Land subsidence due to groundwater exploitation in Greece

Problems

• Over the past few decades, Greece has seen a dramatic increase in groundwater extraction. This is largely due to the country's growing agricultural sector, which relies heavily on irrigation, and the mining industry. As a result, water table levels have dropped by tens of meters in some areas.
  
  This over-extraction of groundwater has led to a phenomenon known as land subsidence. When groundwater is removed, the land above it can sink or subside. In Greece, subsidence rates range from 1 to over 4 inches per year, and the problem is becoming apparent throughout the country.
  
  Most aquifers in Thessaly Plain are under a regime of overexploitation, resulting in a systematic drawdown of the groundwater level. In the Farsala—Stavros subplain, consistent overexploitation led to the complete draining of the overlay shallow unconfined aquifer and the progressive drawdown of the successive confined artesian aquifers. 
  
  This phenomenon resulted in the compaction of the compressible intercalated clayey horizons and the manifestation of intensive land subsidence since 2002. 

• The Impact

  The impact of land subsidence in Greece is far-reaching. Infrastructure such as buildings, roads, and public utilities have been damaged, particularly in areas like Thessaly. In some cases, the land has subsided so much that it has led to a progressive marine invasion, as seen on the west side of Thessaloniki.
  
  Moreover, the subsidence has also affected the country's wetlands, which were drained from the 1920s to 1960s for malaria control, flood prevention, and to increase cultivated lands. This has led to the oxidation of rich peat soils and further land subsidence. 

• The Future

  If left unchecked, land subsidence due to groundwater exploitation could have severe consequences for Greece. The productive Messara Plain in Crete, for example, is subsiding at a rate of at least 2 cm per year due to a 40-meter groundwater drop over the last 20 years.
  
  To address this problem, extensive water diversion and aquifer replenishment projects are essential in conjunction with water conservation and crop selection measures.