Erosion Control

That Sinking Feeling

  • Email This Post Email This Post

Janice Kasperson - Erosion Control Editor
Here’s one more result of the California drought: The state is sinking. Parts of it, at least, are subsiding because of increased pumping of groundwater.

The problem isn’t exactly new. As this article reports, in 1975 the US Geological Survey noted that half the land in the San Joaquin Valley is prone to sinking. But the current drought conditions mean that farmers are relying more heavily on groundwater for irrigation, and as much as 65% of the state’s water is now coming from groundwater supplies (as opposed to about 40% in years with normal rainfall). Wells are going deeper, tapping into aquifers as far as 3,000 feet below the surface.

Here’s one more result of the California drought: The state is sinking. Parts of it, at least, are subsiding because of increased pumping of groundwater. The problem isn’t exactly new. As this article reports, in 1975 the US Geological Survey noted that half the land in the San Joaquin Valley is prone to sinking. But the current drought conditions mean that farmers are relying more heavily on groundwater for irrigation, and as much as 65% of the state’s water is now coming from groundwater supplies (as opposed to about 40% in years with normal rainfall). Wells are going deeper, tapping into aquifers as far as 3,000 feet below the surface. [text_ad] The result is that some areas are now sinking more than a foot a year, and that’s causing expensive damage to infrastructure like canals and well casings. By some estimates, repairs will cost billions of dollars. The same article notes that as canals sink, many irrigation districts “raise the sides of sagging canals so they can increase the water level and maintain a gravitational flow. As a result, at least one bridge now sits below the waterline.” Ironically, the damaged infrastructure includes the huge California Aqueduct that carries water 400 miles from the northern part of the state to the parched south; repairs to that canal alone have been in the tens of millions of dollars, with more work needed. And a project to return water to a section of the San Joaquin River—which has also been depleted by irrigation—has temporarily stopped while engineers try to calculate how much the land will continue to sink and take that into account in the construction. Researchers at NASA’s Jet Propulsion Laboratory are using satellite imagery to track the rates and locations of the subsidence. A potential danger—one that has not yet occurred—is that natural gas pipelines could be damaged by the shifting ground. A wetter winter is forecast, but that might bring additional problems: In areas where the land has already subsided, runoff patterns will have changed, leading to pooling of water and potential flooding.

The result is that some areas are now sinking more than a foot a year, and that’s causing expensive damage to infrastructure like canals and well casings. By some estimates, repairs will cost billions of dollars. The same article notes that as canals sink, many irrigation districts “raise the sides of sagging canals so they can increase the water level and maintain a gravitational flow. As a result, at least one bridge now sits below the waterline.”

Ironically, the damaged infrastructure includes the huge California Aqueduct that carries water 400 miles from the northern part of the state to the parched south; repairs to that canal alone have been in the tens of millions of dollars, with more work needed. And a project to return water to a section of the San Joaquin River—which has also been depleted by irrigation—has temporarily stopped while engineers try to calculate how much the land will continue to sink and take that into account in the construction. Researchers at NASA’s Jet Propulsion Laboratory are using satellite imagery to track the rates and locations of the subsidence.

A potential danger—one that has not yet occurred—is that natural gas pipelines could be damaged by the shifting ground.

A wetter winter is forecast, but that might bring additional problems: In areas where the land has already subsided, runoff patterns will have changed, leading to pooling of water and potential flooding.

Related Posts

Leave a Reply

Your email address will not be published. Required fields are marked *

FORESTER