Some Serious SubsidenceThis is a location in California’s San Joaquin Valley, which sits betwe
Some Serious SubsidenceThis is a location in California’s San Joaquin Valley, which sits between the Pacific Coastline and the Sierra Nevada Mountains. Its location causes it to get some rain, but the rains are fickle and influenced by the changes in currents and weather patterns in the Pacific Ocean. Sometimes, the rains are weak or not there.The climate of the San Joaquin valley is wonderfulfor growing crops – not too hot, not too cold in most years, and the soils are fertile. The only ingredient missing is a regular water supply. In rainy years, the rain can support agriculture, but in dry years it can’t, leaving groundwater as the main water source.Groundwater exists in the spaces between loose sediments, tens to hundreds of meters beneath the surface. Waters trapped at that depth are under pressure and actually absorb some of the weight of the overlying sediments, keeping pores open and holding the ground up.If the groundwater is pumped out of these systems, the ground loses part of its support, like taking the foundation out from beneath a house, and starts to sink.The markers on this telephone pole are labeled 1925, 1955, and 1977. These markers show the location of the ground in those years – with just 50 years of pumping; the ground in this spot sank by over 10 meters.I wish I could see where the ground surface in this spot sits today, after the drought in recent years.-JBBImage credit: USGShttps://pubs.usgs.gov/circ/circ1182/pdf/06SanJoaquinValley.pdf -- source link
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