Californians are in the fourth year of one of the worst droughts the state has seen in the past century. Having only gotten just over 4 inches of rain on average in the last year, Californians are faced with depleted reservoir stores and must turn to their underground water stores that can’t refill fast enough. The drought is literally sucking California dry, and much like a sponge – the state is shriveling.
NASA released a report on Wednesday of last week (8/19/15) that illustrated this shriveling, or in more technical terms – subsidence ([sub-SIDE-dense] noun. the general caving in or sinking of an area of land). They collaborated with Japan and Canada to use some of the world’s top of the line satellite and aircraft technology to create maps of this subsidence, accurate within fractions of an inch. By compiling data of the four year period of 2006 and 2010, and a more recent eight month period between May 2014 and January 2015, they were able to demonstrate how the subsistence in California has changed physically over time.
The largest affected area spans 60 miles around Corcoran, CA. Between 2006 and 2010 the ground sank approximately 37 inches at its deepest point – a rate of about 0.8 inches per month. Between May 2014 and January 2015, the ground sank an additional 13 inches – a rate of about 1.6 inches per month (illustrated in the image above). The rate of subsidence is not just continuing, but growing larger and becoming more of a problem.
NASA attributes this subsidence to the pumping of water from the stores beneath the ground, known as aquifers. Drawing water from the ground generally isn’t a problem, but when the ground doesn’t refill it compacts and the surface sinks. Some types of aquifers are able to bounce back after compaction – these layers of the water table are unconfined and are easily permeable. The trouble is when the other layers are drained, which are known as confined and are less permeable therefore harder to refill. When they become compacted, they can’t bounce back and they lose future water storage potential. For a state with a drought problem, this isn’t good news.
The trouble that the state already faces from the drought (increased wildfire activity, endangerment of wildlife, and the troubles in the agricultural sector with crop, revenue, and job losses) is only being added to with these rapid geographical changes. The subsidence is responsible for costly damages to all sorts of structures: bridges, roads, and even canals that deliver water up and down the state.
There are no simple fixes to this issue, but legislation and policies show that the state is taking it seriously. Plans are being made to do things like monitor the pumping of groundwater and prevent further damage to underwater stores beneath the state, as well as fixing structures that have been affected by the subsidence.