Responding to my Sunday story, a few readers contacted me to say sinking farmland isn’t new.
You’re right. I didn’t have a chance to write much history.
My story Sunday was about the sinking land around the San Joaquin River and how it would affect the replacement of Sack Dam. It’s contributing to delays in the restoration of the river.
But I’ve been writing occasionally about land subsidence on the San Joaquin Valley’s west side for the last 20 years, and I find it fascinating.
Here’s the first sentence of a story I wrote on Earth Day 2007:
“The land dipped 30 feet between 1925 and 1977 near Mendota — and it’s still going down in what the U.S. Geological Survey calls the largest human alteration of the Earth’s surface. Ever.”
Layers of soil beneath the land surface deflate as groundwater pumping continues. It’s responsible for millions of dollars in damage to irrigation canals. And it could threaten such landmarks as the California Aqueduct and Interstate 5.
You might have seen the famous photograph of a utility pole near Mendota. The 1977 photo features USGS scientist Joseph Poland, who discovered the sinking ground.
High above Poland’s head there are two small signs with the years 1955 and 1925, marking the level of the ground in those years. As you can see, it’s dramatic.