By: Mike Lowe
Contains a 9-page report describing the potential causes of subsidence in sedimentary basins and providing recommendations for avoiding or minimizing subsidence. Land subsidence can be caused by a variety of processes, but most land subsidence in the United States is associated with aquifer compaction caused pressure decline associated with groundwater withdrawal. In basin-fill aquifers, most of the aquifer compaction is due to the slow dewatering and compression of fine-grained sediments. Land subsidence can also be caused by contraction as fractured rock reservoirs cool. Land subsidence may result in various types of land-surface movements that can potentially cause problems if human development exists within the subsiding area. Although uncommon, geothermal development can and has caused aquifer compaction, for example in the Dixie Valley, Nevada, and at The Geysers geothermal area of California. Land subsidence can be avoided at geothermal project sites by re-injecting all production water back into the aquifer it was withdrawn from so that pressure changes are minimized. Where land subsidence associated with geothermal energy production does occur, it can be reduced through monitoring combined with aquifer management.