Incredibly Sinking State: The Lowdown on Subsidence | KCET
Incredibly Sinking State: The Lowdown on Subsidence
Parts of central California are sinking like a mishandled soufflé - possibly two feet a year since 2008 -- as agri-businesses pump more and more groundwater to backfill losses from a drought-stressed state water system. Field pumps that were idle most of the year now work day and night sucking up irrigation water from aquifers under thousands of square miles of farmland.
The groundwater drain causes the land surface to drop, putting highways, bridges, dams, flood control channels, and pipelines at risk.
Subsidence even affects the flow of rivers and creeks when their channels are interrupted by sinking ground. Installation of pumps to move surface water downstream and out of subsidence zones can cost millions of dollars and further burdens the state's electrical generating capacity.
Pumping the state's water already consumes about five percent of the state's electricity.
In April, the state Department of Water Resources reported that approximately 60 percent of all the water California consumes is pumped from underground sources, with many of these sources at risk for ground subsidence. Agriculture uses most of the state's groundwater, with agriculture's share increasing as even more wells are drilled in response to another year of drought.
Increased pumping and the drilling of new wells may, according the New York Times, increase groundwater use to nearly 75 percent of the state's water budget.
Completion of the state aqueduct system in the 1960s was intended, in part, to reduce groundwater pumping and stop the subsidence that had lowered the floor of much of the Central Valley by almost 30 feet between 1925 and 1955. Today, as measurements mark new and unusually rapid ground level drop north of Bakersfield, state geologists have only limited data to predict future ground movement.
By some rough estimates, the current rate of sinking is greater than at any time in the past 50 years.
Only last year did the legislature pass its first law to manage groundwater extraction statewide. But agri-businesses won't be required to comply fully with extraction limits until at least 2040. And as is true throughout the state water system, how much water is pumped and by whom will be kept secret.
By contrast, pumping from the groundwater basins of Los Angeles County has been closely monitored since the 1960s by a court-appointed Watermaster and by the Central and West Basin Municipal Water Districts and the Southern California Water Replenishment District.
While the water districts have had their political troubles in recent years, none of them has been lax in accounting for and reporting every acre-foot of water pumped from the aquifers that lie below much of Los Angeles County.
The plumbing under the county has been anxiously watched since 1900, when production from free-flowing artesian wells declined and worries over where Los Angeles would get its water peaked. In the 1940s, salt water from the Pacific began to turn fresh water in the West Basin brackish after a decade of industrial and agricultural over drafting. Unregulated pumping in the Central Basin caused water levels in existing wells to fall. In parts of the San Gabriel Valley and southeastern Los Angeles County, wells were abandoned and new wells drilled hundreds of feet deeper to reach untapped aquifers.
Court-ordered groundwater management, based on compacts among the pumpers, apportioned water rights and ended over pumping in Los Angeles County. That system continues to regulate the flow of water into and out of the basins.
But it wasn't water that showed us the true costs of taking too much from under our feet. It was oil.
Oil had been taken from wells at the Los Angeles/Long Beach harbor as early as 1865, but it was the drilling of the first producing well on Signal Hill in 1921 that set off a frenzy of oil exploration. By the 1930s, more than 450 oil wells dotted Long Beach harbor jetties and Terminal Island landfill.
By 1943, it was clear that Long Beach harbor was sinking, almost certainly due to oil extraction. The eastern end of Terminal Island had dropped nearly four feet in eight years. Even the Long Beach breakwater was two feet lower than its "as built" elevation. By 1947, surveys of the rate of subsidence pointed to an eventual drop of 22 to 25 feet, putting most of the port's Navy facilities and the nearby commercial docks under water.
Lateral earth movement began crushing well casings in 1949, and a drop of another 18 inches brought high tides within a few yards of Terminal Island businesses. Some facilities and industrial plants, now walled within protective concrete barriers, were already below sea level.
In 1950, the subsidence zone reached downtown Long Beach, five miles from the port. Pine Avenue -- Long Beach's main commercial street -- was already two feet lower. In an eerie foreshadowing of sea level rise from climate change, a Long Beach neighborhood of 100 homes was flooded in 1951 when unusually high tides flowed up the city's storm drain system.
The worsening subsidence made bridges occasionally impassible, backed up gravity-fed sewer lines, and lowered the height of flood control levees along the Los Angeles River. By 1956, ground subsidence covered an elongated bowl covering 22 square miles. All of the Long Beach shoreline, from the port south to downtown Long Beach, was on the verge of sinking into San Pedro Bay.
Like the agri-businesses busily pumping down the landscape of the Central Valley today, harbor oil pumpers were caught in a "tragedy of the commons" -- a situation in which many independent actors, out of reasonable self-interest, collectively act unreasonably to over consume a shared resource. In Long Beach, the resource was oil. In the Central Valley, it's water.
It was generally agreed that re-pressurizing the Long Beach Harbor oil field would slow or even stop the rate of subsidence, based on the effects of injection wells that had already begun replacing oil with seawater. But fragmented ownership in the harbor oil field led to resistance to re-pressurization with seawater.
It required the threat of a huge federal lawsuit in 1958 to compel the various parties -- 400 oil companies and dozens of property owners, as well as port officials, the state, and the city of Long Bach -- to adopt a mitigation plan based on pumping hundreds of millions of gallons of seawater into the harbor oil field to replace the missing oil. Amazingly, the plan worked almost at once.
Stopping subsidence didn't restore the landscape, however. Parts of Long Beach remain many feet lower than they were before oil extraction began. The port lost a significant part of its industrial base as manufacturers moved out of the subsidence area. Long Beach was re-branded as the "sinking city." The Navy, formerly one of the city's biggest employers eventually left.
Agri-businesses in the Central Valley don't have a federal lawsuit to compel collective action to mitigate their subsidence problem. State government -- as in the 1950s -- seems incapable of responding intelligently and quickly to a "tragedy of the commons" whose effects are worsening and whose costs -- in the form of damaged public infrastructure -- will be shouldered by taxpayers.
Consequences that local history had already made very clear.
*Original caption: Sailors of cruiser USS Bremerton at Berth 12, adjacent to Long Beach Navy Landing at foot of Pico Avenue, working on ship's hawsers as 6.2 feet tide raised water level within 3 feet of dock surface 8:33 am today (Friday) 10-03-1952.
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