The land in the state of California is sinking in places in the Central Valley. A canal that delivers vital water supplies from Northern California to Southern California is sinking in places and so are stretches of a riverbed undergoing historic restoration. Well casings on farms are also left standing as the ground falls below them.
The sinking of the land, known as subsidence, has been attributed to the extended use of groundwater in this drought that has persisted for four years now. This increased use of the groundwater has caused the land to sink in many different places causing damage to infrastructure over a wide expanse of California land.
Experts say that this slow land subsidence is costing the state expensively as regards repairs to infrastructure and the future appears bleak because they do not envisage the subsidence coming to a halt anytime soon.
“It’s shocking how a huge area is affected, but how little you can tell with your eye,” said James Borchers, a hydro-geologist, who studies subsidence. He said that there is need to study the area that is prone to this land sinking phenomenon so as to detect and address it before key pieces of infrastructure like bridges and pipelines can be affected.
Land subsidence comes about when the water is drawn out of the aquifers beneath the surface. When depleted, the ground above the aquifers sags so as to fill up the empty space beneath. This manifests as the land on the surface sinking. Roads develop cracks as the ground beneath the tarmac falls in whereas the other built infrastructure loses its structural integrity.
The Central Valley in California is the most agriculturally productive region in the United States. It has been hit by a record four year long drought that has led majority of the farmers to rely heavily on groundwater for irrigation of their crops. In the wet seasons, only 40 percent of the groundwater is used for irrigation whereas 65 per cent is used in the dry years.
With more of the nearer aquifers being utilized, deeper wells were sought out by the farmers – some as far down as 3000 feet – so as to supply their farms with water. Thousands of well casings have been destroyed and canal linings have buckled due to the decades of over pumping. The sides of irrigation canals have been lifted in irrigation districts in low spots so that the water can still flow at an acceptable level under the influence of the gravitational force.
A consequence of this is the fact that one bridge now stands below the waterline. Rebuilding another canal would cost 4.5 million dollars whereas repairs to the existing one, according to general manager of the Central California Irrigation District in Los Banos, Chris White, would amount to over $2.5 million.
For decades, the phenomenon of the land sinking has been rife in California and it has been shown that it is accelerating. Research by personnel at NASA’s Jet Propulsion Laboratory showed that land near Coracon sank 13 inches last year. There are parts of the massive California Aqueduct that also sunk nearly 13 inches.
According to Ted Thomas, a spokesman for the state’s Department of Water Resources, repairs have been made on the aqueduct over the past forty years and the bill has amounted to over $40 million.
Sinking land has stopped work on part of a historic project to return water flows to an irrigation-depleted section of the San Joaquin River. Before construction of a passageway for fish can begin, officials need to assess how fast the land will sink in the future, said Alicia Forsythe of the U.S. Bureau of Reclamation.