6 replies to this topic

[AntsTexas]

As Californians continue pumping groundwater in response to the historic drought, the California Department of Water Resources today released a new NASA report showing land in the San Joaquin Valley is sinking faster than ever before, nearly 2 inches (5 centimeters) per month in some locations

 

http://www.jpl.nasa....linkId=16422517

[Crystals]

Interesting.

I wonder if they offer maps like that for other locations as well...

[Pulliamj]

The ground sinks because the water is no longer there and gravity pulls down and fills the void? That's what I'm thinking. I have not heard of this before. What happens if it rains a lot? I doubt the ground can go back up. I'm guessing the storage will never be the same once the ground level changes.

[William. T]

The ground sinks because the water is no longer there and gravity pulls down and fills the void? That's what I'm thinking. I have not heard of this before. What happens if it rains a lot? I doubt the ground can go back up. I'm guessing the storage will never be the same once the ground level changes.

I think the ground would be a soggy mess if there are any rains. On the bright side, Argentines don't like the change in moisture levels.

Edited by William. T, August 20 2015 - 5:44 AM.

[AntsTexas]

mud/ground slides too?

[dspdrew]

Yeah, the farms are sucking the land dry.

[Foogoo]

The ground sinks because the water is no longer there and gravity pulls down and fills the void? That's what I'm thinking. I have not heard of this before. What happens if it rains a lot? I doubt the ground can go back up. I'm guessing the storage will never be the same once the ground level changes.

You've essentially hit the nail on the head. Pore water pressure (water filling the voids between soil grains) helps hold the structure of the ground. If a significant amount of that water is removed, the voids have nothing to keep their shape and collapse. And yes, once it collapses, it can't be restored. This is how groundwater basins can be permanently destroyed due to overpumping.

 

Most groundwater basins in urban Socal are adjudicated, in other words, regulated as a result of lawsuits which led to judicial proceedings and hydrogeologic studies that govern who can pump how much so the basins won't be overpumped. Most of the Central Valley is unadjudicated so it's a free for all, but that will hopefully change with the passing of the Sustainable Groundwater Management Act that was designed to address this issue.