop in June and persist through much of the summer season.

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Contact Randy Mann at [email protected].