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.
If you’re interested in tracking reservoir storage, river flows and the snow-water content in the Sierra, the state has a web site for you — California Data Exchange Center, known as CDEC.
I am particularly interested in the amount of water frozen in the snow. Water content gives you an idea of how much water can be expected next spring and summer when the snowpack melts.
About this time of year, I like to compare the snowpack at this point to the snowpack last year. You can do that at this page.
As of Nov. 21, the Sierra is about the same as it was last year. It is less than average, but most of the season is still ahead.
River flows become more important later in the wet season, but any time is a good time to look up reservoir levels. Reservoirs are the bank account of water from previous seasons. They’re still looking pretty good, even though last year was a little dry.
Follow CDEC, and you’ll have an idea of what farmers, hydroelectric projects and many industries are watching this winter in California.
It’s nearly Thanksgiving. The weather has been delightful. And the California water world is watching, waiting and hoping for pregnant storms from the Pacific.
Rain and snow are expected this weekend, so farmers and water managers may breathe a little easier for the holiday.
They know it’s early in the season. But their anxiety level will climb in the next six weeks if they don’t see stormy weather.
Here’s what’s rolling through their minds:
— The snowpack is puny, even this early in the season.
— The snow and rain season last year was far below average in many places, especially in the southern Sierra. They don’t want to see back-to-back dry years.
— Reservoirs, which were at or above average earlier this year, are still looking pretty good, but they’re starting to slip.
— El Nino — warm water in the Pacific that sometimes is a sign of wet times ahead in California — has fizzled. So the odds of a wet season have become a coin flip again.
Long-time water experts say they’re not really sweating it yet. Water engineer Lance Johnson of Shaver Lake has spent decades watching the weather, working on east- and west-Valley farm water supply and analyzing trends.
His comment: “Precipitation in the San Joaquin River watershed is currently just 34% of normal and just barely greater than 1977, the direst year on record. But it is too early in the water year to get overly concerned as a few good storms can turn that around.”